Posted on by Fraser Cain

First Direct Image of An Exoplanet?

A research paper by an international team of astronomers [2] provides sound arguments in favour, but the definitive answer is now awaiting further observations.

On several occasions during the past years, astronomical images revealed faint objects, seen near much brighter stars. Some of these have been thought to be those of orbiting exoplanets, but after further study, none of them could stand up to the real test. Some turned out to be faint stellar companions, others were entirely unrelated background stars. This one may well be different.

In April of this year, the team of European and American astronomers detected a faint and very red point of light very near (at 0.8 arcsec angular distance) a brown-dwarf object, designated 2MASSWJ1207334-393254. Also known as “2M1207”, this is a “failed star”, i.e. a body too small for major nuclear fusion processes to have ignited in its interior and now producing energy by contraction. It is a member of the TW Hydrae stellar association located at a distance of about 230 light-years. The discovery was made with the adaptive-optics supported NACO facility [3] at the 8.2-m VLT Yepun telescope at the ESO Paranal Observatory (Chile).

The feeble object is more than 100 times fainter than 2M1207 and its near-infrared spectrum was obtained with great efforts in June 2004 by NACO, at the technical limit of the powerful facility. This spectrum shows the signatures of water molecules and confirms that the object must be comparatively small and light.

None of the available observations contradict that it may be an exoplanet in orbit around 2M1207. Taking into account the infrared colours and the spectral data, evolutionary model calculations point to a 5 jupiter-mass planet in orbit around 2M1207. Still, they do not yet allow a clear-cut decision about the real nature of this intriguing object. Thus, the astronomers refer to it as a “Giant Planet Candidate Companion (GPCC)” [4].

Observations will now be made to ascertain whether the motion in the sky of GPCC is compatible with that of a planet orbiting 2M1207. This should become evident within 1-2 years at the most.

Just a speck of light
Since 1998, a team of European and American astronomers [2] is studying the environment of young, nearby “stellar associations”, i.e., large conglomerates of mostly young stars and the dust and gas clouds from which they were recently formed.

The stars in these associations are ideal targets for the direct imaging of sub-stellar companions (planets or brown dwarf objects). The leader of the team, ESO astronomer Gael Chauvin notes that “whatever their nature, sub-stellar objects are much hotter and brighter when young – tens of millions of years – and therefore can be more easily detected than older objects of similar mass”.

The team especially focused on the study of the TW Hydrae Association. It is located in the direction of the constellation Hydra (The Water-Snake) deep down in the southern sky, at a distance of about 230 light-years. For this, they used the NACO facility [3] at the 8.2-m VLT Yepun telescope, one of the four giant telescopes at the ESO Paranal Observatory in northern Chile. The instrument’s adaptive optics (AO) overcome the distortion induced by atmospheric turbulence, producing extremely sharp near-infrared images. The infrared wavefront sensor was an essential component of the AO system for the success of these observations. This unique instrument senses the deformation of the near-infrared image, i.e. in a wavelength region where objects like 2M1207 (see below) are much brighter than in the visible range.

The TW Hydrae Association contains a star with an orbiting brown dwarf companion, approximately 20 times the mass of Jupiter, and four stars surrounded by dusty proto-planetary disks. Brown dwarf objects are “failed stars”, i.e. bodies too small for nuclear processes to have ignited in their interior and now producing energy by contraction. They emit almost no visible light. Like the Sun and the giant planets in the solar system, they are composed mainly of hydrogen gas, perhaps with swirling cloud belts.

On a series of exposures made through different optical filters, the astronomers discovered a tiny red speck of light, only 0.8 arcsec from the TW Hydrae Association brown-dwarf object 2MASSWJ1207334-393254, or just “2M1207”, cf. PR Photo 26a/04. The feeble image is more than 100 times fainter than that of 2M1207. “If these images had been obtained without adaptive optics, that object would not have been seen,” says Gael Chauvin.

Christophe Dumas, another member of the team, is enthusiastic: “The thrill of seeing this faint source of light in real-time on the instrument display was unbelievable. Although it is surely much bigger than a terrestrial-size object, it is a strange feeling that it may indeed be the first planetary system beyond our own ever imaged.”

Exoplanet or Brown Dwarf?
What is the nature of this faint object [4]? Could it be an exoplanet in orbit around that young brown dwarf object at a projected distance of about 8,250 million km (about twice the distance between the Sun and Neptune)?

“If the candidate companion of 2M1207 is really a planet, this would be the first time that a gravitationally bound exoplanet has been imaged around a star or a brown dwarf” says Benjamin Zuckerman of UCLA, a member of the team and also of NASA’s Astrobiology Institute.

Using high-angular-resolution spectroscopy with the NACO facility, the team has confirmed the substellar status of this object – now referred to as the “Giant Planet Candidate Companion (GPCC)” – by identifying broad water-band absorptions in its atmosphere, cf. PR Photo 26b/04.

The spectrum of a young and hot planet – as the GPCC may well be – will have strong similarities with an older and more massive object such as a brown dwarf. However, when it cools down after a few tens of millions of years, such an object will show the spectral signatures of a giant gaseous planet like those in our own solar system.

Although the spectrum of GPCC is quite “noisy” because of its faintness, the team was able to assign to it a spectral characterization that excludes a possible contamination by extra-galactic objects or late-type cool stars with abnormal infrared excess, located beyond the brown dwarf.

After a very careful study of all options, the team found that, although this is statistically very improbable, the possibility that this object could be an older and more massive, foreground or background, cool brown dwarf cannot be completely excluded. The related detailed analysis is available in the resulting research paper that has been accepted for publication in the European journal Astronomy & Astrophysics (see below).

Implications

The brown dwarf 2M1207 has approximately 25 times the mass of Jupiter and is thus about 42 times lighter than the Sun. As a member of the TW Hydrae Association, it is about eight million years old.

Because our solar system is 4,600 million years old, there is no way to directly measure how the Earth and other planets formed during the first tens of millions of years following the formation of the Sun. But, if astronomers can study the vicinity of young stars which are now only tens of millions of years old, then by witnessing a variety of planetary systems that are now forming, they will be able to understand much more accurately our own distant origins.

Anne-Marie Lagrange, a member of the team from the Grenoble Observatory (France), looks towards the future: “Our discovery represents a first step towards opening a whole new field in astrophysics: the imaging and spectroscopic study of planetary systems. Such studies will enable astronomers to characterize the physical structure and chemical composition of giant and, eventually, terrestrial-like planets.”

Follow-up observations
Taking into account the infrared colours and the spectral data available for GPCC, evolutionary model calculations point to a 5 jupiter-mass planet, about 55 times more distant from 2M1207 than the Earth is from the Sun (55 AU). The surface temperature appears to be about 10 times hotter than Jupiter, about 1000 ?C; this is easily explained by the amount of energy that must be liberated during the current rate of contraction of this young object (indeed, the much older giant planet Jupiter is still producing energy in its interior).

The astronomers will now continue their research to confirm or deny whether they have in fact discovered an exoplanet. Over the next few years, they expect to establish beyond doubt whether the object is indeed a planet in orbit around the brown dwarf 2M1207 by watching how the two objects move through space and to learn whether or not they move together. They will also measure the brightness of the GPCC at multiple wavelengths and more spectral observations may be attempted.

There is no doubt that future programmes to image exoplanets around nearby stars, either from the ground with extremely large telescopes equipped with specially designed adaptive optics, or from space with special planet-finder telescopes, will greatly profit from current technological achievements.

More information
The results presented in this ESO Press Release are based on a research paper (“A Giant Planet Candidate near a Young Brown Dwarf” by G. Chauvin et al.) that has been accepted for publication and will soon appear in the leading research journal “Astronomy and Astrophysics”. A preprint is available here.

Notes
[1]: This press release is issued simultaneously by ESO and CNRS (in French) .

[2]: The team consists of Gael Chauvin and Christophe Dumas (ESO-Chile), Anne-Marie Lagrange and Jean-Luc Beuzit (LAOG, Grenoble, France), Benjamin Zuckerman and Inseok Song (UCLA, Los Angeles, USA), David Mouillet (LAOMP, Tarbes, France) and Patrick Lowrance (IPAC, Pasadena, USA). The American members of the team acknowledge funding in part by NASA’s Astrobiology Institute.

[3]: The NACO facility (from NAOS/Nasmyth Adaptive Optics System and CONICA/Near-Infrared Imager and Spectrograph) at the 8.2-m VLT Yepun telescope on Paranal offers the capability to produce diffraction-limited near-infrared images of astronomical objects. It senses the radiation in this wavelength region with the N90C10 dichroic; 90 percent of the flux is transmitted to the wavefront sensor and 10 percent to the near-infrared camera CONICA. This mode is particularly useful for sharp imaging of red and very-low-mass stellar or substellar objects. The adaptive optics corrector (NAOS) was built, under an ESO contract, by Office National d’Etudes et de Recherches A?rospatiales (ONERA), Laboratoire d’Astrophysique de Grenoble (LAOG) and the LESIA and GEPI laboratories of the Observatoire de Paris in France, in collaboration with ESO. The CONICA camera was built, under an ESO contract, by the Max-Planck-Institut f?r Astronomie (MPIA) (Heidelberg) and the Max-Planck Institut f?r extraterrestrische Physik (MPE) (Garching) in Germany, in collaboration with ESO.

[4]: What is the difference between a small brown dwarf and an exoplanet ? The border line between the two is still being investigated but it appears that a brown dwarf object is formed in the same way as stars, i.e. by contraction in an interstellar cloud while planets are formed within stable circumstellar disks via collision/accretion of planetesimals or disk instabilities. This implies that brown dwarfs are formed faster (less than 1 million years) than planets (~10 million years). Another way of separating the two kinds of objects is by mass (as this is also done between brown dwarfs and stars): (giant) planets are lighter than about 13 jupiter-masses (the critical mass needed to ignite deuterium fusion), brown dwarfs are heavier. Unfortunately, the first definition cannot be used in practice, e.g., when detecting a faint companion as in the present case, since the observations do not provide information about the way the object was formed. On the contrary, the above mass criterion is useful in the sense that spectroscopy and astrometry of a faint object, together with the appropriate evolutionary models, may reveal the mass and hence the nature of the object.

Original Source: ESO News Release

Posted on by Fraser Cain

Here’s How You Can Help

I’ve got to say I definitely feel appreciated maintaining this website and newsletter. I get lots of supportive email every day – my boosted ego thanks you (keep it coming, though). Since it’s largely a one-man show, people have been wondering how they can help out. Well… I’m glad you asked, here are some ways you can help me maintain and improve Universe Today.

Tell your friends about the site. Point them at a specific story, or forward them a copy of the newsletter and encourage them to subscribe.

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Posted on by Fraser Cain

Opportunity’s Landing Site Could Have Once Been Under Water

Spacecraft observations of the landing area for one of NASA’s two Mars rovers now indicate there likely was an enormous sea or lake covering the region in the past, according to a new University of Colorado at Boulder study.

Research Associate Brian Hynek of the Laboratory for Atmospheric and Space Physics said data from the Mars Global Surveyor and Mars Odyssey spacecraft now show that the region surrounding the Opportunity rover’s landing site probably had a body of water at least 330,000 square kilometers, or 127,000 square miles. That would make the ancient sea larger in surface area than all the Great Lakes combined, or comparable to Europe’s Baltic Sea.

In March, Opportunity instruments scanning the Meridiani Planum landing region confirmed that rock outcrops there, rich in the iron oxide mineral hematite, also contained the types of sulfate that only could have been created by interactions of water with Martian rock. Hynek used thermal emission data and camera images from the orbiting spacecraft to show such bedrock outcrops extend outward for many miles north, east and west.

“If the outcrops are a result of sea deposition, the amount of water once present must have been comparable to the Baltic Sea or all of the Great Lakes combined,” he said. Hynek speculated that future studies may show that the ancient sea was even larger.

A paper on the subject by Hynek appears in the Sept. 9 issue of Nature.

The thermal emission imaging system, or THEMIS, aboard Mars Odyssey is used to infer the particle size of rocks near or on the surface of Mars, he said.

High thermal inertia measurements indicate a prevalence of larger chunks of rock, which heat up more slowly in daylight and cool more slowly in evenings. Low thermal inertia measurements are from fine-grained particles that heat and cool more quickly.

The thermal maps of Mars developed by Hynek indicate the rocky outcrops associated with ancient water extend far outside the boundaries of the landing area. “The thermal inertia for this area is relatively high, an indication the region contains substantial bedrock,” he said.

Hynek speculated that if the outcrops at the landing site are the result of sea deposition, as believed, the body of water must have been deep enough and persisted long enough to build up sediments roughly one-third of a mile deep. “For this to occur, the ancient global climate of Mars must have been different from its present climate and have lasted for an extended period,” Hynek wrote in the Nature paper.

“I believe new findings showing evidence of large amounts of water on Mars over long periods of time could increase the science potential for those seeking evidence of past or present life on Mars,” said Hynek.

Hematite deposits on Earth come primarily from the presence of long-standing water or groundwater systems, Hynek said. Many scientists believe the requirement for primitive life forms, at least on Earth, include water or some other liquid, a source of energy and access to elements to construct complex molecules.

“It is important to understand how extensive these water-rich environments were and how long they persisted, because life required at least some degree of environmental stability in order to begin and to evolve,” said NASA-Ames Research Center astrobiologist David Des Marais regarding Hynek’s study.

“Orbital observations and future landed missions will provide crucial details about the long-term legacy of liquid water on Mars, and whether life ever became a part of that legacy,” said Des Marais, a member of the Mars rover science team.

CU-Boulder doctoral student Nathaniel Putzig and LASP Research Associate Michael Mellon assisted in the data processing for the remote sensing images used in the Nature study.

The Mars rover, Spirit, landed in the Gusev Crater on Jan. 4. Opportunity, its twin, landed on the Meridiani Planum on the opposite side of the planet Jan. 25. Both rovers still are under operation by NASA and returning science data.

Original Source: CU Boulder News Release

Posted on by Fraser Cain

Bizarre Matter Found in a Neutron Star

Scientists have obtained their best measurement yet of the size and contents of a neutron star, an ultra-dense object containing the strangest and rarest matter in the Universe.

This measurement may lead to a better understanding of nature’s building blocks — protons, neutrons and their constituent quarks — as they are compressed inside the neutron star to a density trillions of times greater than on Earth.

Dr. Tod Strohmayer of NASA’s Goddard Space Flight Center in Greenbelt, Md., and his colleague, Adam Villarreal, a graduate student at the University of Arizona, present these results today during a Web-based press conference in New Orleans at the meeting of the High Energy Astrophysics Division of the American Astronomical Society.

They said their best estimate of the radius of a neutron star is 7 miles (11.5 kilometers), plus or minus a stroll around the French Quarter. The mass appears to be 1.75 times that of the Sun, more massive than some theories predict. They made their measurements with NASA’s Rossi X-ray Timing Explorer and archived X-ray data

The long-sought mass-radius relation defines the neutron star’s internal density and pressure relationship, the so-called equation of state. And this, in turn, determines what kind of matter can exist inside a neutron star. The contents offer a crucial test for theories describing the fundamental nature of matter and energy and the strength of nuclear interactions.

“We would really like to get our hands on the stuff at the center of a neutron star,” said Strohmayer. “But since we can’t do that, this is about the next best thing. A neutron star is a cosmic laboratory and provides the only opportunity to see the effects of matter compressed to such a degree.”

A neutron star is the core remains of a star once bigger than the Sun. The interior contains matter under forces that perhaps existed at the moment of the Big Bang but which cannot be duplicated on Earth. The neutron star in today’s announcement is part of a binary star system named EXO 0748-676, located in the constellation Volans, or Flying Fish, about 30,000 light-years away, visible in southern skies with a large backyard telescope.

In this system, gas from a “normal” companion star plunges onto the neutron star, attracted by gravity. This triggers thermonuclear explosions on the neutron star surface that illuminate the region. Such bursts often reveal the spin rate of the neutron star through a flickering in the X-ray light emitted, called a burst oscillation. (Refer to Items 1 – 6 for an artist’s concept of this process. A movie and a detailed caption can be found in the blue column on the right.)

The scientists detected a 45-hertz burst oscillation frequency, which corresponds to a neutron star spin rate of 45 times per second. This is a leisurely pace for neutron stars, which are often seen spinning over 300 times per second.

The scientists next capitalized on EXO 0748-676 observations with the European Space Agency’s XMM-Newton satellite from 2002, led by Dr. Jean Cottam of NASA Goddard. Cottam’s team had detected spectral lines emitted by hot gas, similar in look to the lines of a cardiogram. These lines had two features. First, they were Doppler shifted. This means the energy detected was an average of the light spinning around the neutron star, moving away from us and then towards us. Second, the lines were gravitationally redshifted. This means that gravity pulled on the light as it tried to escape the region, stealing a bit of its energy.

Strohmayer and Villarreal determined that the 45-hertz frequency and the observed line widths from Doppler shifting are consistent with a neutron star radius between 9.5 and 15 kilometers, with the best estimate at 11.5 kilometers. The relationship among burst frequency, Doppler shifting and radius is that the velocity of gas swirling around the star’s surface depends on the star’s radius and its spin rate. In essence, a faster spin corresponds to a wider spectral line (a technique similar to how a state trooper can detect speeding cars).

Cottam team’s gravitational redshift measurement offered the first measure of a mass-radius ratio, albeit without knowledge of a mass and radius. This is because the degree of redshifting (strength of gravity) depends on the mass and radius of the neutron star. Some scientists had questioned this measurement, for the spectral lines detected seemed too narrow. The new results strengthen the gravitational redshift interpretation of the Cottam team’s spectral lines (and thus the mass-radius ratio) because a slower-spinning star can easily produce such relatively narrow lines.

So, ever more confident of the mass-radius ratio and now knowing the radius, the scientists could calculate the neutron star’s mass. The value was between 1.5 and 2.3 solar masses, with the best estimate at 1.75 solar masses.

The result supports the theory that matter in the neutron star in EXO 0748-676 is packed so tightly that almost all protons and electrons are squeezed into neutrons, which swirl about as a superfluid, a liquid that flows without friction. Yet the matter isn’t packed so tightly that quarks are liberated, a so-called quark star.

“Our results are really starting to put the squeeze on the neutron star equation of state,” said Villareal. “It looks like equations of state which predict either very large or very small stars are nearly excluded. Perhaps more exciting is that we now have an observational technique that should allow us to measure the mass-radius relations in other neutron stars.”

A proposed NASA mission called the Constellation X-ray Observatory would have the ability to make such measurements, but with much greater precision, for a number of neutron star systems.

Original Source: NASA News Release

Posted on by Fraser Cain

Genesis Capsule Recovery Underway

The Genesis sample return capsule entered Earth’s atmosphere at 9:52:47 a.m. Mountain Daylight Time 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 kilometers 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, Calif. “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, Calif., who took part in the initial reconnaissance of the capsule. “I observed the capsule penetrated the soil about 50 percent 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 moved into the cleanroom at the U.S. Army Dugway Proving Ground in Utah early Wednesday evening. 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 will begin examining the contents of the canister on Thursday morning.

The Genesis mission was launched in August 2001 on a journey to capture samples from the storehouse of 99 percent 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.

JPL manages the Genesis mission for NASA’s Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, developed and operated the spacecraft. JPL is a division of the California Institute of Technology.

For information about the Genesis Sample Return Mission on the Internet, visit http://www.nasa.gov/genesis. For background information about Genesis, visit http://genesismission.jpl.nasa.gov.

Original Source: Genesis Status Reports

Posted on by Fraser Cain

Cassini Finds a New Ring Around Saturn

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 said. 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, Colo., 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 S 4. S4 is roughly the same size as S3.

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.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo. UK scientists are playing significant roles in the mission with involvement in six of the 12 instruments onboard the Cassini orbiter and two of the six instruments on the Huygens probe.

Cassini-Huygens is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science and Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The Composite Infrared Spectrometer team is based at NASA’s Goddard Space Flight Center, Greenbelt, Md. For this image and for the latest news about the Cassini-Huygens mission, visit http://www.nasa.gov/cassini. For in-depth mission information, visit http://saturn.jpl.nasa.gov. For more information on the Composite Infrared Spectrometer, visit http://cirs.gsfc.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

How About a Gigapixel Digital Camera?

ESA?s ?discovery machine? Gaia is designed to photograph one thousand million stars and hundreds of thousands of other celestial objects, so its camera will have to be something truly special.

Indeed, when Gaia lifts off from ESA?s Spaceport at Kourou in French Guiana, sometime after 2010, it will be carrying the largest digital camera in the Solar System. Essentially, Gaia will survey anything in the Universe that it can lay its electronic eyes on. As it spins gently in its orbit, 1.5 million kilometres away from Earth, it will scan the entire sky for stars, planets, asteroids, distant galaxies and everything in between.

The aim is to detect every celestial object down to about a million times fainter than the unaided human eye can see. To do that, it needs a large camera. In fact, there will be 170 separate cameras in Gaia, tiled together in a mosaic to register every object that passes through the field of view.

Scientists call each individual camera a ?charge-coupled device? (CCD). An additional instrument will take the total number of CCDs to over 200.

Each CCD is itself a major piece of hi-tech kit that converts light into electrical charge and stores it in tiny traps known as ?pixels? until the computer reads out this information. With about nine million pixels, Gaia?s CCDs are each between 5 and 10 times larger than those used in digital cameras currently on sale in our shops.

The size of each CCD presents some unique manufacturing challenges. Even in the purest silicon, defects can occur. Typically, with the CCDs that are used in our digital cameras on Earth, perhaps 20 or more are manufactured from the same silicon wafer and one or two rejects are tolerable.

However, the Gaia CCDs are so large that only two will fit onto each silicon wafer. So the chance of a defect occurring in a Gaia CCD is considerable.

To help refine the manufacturing process, ESA is running a prototype production line with the company e2v, who specialise in cutting-edge research quality CCDs. They are the same company that provided most of the scientific CCDs for ESA’s orbiting X-ray observatory XMM-Newton.

?For XMM-Newton, e2v provided 23 flight quality CCDs. This was a major achievement, but for Gaia, we aim to fly more than 200 in all,? says Alexander Short, one of Gaia?s CCD experts at the European Space Technology and Research Centre (ESTEC), in the Netherlands.

Once Gaia is in space, solar activity such as solar flares and ?coronal mass ejections? could damage the CCDs and blur the images.

To minimise the effects of this ?radiation damage? during the mission, Short and colleagues are working on shielding and a number of other solutions to ensure that Gaia can become the most successful discovery machine in the history of astronomy.

Original Source: ESA News Release

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Genesis Capsule Crashes

Helicopters were waiting in Utah to gently catch a capsule from the Genesis probe carrying precious samples of the Sun’s solar wind, but the safe recovery didn’t happen. It appears that the capsule’s parachute failed to open as it entered the Earth atmosphere, and it crashed into the ground at 161 km/h (100 mph). It could take some time to recover the capsule because the charges designed to open the parachute might still be live, and could still explode. The $264 million mission was launched in 2001, and carried delicate wafers of pure silicon, gold, sapphire, and diamond designed to gently catch solar wind particles. It’s unknown how much of the experiment can be recovered at this point.

Posted on by Fraser Cain

Cleaning Up Kennedy Space Center After Frances

For one of the world’s biggest buildings, before and after images captured the force of the storm. With its footprint the size of Texas, hurricane Frances had pounded Cape Canaveral over the weekend and left a natural scar on one of the world’s manmade wonders.

Originally built for assembly of Apollo/Saturn vehicles and later modified to support Space Shuttle operations, the Vehicle Assembly Building (VAB) is often referred to as the only enclosed space big enough for interior clouds to form. But when a hurricane looms off the Florida coast and dark clouds gather to drench the beaches, the novelty of forming interior clouds loses some of its charm.

It is not the tallest, just one of the more spacious. Its high-bay area is 525 feet tall (more than 45 stories high), while its low-bay area is 210 feet tall. The VAB occupies 8 acres of land, making it the largest in volume (129 million cubic feet). The volume is like half the height of the tallest skyscraper, but then with that same tower turned on three axes, with nearly equal height, width and depth. When open, the T-shaped door alone is more than 40 stories tall.

When constructed in the 1960’s to stack the Saturn rockets–each about the size of an aircraft carrier if stood up vertically–the VAB came to symbolize big-scale thinking. In addition to sheltering the Apollo rockets, it could accomodate rollbacks of a shuttle during the predictable fall hurricane season. In total, six skyscrapers could fit inside what is the landmark against an otherwise flat Florida marsh lacking an urban skyline. But from its outset, if NASA needed a building to shelter a moon rocket, then a group of construction engineers would conceive hoisting the biggest one of its kind.

Max Urbahn, who headed the design team of architects and engineers for the Vehicle Assembly Building stated the design challenge well when he said: “The VAB is not so much a building to house a moon vehicle as a machine to build a moon craft. The Launch Control Center that monitors and tests every component that goes into an Apollo vehicle is not so much a building as an almost-living brain.”

When General Thomas Stafford testified to the Presidential blue-ribbon commission on “Moon to Mars and Beyond”, he cited specifically how remarkable the early sixties were for construction on the Florida coast. “In the early 1960’s the Cape was strictly palmettos, rattlesnakes, and palm trees. In 6 years, that was built to the Vehicle Assembly Building (VAB), and we launched the first Saturn flag. And most of it was done with a slide rule.”

As the VAB tried to weather 100 mile-per-hour gales, the adage that ‘build it and they will come’ took on special significance: those who had to evacuate included nearly the entire 14,000 person Kennedy Space Center (KSC). According to its design specifications, the VAB doors can withstand winds of 125 miles per hour and can be opened and closed in a 63 mile-per-hour wind. The building lived up to its design, but its integrity was questionable earlier in the week when Frances looked like it might make landfall with 140 mph force winds.

As NASA Administrator, Sean O’Keefe described in a statement: “Kennedy Space Center suffered significant damage as Hurricane Frances swept across Florida.” After the weekend, early assessment of this landmark facility showed about 820 panels were torn off the VAB during the storm. Initial review of the interior, however, indicated no serious damage to equipment, including two Space Shuttle External Tanks.

Preliminary inspections of the center’s two launch pads indicate they appear in good shape. The SWIFT spacecraft for studying Gamma Ray Bursts, which is scheduled for launch early next month, also appears fine, but the building where it rode out the storm did sustain damage. Also, power was restored today to the third and final Orbital Processing Facility, which houses the Space Shuttle Discovery.

In addition to housing the shuttle rocket stacks, many astrobiology missions have historical ties to critical assets at the Cape. From the Hubble telescope launch to various human missions on space station, the shuttle stack has been mounted in the VAB. In fact the skyline at Cape Canaveral gives a running account of important astrobiology objectives. During a controlled explosion in October 2000, the historical launch pad 41 dating back to 1965 gave way to a new Atlas V tower. That part of the now modified Florida skyline had witnessed the launch of two Viking missions to Mars and Voyager’s planetary probe, both of which had led the way for modern astrobiology missions to the inner and outer solar system.

O’Keefe spoke to the NASA tradition of recovery, when he concluded that “We have a documented history of overcoming adversity and pulling together.” NASA has not assessed yet whether the storm damage will affect the planned spring reflight of the shuttle as it returns to orbit since the Columbia tragedy.

Original Source: NASA Astrobiology Article

Posted on by Fraser Cain

Dark Matter is Tugging at a Galactic Cluster

A nearby galaxy cluster is facing an intergalactic headwind as it is pulled by an underlying superstructure of dark matter, according to new evidence from NASA’s Chandra X-ray Observatory. Astronomers think that most of the matter in the universe is concentrated in long large filaments of dark matter and that galaxy clusters are formed where these filaments intersect.

A Chandra survey of the Fornax galaxy cluster revealed a vast, swept-back cloud of hot gas near the center of the cluster. This geometry indicates that the hot gas cloud, which is several hundred thousand light years in length, is moving rapidly through a larger, less dense cloud of gas. The motion of the core gas cloud, together with optical observations of a group of galaxies racing inward on a collision course with it, suggests that an unseen, large structure is collapsing and drawing everything toward a common center of gravity.

“At a relatively nearby distance of about 60 million light years, the Fornax cluster represents a crucial laboratory for studying the interplay of galaxies, hot gas and dark matter as the cluster evolves.” said Caleb Scharf of Columbia University in New York, NY, lead author of a paper describing the Chandra survey that was presented at an American Astronomical Society meeting in New Orleans, LA. “What we are seeing could be associated directly with the intergalactic gas surrounding a very large scale structure that stretches over millions of light years.”

The infalling galaxy group, whose motion was detected by Michael Drinkwater of the University of Melbourne in Australia, and colleagues, is about 3 million light years from the cluster core, so a collision with the core will not occur for a few billion years. Insight as to how this collision will look is provided by the elliptical galaxy NGC 1404 that is plunging into the core of the cluster for the first time. As discussed by Scharf and another group led by Marie Machacek of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., the hot gas cloud surrounding this galaxy has a sharp leading edge and a trailing tail of gas being stripped from the galaxy.

“One thing that makes what we see in Fornax rather compelling is that it looks a lot like some of the latest computer simulations,” added Scharf. “The Fornax picture, with infalling galaxies, and the swept back geometry of the cluster gas – seen only with the Chandra resolution and the proximity of Fornax – is one of the best matches to date with these high-resolution simulations.”

Over the course of hundreds of millions of years, NGC 1404’s orbit will take it through the cluster core several times, most of the gas it contains will be stripped away, and the formation of new stars will cease. In contrast, galaxies that remain outside the core will retain their gas, and new stars can continue to form. Indeed, Scharf and colleagues found that galaxies located in regions outside the core were more likely to show X-ray activity which could be associated with active star formation.

The wide-field and deep X-ray view around Fornax was obtained through ten Chandra pointings, each lasting about 14 hours. Other members of the research team were David Zurek of the American Museum of Natural History, New York, NY, and Martin Bureau, a Hubble Fellow currently at Columbia.

NASA’s Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA’s Office of Space Science, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

Additional information and images are available at:

http://chandra.harvard.edu
and
http://chandra.nasa.gov

Original Source: Chandra News Release