Far Ultraviolet Spectroscopic Explorer (FUSE)

[Rykster]

NASA Telescope Viewing Heavens Once Again

LOS ANGELES - A NASA telescope is operating normally again after a mishap nearly ended its mission two years ago, scientists said Thursday.

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The orbiting telescope called FUSE — Far Ultraviolet Spectroscopic Explorer — returned to full strength last month after engineers fixed the problem with its onboard software control system, said William Blair of the Johns Hopkins University, who is part of the project.

"The old satellite still has some spunk," Blair said in a statement.

Launched in 1999, FUSE views objects by splitting light into thousands of spectra, or bands. So far, the telescope has detected a circle of hot gas surrounding the Milky Way, and found evidence of molecular hydrogen in Mars' atmosphere.

In 2001, two of the telescope's four reaction wheels, which control its direction, failed, but resumed again two months later. But in 2004, a third reaction wheel stopped spinning.

FUSE is managed by NASA's Goddard Space Flight Center.

___

On the Net:

FUSE mission. | Source: NASA Telescope

[Glacies]

Fascinating stuff, and when you include pictures, well you can't go wrong now can you?

[Rykster]

I always try to include my source and the data behind it. Otherwise, I wouldn't post it!

[Glacies]

I always try to include my source and the data behind it.

which serves to add a great deal of credibility and quoteability to your posts.

[Rykster]

Thank you, that really was a nice quote.

[Waspie_Dwarf]

NASA's Fuse Finds Infant Solar System Awash in Carbon

Scientists using NASA's Far Ultraviolet Spectroscopic Explorer, or FUSE, have discovered abundant amounts of carbon gas in a dusty disk surrounding a young star named Beta Pictoris.

The star and its emerging solar system are less than 20 million years old, and planets may have already formed. The abundance of carbon gas in the remaining debris disk indicates that Beta Pictoris' planets could be carbon-rich worlds of graphite and methane, or the star's environs might resemble our own solar system in its early days.

A team led by Aki Roberge of NASA's Goddard Space Flight Center in Greenbelt, Md., presents the observation in the June 8 issue of Nature. The new measurements make Beta Pictoris the first disk of its kind whose gas has been comprehensively studied. The discovery settles a long-standing scientific mystery about how the gas has lingered in this debris disk, yet raises new questions about the development of solar systems.

"There is much, much more carbon gas than anyone expected," said Roberge, a NASA postdoctoral fellow and lead author on the Nature report. "Could this be what our own solar system looked like when it was young? Are we seeing the formation of new types of worlds? Either prospect is fascinating."


Image above: In the Beta Pictoris Disk.
Artist's conception of the dust and gas disk surrounding
the star Beta Pictoris. A giant planet may have already
formed and terrestrial planets may be forming. The
inset panels show two possible outcomes for mature
terrestrial planets around Beta Pic. The top one is a
water-rich planet similar to the Earth; the bottom one
is a carbon-rich planet, with a smoggy, methane-rich
atmosphere similar to that of Titan, a moon of Saturn.
+ High resolution.
Credit: NASA/FUSE/Lynette Cook

Beta Pictoris, about 60 light years away from Earth, is 1.8 times more massive than our sun. At eight to 20 million years old, it is very young. This young star's disk was discovered in 1984. Earlier observations with the Hubble Space Telescope and the Keck telescope hinted that a Jupiter-like planet may have already formed in this disk, and rocky terrestrial planets may be forming. Such planets would be too small and faint to observe with current instruments. The terrestrial planets in our solar system -- Mercury, Venus, Earth and Mars -- formed from the collision of smaller planetary bodies such as asteroids about five billion years ago. During the few hundred million years after Earth was formed, asteroids and comets might have smashed into our planet to deliver virtually all of the water and organic material we see today. These materials are the building blocks of life on Earth.

Asteroids and comets orbiting Beta Pictoris might contain large amounts of carbon-rich material, such as graphite and methane. Planets forming from or impacted by such bodies would be very different from those in our solar system and might have methane-rich atmospheres, like Titan, a moon of Saturn.

"What we have learned in the past ten years is that our galaxy is filled with other solar systems, and each one is different from the next," said Marc Kuchner of NASA Goddard, an expert on extra-solar planets. "Beta Pictoris may be telling us something about the variety of planets that might be out there; some might be carbon planets, very different from the Earth."

Alternatively, Beta Pictoris might be similar to how our solar system was long ago. While local asteroids and comets don't seem carbon-rich today, some research suggests that certain meteorites called enstatite chondrite meteorites formed in a carbon-rich environment. Some scientists also speculate that Jupiter has a carbon core.


Image above: The Debris Disk Around Beta Pictoris.
This image of the circumstellar disk around Beta Pictoris
shows (in false colors) the light reflected by dust around
the young star at infrared wavelengths. The Beta Pic
disk is very likely an infant solar system in the process
of forming terrestrial planets. + High resolution
Credit: Jean-Luc Beuzit, et al. Grenoble Observatory,
European Southern Observatory

"We might be observing processes that occurred early in our solar system's development," said Nature co-author Alycia Weinberger of the Carnegie Institution of Washington.

Other co-authors on the report are Paul Feldman, Johns Hopkins University, Baltimore, and Magali Deleuil and Jean-Claude Bouret, Laboratoire d'Astrophysique de Marseille in France. The FUSE project is a NASA Explorer mission, developed in cooperation with France's Centre National d'Etudes Spatiales and the Canadian Space Agency by Johns Hopkins University in Baltimore; University of Colorado, Boulder; and University of California, Berkeley. Goddard manages the program for NASA's Science Mission Directorate.

+ Click here for more details and visuals

Related links:

+ Far Ultraviolet Spectroscopic Explorer

+ ExoPlanets and Stellar Astrophysics Laboratory

+ NASA Goddard's Universe Division

+ NASA Planetary Photojournal

Source: NASA - Exploring the Universe - Stars and Galaxies

[Waspie_Dwarf]

NASA FUSE Satellite Solves the Case of the Missing Deuterium

Call it CSI Milkyway. Scientists using NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) have solved a 35-year-old mystery about the whereabouts of deuterium, an isotope of hydrogen often called "heavy hydrogen."

Image Above: This is a false-color image of the star AE Aurigae (bright source of light slightly off center of image) embedded in a region of space containing smoke-like filaments of carbon-rich dust grains, a common phenomenon. Such dust might be hiding deuterium, an isotope of hydrogen, and stymieing astronomers' efforts to study star and galaxy formation. The FUSE satellite has surveyed the local deuterium concentration in the galaxy and found far more than expected. Because deuterium is a tracer of star and galaxy evolution, this discovery could radically alter theories about how stars and galaxy form.
Credit: T.A. Rector and B.A. Wolpa, NOAO, AURA, and NSF.
(Download Image: + Larger Version | + High Resolution Version)

The answer "is as unsettling as it is exciting," says the science team leader because this finding could radically alter theories about star and galaxy formation.

Deuterium, which contains one proton and one neutron, was created a few minutes after the Big Bang. Its presence today in the local universe serves as a tracer for star creation and galaxy building throughout the eons. This is because any deuterium used in stars is forever destroyed. Nearly all the deuterium seen today is "pure," having never been burned by stars. Knowing how much deuterium was created in the Big Bang and how much still exists today allows scientists to estimate how much gas has been used to create stars.

Deuterium emits a telltale spectral fingerprint in the ultraviolet energy range. But for the last 35 years, there's been a problem with this straightforward measurement.

Image above: FUSE studies primordial chemical relics of the Big Bang, from which all the stars, planets and life evolved. FUSE was launched aboard a Boeing Delta II rocket, and lifted off from Cape Canaveral Air Station, Florida on June 24, 1999.
Credit: NASA
(Download Image: + Larger Version)

"Since the 1970s we have been unable to explain why deuterium levels vary all over the place," said team leader Jeffrey Linsky of JILA, a joint institute of the University of Colorado, Boulder, and the National Institute of Standards and Technology.

In the 1970s, NASA's Copernicus satellite found deuterium distribution in the Milky Way galaxy to be patchy. There was more in one direction and, inexplicably, far less in other directions. Early FUSE observations confirmed this, a perplexing result because deuterium should be evenly mixed and as readily available as other elements for the creation of new stars.

In 2003, Bruce Draine of Princeton University, a tem member on the new result, developed computer models that showed how deuterium, compared to hydrogen, might preferentially bind to interstellar dust grains, changing from an easily detectable gaseous form to an unobservable solid form. The new FUSE data strongly support this theory.

In regions that remain undisturbed for long periods, such as the "local bubble" around our sun a few hundred light-years across, deuterium atoms systematically leave the gas phase and replace normal hydrogen atoms in dust grains. FUSE cannot detect this non-gaseous form, which explains the low detection level of 15 parts per million hydrogen atoms in our neighborhood and values as low as 5 parts per million elsewhere. When a region is disturbed by a supernova or hot stars, dust grains are vaporized, releasing deuterium atoms back into a gas phase. FUSE detects high deuterium levels in such regions.

That's part one: mystery solved. But the FUSE team has found far more deuterium elsewhere than expected. So enter part two: the new mystery.

Image above: This animation depicts the difference between normal hydrogen and "heavy hydrogen," or deuterium. Deuterium is not a separate element, but rather an isotope of hydrogen. Observing the spectral fingerprint of deuterium is one of the key science goals of the FUSE mission.
Credit: NASA & JHU.
Click on image to play animation.

Primordial deuterium concentrations are about 27 parts per million hydrogen atoms. Various non-FUSE studies have made these estimates, and they all jibe rather well. Most recently NASA's Wilkinson Microwave Anisotropy Probe confirmed this approximation.

FUSE finds concentrations as high as 23 parts per million in our galaxy. Scientists had assumed, based on theory, that at least a third of the local deuterium would have been destroyed over time. The more gas that cycles through stars, the lower the amount of deuterium that survives, so the local (modern) universe would have less deuterium than the distant (early) universe. But only about 15 percent of the deuterium has been destroyed, FUSE has found.

"The peak galactic detection levels are likely close to the real total deuterium abundance in the Milky Way, with the rest of it in hiding, not destroyed," said Warren Moos of Johns Hopkins University in Baltimore, FUSE Principal Investigator and co-author on the report in the August 20 issue of The Astrophysical Journal.

If the peak levels are 23 parts per million, this implies that either significantly less material has been converted to helium and heavier elements in stars or that much more primordial gas has rained down onto our galaxy over its lifetime than had been thought. In either case, our models of the chemical evolution of the Milky Way galaxy will have to be revised significantly to explain this new result, said George Sonneborn of NASA Goddard Space Flight Center in Greenbelt, Md., co-author and mission project scientist.

FUSE is a sensitive probe of how much gas has entered into galaxies and has been processed in stars. So theories, as is always the case, must match observations and not the other way around.

Christopher Wanjek
NASA Goddard Space Flight Center

Source: NASA - Exploring the Universe - Stars and Galaxies

[Startraveler]

That comes on the heels of this:

Where did all the lithium go?

9 August 2006

Astronomers may have solved the embarrassing problem of why the universe has so much less lithium than predicted by standard cosmology. By observing a set of stars in a distant globular cluster, Andreas Korn of Uppsala University in Sweden and colleagues in Denmark, France and Russia have concluded that the lithium diffuses over time into the stars' hot interiors, where it is then burnt up (Nature 442 657). Apart from confirming that our understanding of the Big Bang is correct, the discovery is also vindication for theoretical astrophysicists, who had predicted this diffusion effect all along.

Lithium -- together with hydrogen and helium -- is one of very few elements to have been synthesised in the Big Bang. However, experimental observations have shown that the amount of lithium in the atmospheres of the universe's very oldest stars is about one third of the value predicted by recent analyses of the fluctuations in the cosmic microwave background. Researchers have therefore not been sure what is wrong -- theory or observation.

Korn and co-workers may now have an answer to this question. Using a spectrometer on the European Southern Observatory's Very Large Telescope in Chile, they studied 18 stars in a distant globular cluster called NGC 6397, which formed roughly a few hundred million years after the Big Bang. Globular clusters are useful to study this problem because the stars are all the same age and had the same initial chemical composition, but are at different stages of evolution.

By comparing their observations with theoretical models of how nuclei behave in the atmospheres of stars, the researchers conclude that lithium diffuses into the interiors of stars over time, where it is burnt up at temperatures of over 2.5 million Kelvin. Calcium, iron and other "metallic" nuclei, in contrast, can survive the trip through the stellar interior.

The researchers estimate that these stars originally contained 78% more lithium as we observe today. In other words, the initial amount of lithium agrees with predictions from Big Bang nucleosynthesis. "This finding restores confidence in standard big-bang nucleosynthesis, quantitative spectroscopy and sophisticated stellar evolution models," the authors say.

Although Korn is happy that the work resolves what he calls "one of the most distressing discrepancies we had in connection with the Big Bang theory", he warns that researchers will have to be more careful when interpreting the spectra of old, unevolved stars "because the elemental abundances they show us are not eternal, but a function of time". He also says that the onus is now on theorists to fully explain why the lithium behaves in this way.

PhysicsWeb

[leadbelly]

Both, very, very interesting. I assume high velocity clouds are not part of the solution, or it would have been mentioned.

I remember a few years ago, FUSE, HST, and Keck did a study on interstellar gas using QSOs for background illumination. I may be mistaken, but it was somewhat significant, and raised abundances of hydrogen plus helium to about 9-10% of the Universe.

So, primordial D was 27 ppm; stars deplete it to ~15 ppm; dust incorporates it and reduces background deuterium to 5 ppm; high energy events seperate it out again, to as high as 23 ppm.

One thing they did not mention was high velocity clouds. They have been estimated at 23%, as well.

So, they are wondering overall about the higher limits on D. There was another spectrometer mission to study EUV ranges for interstellar gas, in order to help set constraints for other spectral observations outside the local bubble. They did not find what was predicted by the model they chose. They found less ionized Fe then was estimated, and on top of that, raised limits (if I understood) the possibilitiy that much soft x-ray background could be caused not by local interstellar ionized Fe, but by interactions betwen the solar wind and Earth's exosphere, or even emissions from further out within the heliosphere could mask what were once thought to be a source of interstellar soft x-rays.

FUSE is in low earth orbit. Even though I would not question their data, it seems even better for them if the local interstellar medium is as clear as it is now appearing to be- less noise.

[Waspie_Dwarf]

NASA's FUSE Satellite Catches Collision of Titans

05.28.07

Using NASA’s Far Ultraviolet Spectroscopic Explorer (FUSE) satellite and ground-based telescopes, astronomers have determined, for the first time, the properties of a rare, extremely massive, and young binary star system.


Image above: An artist depicts the binary system
LH54-425, which consists of two very massive stars.
The larger star’s powerful wind overpowers the smaller
star’s wind, creating a region of hot gas where the
outflows collide. LH54-425 is in the Large Magellanic
Cloud, a satellite galaxy of the Milky Way about 165,000
light-years from Earth.
Click image to enlarge.
+ High resolution TIF
Credit: NASA illustration by Casey Reed.

The system, known as LH54-425, is located in the Large Magellanic Cloud, a satellite galaxy of our Milky Way. The binary consists of two O-stars, the most massive and luminous types of stars in the Universe.

Spectra obtained by Georgia State University astronomer Stephen Williams at the 1.5-meter (4.9 foot) telescope at the Cerro Tololo Inter-American Observatory in Chile show that the two stars contain about 62 and 37 times the mass of our Sun. “The stars are so close to each other -- about one-sixth the average Earth-Sun distance -- that they orbit around a common center of mass every 2.25 days,” says Williams’ colleague Douglas Gies of Georgia State University, Atlanta. With a combined mass of about 100 suns, the system is one the most extreme binaries known. The stars are probably less than 3 million years old.

Each star blows off a powerful stellar wind, and FUSE’s observations have provided the first details of what happens when the two supersonic winds collide. The wind collision zone wraps around the smaller star and produces a curved surface of superheated gases that emit X-rays and far-ultraviolet radiation. FUSE is ideal for these measurements because the lines that best indicate the properties of stellar winds show up in the far ultraviolet part of the spectrum, where FUSE is most sensitive.


Image above: This image from the FUSE satellite
shows how LH54-425’s ultraviolet spectrum changes
during the 2.25-day orbit. The vertical wavy bands
are Doppler shifts due to the stars orbiting each
other at 1.1 million miles per hour. The arrow at the
top shows a one-million-mile-per-hour shift. The wavy
features are produced by very hot gases in the stellar
winds that contain silicon and phosphorus.
Click image to enlarge.
Credit: George Sonneborn (NASA/GSFC) and FUSE.

FUSE project scientist George Sonneborn of NASA Goddard Space Flight Center, Greenbelt, Md., is presenting these results today in a poster at the spring 2007 American Astronomical Society meeting in Honolulu, Hawaii.

The more massive star is shedding material at a rate of 500 trillion tons per second (about 400 times greater than the rate the sun loses mass through the solar wind), with a speed of 5.4 million miles per hour. The smaller star is ejecting mass at about one-tenth the rate of its sibling. The mass loss rate of both stars is consistent with other single stars having the same temperature and luminosity.

As the stars age and swell in size, they will begin to transfer substantial amounts of mass to each other. This process could begin in a million years. The stars are orbiting so close to each other that they are likely to merge as they evolve, producing a single extremely massive star like the more massive member of the Eta Carinae binary system. Eta Carinae is one of the most massive and luminous stars in the Milky Way Galaxy, with perhaps 100 solar masses.


Image above: This false-color image from the Curtis Schmidt
Telescope in Chile shows a large star-forming region in the Large
Magellanic Cloud. The binary system LH54-425 is arrowed. It is
located in the star cluster LH54.
Click image to enlarge.
Credit: Chris Smith and the University of Michigan Curtis Schmidt
Telescope at CTIO.

“The merger of two massive stars to make a single super star of over 80 suns could lead to an object like Eta Carinae, which might have looked like LH54-425 one million years ago,” says Sonneborn. “Finding stars this massive so early in their life is very rare. These results expand our understanding of the nature of very massive binaries, which was not well understood. The system will eventually produce a very energetic supernova.”

“These stars are evolving in the blink of an eye compared to the sun, which has looked pretty much the same for over 4 billion years,” adds Rosina Iping of the Catholic University, Washington and NASA Goddard, leader of the team that observed LH54-425 with FUSE. “But this binary looks totally different from Eta Carinae even though there is maybe only one million years difference in age. These massive stars zoom through their life cycle really fast. Will this binary system produce something like Eta Carinae? We don’t know.”

Launched in 1999, FUSE is a NASA Explorer mission developed in cooperation with the French and Canadian space agencies by Johns Hopkins University, University of Colorado, and University of California, Berkeley. NASA’s Goddard Space Flight Center, Greenbelt, Md., manages the program.


Bob Naeye
Goddard Space Flight Center

Source: NASA/GSFC - News

[Waspie_Dwarf]

FUSE Reaches the End; Astronomers Say Farewell

The Johns Hopkins University press release is reproduced below:

Office of News and Information
Johns Hopkins University
901 South Bond Street, Suite 540
Baltimore, Maryland 21231
Phone: 443-287-9960 | Fax: 443-287-9920

October 8, 2007
FOR IMMEDIATE RELEASE
CONTACT: Lisa De Nike
(443) 287-9960
lde@jhu.edu

The intrepid never-say-die space telescope known as FUSE has finally reached its mission's end and will be turned off after more than eight years of discoveries on everything from planets and nearby stars to galaxies and quasars billions of light-years away.



The satellite's control room on the Johns Hopkins Homewood campus will go dark on Oct. 18, leaving the satellite itself — its pointing system so often pulled from the brink of inoperability by enterprising engineers and scientists in that control room — to continue circling the Earth. Eventually, decades from now, its orbit will decay and the satellite will burn up in the atmosphere.

"It has been a great run. Who would have believed that a mission designed for three years would have gone on producing great science for eight," said Warren Moos, Gerhard H. Dieke Professor of Physics and Astronomy at Johns Hopkins and FUSE principal investigator. "What a testament to the ingenuity and hard work of the FUSE team."

FUSE, short for Far Ultraviolet Spectroscopic Explorer, was a Johns Hopkins-managed NASA mission that complemented the Hubble Space Telescope with observations at short ultraviolet light wavelengths below the range in which Hubble operates. Its original, three-year science mission was extended by NASA three times.

Astronomers from around the world have published more than 1,200 papers based on data from the satellite, which was launched atop a Delta-II rocket in June 1999 from Cape Canaveral. FUSE produced not pictures of distant objects but spectrographs, which are digital "charts" that break down the light emitted by those objects. By analyzing FUSE data, astronomers were able to measure temperatures, densities and chemical compositions of objects near and far, helping to place them in context in the history of the universe.

Groundbreaking science done during FUSE's eight years include a rare glimpse into molecular hydrogen in Mars' atmosphere, confirmation of a hot gas halo surrounding the Milky Way galaxy and a first-ever observation of molecular nitrogen outside our solar system, among others.

George Sonneborn, FUSE project scientist at NASA Goddard Space Flight Center in Greenbelt, Md., said, "JHU has done a fantastic job delivering a top-quality science mission for NASA."

FUSE is the largest astrophysics mission that NASA has ever handed off to a university to develop and then operate. The 18-foot-tall, 3,000-pound satellite has been run by a group of about 25 scientists, engineers and support staff from a basement-level control room in the Bloomberg Center for Physics and Astronomy.

Though FUSE's mission has been astoundingly successful from a scientific point of view, it faced a number of "death-defying" adventures dating back to late 2001. That's when, during a two-week period, two of the four "momentum wheels" that helped researchers aim the satellite at its targets stopped working. At least three wheels were needed to point FUSE with the precision needed for accurate astronomical observations.

Left with no other choices, the operations team conceived of and created a modified control system that used other devices onboard the satellite-electromagnets called magnetic torquer bars — to stabilize the satellite's pointing by periodically pushing or pulling the satellite against Earth's magnetic field. In just eight weeks, FUSE was back in business.

"It was a tenuous control at first, but it was certainly better than nothing," recounted Bill Blair, a research professor in the Henry A. Rowland Department of Physics and Astronomy and FUSE's chief of operations. "But with time, tweaks and experience, we got back into a very respectable science operations mode."

The satellite remained stable until Dec. 27, 2004, when yet another momentum wheel stopped operating, leaving the satellite with just one.

"True to form, we figured out how to use the magnetic trick to work with the single remaining wheel. But it was a lot harder than it sounds," Blair said.

It took most of 2005 to coax the satellite back into an effective operational mode, but from November 2005 into the spring of this year, FUSE was again gathering data. On May 8, however, the last momentum wheel malfunctioned. Researchers and engineers believe that some source of excess friction slowed the wheel. After studying the problem, the operations team was able to restart the wheel and put the telescope back into service.


FUSE Satellite Control Center at JHU, March 2005

"From June 12 to July 12, the wheel performed again almost flawlessly," Blair said. "But then the 'wheels came off,' so to speak. The wheel operated perfectly right up to the end, and then it just stopped dead, probably indicating a catastrophic failure of some kind."

After a month of creative troubleshooting, the FUSE team had to face the sad fact that the satellite's science mission was, at last, at its end.

"The magnetic system just doesn't have enough muscle by itself to point and hold the satellite for astronomical observations," Blair said. "We contacted NASA and told them the science mission was over."

Now the team has less than a year to close out the mission, including reprocessing and archiving some 131 million seconds of science data, writing final reports and providing final documentation of the mission. FUSE's scientific data will remain available to astronomers for years, however, through a data archive at the Space Telescope Science Institute, which is located on the Homewood campus.

One part of the closeout process is concluding on-orbit operations and turning off the satellite. Until now, FUSE has continued to take end-of-mission calibration data and perform engineering tests of various kinds. But Oct. 18, FUSE gets "put to sleep" for good. After 30 years or so, its orbit will decay and FUSE will burn up in the atmosphere.

"After that Thursday, FUSE will be just another piece of space junk, orbiting the earth every 100 minutes or so. It is a sad and ignominious end to such an outstandingly successful mission," Blair said. "But a tremendous scientific legacy is left behind. I commend the team of scientists and engineers who have worked so hard over the years to wring every last bit of science we could out of this amazing satellite."

For more on FUSE, go to fuse.pha.jhu.edu.

Source: JHU Press Release

[Waspie_Dwarf]

NASA Concludes Successful FUSE Mission

The press release is reproduced below:

Oct. 17, 2007

Grey Hautaluoma
Headquarters, Washington
202-358-0668
grey.hautaluoma-1@nasa.gov

Robert Naeye
Goddard Space Flight Center, Greenbelt, Md.
301-286-4453
robert.p.naeye@nasa.gov


RELEASE: 07-227

NASA Concludes Successful FUSE Mission

WASHINGTON - After an eight-year run that gave astronomers a completely new perspective on the universe, NASA has concluded the Far Ultraviolet Spectroscopic Explorer mission. The satellite, known as FUSE, became inoperable in July when the satellite lost its ability to point accurately and steadily at areas of interest. NASA will terminate the mission Oct. 18.

"FUSE accomplished all of its mission goals and more," said Alan Stern, associate administrator for the Science Mission Directorate at NASA Headquarters, Washington. "FUSE vastly increased our understanding of our galaxy's evolution and many exotic phenomena and left a strong legacy on which to build the next generation of investigations and missions."

Launched in 1999, FUSE helped scientists answer important questions about the conditions in the universe immediately following the Big Bang, how chemicals disperse throughout galaxies, and the composition of interstellar gas clouds that form stars and solar systems.

"FUSE helped pioneer low-cost, principal investigator-led astronomy missions," said Jon Morse, director of the Astrophysics Division at NASA Headquarters.

Examples of the many successes FUSE achieved during its mission are:

- By measuring abundances of molecular hydrogen (made of two hydrogen atoms), FUSE showed that a large amount of water has escaped from Mars, enough to form a global ocean 100 feet deep.

- FUSE observed a debris disk that is surprisingly rich in carbon gas orbiting the young star Beta Pictoris. The carbon overabundance indicates either the star is forming planets that could end up as exotic, carbon-rich worlds of graphite and methane, or Beta Pictoris is revealing an unsuspected phenomenon that also occurred in the early solar system.

- FUSE discovered far more deuterium, a form of hydrogen with a proton and a neutron instead of just one proton, in the Milky Way galaxy than astronomers had expected. Deuterium was produced in the early universe, but this isotope is destroyed easily in stellar nuclear reactions. "FUSE showed that less deuterium has been burned in stars over cosmic time, in agreement with modern models for the evolution of the galaxy and the recent Wilkinson Microwave Anisotropy Probe results," said Warren Moos, FUSE principal investigator, Johns Hopkins University, Baltimore.

- FUSE saw that an atmosphere of very hot gas surrounds the Milky Way. The ubiquity of hot gas around our galaxy demonstrates the galaxy is even more dynamic than expected.

- By detecting highly ionized oxygen atoms in intergalactic space, FUSE showed that about 10 percent of matter in the local universe consists of million-degree gas floating between the galaxies. This discovery might help resolve the long-standing mystery of the universe's "missing baryons." Baryons are subatomic particles, often protons and neutrons. Calculations of how many baryons were produced in the very early universe predict about twice as many baryons as astronomers have observed. The rest of the missing baryons might exist as even hotter gas, which could be observed by future X-ray observatories such as NASA's Constellation-X.

"FUSE collected quality science data for eight years, longer than its five-year goal. By any measure, FUSE was a success," said George Sonneborn, FUSE project scientist at NASA's Goddard Space Flight Center, Greenbelt, Md.

Although FUSE's mission has ended, NASA's ultraviolet study of the universe continues. In 2008, NASA will conduct a servicing mission to the Hubble Space Telescope to install a new ultraviolet spectrograph on the telescope and repair another. The new Cosmic Origins Spectrograph, or COS, is designed to study remote galaxies and nearby stars in the ultraviolet. Hubble's Space Telescope Imaging Spectrograph also will be repaired. That instrument had ultraviolet capabilities complementary to the COS and was used in conjunction with FUSE when both were operational. The spectrograph failed due to an electronic short in August 2004 after more than seven years of in-orbit operations.

FUSE was a joint mission of NASA, the Canadian Space Agency and the French Space Agency, the Centre National d'Etudes Spatiales. The Johns Hopkins University built the telescope and managed the mission. The University of Colorado, Boulder, built FUSE's spectrograph. The University of California, Berkeley, made the detectors. For more information, visit:

- end -

Source: NASA Press Release 07-227