Posted on by Fraser Cain

Are Galaxy Clusters Corrupting Our View of the Big Bang?

Image credit: RAS
In recent years, astronomers have obtained detailed measurements of the cosmic microwave background radiation – the ‘echo’ from the birth of the Universe during the Big Bang.

These results appear to indicate with remarkable precision that our Universe is dominated by mysterious ‘cold dark matter’ and ‘dark energy’. But now a group of UK astronomers has found evidence that the primordial microwave echoes may have been modified or ‘corrupted’ on their 13 billion year journey to the Earth.

The results from a team at the University of Durham, led by Professor Tom Shanks, are based on a new analysis of data from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) satellite.

The team has found that nearby galaxy clusters appear to lie in regions of sky where the microwave temperature is lower than average. This behaviour could be accounted for if the hot gas in the galaxy clusters has interacted with the Big Bang photons as they passed by and corrupted the information contained in this echo of the primordial fireball. Russian physicists R. A. Sunyaev and Ya. B. Zeldovich predicted such an effect in the early 1970’s, shortly after the discovery of the cosmic microwave background radiation.

This Sunyaev-Zeldovich effect has previously been seen in the cases of detailed observations of the microwave background in the vicinity of a few rich galaxy clusters and the WMAP team themselves have reported seeing the effect in their own data, close to cluster centres.

Now the Durham team has found evidence that hot gas in the clusters may influence the microwave background maps out to a radius of nearly 1 degree from the galaxy cluster centres, a much larger area than previously detected. This suggests that the positions of “clusters of clusters” or “superclusters” may also coincide with cooler spots in the pattern of microwave background fluctuations.

“The photons in the microwave background radiation are scattered by electrons in nearby clusters,” said Professor Shanks. “This causes important changes to the radiation by the time it reaches us.”

“If the galaxy clusters located several billion light years from Earth also have the same effect, then we must consider whether it is necessary to modify our interpretation of the satellite maps of the microwave background radiation.”

If the Durham result is confirmed, then the consequences for cosmology could be highly significant. The signature for dark energy and dark matter lies in the detailed structure of the ripples detected in the microwave background, tiny temperature variations that were created at a time when the radius of the Universe was a thousand times smaller than it is today.

If this primordial pattern has been corrupted by processes taking place in the recent past, long after galaxies and galaxy clusters formed, then it will, at best, complicate the interpretation of the microwave echo and, at worst, begin to undermine the previous evidence for both dark energy and cold dark matter.

“The power of this wonderful WMAP data is that it indicates that interpreting the microwave background ‘echo’ may be less straightforward than previously thought,” said team member Sir Arnold Wolfendale (previously Astronomer Royal).

The WMAP team has already reported that their measurements of the Big Bang’s microwave echo may have been compromised by the process of galaxy formation at an intermediate stage in the Universe’s history. They presented evidence that gas heated by first-born stars, galaxies and quasars may have also corrupted the microwave signal when the Universe was 10 or 20 times smaller than at the present day. Thus both the WMAP and Durham results suggest that the microwave echo of the Big Bang may have had to come through many more obstacles on its journey to the Earth than had previously been thought, with consequent possible distortion of the primordial signal.

“Our results may ultimately undermine the belief that the Universe is dominated by an elusive cold dark matter particle and the even more enigmatic dark energy,” said Professor Shanks.

Although the observational evidence for the standard model of cosmology remains strong, the model does contain very uncomfortable aspects. These arise first because it is based on two pieces of “undiscovered physics” – cold dark matter and dark energy – neither of which has been detected in the laboratory. Indeed, the introduction of these two new components greatly increases the complication of the standard Big Bang inflationary model.

The problems of dark energy run particularly deep: for example, its observed density is so small that it may be quantum mechanically unstable. It also creates problems for the theories of quantum gravity, which suggest that we may live in a Universe with 10 or 11 dimensions, all of them shrunk, with the exceptions of three in space and one in time.

Many theorists would therefore like an escape route from today’s standard model of cosmology and it remains to be seen how far these observations discussed by the Durham group will go in this direction. But if correct, they suggest that the rumours that we are living in a “New Era of Precision Cosmology” may prove to be premature!

Original Source: RAS News Release

Posted on by Mark Mortimer

Interview with Michael Benson

Michael Benson, author of Beyond: Visions of the Interplanetary Probes (read Universe Today’s review) took some time from his busy schedule, and nasty cold, to answer some of our questions about his book and interest in astronomy and space exploration. Benson was interviewed by Mark Mortimer.

Universe Today: You say this book is the cumulation of sifting through tens of thousands of image files on computers. What was your selection criteria for the few that made it into the book?

Michael Benson: Well, to start off with, the jaw-drop factor, of course. Stuff that was incredible, I tried my best to get in. After that, though, of course you have the inevitable limitations of the book medium, with its fixed number of pages, plus then I had to divide the solar system up into chapters and try to give each one at least its due if not more, pretty soon I realized I had to winnow the available images down to not as many as I would have liked. And then there was the color versus B&W question — I wanted to get in as many good color shots as I could, though I have a real weakness for black and white photography. Essentially, though, whatever really made me gaze in amazement got in. I have to say, though, that I have a lot of really first-rate processed pictures on my hard drive that I’d love to use elsewhere sometime. Some of it has never been seen before, except for by a small cadre of planetary scientists, and then usually in black and white.

UT: As an artist did you feel like an outsider when discussing these images or did you feel like a member of the group of technicians?

MB: Neither. I always approached them as an aesthetic challenge — how to get them to “pop” — to reveal that they weren’t shot through a digitized grid but through optically pure glass, as it were. And much of the work behind getting them to the right place was technical — using photoshop or other programs — but this is also the tool of a photographer, or ‘artist’ if you will. And even when working with Dr. Paul Geissler, who is an eminent planetary scientist and remote imaging expert, I didn’t feel like an outsider — we had a good collaboration — nor like I belonged to some group of techies either. (I don’t think he feels like the latter either, come to think of it, though he recently took a job at the US Geological Survey — which makes highly accurate maps of all the planets based on space imaging! Which is about as technical as it gets.)

UT: How would you compare the artistic qualities and values of colour to black and white in this medium?

MB: I like both for different reasons. It also depends on the planetary body being represented, to an extent. Black and white pictures of Jupiter’s implacably volcanic, sulphurously yellow-orange moon Io, for example, practically don’t make any sense in a book of this type. They make perfect sense when it comes to conducting science, but would’ve been a bit hard to justify having them in my book, given that Io is by far the most lurid object in the Solar System. And by the same token Europa, Io’s closest neighboring moon, which is a spherical iceberg of fissured, chaotic ice, doesn’t really need to be in color — though it also looks awesome in color. But you get the essence of its story in black and white, if I can put it that way. (Though part of that essence is in fact its mystery — what’s going on under that global ice-cap?)

UT: Do you have a favourite/most photogenic planet? For example Venus seems to be heavily weighed in the book.

MB: Actually, Venus gets fewer pages than either Mars or Jupiter. Jupiter may be the most complex and compelling, though Saturn is a close second, because of its perfect rings. Saturn could scarcely be _more_ photogenic — we’re very lucky to have it in the solar system, because it shows what cosmic perfection really is. And as for Jupiter, as I said in my book, it’s a solar system in miniature — it’s endlessly fascinating and kinetic. The last quality is hard to show with stills, but not impossible.

UT: How were you able to convince a publisher to go for a book of images freely available on the web?

MB: Many of the images were available in raw form at specialized planetary science sites, not “freely available,” in the sense that they required substantial processing and mosacking, rendering into color or what have you. Plus even the images that are more readily available — for example, at NASA’s outreach site A Planetary Photojournal — still required substantial processing, most of them, to get them to work at the resolution quality we have available on the page, as opposed to the screen, where lower resolutions still work.

But the premise of the question is a bit flawed. Publishers are delighted if they can base a book on public domain images, because then they don’t have to pay for it!

UT: Considering the forward, do you think a living carbon based life form will explore our solar system? Other star systems? Do you think humans will do this?

MB: I do. We suffer a bit of temporal tunnel vision as a species. Even if we don’t do it for a hundred or two hundred years in the case of the solar system — and much later for the stars — I still think we’ll do it. Our current hesitation about it has to do with the sluggish pace of crewed exploration after Apollo and also the sense that the environments are so hostile that it might not be desirable to do it. But technology will march onwards and make these such things easier. And then, as soon as it is possible for tourists to actually go to, for example, Jupiter, there will be a huge rush to go there. Or Mars, of course. Or the Moon…

UT: Considering the afterward, where do you think people fit into the universal schema of things?

MB: Oh, I tend to agree with Ren — Lawrence Weschler — that for now at least we seem to be the only creatures that can experience that sense of awe that is ultimately one of the roots of our sentience. My discussion with him had to do with whether machines could ever experience this. I believe one day they will, he’s not so sure. Wasn’t it Asimov who, when asked if he really believed machines would one day think, said “well, I’m a machine, and I think”?

But in the end I think Ren’s daughter Sara is right in saying that the universe in a sense needs us, because we are capable of appreciating its beauty. Another way of putting it, I suppose, is that we are one of the ways in which the universe can appreciate its own splendor. And of course we are pieces of work ourselves, just to coin a phrase!

UT: No 3D images are in the book though we are presently getting some from Mars. What is your opinion of the artistic value of 3D images for this subject and media?

MB: Well, as someone who has barely pried my 3-D glasses of my nose for the last couple weeks, as I peer in fascination at the images from the Spirit and Opportunity rovers, I don’t know how objective I can be on the question. I really like it — though more for that “you are there” sensation than for aesthetic reasons I suppose. But there is no reason why 3-D images can’t be savored for their aesthetic qualities as well. I’ll be able to answer with more conviction on the question after this whole rover experiment is over, because there will really be many thousands of 3-D pictures to go through by then, and no doubt some of them will work on the multiple levels required to be considered art. So the jury — not that I consider myself a jury — is out on the question, but not for too long. Personally, I’d love to see a purple-orange cactus appear on the lip of a crater one of these days — though the artistic qualities of the shot will be the last thing on anyone’s mind if that happens!

Posted on by Fraser Cain

Hubble Sees Atmosphere Blowing Off a Planet

Image credit: ESA
The well-known extrasolar planet HD 209458b, provisionally nicknamed Osiris, has surprised astronomers again. Oxygen and carbon have been found in its atmosphere, evaporating at such an immense rate that the existence of a new class of extrasolar planets ? ?the chthonian planets? or ?dead? cores of completely evaporated gas giants – has been proposed.

Oxygen and carbon have been detected in the atmosphere of a planet beyond our Solar System for the first time. Scientists using the NASA/ESA Hubble Space Telescope have observed the famous extrasolar planet HD 209458b passing in front of its parent star, and found oxygen and carbon surrounding the planet in an extended ellipsoidal envelope – the shape of a rugby-ball. These atoms are swept up from the lower atmosphere with the flow of the escaping atmospheric atomic hydrogen, like dust in a supersonic whirlwind.

The team led by Alfred Vidal-Madjar (Institut d?Astrophysique de Paris, CNRS, France) reports this discovery in a forthcoming issue of Astrophysical Journal Letters.

The planet, called HD 209458b, may sound familiar. It is already an extrasolar planet with an astounding list of firsts: the first extrasolar planet discovered transiting its sun, the first with an atmosphere, the first observed to have an evaporating hydrogen atmosphere (in 2003 by the same team of scientists) and now the first to have an atmosphere containing oxygen and carbon. Furthermore the ?blow-off? effect observed by the team during their October and November 2003 observations with Hubble had never been seen before.

In honour of such a distinguished catalogue this extraordinary extrasolar planet has provisionally been dubbed ?Osiris?. Osiris is the Egyptian god who lost part of his body ? like HD 209458b – after his brother killed and cut him into pieces to prevent his return to life.

Oxygen is one of the possible indicators of life that is often looked for in experiments searching for extraterrestrial life (such as those onboard the Viking probes and the Spirit and Opportunity rovers), but according to Vidal-Madjar: ?Naturally this sounds exciting – the possibility of life on Osiris – but it is not a big surprise as oxygen is also present in the giant planets of our Solar System, like Jupiter and Saturn?.

What, on the other hand was surprising was to find the carbon and oxygen atoms surrounding the planet in an extended envelope. Although carbon and oxygen have been observed on Jupiter and Saturn, it is always in combined form as methane and water deep in the atmosphere. In HD 209458b the chemicals are broken down into the basic elements. But on Jupiter or Saturn, even as elements, they would still remain invisible low in the atmosphere. The fact that they are visible in the upper atmosphere of HD 209458b confirms that atmospheric ?blow off? is occurring.

The scorched Osiris orbits ?only? 7 million kilometres from its yellow Sun-like star and its surface is heated to about 1,000 degrees Celsius.

Whereas hydrogen is a very light element – the lightest in fact – oxygen and carbon are much heavier in comparison. This has enabled scientists to conclude that this phenomenon is more efficient than simple evaporation. The gas is essentially ripped away at a speed of more than 35,000 km/hour. ?We speculate that even heavier elements such as iron are blown off at this stage as well? says team member Alain Lecavelier des Etangs (Institut d’Astrophysique de Paris, CNRS, France).

The whole evaporation mechanism is so distinctive that there is reason to propose the existence of a new class of extrasolar planets – the chthonian planets, a reference to the Greek God Kht?n, used for Greek deities from the hot infernal underworld (also used in the French word autochton). The chthonian planets are thought to be the solid remnant cores of ?evaporated gas giants?, orbiting even closer to their parent star than Osiris. The detection of these planets should soon be within reach of current telescopes both on the ground and in space.

The discovery of the fierce evaporation process is, according to the scientists, ?highly unusual?, but may indirectly confirm theories of our own Earth?s childhood. ?This is a unique case in which such a hydrodynamic escape is directly observed. It has been speculated that Venus, Earth and Mars may have lost their entire original atmospheres during the early part of their lives. Their present atmospheres have their origins in asteroid and cometary impacts and outgassing from the planet interiors?, says Vidal-Madjar.

Original Source: ESA News Release

Posted on by Fraser Cain

James Cameron’s Plans for Mars

Image credit: James Cameron
As an artist and filmmaker, James Cameron is credited on major Hollywood productions in virtually all roles: writer, director, producer, editor, visual effects, actor, art director, and even crew. Cameron wrote and directed such science fiction classics as “Terminator 2: Judgement Day” (1991), “The Abyss” (1989), and “Aliens” (1986). He received an Academy Award for Best Director for 1997’s “Titanic,” which was also the largest grossing film in history.

Astrobiology Magazine’s Executive Producer, Helen Matsos, sat down with James Cameron and discussed his project slate. During their discussions, Cameron shared how he became interested in Mars and his unique renderings commissioned to represent the key stages in a future human mission to the red planet. As Cameron said about his directorial view: “I think that any kind of exploration should always try to acquire the highest level of imaging. That’s how you engage people — you can put them there, give them the sense that they’re standing there on the surface of Mars.”

The Design Reference Mission (DRM) covers Earth launch to Mars landing, Mars cruise to Mars launch, and Earth return. The mission entails sending cargo ahead, docking the crew at the space station, then meeting up with the cargo supplies once on Mars.

Cameron underscored the need to illustrate the details for each stage of the DRM. And whether deploying a crew or robotic explorers, the mission needed to connect more to a shared human story of discovery. A future Astrobiology Magazine feature will highlight Cameron’s reflections on making such a mission come to life, but this director’s preview offers tantalizing visual cues to what is going on robotically today on Mars.

“The [1997] Sojourner Rover became a character to millions of people, a protagonist in a story. How long is it going to survive, could it perform its mission? It wasn’t anthropomorphic in any way, there was absolutely no emotion in a little solar powered machine that was being commanded from eighty million miles away, and yet people thought of it as a character. The reason we thought of it as a character is that it represented us in a way. It was our consciousness moving that vehicle around on the surface of Mars. It’s our collective consciousness — focused down to that little machine – that put it there. So it was a celebration of who and what we are.”

“It takes our entire collective consciousness and projects it there – to that point in time and space. That’s what the Sojourner Rover did.”

“I was involved in a private company that was going to try to land two rovers on the Moon. That collapsed in the dot com crash – they ran out of money. I’m loosely involved with people who are going to be doing future robotic missions to Mars. I’m involved in terms of imaging, and of how imaging might be improved in terms of story telling. I’ve been very interested in the Humans to Mars movement –the ‘Mars Underground’ — and I’ve done a tremendous amount of personal research for a novel, a miniseries, and a 3-D film.”

“In doing this fictional story about the first humans to Mars — a subject that has been done in the movies, but never done very well, I think — people in the Hollywood community have no idea of what that means. The average person walking around has no idea of what’s involved. I called up NASA and said ‘who’s in charge of Mars?’ It turns out that NASA has (scientists studying Mars) everywhere, but there’s no one person in charge. It’s taken me years to ferret around and talk to everybody.”

In the course of designing this project, we never got past the design stage, although we will eventually. Right now it’s just, ‘what’s everything going to look like?’ What it looked like was determined by how it worked, and how it worked was determined by the mission architecture. ”

“The thing I found about human mission architectures for going to Mars is that if you change one piece or one assumption, it has a ripple effect through the whole thing, and it looks different coming out the other end. You do things differently, your spacecraft are configured differently, your surface mission looks different, the time you spend on the planet looks different. So a certain set of fundamental assumptions had to be made and then we had to design everything for what it was going to look like.”

“I wanted it to be highly realistic. Obviously I don’t think we can predict now, twenty-some years before the fact, exactly how it is going to be done, but we can make a set of very plausible assumptions. We got involved in the design of it, and predicated it on a series of assumptions, and then I went to JSC (Johnson Space Center) to talk to some of the people in the human exploration and development group. I asked, ‘Does this look like what you guys thought?’ They had created overall architectural guidelines in the DRM – the Design Reference Mission – but there were no pictures. Nobody knew what it was really going to look like.”

I said, ‘Look, this is our proposal for what a Hab would look like, and what a pressurized rover would look like, and we made certain assumptions based on how we operate deep submersibles, for example, in terms of how the manipulators would work taking samples and so on.’ And they said, ‘Hey, this is neat! Thanks! If you ever want to get out of filmmaking, come here and hang with us.’

The stages of the Cameron’s Mars Reference Design take a crew and cargo ship from a heavy-lift launch to the flat, red plains of Mars. See the slideshow version.

A Biconic Aeroshell and Fairing is used to transport payloads into space atop a heavy launch vehicle. A single cargo mission will preceed the crew to Mars. The cargo mission provides all the necessary equipment a Mars crew will require to explore the Martian surface for 500 to 600 days.

Included in this cargo are the Cargo Landing Vehicle (CLV), an In Situ Propellant Production Plant Reactor and two inflatable surface Habitats (Hab). This cargo will be placed in the Biconin Aeroshell and will Aerobraking to slow its descent into the martian atmosphere. A heavy-lift launch vehicle will deliver the Crew Transfer Vehicle (CTV) into low Earth orbit (LEO). The CTV will deploy in orbit and rendezvous with the crew at the International Space Station (ISS).

The CTV comprises several systems:an inflatable habitat called the TransHab; the Crew Lander and Rover; and the Aeroshell. The petals of the Aeroshell deploy and lock in place. After cruise, the CTV will tumble end-over-end during Trans-Mars Injection (TMI), creating a 0.38 times earth gravity environment, identical to conditions on Mars. The Crew Lander and Rover, along with their aeroshell will separate from the CTV and enter into the martian atmosphere.

Upon successful aerobraking in the Mars’ atmosphere, the Biconic aeroshell will fall away as large parachutes further assist to slow the CLV in its powered landing. The crew will use steering flaps and reaction control thrusters to guide their entry. During descent, the packed Habs are jettisoned.

The jettisoned Habs will inflate during its independent descent, providing airbag protection to the Cargo Modules housed inside. The aeroshell itself is jettisoned and large parachutes are used to slow the Crew Lander and Rover during descent.

The Crew Lander and Rover will use powerful engines to hover before landing. The Rover’s variable suspension will be capable of absorbing the shock of landing as well as increasing the Rover’s ground clearance. In addition to the Rover’s descent engines, the vehicle will serve as transport and mobile laboratory. A robotic manipulator and crane will allow the crew to interact remotely with the surface. Forward and dorsal docking tunnels simplify crew transfers to the Hab. Power will come from crygenic fuel tanks and a photovoltaic array. The vehicle’s port side includes a centrifugal blower to keep dust to a minimum.

On the surface, the crew must locate both Habs and transport them to the CLV site. The Crew Lander/Rover docks with one of the Habs via the forward hatch. The Mars Mission Base will have a modular design of components that allow for several geometric configurations and expansion.

After landing, the In Situ Propellant Production (ISPP) plant deploys nuclear reactors to power the production of water, oxygen and methane using hydrogen and carbon dioxide as raw materials.

The CLV and ISPP will provide liquid oxygen and methane (LOX/CH4) propellant to the Ascent Crew vehicle. The Ascent Crew vehicle will rendezvous with the Earth Return Vehicle in orbit around Mars.

Original Source: Astrobiology Magazine

Posted on by Fraser Cain

Opportunity Rolls Off the Lander

Image credit: NASA/JPL
NASA’s Mars Exploration Rover Opportunity drove down a reinforced fabric ramp at the front of its lander platform and onto the soil of Mars’ Meridiani Planum this morning.

Also, new science results from the rover indicate that the site does indeed have a type of mineral, crystalline hematite, that was the principal reason the site was selected for exploration.

Controllers at NASA’s Jet Propulsion Laboratory received confirmation of the successful drive at 3:01 a.m. Pacific Standard Time via a relay from the Mars Odyssey orbiter and Earth reception by the Deep Space Network. Cheers erupted a minute later when Opportunity sent a picture looking back at the now-empty lander and showing wheel tracks in the martian soil.

For the first time in history, two mobile robots are exploring the surface of another planet at the same time. Opportunity’s twin, Spirit, started making wheel tracks halfway around Mars from Meridiani on Jan. 15.

“We’re two for two! One dozen wheels on the soil.” JPL’s Chris Lewicki, flight director, announced to the control room.

Matt Wallace, mission manager at JPL, told a subsequent news briefing, “We knew it was going to be a good day. The rover woke up fit and healthy to Bruce Springsteen’s ‘Born to Run,’ and it turned out to be a good choice.”

The flight team needed only seven days since Opportunity’s landing to get the rover off its lander, compared with 12 days for Spirit earlier this month. “We’re getting practice at it,” said JPL?s Joel Krajewski, activity lead for the procedure. Also, the configuration of the deflated airbags and lander presented no trouble for Opportunity, while some of the extra time needed for Spirit was due to airbags at the front of the lander presenting a potential obstacle.

Looking at a photo from Opportunity showing wheel tracks between the empty lander and the rear of the rover about one meter or three feet away, JPL’s Kevin Burke, lead mechanical engineer for getting the rover off the lander, said “We’re glad to be seeing soil behind our rover.”

JPL’s Chris Salvo, flight director, reported that Opportunity will be preparing over the next couple days to reach out with it robotic arm for a close inspection of the soil.

Gray granules covering most of the crater floor surrounding Opportunity contain hematite, said Dr. Phil Christensen, lead scientist for both rovers’ miniature thermal emission spectrometers, which are infrared-sensing instruments used for identifying rock types from a distance. Crystalline hematite is of special interest because, on Earth, it usually forms under wet environmental conditions. The main task for both Mars Exploration Rovers in coming weeks and months is to read clues in the rocks and soil to learn about past environmental conditions at their landing sites, particularly about whether the areas were ever watery and possibly suitable for sustaining life.

The concentration of hematite appears strongest in a layer of dark material above a light-covered outcrop in the wall of the crater where Opportunity sits, Christensen said. “As we get out of the bowl we’re in, I think we’ll get onto a surface that is rich in hematite,” he said.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Stars Can Survive Being Engulfed

Image credit: Chandra
The V471 Tauri system comprises a white dwarf star (the primary) in a close orbit – one thirtieth of the distance between Mercury and the Sun – with a normal Sun-like star (the secondary). The white dwarf star was once a star several times as massive as the Sun. Chandra data on this system provide the best evidence yet that a star can be engulfed by its companion star and survive.

The illustration shows X-ray spectra made by Chandra’s Low Energy Transmission Grating Spectrometer of two individual stars and V471 Tauri: a red giant star (Beta Ceti, top panel), V471 Tauri, and a Sun-like star (Epsilon Eridani). The peak in the spectrum due to carbon ions is much smaller in the giant star than in the Sun-like star, whereas the carbon peak in V471 is intermediate between the two. These differences provide important clues to the different evolutionary histories of the stars.

Nuclear fusion reactions in the core of such a star convert carbon into nitrogen over a period of about a billion years. When the fuel in the core of the star is exhausted, the core collapses, triggering more energetic nuclear reactions that cause the star to expand and transform into a red giant before eventually collapsing to become a white dwarf.

The carbon-poor material in the core of the red giant is mixed with outer part of the star, so its atmosphere will have a deficit of carbon, as compared with Sun-like stars, as shown in the figure. If a red giant is part of binary system of closely orbiting stars, the evolution of the secondary star can be dramatically affected.

Theoretical calculations indicate that the red giant can completely envelop its companion star. During this common envelope phase, friction causes the companion star to spiral inward rapidly where it will either be destroyed by the red giant, or it will survive when much of the envelope is spun away.

If the companion star manages to survive, it will bear the marks of its ordeal in the form of contamination by carbon-poor material that it accreted while it was inside the red giant envelope. The X-ray spectrum of V471 Tauri in the middle panel shows just this effect – the carbon peak is intermediate between that of a Sun-like star and an isolated red giant star. The data indicate that about 10 percent of the star’s mass has been accreted from the red giant.

In the future the companion star can return the favor. It will expand and dump material back onto the white dwarf. If enough material is dumped on the white dwarf, it could cause the white dwarf to explode as a supernova.

Original Source: Chandra News Release

Posted on by Fraser Cain

NASA is Getting More Opinions on Hubble

After receiving complaints, NASA Administrator Sean O’Keefe has said he’s looking for a second opinion on what to do about the Hubble Space Telescope. NASA had recently announced that it would cancel the next servicing mission for the aging telescope, which will likely fail by 2007. O’Keefe is looking to retired Admiral Harold Gehman, who chaired the independent Columbia Accident Investigation Board. Gehman has yet to say if he’ll take up the task of investigating the case for Hubble.

Posted on by Fraser Cain

Spirit is On the Mend

Image credit: NASA/JPL
NASA’s Spirit rover on Mars has resumed taking pictures as engineers continue work on restoring its health. Meanwhile, Spirit’s twin, Opportunity, extended its rear wheels backward to driving position last night as part of preparations to roll off its lander, possibly as early as overnight Saturday-to-Sunday.

Spirit shot and transmitted a picture yesterday to show the position of its robotic arm. “The arm is exactly where we expected,” said Jennifer Trosper, mission manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. It is still extended in the same position as when the rover developed communication and computer problems on Jan. 22. A mineral-identifying instrument called a Moessbauer spectrometer, at the tip of the arm, is positioned at a rock nicknamed Adirondack.

Engineers have been carefully nursing Spirit back toward full operations for the past week. They are sending commands today for the rover to begin making new scientific observations again, starting with panoramic camera images of nearby rocks. Today’s commands also tell the rover to send data stored by two instruments since they took readings on Adirondack last week — the Moessbauer spectrometer and the alpha particle X-ray spectrometer, which identifies the chemical elements in a target.

“We know we still have some engineering work to do, but we think we understand the problem well enough to do science in parallel with that work,” Trosper said. Several attempts to get a full trace of data related to the rover’s problem have only partially succeeded. The engineers might choose to reformat the rover’s flash memory in the next few days.

A health check of Spirit’s camera mast is on the agenda for today. Another health check, of an actuator motor for a periscope mirror of the miniature thermal emission spectrometer, is planned for Friday.

Halfway around Mars from Spirit, Opportunity’s lander platform successfully tilted itself forward by pulling airbag material under the rear portion of the lander then flexing its rear petal downward. “What this did is drive our front edge lower,” said JPL’s Matt Wallace, mission manager. “The tips of the egress aid (a reinforced fabric ramp) are now in the soil. That makes egress look perfect. It’s going to be an easy ride.” The rover also retracted a lift mechanism underneath the rover, to get it out of the way for the egress, or drive-off.

During Opportunity’s sol 6, the martian day that started today at 10:26 a.m. PST, the rover will be commanded to lower the middle pair of its six wheels and to release its robotic arm from the latch that has held it since before launch.

Yesterday, Opportunity used its minature thermal emission spectrometer on a portion of the landing neighborhood that includes a rock outcrop. The instrument identifies the composition of rocks and soils from a distance. Opportunity did not return the data from those observations before going to sleep for the martian night, but may later today.

The rovers’ main task in coming weeks and months is to explore their landing sites for evidence in the rocks and soil about whether the sites’ past environments were ever watery and possibly suitable for sustaining life.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA’s Office of Space Science, Washington, D.C. Images and additional information about the project are available from JPL at http://marsrovers.jpl.nasa.gov and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu.

Original Source: NASA/JPL News Release

Posted on by Mark Mortimer

Book Review: Beyond: Visions of the Interplanetary Probes

People usually associate squads of bespectacled engineers and scientists as being the sole guardians of space. Beyond: Visions of the Interplanetary Probes by Michael Benson is the type of book that rationalizes and moreover encourages the inclusion of other specialists, especially those in the arts. Containing 295 photographs chosen both for their artistic, awe inspiring impact as well as their voluminous scientific content, the reader will want to quickly put aside numerical calculations about orbital mechanics and let their eyes float across the vistas of other planets. It is easy to imagine that only a thin visor of a helmet separates them from the visions in the book. Michael Benson’s collection of breathtakingly clear images gives credit to the machines that took the pictures and the will of all the bespectacled and clear sighted individuals who worked so hard to get the machines to their complete their mission.

This book is all about its photographs. These come as both true colour and black and white. They range from compact portraits to large expanses. In keeping true to the sources, collages of contiguous single frames give fantastic perspectives including a 110cm x 26cm full colour image of a dust cloud as it storms across a broad swathe of the Martian surface. Each image is silhouetted against a matte black background that enhances the reader’s feeling of ‘being there’. My personal favourites are views of satellites with their host planet behind them and the satellite’s shadow etched on the host’s surface. The details evident in black and white shots of crater rims softened by dunes are better than most tour guides of earthly locales. These photographs are like beauty contest entrants each vying to allure the judge to vote for them.

The photographs are grouped into chapters or collections for each planet, except Pluto, for which no clear images exist. Chapters are introduced with a brief passage discussing the imaging history, the relevant probes and some of the provocative visual features. Often a planet’s chapter includes its satellites though there is a separate chapter for Earth’s moon as well as a chapter for asteroids within the Asteroid Belt. Either adjoining or nearby each photograph is a caption identifying the probe that acquired the image, the date this occurred and a description. As a bonus, there are black and white block drawings of the probes themselves. Leading this beauty contest is a provocative essay where Arthur C. Clarke muses about future explorers. After showing off all the contestants, Benson delivers a short essay on the selection process and the image processing. The book concludes in an afterward by Lawrence Weschler where he contemplates the relative importance of humankind in the context of so much other-world beauty.

I liked the black background and paper type of the book though black, as is its nature, shows up printing artifacts (not many) and fingerprints (becoming more frequent). In addition, sometimes description on the captions do not identify the significance of a picture. Perhaps this may be because there are no features to remark on and only the emotive force caused a picture to be selected.

The clarity of the photographs is so great that I can easily forget myself and try to touch the textures and shapes to gain a tactile sense. It seems I need more than one sense to fully absorb the grandiose scale of the subjects themselves and the specialised effort that made them come into being. I have been perhaps a little bit too guilty of self importance, but after viewing this book my self estimation of where I stand in the scale of things has changed, for the better.

Learn more about the book from Amazon.com

Review by Mark Mortimer

Posted on by Fraser Cain

O’Keefe Grilled About Space Initiative

NASA Administrator Sean O’Keefe faced some tough questions from US senators on Wednesday as they attempted to learn how the agency would actually pay for the ambitious plan presented by President Bush a few weeks ago. Senator Bill Nelson was concerned that Bush didn’t mention the space initiative in his State of the Union announcement just six days later, “if we don’t put the full weight of the president behind it, I’m afraid it’s going to fizzle.”