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(Added 09/30/04) The Genesis team is preparing to ship its samples of the sun from the mission's temporary cleanroom at the U.S. Army Proving Ground, Dugway, Utah, to NASA's Johnson Space Center, Houston.

"We have essentially completed the recovery and documentation process and now are in the business of preparing everything for transport," explained Eileen Stansbery, Johnson Space Center assistant director of astromaterials research and exploration science. "We still have a way to go before we can quantify our recovery of the solar sample. I can tell you we have come a long way from September 8, and things are looking very, very good."

A major milestone in the process was the recovery of the Genesis mission's four separate segments of the concentrator target. Designed to measure the isotopic ratios of oxygen and nitrogen, the segments contain within their structure the samples that are the mission's most important science goal.

"Retrieving the concentrator target was our number one priority," Stansbery said. "When I first saw three of the four target segments were intact, and the fourth was mostly intact, my heart leapt. Inside those segments are three years of the solar samples, which to the scientific community, means eons worth of history of the birth of our solar system. I saw those, and I knew we had just overcome a major hurdle."

Other milestones in the recovery process included the discovery that the gold foil collector was undamaged and in excellent condition. The gold foil, which is expected to contain almost a million billion atoms of solar wind, was considered the number two priority for science recovery. The polished aluminum collector was misshapen by the impact. However, it is intact and expected to also yield secrets about the sun. Another occurred when the cleanroom team disassembled the collector arrays. They revealed, among large amounts of useable array material, some almost whole sapphire and coated sapphire collectors and a metallic glass collector.

Packing solar samples for transport is a little different than packing a house-worth of belongings for a cross-country move. After the meticulous process of inspection and documentation, each segment of collector gets its own ID number, photograph and carrying case. The samples and shipping containers fill the space of about two full size refrigerators. The Genesis material will probably move to the Johnson Space Center within the next week.

"If you had told me September 8 that we would be ready to move Genesis samples to Houston within the month I would have replied, 'no way,'" remarked Genesis Project Manager Don Sweetnam of NASA's Jet Propulsion Laboratory, Pasadena, CA. "But here we are, with an opportunity to fulfill our major science objectives. It is a great day for Genesis, and I expect many more to come."

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-245.

(Added 09/30/04) The explosion of a massive star blazes with the light of 200 million suns in this NASA Hubble Space Telescope image. The arrow at top right points to the stellar blast, called a supernova. The supernova is so bright in this image that it easily could be mistaken for a foreground star in our Milky Way Galaxy. And yet, this supernova, called SN 2004dj, resides far beyond our galaxy. Its home is in the outskirts of NGC 2403, a galaxy located 11 million light-years from Earth. Although the supernova is far from Earth, it is the closest stellar explosion discovered in more than a decade.

The star that became SN 2004dj may have been about 15 times as massive as the sun and only about 14 million years old. A team of astronomers led by Jesus Maiz of the Space Telescope Science Institute discovered that the supernova was part of a compact cluster of stars known as Sandage 96, whose total mass is about 24,000 times the mass of the sun. Many such clusters - the blue regions - as well as looser associations of massive stars, can be seen in this image. The large number of massive stars in NGC 2403 leads to a high supernova rate. Two other supernovae have been seen in this galaxy during the past half-century.

The heart of NGC 2403 is the glowing region at lower left. Sprinkled across the region are pink areas of star birth. The many faint stars visible in the Hubble image belong to NGC 2403, but the handful of very bright stars in the image belong to our own Milky Way Galaxy and are only a few hundred to a few thousand light-years away. This image was taken on August 17, two weeks after an amateur astronomer discovered the supernova.

Japanese amateur astronomer Koichi Itagaki discovered the supernova on July 31, 2004, with a small telescope. Additional observations soon showed that it is a "Type II supernova," resulting from the explosion of a massive, hydrogen-rich star at the end of its life. The cataclysm probably occurred when the evolved star's central core, consisting of iron, suddenly collapsed to form an extremely dense object called a neutron star. The surrounding layers of gas bounced off the neutron star and also gained energy from the flood of neutrinos that may have been released, thereby violently expelling these layers.

This explosion is ejecting heavy chemical elements, generated by nuclear reactions inside the star, into the cosmos. Like other Type II supernovae, this exploding star is providing the raw material for future generations of stars and planets. Elements on Earth such as oxygen, calcium, iron, and gold came long ago from exploding stars such as this one.

Astronomers will continue to study SN 2004dj over the next few years, as it slowly fades from view, in order to gain a better understanding of how certain types of stars explode and what kinds of chemical elements they eject into space.

This color-composite photograph was obtained by combining images through several filters taken with the Wide Field Camera of the Advanced Camera for Surveys. The colors in the image highlight important features in the galaxy. Hot, young stars are blue. Older stars and dense dust lanes near the heart of the galaxy are red. The hydrogen-rich, star-forming regions are pink. The dense concentration of older stars in the galaxy's central bulge is yellow. In addition to the visible-light image shown here, ultraviolet images and spectra are being obtained with Hubble's Advanced Camera for Surveys. Astronomers are also using ground-based telescopes to study the supernova.

Adapted from the information on http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/23/.

(Added 09/26/04) As NASA's Spirit and Opportunity rovers resumed reliable contact with Earth after a period when Mars passed nearly behind the sun, the space agency extended funding for an additional six months of rover operations, as long as they keep working.

Both rovers successfully completed their primary three-month missions on the surface of Mars in April and have already added about five months of bonus exploration during the first extension of their missions.

"Spirit and Opportunity appear ready to continue their remarkable adventures," said Andrew Dantzler, solar system division director at NASA Headquarters, Washington. "We're taking advantage of that good news by adding more support for the teamwork here on Earth that's necessary for operating the rovers."

Neither rover drove during a 12-day period this month, while radio transmissions were unreliable because of the sun's position between the two planets. Daily planning and commanding of rover activities recommenced Monday for Opportunity and today for Spirit.

"It is a relief to get past this past couple of weeks," said Jim Erickson, project manager for both rovers at NASA's Jet Propulsion Laboratory, Pasadena, CA. "Not only were communications disrupted, but the rovers were also going through the worst part of Mars southern-hemisphere winter from a solar-energy standpoint."

"Although Spirit and Opportunity are well past warranty, they are showing few signs of wearing out," Erickson said. "We really don't know how long they will keep working, whether days or months. We will do our best to continue getting the maximum possible benefit from these great national resources."

Rover science team members will spend less time at JPL during the second mission extension. They are able to attend daily planning meetings by teleconferencing from their home institutions in several states and in Europe. "All 150 science team members and collaborators have been provided the tools to be able to participate remotely," explained JPL's Dr. John Callas, science manager for the rover project. Workstations researchers used at JPL are at their home institutions. Planning tools include video feeds, workstation display remote viewing, and audio conferencing.

Besides reducing costs, remote operations allow scientists to spend more time at home. "We get back to more normal lives, back to our families, and we still get to explore Mars every day," remarked Dr. Steve Squyres of Cornell University, Ithaca, NY, principal investigator.

Another change in operations is a shift from seven days per week to five days per week from October through December. This accommodates a temporary trim of about 20% in the project's engineering team to about 100 members. The rovers' reduced energy supply, during the rest of the martian winter, makes the inactive days valuable for recharging batteries. By January, the energy situation will have improved for the solar-powered rovers, provided they are still operating. The team size will rebound to support daily operations.

As Mars emerges from behind the sun, Spirit is partway up the west spur of highlands called the "Columbia Hills," a drive of more than 3 kilometers (2 miles) from its landing site. Opportunity is inside stadium-size "Endurance Crater," headed toward the base of a stack of exposed rock layers in "Burns Cliff," and a potential exit route on the crater's south side.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-234.

(Added 09/26/04) Scientists examining Saturn's contorted F ring, which has baffled them since its discovery, have found one small body, possibly two, orbiting in the F ring region, and a ring of material associated with Saturn's moon Atlas.

A small object was discovered moving near the outside edge of the F ring, interior to the orbit of Saturn's moon Pandora. The object was seen by Dr. Carl Murray, imaging team member at Queen Mary, University of London, in images taken on June 21, 2004, just days before Cassini arrived at Saturn. "I noticed this barely detectable object skirting the outer part of the F ring. It was an incredible privilege to be the first person to spot it," he remarked. Murray's group at Queen Mary then calculated an orbit for the object.

Scientists cannot yet definitively say if the object is a moon or a temporary clump. If it is a moon, its diameter is estimated at four to five kilometers (two to three miles) and it is located 1,000 kilometers (620 miles) from the F ring, Saturn's outmost ring. It is at a distance of approximately 141,000 kilometers (86,000 miles) from the center of Saturn and within 300 kilometers (190 miles) of the orbit of the moon Pandora. The object has been provisionally named S/2004 S3.

Scientists are not sure if the object is alone. This is because of results from a search through other images that might capture the object to pin down its orbit. The search by Dr. Joseph Spitale, a planetary scientist working with team leader Dr. Carolyn Porco at the Space Science Institute in Boulder, CO, revealed something strange. Spitale said, "When I went to look for additional images of this object to refine its orbit, I found that about five hours after first being sighted, it seemed to be orbiting interior to the F ring," said Spitale. "If this is the same object then it has an orbit that crosses the F ring, which makes it a strange object." Because of the puzzling dynamical implications of having a body that crosses the ring, the inner object sighted by Spitale is presently considered a separate object with the temporary designation S/2004 S4. S4 is roughly the same size as S3.

Saturn's New Ring S/2004 1R In the process of examining the F ring region, Murray also detected a previously unknown ring, S/2004 1R, associated with Saturn's moon, Atlas. "We knew from Voyager that the region between the main rings and the F ring is dusty, but the role of the moons in this region was a mystery," said Murray. "It was while studying the F ring in these images that I discovered the faint ring of material. My immediate hunch was that it might be associated with the orbit of one of Saturn's moons, and after some calculation I identified Atlas as the prime suspect."

The ring is located 138,000 kilometers (86,000 miles) from the center of Saturn in the orbit of the moon Atlas, between the A ring and the F ring. The width of the ring is estimated at 300 kilometers (190 miles). The ring was first spotted in images taken after orbit insertion on July 1, 2004. There is no way of knowing yet if it extends all the way around the planet.

"We have planned many images to search the region between the A and F rings for diffuse material and new moons, which we have long expected to be there on the basis of the peculiar behavior of the F ring," said Porco. "Now we have found something but, as is usual for the F ring, what we see is perplexing."

Searches will continue for further detections of the newfound body or bodies seen in association with the F ring. If the two objects indeed turn out to be a single moon, it will bring the Saturn moon count to 34. The newfound ring adds to the growing number of narrow ringlets around Saturn.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-222.

(Added 09/26/04) The Genesis mission was launched in August 2001 on a journey to capture samples from the storehouse of 99% of all the material in our solar system -- the Sun. The samples of solar wind particles, collected on ultra-pure wafers of gold, sapphire, silicon and diamond, were designed to be returned for analysis by Earth-bound scientists.

The Genesis sample return capsule entered Earth's atmosphere at 9:52:47 A.M. MDT on September 8 and entered the preplanned entry ellipse in the Utah Test and Training Range as predicted. However, the Genesis capsule, as a result of its parachute not deploying, impacted the ground at a speed of 311 km per hour (193 miles per hour). The impact occurred near Granite Peak on a remote portion of the range. No people or structures were anywhere near the area.

"We have the capsule," said Genesis project manager Don Sweetnam of NASA's Jet Propulsion Laboratory, Pasadena, CA. "It is on the ground. We have previously written procedures and tools at our disposal for such an event. We are beginning capsule recovery operations at this time."

By the time the capsule entered Earth's atmosphere, the flight crews tasked to capture Genesis were already in the air. Once it was confirmed the capsule touched down out on the range, the flight crews were guided toward the site to initiate a previously developed contingency plan. They landed close to the capsule and, per the plan, began to document the capsule and the area.

"For the velocity of the impact, I thought there was surprisingly little damage," said Roy Haggard of Vertigo Inc., Lake Elsinore, CA, who took part in the initial reconnaissance of the capsule. "I observed the capsule penetrated the soil about 50% of its diameter. The shell had been breached about three inches and I could see the science canister inside and that also appeared to have a small breach," he said.

The science canister from the Genesis mission was later moved into the cleanroom at the U.S. Army Dugway Proving Ground in Utah. First, a team of specialists plucked pieces of dirt and mud that had lodged in the canister after the mission’s sample return capsule landed at high speed in the Utah desert.

The Genesis team began examining the contents of the canister on Thursday morning. "This may result in snatching victory from the jaws of defeat," said Dr. Roger Wiens of the Los Alamos National Laboratory in New Mexico, a member of the Genesis science team, the next day. "We are very encouraged." Based on initial inspection, it is possible a repository of solar wind materials may have survived that will keep the science community busy for some time.

"We are pleased and encouraged by the preliminary inspection," said NASA Administrator Sean O'Keefe. "The outstanding design and sturdy construction of Genesis may yield the important scientific results we hoped for from the mission."

The mission's main priority is to measure oxygen isotopes to determine which of several theories is correct regarding the role of oxygen in the formation of the solar system. Scientists hope to determine this with isotopes collected in the four target segments of the solar wind concentrator carried by the Genesis spacecraft. "From our initial look, we can see that two of the four concentrator segments are in place, and all four may be intact," Wiens said.

The mission's second priority is to analyze nitrogen isotopes that will help us understand how the atmospheres of the planets in our solar system evolved. "These isotopes will be analyzed using gold foil, which we have also found intact," Wiens said. Other samples of solar winds are contained on hexagonal wafers.

Another type of collector material, foils contained on the canister's lid, were designed to collect other isotopes in the solar wind. It appears approximately three-fourths of these are recoverable, according to Dr. Dave Lindstrom, mission program scientist at NASA Headquarters. However, these foils have been exposed to elements of the Utah desert.

At present, the science canister that holds the majority of the mission's scientific samples is lying upside down - on its lid. Scientists are very methodically working their way "up" from the bottom portion of the canister by trimming away small portions of the canister's wall. The team continues to extract, from the interior of the science canister, small but potentially analyzable fragments of collector array material. One-half of a sapphire wafer was collected Tuesday - the biggest piece of collector array to date.

The condition of these segments will be better known over the next few days, after the canister's solar wind concentrator is extricated. At this time, it is believed that three of these segments are relatively intact and that the fourth may have sustained one or more fractures. There are no concrete plans regarding the shipping date of the Genesis capsule or its contents from Dugway to the Johnson Space Center in Houston. The team continues its meticulous work and believes that a significant repository of solar wind materials may have survived that will keep the science community busy for some time.

The Genesis team shipped its first scientific sample from the mission's specially constructed cleanroom at the U.S. Army Proving Ground in Dugway, Utah, on September 23 - 15 days after the craft landed in the desert. The sample, containing what are known as "lid foils," was attached to the interior lid of the Genesis sample return capsule.

"This is the first batch in what we are growing more confident will be many more scientifically valuable samples," said Genesis Project Manager Don Sweetnam of NASA's Jet Propulsion Laboratory, Pasadena, CA. "It appears that we have recovered about 75 to 80 percent of these lid foils. A great deal of credit has to go to the dedicated men and women of Genesis who continue to do very precise, detailed work out there in the Utah desert."

After the sample was shipped from Utah, it was received by Genesis co-investigator Nishiizumi Kunihiko from the University of California, Berkeley, Space Sciences Laboratory.

In addition to the lid foils, there was optimistic news about the collector array. Team members from JPL arrived in Utah on Monday with a special fixture to aid in handling the science canister's stack of four collector arrays. The stack was successfully removed as one piece. With the stack on the fixture, the team has begun the process of disassembling the arrays. Several large pieces of individual collector materials, including one completely intact hexagon, were recovered from the top array.

The Genesis cleanroom activities are focused on getting the materials ready for shipping. A date has not yet been selected for transporting the Genesis science canister and recovered collector materials from Dugway to NASA's Johnson Space Center in Houston. The team continues its meticulous work and believes that a significant repository of solar wind materials has survived that will keep the science community busy working on their science objectives.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-219, http://www.jpl.nasa.gov/news/news.cfm?release=2004-221, http://www.jpl.nasa.gov/news/news.cfm?release=2004-225, http://www.jpl.nasa.gov/news/news.cfm?release=2004-228, http://www.jpl.nasa.gov/news/news.cfm?release=2004-231, and http://www.jpl.nasa.gov/news/news.cfm?release=2004-236.

(Added 09/26/04) A new class of planets beyond our solar system of unprecedented small size - about 10 to 20 times the size of Earth - has recently been detected. The planets make up a new class of Neptune-sized extrasolar planets. In addition, one of the new planets joins three others around the nearby star 55 Cancri to form the first known four-planet system.

The discoveries consist of two new planets. They were discovered by the world renowned planet-hunting team of Drs. Paul Butler and Geoffrey Marcy of the Carnegie Institute of Washington and University of California, Berkeley, respectively; and Barbara McArthur of the University of Texas, Austin. Both findings were peer-reviewed and accepted for future publication in the Astrophysical Journal. NASA and the National Science Foundation funded the research.

"These Neptune-sized planets prove that Jupiter-sized, gas giants aren't the only planets out there," Marcy said. Butler added, "We are beginning to see smaller and smaller planets. Earth-like planets are the next destination." Future NASA planet-hunting missions, including Kepler, the Space Interferometry Mission and the Terrestrial Planet Finder, will seek such Earth-like planets. Nearly 140 extrasolar planets have been discovered.

Both of the new planets stick very close to their parent stars, whipping around them in a matter of days. The first planet, discovered by Marcy and Butler, circles a small star called Gliese 436 about every 2.5 days at just a small fraction of the distance between Earth and the Sun, or 4.1 million kilometers (2.6 million miles). This planet is only the second known to orbit an M dwarf, a type of low-mass star 40% the size of our own sun. Gliese 436 is located in our galactic backyard, 30 light-years away in the constellation Leo.

The second planet, found by McArthur, speeds around 55 Cancri in just under three days, also at a fraction of the distance between Earth and the sun, at approximately 5.6 million kilometers (3.5 million miles). Three larger planets also revolve around the star every 15, 44 and 4,520 days, respectively. Marcy and Butler discovered the outermost of these in 2002. It is still the only known Jupiter-like gas giant to reside as far away from its star as our own Jupiter. The 55 Cancri is about 5 billion years old, a bit lighter than the sun, and is located 41 light-years away in the constellation Cancer. "55 Cancri is a premier laboratory for the study of planetary system formation and evolution," McArthur said.

Because the new planets are smaller than Jupiter, it is possible they are made of rock, or rock and ice, rather than gas. According to the scientists, the planets may have, like Earth, formed through gradual accumulation of rocky bodies. "A planet of Neptune's size may not have enough mass to hold onto gas, but at this point we don't know," Butler said.

Both discoveries were made using the "radial velocity" technique, in which a planet's gravitational tug is detected by the wobble it produces in the parent star. Butler, Marcy and collaborators, including Dr. Deborah Fischer of San Francisco State University and Dr. Steven Vogt of the University of California, Santa Cruz, discovered their "Neptune" after careful observation of 950 nearby stars with the W.M. Keck Observatory in Mauna Kea, Hawaii. They were able to spot such a relatively small planet, because the star it tugs on is small and more susceptible to wobbling.

McArthur and collaborators Drs. Michael Endl, William Cochran and Fritz Benedict of the University of Texas discovered their "Neptune" after obtaining over 100 observations of 55 Cancri from the Hobby- Eberly Telescope at McDonald Observatory in West Texas. Combining this data with past data from Marcy, Fischer and Butler from the Lick Observatory in California, and archival data from NASA's Hubble Space Telescope, the team was able to model the orbit of 55 Cancri's outer planet. This, in turn, allowed them to clearly see the orbits of the other three inner planets, including the new Neptune-sized one.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-212.

(Added 09/26/04) NASA's Mars Odyssey orbiter begins working overtime today after completing a prime mission that discovered vast supplies of frozen water, ran a safety check for future astronauts, and mapped surface textures and minerals all over Mars, among other feats.

"Odyssey has accomplished all of its mission-success criteria," announced Dr. Philip Varghese, project manager for Odyssey at NASA's Jet Propulsion Laboratory, Pasadena, CA. The spacecraft has been examining Mars in detail since February 2002, more than a full Mars year of about 23 Earth months. NASA has approved an extended mission through September 2006.

"This extension gives us another martian year to build on what we have already learned," explained JPL's Dr. Jeff Plaut, project scientist for Odyssey. "One goal is to look for climate change. During the prime mission we tracked dramatic seasonal changes, such as the comings and goings of polar ice, clouds and dust storms. Now, we have begun watching for year-to-year differences at the same time of year."

The extension will also continue Odyssey's support for other Mars missions. About 85% of images and other data from NASA's twin Mars rovers, Spirit and Opportunity, have reached Earth via communications relay by Odyssey, which receives transmissions from both rovers every day. The orbiter helped analyze potential landing sites for the rovers and is doing the same for NASA's Phoenix mission, scheduled to land on Mars in 2008. Plans call for Odyssey to aid NASA's Mars Reconnaissance Orbiter, due to reach Mars in March 2006, by monitoring atmospheric conditions during months when the newly arrived orbiter uses calculated dips into the atmosphere to alter its orbit into the desired shape.

Odyssey was launched April 7, 2001, and used the same dips into the atmosphere, known as aerobraking, to shape its orbit during the initial months after it reached Mars on October 23, 2001. The spacecraft carries three research systems: a camera system made up of infrared and visible-light sensors; a spectrometer suite with a gamma ray spectrometer, a neutron spectrometer and a high-energy neutron detector; and a radiation environment detector.

Less than a month after the science mapping campaign began, the team announced a major discovery. The gamma ray and neutron instruments detected copious hydrogen just under Mars' surface in the planet's south polar region. Researchers interpret the hydrogen as frozen water - enough within about a meter (3 ft) of the surface, if the ice were melted, to fill Lake Michigan a couple times.

Here are a few of Odyssey's other important accomplishments so far:

As summer came to northern Mars and the north polar covering of frozen carbon dioxide shrank, Odyssey found abundant frozen water in the north, too.
Infrared mapping showed that a mineral called olivine is widespread. This indicated the environment has been quite dry, because water exposure alters olivine into other minerals.
Findings indicated the amount of frozen water in some relatively warm regions on Mars is too great to be in equilibrium with the atmosphere, suggesting that Mars may be going through a period of climate change. Features visible near small, young gullies in some Odyssey images may be slowly melting snowpacks left over from a martian ice age.
The first experiment sent to Mars specifically in preparation for human missions found that radiation levels around Mars, from solar flares and cosmic rays, are two to three times higher than around Earth.
Odyssey's camera system obtained the most detailed complete global maps of Mars ever, with daytime and nighttime infrared images at a resolution of 100 meters (328 feet).

"We've accomplished everything we set out to do, and more," said JPL's Robert Mase, Odyssey mission manager. Although an unusually powerful solar flare in October 2003 knocked out the radiation environment instrument, Odyssey is otherwise in excellent health. The spacecraft has enough fuel onboard to keep operating through this decade and the next at current consumption rates. The mission extension, with a budget of $35 million, essentially doubles the science payoff from Odyssey for less than one-eighth of the mission's original $297 million cost.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-209.

(Added 09/26/04) Astronomers have used an x-ray image to make the first detailed study of the behavior of high-energy particles around a fast moving pulsar. The image, from NASA's Chandra X-ray Observatory, shows the shock wave created as a pulsar plows supersonically through interstellar space. These results will provide insight into theories for the production of powerful winds of matter and antimatter by pulsars.

Chandra's image of the glowing cloud, known as the Mouse, shows a stubby bright column of high-energy particles, about four light years in length, swept back by the pulsar's interaction with interstellar gas. The intense source at the head of the x-ray column is the pulsar, estimated to be moving through space at about 1.3 million miles per hour.

A cone-shaped cloud of radio-wave-emitting particles envelopes the x-ray column. The Mouse, AKA G359.23-0.82, was discovered in 1987 by radio astronomers using the National Science Foundation's Very Large Array in New Mexico. It gets its name from its appearance in radio images that show a compact snout, a bulbous body, and a remarkable long, narrow, tail that extends for about 55 light years.

"A few dozen pulsar wind nebulae are known, including the spectacular Crab Nebula, but none have the Mouse's combination of relatively young age and incredibly rapid motion through interstellar space," commented Bryan Gaensler of the Harvard-Smithsonian Center for Astrophysics and lead author of a paper on the Mouse. "We effectively are seeing a supersonic cosmic wind tunnel, in which we can study the effects of a pulsar's motion on its pulsar wind nebula, and test current theories."

Pulsars are known to be rapidly spinning, highly magnetized neutron stars - objects so dense that a mass equal to that of the Sun is packed into a diameter of about 12 miles. Their formation is associated with a Type II supernova, the collapse and subsequent explosion of a massive star. The origin of a pulsar's high velocity is not known, but many astrophysicists suspect that it is directly related to the explosive circumstances involved in the birth of the pulsar.

The rapid rotation and strong magnetic field of a pulsar can generate a wind of high-energy matter and antimatter particles that rush out at near the speed of light. These pulsar winds create large, magnetized bubbles of high-energy particles called pulsar wind nebulae. The x-ray and radio data on the Mouse have enabled Gaensler and his colleagues to constrain the properties of the ambient gas, to estimate the velocity of the pulsar, and to analyze the structure of the various shock waves created by the pulsar, the flow of particles away from the pulsar, and the magnetic field in the nebula.

Adapted from the information on http://chandra.harvard.edu/press/04_releases/press_092304.html.

(Added 09/26/04) The Hubble Heritage Team has released September's image of the planetary nebula NGC 6543, also known as the Cat's Eye Nebula. 3,000 light-years from us, the nebula lies in the constellation Draco; this image covers approximately 1.2 arcminutes across (1.2 light-years). The image is combined from data taken on May 4, 2002, for a total exposure time of 1.2 hours.

This image is a composite of three filters ([O III] (F502N), [O III] (F505N), and H-α+[N II] (F658N)), and it offers a view of what our sun might look like in 6 billion years.

Though the Cat's Eye Nebula was the first planetary nebula to be discovered, it is one of the most complex such nebulae seen in space. A planetary nebula forms when sun-like stars gently eject their outer gaseous layers that form bright nebulae with amazing and confounding shapes. In 1994, Hubble first revealed NGC 6543's surprisingly intricate structures, including concentric gas shells, jets of high-speed gas, and unusual shock-induced knots of gas.

As if the Cat's Eye itself isn't spectacular enough, this new image taken with Hubble's Advanced Camera for Surveys (ACS) reveals the full beauty of a bull's eye pattern of eleven or even more concentric rings, or shells, around the Cat's Eye. Each 'ring' is actually the edge of a spherical bubble seen projected onto the sky -- that's why it appears bright along its outer edge.

Observations suggest the star ejected its mass in a series of pulses at 1,500-year intervals. These convulsions created dust shells, each of which contain as much mass as all of the planets in our solar system combined (still only 1% of the sun's mass). These concentric shells make a layered, onion-skin structure around the dying star. The view from Hubble is like seeing an onion cut in half, where each skin layer is discernible.

Until recently, it was thought that such shells around planetary nebulae were a rare phenomenon. However, Romano Corradi (Isaac Newton Group of Telescopes, Spain) and collaborators, in a paper published in the European journal Astronomy and Astrophysics in April 2004, have instead shown that the formation of these rings is likely to be the rule rather than the exception.

The bull's-eye patterns seen around planetary nebulae come as a surprise to astronomers because they had no expectation of episodes of mass loss at the end of stellar lives that repeat every 1,500 years. Several explanations have been proposed, including cycles of magnetic activity somewhat similar to our own s0un's sunspot cycle, the action of companion stars orbiting around the dying star, and stellar pulsations. Another school of thought is that the material is ejected smoothly from the star, and the rings are created later on due to formation of waves in the outflowing material. It will take further observations and more theoretical studies to decide between these and other possible explanations.

Approximately 1,000 years ago, the pattern of mass loss suddenly changed, and the Cat's Eye Nebula started forming inside the dusty shells. It has been expanding ever since, as discernible in comparing Hubble images taken in 1994, 1997, 2000, and 2002. The puzzle is what caused this dramatic change? Many aspects of the process that leads a star to lose its gaseous envelope are still poorly known, and the study of planetary nebulae is one of the few ways to recover information about these last few thousand years in the life of a sun-like star.

Adapted from the information on http://heritage.stsci.edu/2004/27/.

(Added 08/24/04) Ten years and one month ago, between July 16-22, 1994, more than 20 fragments of the comet P/Shoemaker-Levy 9 collided with the planet Jupiter, all at about the same latitude, 45° S. Fragments were up to 1.2 miles (2 km) in diameter, and they sent plumes of hot gas into the atmosphere. Dark scars on Jupiter lasted for weeks.

Over a decade later, Jupiter's atmosphere still contains remnants of the comet impact, but scientists said last week that they are puzzled by how two substances have spread into different locations. In addition, the new study discovered two previously undetected chemicals in Jupiter's volumous gas layers.

The Cassini spacecraft, now orbiting Saturn, studied Jupiter as it flew by in 2000 and 2001. Shocks created by the impacts led to high-temperature chemical reactions that produced hydrogen cyanide, which remains in the air but has spread around in the last ten years. The comet also delivered carbon monoxide and water. Scientists believe that interaction with sunlight converted the carbon monoxide into carbon dioxide.

The hydrogen cyanide has diffused both north and sough, mixed by wave activity. Jupiter's many cloud bands carry material around the planet swiftly, but the bands do not mix easily. Not surprisingly then, the hydrogen cyanide is most abundant in a belt at the latitude where the comet was absorbed. 5° both north and south, its presence drops off sharply.

Surprisingly, the highest concentration of carbon monoxide has shifted away from the latitude of the impact. It is most prevalent poleward of 60° S and decreases abruptly, toward the equator, north of 50° S. Another smaller spike in its presence occurs at high northern latitudes, around 70-90° N.

"At high latitudes, precipitation of energetic oxygen ions probably occurs, associated with Jupiter's magnetically induced lights, known as aurora. These energetic ions could react with Jupiter's atmosphere to produce hydroxyl, which can oxidize carbon monoxide to produce carbon dioxide. We're scratching our heads, and we need to work through these, and perhaps other, scenarios," explained Flasar, who is principal investigator for Cassini's Composite Infrared Spectrometer.

The study, led by Virgil G. Kunde of the University of Maryland, was published Thursday in the online version of the journal Science.

The work also uncovered two new compounds, diacetylene and a so-called methyl radical, which are products of the breakup of methane by ultraviolet radiation from the sun. These were expected but had not been observed at Jupiter before.

So far as astronomers know, the more than 100 giant planets found outside our solar system might be something like Jupiter. Only one has had its atmosphere probed. Better knowledge of the substances in Jupiter, and how things move around, should help set the stage for grasping the formation and evolution of gaseous extrasolar planets, the researchers say.

"An understanding of the processes governing the composition and distribution of chemical species in Jupiter’s atmosphere is required to successfully understand the chemical composition of extrasolar planets," they write in the journal.

Adapted from the information on http://www.space.com/scienceastronomy/mystery_monday_040823.html.

(Added 08/23/04) This Hubble Space Telescope (HST) image shows an H II region in the Large Magellanic Cloud (LMC), named N44F. 160,000 light-years from us, the region of gas lies in the constellation Dorado; this image covers approximately 2 arcminutes across (98 light-years). The image is combined from data taken on March 25, 2000, for a total exposure time of 37 minutes. This image is a composite of two filters (H-α (F656N) and [S II] (F673N)).

In this unusual image, NASA's Hubble Space Telescope captures a rare view of the celestial equivalent of a geode -- a gas cavity carved by the stellar wind and intense ultraviolet radiation from a hot young star.

Real geodes are baseball-sized, hollow rocks that start out as bubbles in volcanic or sedimentary rock. Only when these inconspicuous round rocks are split in half do we get a chance to appreciate the inside of the rock cavity that is lined with crystals. In the case of Hubble's 35 light-year diameter "celestial geode," the transparency of its bubble-like cavity of interstellar gas and dust reveals the treasures of its interior.

The object, called N44F, is being inflated by a torrent of fast-moving particles (called a "stellar wind") from an exceptionally hot star once buried inside a cold dense cloud. Compared with our sun (which is losing mass through its solar wind), the central star in N44F is ejecting more than a 100 million times more mass per second. Also, the particles move much faster at about 4 million mph (7 million kph), as opposed to about 0.9 million mph (1.5 million kph) for our sun. Because the bright central star does not exist in empty space but is surrounded by an envelope of gas, the stellar wind collides with this gas, pushing it out, like a snowplow. This forms a bubble, whose striking structure is clearly visible in the crisp Hubble image.

The nebula N44F is one of a handful of known interstellar bubbles. Bubbles like these have been seen around evolved massive stars (Wolf-Rayet stars), and also around clusters of stars (where they are called "super-bubbles"). But they have rarely been viewed around isolated stars, as is the case here.

On closer inspection, N44F harbors additional surprises. The interior wall of its gaseous cavity is lined with several four- to eight-light-year-high finger-like columns of cool dust and gas. (The structure of these "columns" is similar to the Eagle Nebula's iconic "pillars of creation" photographed by Hubble a decade ago, and they are seen in a few other nebulae as well). The fingers are created by a blistering ultraviolet radiation from the central star. Like windsocks caught in a gale, they point in the direction of the energy flow. These pillars look small in this image only because they are much farther away from us than the Eagle Nebula's pillars.

N44F is part of the larger N44 complex, which is a large super-bubble, blown out by the combined action of stellar winds and multiple supernova explosions. N44 itself is roughly 1,000 light-years across. Several compact star-forming regions, including N44F, are found along the rim of the central super-bubble.

Adapted from the information on http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/26/.

(Added 08/23/04) A spectacular new image of Cassiopeia A from NASA's Chandra X-ray Observatory released today has nearly 200 times more data than the "First Light" Chandra image of this object made five years ago. The new image reveals clues that the initial explosion caused by the collapse of a massive star was far more complicated than suspected.

"Although this young supernova remnant has been intensely studied for years, this deep observation is the most detailed ever made of the remains of an exploded star," described Martin Laming of the Naval Research Laboratory in Washington, D.C. Laming is part of a team of scientists led by Una Hwang of the Goddard Space Flight Center in Greenbelt, MD. "It is a gold mine of data that astronomers will be panning through for years to come."

Cassiopea A in 3-Color X-Ray The one-million-second (about 11.5 days) observation of Cassiopeia A uncovered two large, opposed jet-like structures that extend to about 10 light years from the center of the remnant. Clouds of iron that have remained nearly pure for the approximately 340 years since the explosion were also detected. In the three-color image on the right, the jets are in the 4:00 and 10:00 positions.

"The presence of the bipolar jets suggests that jets could be more common in relatively normal supernova explosions than supposed by astronomers," explained Hwang.

X-ray spectra show that the jets are rich in silicon atoms and relatively poor in iron atoms. In contrast, fingers of almost pure iron gas extend in a direction nearly perpendicular to the jets. This iron was produced in the central, hottest regions of the star. The high silicon and low iron abundances in the jets indicate that massive, matter-dominated jets were not the immediate cause of the explosion, as these should have carried out large quantities of iron from the central regions of the star.

A working hypothesis is that the explosion produced high-speed jets similar to those in hypernovae that produce gamma-ray bursts, but in this case, with much lower energies. The explosion also left a faint neutron star at the center of the remnant. Unlike the rapidly rotating neutron stars in the Crab Nebula and Vela supernova remnants that are surrounded by dynamic magnetized clouds of electrons, this neutron star is quiet and faint, and pulsed radiation has not been detected from it. It may have a very strong magnetic field generated during the explosion that helped to accelerate the jets, and today resembles other strong-field neutron stars (AKA "magnetars") in lacking a nebula produced by strong winds.

Adapted from the information on http://chandra.harvard.edu/press/04_releases/press_082304.html; the research appeared in an upcoming issue of the Astrophysical Journal.

(Added 08/21/04) Scientists have discovered irregular lumps beneath the icy surface of Jupiter's largest moon, Ganymede. These irregular masses may be rock formations, supported by Ganymede's icy shell for billions of years. This discovery comes nearly a year after the orchestrated demise of NASA's Galileo spacecraft into Jupiter's atmosphere and more than seven years after the data were collected.

The findings have caused scientists to rethink what the interior of Ganymede might contain. The reported bulges reside in the interior, and there are no visible surface features associated with them. This tells scientists that the ice is probably strong enough, at least near the surface, to support these possible rock masses from sinking to the bottom of the ice for billions of years. But this anomaly could also be caused by piles of rock at the bottom of the ice.

"The anomalies could be large concentrations of rock at or underneath the ice surface. They could also be in a layer of mixed ice and rock below the surface with variations in the amount of rock," proposed Dr. John Anderson, a scientist and the paper's lead author at JPL. "If there is a liquid water ocean inside Ganymede's outer ice layer there might be variations in its depth with piles of rock at the ocean bottom. There could be topographic variations in a hidden rocky surface underlying a deep outer icy shell. There are many possibilities, and we need to do more studies."

Ganymede's Mass Anomalies from Galileo Measurements Dr. Gerald Schubert, co-author at UCLA, explained "Although we don't yet have anything definitive about the depth at this point, we did not expect Ganymede's ice shell to be strong enough to support these lumpy mass concentrations. Thus, we expect that the irregularities would be close to the surface where the ice is coldest and strongest, or at the bottom of the thick ice shell resting on the underlying rock. It would really be a surprise if these masses were deep and in the middle of the ice shell."

Ganymede has three main layers: A sphere of metallic iron at the center (the core), a spherical shell of rock (mantle) surrounding the core, and a spherical shell of mostly ice surrounding the rock shell and the core. The ice shell on the outside is very thick, maybe 800 km (497 miles) thick. The surface is the very top of the ice shell. Though it is mostly ice, the ice shell might contain some rock mixed in. Scientists believe there must be a fair amount of rock in the ice near the surface. Variations in this amount of rock may be the source of these possible rock formations.

Scientists stumbled on the results by studying Doppler measurements of Ganymede's gravity field during Galileo's second flyby of the moon in 1996. Scientists were measuring the effect of the moon's gravity on the spacecraft as it flew by. They found unexpected variations.

"Believe it or not, it took us this long to straighten out the anomaly question, mostly because we were analyzing all 31 close flybys for all four of Jupiter's large moons," said Anderson. "In the end, we concluded that there is only one flyby, the second flyby of Ganymede, where mass anomalies are evident."

Scientists have seen mass concentration anomalies on one other moon before, Earth's, during the first lunar orbiter missions in the 1960s. The lunar mass concentrations during the Apollo moon mission era were due to lava in flat basins. However, scientists cannot draw any similarities between these mass concentrations and what they see at Ganymede.

"The fact that these mass anomalies can be detected with just flybys is significant for future missions," said Dr. Torrence Johnson, former Galileo project scientist. "With this type of information you could make detailed gravity and altitude maps that allow us to actually map structures within the ice crust or on the rocky surface. Knowing more about the interior of Ganymede raises the level of importance of looking for gravity anomalies around Jupiter's moons and gives us something to look for. This might be something NASA's proposed Jupiter Icy Moons Orbiter Mission could probe into deeper."

The paper was co-authored by Dr. Robert A. Jacobson and Eunice L. Lau of JPL, with Dr. William B. Moore and Jennifer L. Palguta of UCLA.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-200; the research appeared in the August 13 issue of the journal Science.

(Added 08/21/04) The Cassini spacecraft has uncovered two new moons, and they may be the smallest bodies so far seen around the ringed planet.

The moons are approximately 3 km (2 miles) and 4 km (2.5 miles) across -- smaller than the city of Boulder, CO. The moons, located 194,000 km (120,000 miles) and 211,000 km (131,000 miles) from the planet's center, are between the orbits of two other saturnian moons, Mimas and Enceladus. They are provisionally named S/2004 S1 and S/2004 S2. One of them, S/2004 S1, may be an object spotted in a single image taken by NASA's Voyager spacecraft 23 years ago, called at that time S/1981 S14.

"One of our major objectives in returning to Saturn was to survey the entire system for new bodies," remarked Dr. Carolyn Porco, imaging team leader, Space Science Institute, Boulder, CO. Porco planned the imaging sequences. "So, it's really gratifying to know that among all the other fantastic discoveries we will make over the next four years, we can now add the confirmation of two new moons, skipping unnoticed around Saturn for billions of years until just now."

The moons were first seen by Dr. Sebastien Charnoz, a planetary dynamicist working with Dr. Andre Brahic, imaging team member at the University of Paris. "Discovering these faint satellites was an exciting experience, especially the feeling of being the first person to see a new body of our solar system," said Charnoz. "I had looked for such objects for weeks while at my office in Paris, but it was only once on holiday, using my laptop, that my code eventually detected them. This tells me I should take more holidays."

The smallest previously known moons around Saturn are about 20 km (12 miles) across. Scientists expected that moons as small as S/2004 S1 and S/2004 S2 might be found within gaps in the rings and perhaps near the F ring, so they were surprised these small bodies are between two major moons. Small comets careening around the outer solar system would be expected to collide with small moons and break them to bits. The fact that these moons exist where they do might provide limits on the number of small comets in the outer solar system, a quantity essential for understanding the Kuiper Belt of comets beyond Neptune, and the cratering histories of the moons of the giant planets.

"A comet striking an inner moon of Saturn moves many times faster than a speeding bullet," remarked Dr. Luke Dones, an imaging team member from the Southwest Research Institute in Boulder, CO. "If small, house-sized comets are common, these moons should have been blown apart many times by cometary impacts during the history of the solar system. The disrupted moon would form a ring, and then most of the material would eventually gather back together into a moon. However, if small comets are rare, as they seem to be in the Jupiter system, the new moons might have survived since the early days of the solar system."

Moons surrounding the giant planets generally are not found where they originally formed because tidal forces from the planet can cause them to drift from their original locations. In drifting, they may sweep through locations where other moons disturb them, making their orbits eccentric or inclined relative to the planet's equator. One of the new moons might have undergone such an evolution.

Upcoming imaging sequences will scour the gaps in Saturn's rings in search of moons believed to be there. Meanwhile, Cassini scientists are eager to get a closer look, if at all possible, at their new finds. Porco said, "We are at this very moment looking to see what the best times are for re-targeting. Hopefully, we haven't seen the last of them."

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-202.

(Added 08/21/04) Now that NASA's Mars Exploration Rover Spirit is finally examining bedrock in the "Columbia Hills," it is finding evidence that water thoroughly altered some rocks in Mars' Gusev Crater. Spirit and its twin, Opportunity, completed successful three-month primary missions on Mars in April and are returning bonus results during extended missions. They remain in good health though are beginning to show signs of wear.

On Opportunity, a tool for exposing the insides of rocks stopped working Sunday, but engineers are optimistic that the most likely diagnosis is a problem that can be fixed soon. "It looks like there's a pebble trapped between the cutting heads of the rock abrasion tool," explained Chris Salvo, rover mission manager at NASA's Jet Propulsion Laboratory, Pasadena, CA. "We think we can treat it by turning the heads in reverse, but we are still evaluating the best approach to remedy the situation. There are several options available to us."

Mars Exploration Rover (MER) Spirit - Longhorn rock outcrop with Gusev Crater in Background Opportunity originally landed right beside exposed bedrock and promptly found evidence there for an ancient body of saltwater. On the other hand, it took Spirit half a year of driving across a martian plain to reach bedrock in Gusev Crater. Now, Spirit's initial inspection of an outcrop called "Clovis" on a hill about 9 m (30 ft) above the plain suggests that water may once have been active at Gusev.

"We have evidence that interaction with liquid water changed the composition of this rock," remarked Dr. Steve Squyres of Cornell University, Ithaca, NY, principal investigator for the science instruments on both rovers. "This is different from the rocks out on the plain, where we saw coatings and veins apparently due to effects of a small amount of water. Here, we have a more thorough, deeper alteration, suggesting much more water. To really understand the conditions that altered Clovis, we'd like to know what it was like before the alteration. We have the 'after.' Now we want the 'before.' If we're lucky, there may be rocks nearby that will give us that."

Mars Exploration Rover (MER) Opportunity - Two Types of Pebblesin Endurance Crater Dr. Doug Ming, a rover science team member from NASA's Johnson Space Center, Houston, said indications of water affecting Clovis come from analyzing the rock's surface and interior with Spirit's alpha particle X-ray spectrometer and finding relatively high levels of bromine, sulfur and chlorine inside the rock. He said, "This is also a very soft rock, not like the basaltic rocks seen back on the plains of Gusev Crater. It appears to be highly altered."

Opportunity has completed a transect through layers of rock exposed in the southern inner slope of stadium-sized "Endurance Crater." The rocks examined range from outcrops near the rim down through progressively older and older layers to the lowest accessible outcrop, called "Axel Heiberg" after a Canadian Arctic island. "We found different compositions in different layers," said Dr. Ralf Gellert, of Max-Planck-Institut fur Chemie, Mainz, Germany. Chlorine concentration increased up to threefold in middle layers. Magnesium and sulfur declined nearly in parallel with each other in older layers, suggesting those two elements may have been dissolved and removed by water.

Small, gray stone spheres nicknamed "blueberries" are plentiful in Endurance - just as they were at Opportunity's smaller landing-site crater, "Eagle." Pictures from the rover's microscopic imager show a new variation on the blueberries throughout a reddish-tan slab called "Bylot" in the Axel Heiberg outcrop. "They're rougher textured, they vary more in size, and they're the color of the rock, instead of gray," said Zoe Learner, a science team collaborator from Cornell. "We've noticed that in some cases where these are eroding, you can see a regular blueberry or a berry fragment inside." One possibility is that a water-related process has added a coarser outer layer to the blueberries, she said, adding, "It's still really a mystery."

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-204.

(Added 08/21/04) The Milky Way Galaxy currently holds well over 100 globular clusters, but it once possessed many more. According to the hierarchical theory of galaxy formation, galaxies have grown larger over time by consuming smaller dwarf galaxies and star clusters. Sometimes, it seems that the unfortunate prey is not swallowed whole but instead is munched like a peach, stripped of its outer layers to leave behind only the pit.

New research by Paul Martini (Harvard-Smithsonian Center for Astrophysics) and Luis Ho (Observatories of the Carnegie Institution of Washington) shows that some globular clusters may be remnants of dwarf galaxies that were stripped of their outer stars, leaving only the galaxy's nucleus behind.

Their findings hint at an important yet puzzling connection between the largest globular clusters and the smallest dwarf galaxies. "Star clusters and galaxies are quite different from a structural standpoint - star clusters are much more centrally concentrated, for example - and so the mechanisms that form them must be quite different. Identification of star clusters in the same mass range as galaxies is a very important step toward understanding how both types of objects form," explained Martini.

For their investigation, the team studied 14 globular clusters in the large elliptical galaxy Centaurus A (NGC 5128) using the 6.5-m diameter Magellan Clay telescope at Carnegie's Las Campanas Observatory, Chile. The clusters were selected for their brightness, and since brighter clusters tend to contain more stars and more mass, they were expected to be massive. Yet their results were surprising, showing that the globular clusters of Centaurus A are much more massive than most globulars in the Local Group of galaxies (which includes the Milky Way and Andromeda Galaxies).

"The essence of our findings is that these 14 globulars are 10 times more massive than the smaller globulars in our neighborhood, and whatever process makes them can produce some really huge objects - they begin to overlap with the smallest galaxies," says Martini.

Martini also pointed out the recent discovery of a suspected intermediate-mass black hole in the Andromeda Galaxy globular cluster known as G1, which offers further evidence linking globular clusters to dwarf galaxies. The presence of a moderate-sized black hole is more understandable if it once occupied the center of a dwarf galaxy - a galaxy that lost its outer stars to the pull of Andromeda, leaving it only a shadow of its former self.

Ho, a co-discoverer of the intermediate-mass black hole in G1, adds, "One of the most surprising findings is that the black hole in G1 obeys the same tight correlation between black hole mass and host galaxy mass that has been well established for supermassive black holes in the centers of big galaxies. This puzzling result is more understandable if G1 was once the nucleus of a larger galaxy. A very interesting question is whether some of the massive clusters in Centaurus A also contain central black holes."

Although most of our Galaxy's globular clusters are much smaller than those of Centaurus A, the largest Milky Way globulars (such as the omega Centauri star cluster) rival those of the elliptical galaxy. The similarities between massive globulars in both galaxies may point to similar formation mechanisms. Future studies of these most massive globular clusters will explore connections between the formation processes for star clusters and galaxies.

Centaurus A is located approximately 12.5 million light-years away. It is about 65,000 light-years across and is more massive than the Milky Way and Andromeda galaxies put together. Centaurus A possesses a total of about 2000 globular clusters - more than all of the galaxies in the Local Group combined. Recent Spitzer Space Telescope observations of Centaurus A uncovered evidence that it merged with a spiral galaxy about 200 million years ago.

Adapted from the information on http://cfa-www.harvard.edu/press/pr0426.html; the research appeared in the July 20 issue of the Astrophysical Journal.

(Added 08/21/04) The Hubble Heritage Team has released August's image of the spiral galaxy NGC 3949. 50 million light-years from us, the galaxy lies in the constellation Ursa Major; this image covers approximately 2 arcminutes across (30,000 light-years). The image is combined from data taken on October 1, 2001, for a total exposure time of 16 minutes.

This image is a composite of three filters (B (F450W), V (F606W), and I (F814)), and it offers a view of what our galaxy might look like if we were to somehow get an image from millions of light-years outside of it.

Because we are embedded within our galaxy, it is very difficult to study many of its features. The next-best thing is to look at other galaxies that we believe resemble ours, such as NGC 3949. The galaxy has a blue disk of young stars peppered with bright pink star birth regions. In contrast to the young, blue disk, the bright central bulge is comprised of mostly older, redder stars.

NGC 3949 is a member of a loose cluster of over 70 galaxies located in the direction of the Big Dipper. It is one of the larger galaxies in that cluster.

Adapted from the information on http://heritage.stsci.edu/2004/25/.

(Added 07/31/04) The largest moon of Saturn, Titan, has the thickest atmosphere of any moon in the solar system. Cassini's cameras are starting to reveal some of the intricate structure of this alien atmosphere.

The image on the left shows Titan's atmosphere on July 3, 2004, one day after Cassini's first flyby of the moon. The image was taken in an ultraviolet filter, and it has been falsely colored to show the planet at is appears in visible light. The UV filter shows a high stratospheric haze along with a detached layer.

The lower layer is stratospheric haze. The atmosphere undergoes photochemical processes to form the hazes. Images like this reveal some of the key steps to the formation and evolution of Titan's haze. The process is thought to begin in the high atmosphere, at altitudes above 400 km (250 miles), where UV light breaks down methane and nitrogen molecules. The products are believed to react to form more complex organic molecules containing carbon, hydrogen, and nitrogen that can then combine to form the very small particles seen as haze.

The two distinct layers of atmospheric haze have been brightened and falsely colored violet to enhance their visibility. It is not currently understood why there are two separate haze layers. The bottom of the detached layer is a few hundred kilometers above the surface of the planet, and it is approximately 120 km (75 miles) thick.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-187.

(Added 07/31/04) With 31 known moons, Saturn has the second-most known for a single planet in the solar system. One of them is Iapetus, and since its discovery in 1672, it has been known to have a split personality with one side very bright and the other very dark. New Cassini images reveal more information on this unique moon.

Iapetus was discovered by the Italian-French astronomer Jean Dominique Cassini in 1672. He correctly deduced that the trailing hemisphere is composed of highly reflective material while the leading hemisphere is much darker. Modern measurements show that the trailing hemisphere reflects about 50% of the light that hits it, while the leading is much darker and redder, and it only reflects about 3-4% of the light that hits it.

The moon is about 1,436 km (892 miles) wide. The Cassini image (right) was taken in visible light with the narrow angle camera on July 3, 2004, from a distance of about 3 million km (1.8 million miles) from Iapetus. The brightness variations shown are not due to shadowing nor image processing - they are real. Cassini will continue to image Iapetus and conduct two close encounters, one of them from a distance of only 1,000 km (622 miles).

The patterning of the light and dark is reversed from the other Saturnian and Jovian moons, which tend to be brighter on their leading rather than trailing hemispheres. Voyager images revealed this feature, which was very surprising at the time.

One scenario for the outside deposition of material has the dark particles being ejected from Saturn's moon Phoebe and drifting inwards to coat Iapetus. One observation lending support for an internal origin, however, is the concentration of material on crater floors, which is suggestive of something filling in the craters.

Besides its coloring, Iapetus is odd in other respects. It is in a moderately inclined orbit, taking it far above and bellow the plane in which the rings and most of the moons orbit. It is much less dense than many of the other satellites, which suggests a higher fraction of ice or possibly methane or ammonia in its interior.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-182.

(Added 07/31/04) Until now, astronomers had only directly measured the mass of one star - the sun. Now, a small, red star, located about 1,800 light-years away, has been directly weighed, adding an important calibration to understanding stellar evolution.

Previously, astronomers could only determine the masses of stars that are members of binary systems by using Newton's laws of gravity and Kepler's Laws. The new measurement takes its technique from Einstein's theory of relativity, combined with a large-scale program using ground-based telescopes, and the exquisite resolution of NASA's Hubble Space Telescope.

The star first came into the limelight when it passed directly in front of a much more distant star in 1993, producing a phenomenon called gravitational microlensing. Microlensing - predicted by Einstein's theory of general relativity, occurs because of the warping of space around a massive object like a star. The warped space acts like a lens, focusing and magnifying the light of the background star, causing it to brighten suddenly, as seen by us. There have been several surveys over the past few years to search for these microlensing events.

In most cases, the transiting star is much fainter than the background star. But the light from one of the events discovered in 1993, dubbed MACHO-LMC-5, didn't just brighten. Changes in its color suggested that the background star and the lensing star were of similar brightness. This raised the possibility that the two stars could be observed separately, if astronomers waited a few years to give the foreground star time to move away from its perfect alignment with the background star.

Ground-based telescopes, however, could not resolve the stars as two separate objects. So, astronomers turned to Hubble's Wide Field Planetary Camera 2 in 1999, and later, in 2002 and 2003, to Hubble's Advanced Camera for Surveys. These observations succeeded in showing the two stars separately.

Seeing the two stars allowed astronomers to calculate the foreground star's distance from Earth, using a method called parallax. Due to the motion of the Earth around the Sun, the position of a nearby star will appear to shift relative to stars farther away. By measuring this shift, astronomers can triangulate the distance to the star. Surveyors use a similar method to measure distances on Earth. The distance derived in this way also agrees with the distance inferred from details of the brightness variations in 1993, based on subtle changes resulting from the motion of the Earth during the lensing event.

Once the distance to the lensing star was known, and since the distance to the Large Magellanic Cloud, where the background star is located, is also known, astronomers could calculate the only remaining unknown in the equation for microlensing, which is the mass of the foreground star. Its mass turns out to be one-tenth the mass of our own sun. Although a low mass of about this amount was expected based on the faintness of the red star, astronomers are nevertheless excited by this first application of a new method for measuring stellar masses. They hope to apply it many times in the future, by using the planned Space Interferometry Mission satellite to observe many more microlensing events.

Adapted from the information on http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/24/text/.

(Added 07/31/04) On May 12, 2002, a group of astronomers were observing a supernova in a distant galaxy with a spectrograph on the European Southern Observatory's Very Large Telescope. Across the field fell a meteor, and the spectrograph captured a very high-resolution spectrum of it as it fell through Earth's atmosphere, making it a reference for this field of research.

From the spectrum, the temperature of the meteor trail was estimated to be about 4600 °C. The serendipitous spectrum reveals the tell-tale meteor emissions of oxygen and nitrogen atoms and nitrogen molecules. The VLT spectrum was the first to reveal the far red range where carbon emission lines are predicted; the absence of the lines puts constraints on the role of atmospheric chemistry when life started on earth.

Because the VLT is tuned to observe objects far out in space, it focuses at infinity. The meteor, being only 100 km above the telescope, therefore appears out of focus in the field of view. This is the first spectrum to be obtained by a large telescope with a modern spectrograph.

Adapted from the information on http://www.eso.org/outreach/press-rel/pr-2004/pr-19-04.html.

(Added 07/31/04) McNeil's Nebula, a small nebula approximately 1300 light-years away in the Orion Nebula, was discovered by McNeil, an amateur astronomer from Paducah, KY, in January 2004 with a 3-inch (7.5-cm) telescope. The area had recently been surveyed in both optical and infrared light in late 2003, and also in November 2002 in x-rays. The timing of the nebula's luminescence and the recent surveys of the area have allowed unprecedented science to be conducted.

Recent observations with NASA's Chandra X-ray Observatory have captured an x-ray outburst from a young star, and they reveal a probable scenario for the intermittent brightening of the nebula. It appears that the interaction between the young star's magnetic field and an orbiting disk of gas can cause dramatic, episodic increases in the light from the star and disk, illuminating the surrounding gas.

Chandra's observations, just after the optical burst that allowed the nebula's discovery, show that the source has brightened by a factor of 50 compared with the observations in November 2002. The visible-light eruption provides evidence that the cause of the x-ray outburst is the sudden in fall of matter onto the star's surface from an orbiting disk of gas.

In general, the coupling of the magnetic field of a star and the magnetic field of its circumstellar disk regulates the inflow of gas from the disk onto the star. This slow, steady inflow suddenly can become much more rapid if a large amount of gas accumulates in the disk, and the disk and the star are rotating at different rates. The differing rotation rates would twist and shear the magnetic field, storing up energy. This energy is eventually released in an energetic, x-ray producing outburst as the magnetic field violently rearranges back to a more stable state. During this period, a large amount of gas can fall onto the star, producing the observed optical and infrared outburst.

A new buildup of gas in the disk could lead to a new outburst in the future. Such a scenario may explain why the brightness of McNeil's Nebula appears to vary with time. It is faintly present in surveys of this region of Orion in images taken in the 1960s, but absent from images taken in the 1950s and 1990s.

Adapted from the information on http://chandra.harvard.edu/press/04_releases/press_072204.html; the research appeared in the July 22 issue of the journal Nature.

(Added 07/10/04) Due to the length of this article, it has been divided into three sections: Cassini Makes Orbit, Saturn's Rings as Never Before, and Saturn's Moon - Titan.

Cassini Makes Orbit Saturn from Cassini

The international Cassini-Huygens mission has successfully entered orbit around Saturn. At 9:12 p.m. PDT on Wednesday, June 30, flight controllers received confirmation that Cassini had completed the engine burn needed to place the spacecraft into the correct orbit. This begins a four-year study of the giant planet, its majestic rings and 31 known moons.

"This is a tribute to the team at NASA and our partners at the European Space Agency and the Italian Space Agency, to accomplish this feat taking place 934 million miles [1.5 billion km] away from Earth," proclaimed Dr. Ed Weiler, associate administrator for space science at NASA Headquarters, Washington, D.C. "What Cassini-Huygens will reveal during its tour of Saturn and its many moons, including Titan, will astonish scientists and the public. Everyone is invited to come along for the ride and see all this as it is happening. It truly is a voyage of discovery."

Members of the Cassini-Huygens mission at NASA's Jet Propulsion Laboratory, Pasadena, CA, broke into cheers and high-fives as NASA's Deep Space Network confirmed receipt of the signal indicating successful entry into orbit. "We didn't expect anything less and couldn't have asked for anything more from the spacecraft and the team," remarked Robert T. Mitchell, program manager for the Cassini-Huygens mission at JPL. "This speaks volumes to the tremendous team that made it all happen."

Dr. Charles Elachi, JPL director and team leader on the radar instrument onboard Cassini, said, "It feels awfully good to be in orbit around the lord of the rings. This is the result of 22 years of effort, of commitment, of ingenuity, and that's what exploration is all about."

The mission will face another dramatic challenge in December, when the spacecraft will release the piggybacked Huygens probe – provided by the European Space Agency – which will plunge through the hazy atmosphere of Saturn's largest moon, Titan. "This was America's night. This was NASA doing it right," said Dr. David Southwood, director of scientific programs for the European Space Agency. "They really gave those of us in Europe a challenge. We've got six months to go until we land on Titan. We're just praying that everything will go as well."

Julie Webster, Cassini-Huygens spacecraft team chief, said, "The spacecraft has been an incredible joy to fly. We stand on the shoulders of people who had 40 years of experience building and designing spacecraft."

Cassini traveled nearly 3.5 billion kilometers (2.2 billion miles) to reach Saturn after its launch from Cape Canaveral Air Force Station, FL, on October 15, 1997. During Cassini's four-year mission, it will execute 52 close encounters with seven of Saturn's 31 known moons.

Besides the camera that has sent back many remarkable images (several shown below), other instruments have also been busy collecting data. The magnetospheric imaging instrument took the first image of Saturn's magnetosphere. "With Voyager we inferred what it looked like, in the same way that a blind man feels an elephant. Now we can see the elephant," said Dr. Tom Krimigis of Johns Hopkins Applied Physics Laboratory, Laurel, MD, principal investigator for the magnetospheric imaging instrument. The magnetosphere is a bubble of energetic particles around the planet shaped by Saturn's magnetic field and surrounded by the solar wind of particles speeding outward from the Sun.

"During approach to Saturn, Cassini was greeted at the gate," said Dr. Bill Kurth, deputy principal investigator for the radio and plasma wave science instrument onboard Cassini. "The bow shock where the solar wind piles into the planet's magnetosphere was encountered earlier than expected. It was as if Saturn's county line had been redrawn, and that was a surprise." Cassini first crossed the bow shock about 3 million kilometers (1.9 million miles) from Saturn, which is about 50 percent farther from the planet than had been detected by the Pioneer, Voyager 1 and Voyager 2 spacecraft that flew past Saturn in 1979, 1980 and 1981.

The location of the bow shock varies with how hard the solar wind is blowing, Kurth explained. As the magnetosphere repeatedly expanded and contracted while Cassini was approaching Saturn, the spacecraft crossed the bow shock seven times.

Cassini's examination of Saturn's atmosphere began while the spacecraft was still approaching the planet. Winds on Saturn near the equator decrease dramatically with altitude above the cloud tops. The winds fall off by as much 140 meters per sec (300 mph) over an altitude range of 300 kilometers (200 miles) in the upper stratosphere. This is the first time winds have been measured at altitudes so high in Saturn's atmosphere.

"We are finally defining the wind field in three dimensions, and it is very complex," said Dr. Michael Flasar of NASA Goddard Space Flight Center, Greenbelt, MD, principal investigator for Cassini's composite infrared spectrometer. "Temperature maps obtained now that Cassini is orbiting Saturn are expected to show more detail, helping us to unravel the riddles of Saturn's winds above the cloud tops."

Saturn's Rings as Never Before

Saturn's Rings in UV The first pictures taken by the Cassini spacecraft after it began orbiting Saturn show breathtaking detail of Saturn's rings, and other science measurements reveal that Saturn's magnetic field pulsed in size as Cassini approached the planet.

"For years, we've dreamed about getting pictures like this. After all the planning, waiting and worrying, just seeing these first images makes it all worthwhile," said Dr. Charles Elachi, Cassini radar team leader and director of NASA's Jet Propulsion Laboratory, Pasadena, CA. "We're eager to share these new views and the exciting discoveries ahead with people around the world."

The narrow angle camera on Cassini took 61 images soon after the main engine burn that put Cassini into orbit on Wednesday night. The spacecraft was hurtling at 15 km/s (about 34,000 mph), so only pieces of the rings were targeted. "We won't see the whole puzzle, only pieces, but what we are seeing is dramatic," said Dr. Carolyn Porco, Cassini imaging team leader, Space Science Institute, Boulder, CO. "The images are mind-boggling, just mind-boggling. I've been working on this mission for 14 years and I shouldn't be surprised, but it is remarkable how startling it is to see these images for the first time."

Some images show patterned density waves in the rings, resembling stripes of varying width. Another shows a ring's scalloped edge. "We do not see individual particles but a collection of particles, like a traffic jam on a highway," Porco explained. "We see a bunch of particles together, then it clears up, then there's traffic again."

Saturn's Rings' Composition One early science result intriguing scientists concerns Saturn’s Cassini Division, the large gap between the A and B rings. While Saturn’s rings are almost exclusively composed of water ice, new findings show the Cassini Division contains relatively more "dirt" than ice. Further, the particles between the rings seem remarkably similar to the dark material that scientists saw on Saturn’s moon, Phoebe. These dark particles refuel the theory that the rings might be the remnants of a moon. The F ring was also found to contain more dirt.

Another instrument on Cassini has detected large quantities of oxygen at the edge of the rings. Scientists are still trying to understand these results, but they think the oxygen may be left over from a collision that occurred as recently as January of this year.

"In just two days, our ideas about the rings have been expanded tremendously," remarked Dr. Linda Spilker, of NASA's Jet Propulsion Laboratory, Pasadena, CA, deputy project scientist for the Cassini-Huygens mission. "The Phoebe-like material is a big surprise. What puzzles us is that the A and B rings are so clean and the Cassini Division between them appears so dirty." The visual and infrared mapping spectrometer onboard Cassini revealed the dirt mixed with the ice in the Cassini Division and in other small gaps in the rings, as well as in the F ring.

"The surprising fingerprint in the data is that the dirt appears similar to what we saw at Phoebe. In the next several months we will be looking for the origin of this material," said Dr. Roger Clark, of the U.S. Geological Survey, Denver, CO, and a member of the Cassini science team. Cassini's ultraviolet imaging instrument detected the sudden and surprising increase in the amount of atomic oxygen at the edge of the rings. The finding leads scientists to hypothesize that something may have collided with the main rings, producing the excess oxygen.

Saturn's Rings' Size Dr. Donald Shemansky of the University of Southern California, Los Angeles, co-investigator for Cassini's ultraviolet imaging spectrograph instrument, said, "What is surprising is the evidence of a strong, sudden event during the observation period causing substantial variation in the oxygen distribution and abundance." Although atomic oxygen has not been previously observed, its presence is not a surprise because hydroxyl was discovered earlier from Hubble Space Telescope observations, and these chemicals are both products of water chemistry.

During the ring plane crossing, the radio and plasma wave science instrument on Cassini measured little puffs of plasma produced by dust impacts. While crossing the plane of Saturn's rings, the instrument detected up to 680 dust hits per second. "The particles are comparable in size to particles in cigarette smoke," said Dr. Don Gurnett of the University of Iowa, Iowa City, principal investigator for the instrument. "When we crossed the ring plane, we had roughly 100,000 total dust hits to the spacecraft in less than five minutes. We converted these into audible sounds that resemble hail hitting a tin roof."

Saturn's Moon - Titan

Titan's dense atmosphere is opaque at most wavelengths, but during a flyby, Cassini captured some surface details, including a possible crater, through wavelengths in which the atmosphere is clear. "Although the initial images appear bland and hard to interpret, we're happy to report that, with a combination of instruments, we have indeed seen Titan's surface with unprecedented clarity. We also look forward to future, much closer flybys and use of radar for much greater levels of surface detail," said Dr. Dennis Matson of NASA's Jet Propulsion Laboratory, Pasadena, CA, project scientist for the international Cassini-Huygens mission.

Titan from Cassini Cassini's visible and infrared mapping spectrometer pierced the smog that enshrouds Titan. This instrument, capable of mapping mineral and chemical features of the moon, reveals an exotic surface bearing a variety of materials in the south and a circular feature that may be a crater in the north. Near-infrared colors, some three times redder than the human eye can see, reveal the surface with unusual clarity.

"At some wavelengths, we see dark regions of relatively pure water ice and brighter regions with a much higher amount of non-ice materials, such as simple hydrocarbons. This is different from what we expected. It's preliminary, but it may change the way we interpret light and dark areas on Titan," said JPL's Dr. Kevin Baines, Cassini science-team member. "A methane cloud is visible near the south pole. It's made of unusually large particles compared to the typical haze particles surrounding the moon, suggesting a dynamically active atmosphere there."

This is the first time scientists are able to map the mineralogy of Titan. Using hundreds of wavelengths, many of which have never been used in Titan imaging before, they are creating a global map showing distributions of hydrocarbon-rich regions and areas of icy material.

Cassini's camera also sees through the haze in some wavelengths. "We're seeing a totally alien surface," said Dr. Elizabeth Turtle of the University of Arizona, Tucson. "There are linear features, circular features, curvilinear features. These suggest geologic activity on Titan, but we really don't know how to interpret them yet. We've got some exciting work cut out for us."

Since entering orbit, Cassini has also provided the first view of a vast swarm of hydrogen molecules surrounding Titan well beyond the top of Titan's atmosphere. Cassini's magnetospheric imaging instrument, the first of its kind on any interplanetary mission, provided images of the huge cloud sweeping along with Titan in orbit around Saturn. The cloud is so big that Saturn and its rings would fit within it. "The top of Titan's atmosphere is being bombarded by highly energetic particles in Saturn's radiation belts, and that is knocking away this neutral gas," explained Dr. Stamatios Krimigis of Johns Hopkins Applied Physics Laboratory, Laurel, MD, principal investigator for the magnetospheric imager. "In effect, Titan is gradually losing material from the top of its atmosphere, and that material is being dragged around Saturn."

The study of Titan, Saturn's largest moon, is one of the major goals of the Cassini-Huygens mission. Titan may preserve in deep-freeze many chemical compounds that preceded life on Earth. The July 2 flyby at a closest distance of 339,000 km (210,600 miles) provided Cassini's best look at Titan so far, but over the next four years, the orbiter will execute 45 Titan flybys as close as approximately 950 km (590 miles). This will permit high-resolution mapping of the moon's surface with an imaging radar instrument that can see through the opaque haze of Titan's upper atmosphere. In January 2005, the Huygens probe that is now attached to Cassini will descend through Titan's atmosphere to the surface.

Adapted from the information on http://www.jpl.nasa.gov/news/features.cfm?feature=590, http://www.jpl.nasa.gov/news/news.cfm?release=2004-171, http://www.jpl.nasa.gov/news/news.cfm?release=2004-170, http://www.jpl.nasa.gov/news/news.cfm?release=2004-169, and http://www.jpl.nasa.gov/news/news.cfm?release=2004-168.

(Added 07/10/04) The Hubble Heritage Team has released July's image of an HII region in the Large Magellanic Cloud (LMC) known as N11B, AKA NGC 1763. 160,000 light-years from us, the region lies in the constellation Dorado; this image covers approximately 2.2 arcminutes across (105 light-years). The image is combined from data taken on May 12, 1999, for a total exposure time of 37 minutes.

This image is a composite of two filters ([O III] (503 Å) and H-α (656 Å)), and it offers a panoramic view of glowing gas, dark dust clouds, and young, hot stars. With its high resolution, the Hubble Space Telescope is able to view details of star formation in the LMC as easily as ground-based telescopes are able to observe stellar formation within our own Milky Way galaxy. This new Hubble image zooms in on N11B, which is a small subsection within an area of star formation cataloged as N11.

N11 is the second largest star-forming region in the LMC. Within the LMC, N11 is surpassed in size and activity only by the immense Tarantula Nebula (also known as 30 Doradus.)

The image illustrates a perfect case of sequential star formation in a nearby galaxy where new star birth is being triggered by previous-generation massive stars. A collection of blue- and white-colored stars near the left of the image are among the most massive stars known anywhere in the universe. The region around the cluster of hot stars in the image is relatively clear of gas because the stellar winds and radiation from the stars have pushed the gas away. When this gas collides with and compresses surrounding dense clouds, the clouds can collapse under their own gravity and start to form new stars.

The cluster of new stars in N11B may have been formed this way, as it is located on the rim of the large, central interstellar bubble of the N11 complex. The stars in N11B are now beginning to clear away their natal cloud, and they are carving new bubbles in turn. Yet another new generation of stars is now being born in N11B, inside the dark dust clouds in the center and right-hand side of the image. This chain of consecutive star birth episodes has been seen in more distant galaxies, but it is shown very clearly in this new Hubble image.

Farther to the right of the image, along the top edge, are several smaller dark clouds of interstellar dust with odd and intriguing shapes. They are seen silhouetted against the glowing interstellar gas. Several of these dark clouds are bright-rimmed because they are illuminated and are being evaporated by radiation from neighboring hot stars.

Adapted from the information on http://heritage.stsci.edu/2004/22/.

(Added 06/30/04) Sitting within our galaxy, it is impossible for us to get a picture of what our galaxy looks like - to determine how it would appear to an outside observer. NASA's Spitzer Space Telescope, an orbiting infrared facility that began operations last year, has imaged a spiral galaxy NGC 7331, a galaxy that astronomers believe looks almost exactly as ours would appear to an outsider.

"Being inside our galaxy makes it difficult to see what's going on in the center," explained Dr. J. D. Smith, a member of the team that observed NGC 7331, and an astronomer at the University of Arizona, Tucson. "By looking at a very similar galaxy, we gain a bird's eye-view of what the entire Milky Way might look like." Such an outside perspective will teach astronomers how our own galaxy, as well as others like it, might have formed and evolved.

The latest observations are the first in a large-scale effort to observe 75 nearby galaxies with Spitzer's highly sensitive infrared eyes. Called Spitzer Infrared Nearby Galaxies Survey, the program will combine Spitzer data with that from other ground- and space-based telescopes operating at wavelengths ranging from ultraviolet to radio to create a comprehensive map of the selected galaxies.

The program's first target, NGC 7331, was chosen in part for its striking similarities to the Milky Way. While these so-called twin galaxies do not share the same parents, they have many features in common, including number of stars, mass, spiral arm pattern and star-formation rate of a few stars per year. Whether the Milky Way has an inner star-forming ring like that of NGC 7331 is not known. NGC 7331 is located about 50 million light-years away in the constellation Pegasus.

The new Spitzer image demonstrates the power of the telescope's infrared eyes to dissect galaxies into their various parts. Taken by the telescope's infrared array camera, the false-colored picture readily distinguishes NGC 7331's arms (brownish red), central bulge (blue) and star-forming ring (yellow). The composition of materials making up these regions was also revealed by the Spitzer observations: The central bulge consists primarily of older stars; the ring possesses a large amount of gas and dusty organic molecules called polycyclic aromatic hydrocarbons, which typically glow when illuminated by newborn stars; and the arms contain these same dust grains to a lesser degree. Polycyclic aromatic hydrocarbons are also found on Earth, on burnt toast and in car exhaust among other places. Data from Spitzer's infrared spectrograph instrument were also used to show that the center of NGC 7331 harbors either an unusually high concentration of massive stars, or a moderately active black hole about the same size as the one lurking at the core of our galaxy.

These findings will appear in two papers in the September issue of a special supplement to the Astrophysical Journal. Dr. Michael W. Regan of the Space Telescope Institute, Baltimore, MD, is lead author of a paper detailing observations from the infrared array camera, and Smith is lead author of a paper on the infrared spectrograph results. The Spitzer Infrared Nearby Galaxies Survey project is conducted by a team of about 25 scientists from 12 institutions, and it is led by principal investigator Dr. Robert C. Kennicutt of the University of Arizona, Tucson.

Adapted from the information on http://www.jpl.nasa.gov/news/news.cfm?release=2004-165.

(Added 06/27/04) Spirit, in its study of the rocks around the feet of Columbia Hills, has found hematite in the rock dubbed "Pot of Gold." Hematite was identified from orbit and it was NASA's key reason for choosing Opportunity's landing site on the other Side of Mars. Meanwhile, Opportunity continued its descent into Endurance Crater, and it has found unexpected similarities between lower layers of rock it is examining for the first time and an overlying layer at Eagle Crater - the crater in which it landed - where the rover had discovered evidence that water once soaked the area.

Mars Exploration Rover (MER) Spirit - Nuggets in the Pot of Gold - Hematite "It's gratifying how well these machines keep performing, considering they've now nearly doubled their original three-month missions on Mars," remarked Chris Voorhees, rover mechanical systems engineer at NASA's Jet Propulsion Laboratory, Pasadena, CA. By the end of next week, Spirit will have worked on Mars for half a year. It has driven more than three times the design requirement of 1 km (0.6 mile). The only symptom of wear or aging on either rover so far is increased friction in one wheel on Spirit. The rover team at JPL is beginning to consider good sites for the solar-powered robots to spend the period of martian winter when reduced daily sunshine cuts power supply to a minimum. In the nearer term, though, team members are eager to follow through on the new scientific findings.

Spirit's hematite finding is in a rock dubbed "Pot of Gold," a rock about the size of a softball. "This rock has a shape as if somebody took a potato and stuck toothpicks in it, then put jelly beans on the ends of the toothpicks," explained Dr. Steve Squyres of Cornell University, Ithaca, NY, principal investigator for the rovers' science instruments. "How it got this crazy shape is anyone's guess. I haven't even heard a good theory yet."

Dr. Doug Ming, a rover science-team member from NASA's Johnson Space Center, Houston, said, "There's apparently some type of weathering, a removal of material, but we're still trying to determine whether it's by chemical or mechanical processes." Further study of Pot of Gold could also help scientists assess what the hematite in it tells about past environmental conditions. "Hematite can form in a few different ways. Most of them require water, but it can also result from a dry, thermal oxidation process," Ming said. "It was hematite identified from orbit that made