Jupiter Pummeled, Leaving Bruise The Size Of Pacific Ocean

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ScienceDaily (July 21, 2009) — Scientists have found evidence that another object has bombarded Jupiter, exactly 15 years after the first impacts by the comet Shoemaker-Levy 9.

Following up on a tip by an amateur astronomer, Anthony Wesley of Australia, that a new dark "scar" had suddenly appeared on Jupiter, this morning between 3 and 9 a.m. PDT (6 a.m. and noon EDT) scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif., using NASA's Infrared Telescope Facility at the summit of Mauna Kea, Hawaii, gathered evidence indicating an impact.
New infrared images show the likely impact point was near the south polar region, with a visibly dark "scar" and bright upwelling particles in the upper atmosphere detected in near-infrared wavelengths, and a warming of the upper troposphere with possible extra emission from ammonia gas detected at mid-infrared wavelengths.
"We were extremely lucky to be seeing Jupiter at exactly the right time, the right hour, the right side of Jupiter to witness the event. We couldn't have planned it better," said Glenn Orton, a scientist at JPL.
Orton and his team of astronomers kicked into gear early in the morning and haven't stopped tracking the planet. They are downloading data now and are working to get additional observing time on this and other telescopes.
This image was taken at 1.65 microns, a wavelength sensitive to sunlight reflected from high in Jupiter's atmosphere, and it shows both the bright center of the scar (bottom left) and the debris to its northwest (upper left).
"It could be the impact of a comet, but we don't know for sure yet," said Orton. "It's been a whirlwind of a day, and this on the anniversary of the Shoemaker-Levy 9 and Apollo anniversaries is amazing."
Shoemaker-Levy 9 was a comet that had been seen to break into many pieces before the pieces hit Jupiter in 1994.
Leigh Fletcher, a NASA postdoctoral fellow at JPL who worked with Orton during these latest observations said, "Given the rarity of these events, it's extremely exciting to be involved in these observations. These are the most exciting observations I've seen in my five years of observing the outer planets!"
The observations were made possible in large measure by the extraordinary efforts of the Infrared Telescope Facility staff, including telescope operator William Golisch, who adroitly moved three instruments in and out of the field during the short time the scar was visible on the planet, providing the wide wavelength coverage.
JPL is managed for NASA by the California Institute of Technology in Pasadena.
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Eagle Nebula: An Eagle Of Cosmic Proportions

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ScienceDaily (July 17, 2009) — Located 7000 light-years away, towards the constellation of Serpens (the Snake), the Eagle Nebula is a dazzling stellar nursery, a region of gas and dust where young stars are currently being formed and where a cluster of massive, hot stars, NGC 6611, has just been born.

The powerful light and strong winds from these massive new arrivals are shaping light-year long pillars, seen in the image partly silhouetted against the bright background of the nebula. The nebula itself has a shape vaguely reminiscent of an eagle, with the central pillars being the “talons”.
The star cluster was discovered by the Swiss astronomer, Jean Philippe Loys de Chéseaux, in 1745–46. It was independently rediscovered about twenty years later by the French comet hunter, Charles Messier, who included it as number 16 in his famous catalogue, and remarked that the stars were surrounded by a faint glow. The Eagle Nebula achieved iconic status in 1995, when its central pillars were depicted in a famous image obtained with the NASA/ESA Hubble Space Telescope. In 2001, ESO’s Very Large Telescope (VLT) captured another breathtaking image of the nebula (ESO Press Photo 37/01), in the near-infrared, giving astronomers a penetrating view through the obscuring dust, and clearly showing stars being formed in the pillars.
The newly released image, obtained with the Wide-Field Imager camera attached to the MPG/ESO 2.2-metre telescope at La Silla, Chile, covers an area on the sky as large as the full Moon, and is about 15 times more extensive than the previous VLT image, and more than 200 times more extensive than the iconic Hubble visible-light image. The whole region around the pillars can now be seen in exquisite detail.
The “Pillars of Creation” are in the middle of the image, with the cluster of young stars, NGC 6611, lying above and to the right. The “Spire” — another pillar captured by Hubble — is at the centre left of the image.
Finger-like features protrude from the vast cloud wall of cold gas and dust, not unlike stalagmites rising from the floor of a cave. Inside the pillars, the gas is dense enough to collapse under its own weight, forming young stars. These light-year long columns of gas and dust are being simultaneously sculpted, illuminated and destroyed by the intense ultraviolet light from massive stars in NGC 6611, the adjacent young stellar cluster. Within a few million years — a mere blink of the universal eye — they will be gone forever.
Adapted from materials provided by European Southern Observatory - ESO.

Primitive Asteroids In The Main Asteroid Belt May Have Formed Far From The Sun

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ScienceDaily (July 15, 2009) — Many of the objects found today in the asteroid belt located between the orbits of Mars and Jupiter may have formed in the outermost reaches of the solar system, according to an international team of astronomers led by scientists from Southwest Research Institute (SwRI).

The team used numerical simulations to show that some comet-like objects residing in a disk outside the original orbit of the planets were scattered across the solar system and into the outer asteroid belt during a violent phase of planetary evolution.
Usually, the solar system is considered a place of relative permanence, with changes occurring gradually over hundreds of millions to billions of years. New models of planet formation indicate, however, that at specific times, the architecture of the solar system experienced dramatic upheaval.
In particular, it now seems probable that approximately 3.9 billion years ago, the giant planets of our solar system -- Jupiter, Saturn, Uranus and Neptune -- rearranged themselves in a tumultuous spasm. "This last major event of planet formation appears to have affected nearly every nook and cranny of the solar system," says lead author Dr. Hal Levison of SwRI.
Key evidence for this event was first identified in the samples returned from the Moon by the Apollo astronauts. They tell us about an ancient cataclysmic bombardment where large asteroids and comets rained down on the Moon.
Scientists now recognize that this event was not limited solely to the Moon; it also affected the Earth and many other solar system bodies. "The existence of life on Earth, as well as the conditions that made our world habitable for us, are strongly linked to what happened at this distant time," states Dr. David Nesvorny of SwRI.
The same dynamical conditions that devastated the planets also led to the capture of some would-be impactors in the asteroid belt. "In the classic movie 'Casablanca,' everybody comes to Rick's. Apparently throughout the solar system, the cool hangout for small objects is the asteroid belt," says Dr. William Bottke of SwRI.
Once in the asteroid belt, the embedded comet-like objects began to beat up both themselves and the asteroids. "Our model shows that comets are relatively easy to break up when hit by something, at least when compared to typical asteroids. It is unavoidable that some of the debris went on to land on asteroids, the Moon and the Earth. In fact, some of the leftovers may still be arriving today," says Dr. Alessandro Morbidelli of the Observatoire de la Cote d'Azur in Nice, France.
The team believes the surprising similarities between some micrometeorites landing on Earth and comet samples returned by NASA's Stardust mission are no accident. "There has been lots of debate about the nature of micrometeorites reaching the Earth," says Dr. Matthieu Gounelle of the Museum National d'Histoire Naturelle in Paris. "Some believe they are asteroidal, while others argue they are cometary. Our work suggests that in a sense, both camps may be right."
"Some of the meteorites that once resided in the asteroid belt show signs they were hit by 3.5 to 3.9 billion years ago. Our model allows us to make the case they were hit by captured comets or perhaps their fragments," adds Dr. Kleomenis Tsiganis of Aristotle University of Thessaloniki, Greece. "If so, they are telling us the same intriguing story as the lunar samples, namely that the solar system apparently went berserk and reconfigured itself about 4 billion years ago."
Overall, the main asteroid belt contains a surprising diversity of objects ranging from primitive ice/rock mixtures to igneous rocks. The standard model used to explain this assumes that most asteroids formed in place from a primordial disk that experienced radical chemical changes within this zone. This model shows, however, that the observed diversity of the asteroid belt is not a direct reflection of the intrinsic compositional variation of the proto-planetary disk. These results fundamentally change our view of the asteroid belt.
Additional tests of this model will come from studies of meteorites, the asteroid belt, planet formation and the Moon. "The Moon and the asteroid belt may be the best and most accessible places in the solar system to understand this critical part of solar system history," says Levison. "We believe key evidence from these cold airless bodies may help us unlock the biggest 'cold case' of all time."
Funding for this research was provided by NASA's Outer Planets Research and Origins of Solar Systems programs. Additional support was provided by NASA's Lunar Science Institute.
Journal reference:
Levison et al. Contamination of the asteroid belt by primordial trans-Neptunian objects. Nature, 2009; 460 (7253): 364 DOI: 10.1038/nature08094
Adapted from materials provided by Southwest Research Institute, via EurekAlert!, a service of AAAS.

How Saturn's Moon Got Its Stripes

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ScienceDaily (July 15, 2009) — A new study has revealed the origins of tiger stripes and a subsurface ocean on Enceladus- one of Saturn’s many moons. These geological features are believed to be the result of the moon’s unusual chemical composition and not a hot core, shedding light on the evolution of planets and guiding future space exploration.

Dr Dave Stegman, a Centenary Research Fellow in the School of Earth Sciences at the University of Melbourne, led the study and says that part of the intrigue with Enceladus is that it was once presumed to be a lifeless, frozen ice ball until a water vapour plume was seen erupting from its surface in 2006.
“NASA’s Cassini spacecraft recently revealed Enceladus as a dynamic place, recording geological features such as geysers emerging from the ‘tiger stripes’ which are thought to be cracks caused by tectonic activity on the south pole of the moon’s surface,” says Dr Stegman.
The moon is also one of the brightest objects in our solar system because the ice covering its surface reflects almost 100 percent of the sunlight that strikes it. One of Saturn’s 53 moons (so far identified) Enceladus reflects so much of the sun’s energy that its surface temperature is about -201° C (-330° F).
Grappling with how an inaccessible small moon with a completely frozen interior was capable of displaying geological activity, Dr Stegman and colleagues used computer simulations to virtually explore it.
Ammonia, usually found on Earth as an odorous gas used to make fertilizers, has been indirectly observed to be present in Enceladus and formed the basis of the study which is the first to reveal the origins of the subsurface ocean.
The model reveals that Enceladus initially had a frozen shell composed of a mixture of ammonia and water ice surrounding a rocky core. Over time, as Enceladus interacted with other moons, a small amount of heat was generated above the silicate core which made the ice shell separate into chemically distinct layers. An ammonia-enriched liquid layer formed on top of the core while a thin layer of pure water ice formed above that. The work will be published in the August issue of the planetary science journal, Icarus.
“We found that if a layer of pure water ice formed near the core, it would have enough buoyancy to rise upwards, and such a redistribution of mass can generate large tectonic stresses at the surface,” says Dr Stegman. “However, the pure water ice rising up is also slightly warmer which causes the separation to occur again, this time forming an ammonia-enriched ocean just under the surface. The presence of ammonia, which acts as an anti-freeze, then helps keep the ocean in its liquid state.”
“These simulations are an important step in understanding how planets evolve and provide questions to focus future space exploration and observations. It will hopefully progress our understanding of how and why planets and moons are different to each other.”
Adapted from materials provided by University of Melbourne.

New Map Hints At Venus's Wet, Volcanic Past

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ScienceDaily (July 14, 2009) — Venus Express has charted the first map of Venus's southern hemisphere at infrared wavelengths. The new map hints that our neighbouring world may once have been more Earth-like, with both, a plate tectonics system and an ocean of water.

The map comprises over a thousand individual images, recorded between May 2006 and December 2007. Because Venus is covered in clouds, normal cameras cannot see the surface, but Venus Express used a particular infrared wavelength that can see through them.
Although radar systems have been used in the past to provide high-resolution maps of Venus's surface, Venus Express is the first orbiting spacecraft to produce a map that hints at the chemical composition of the rocks. The new data is consistent with suspicions that the highland plateaus of Venus are ancient continents, once surrounded by ocean and produced by past volcanic activity.
"This is not proof, but it is consistent. All we can really say at the moment is that the plateau rocks look different from elsewhere," says Nils Müller at the Joint Planetary Interior Physics Research Group of the University Münster and DLR Berlin, who headed the mapping efforts.
The rocks look different because of the amount of infrared light they radiate into space, similar to the way a brick wall heats up during the day and gives off its heat at night. Besides, different surfaces radiate different amounts of heat at infrared wavelengths due to a material characteristic known as emissivity, which varies in different materials. The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument captured this infrared radiation during Venus's night-time orbits around the planet's southern hemisphere.
The eight Russian landers of the 1970s and 1980s touched down away from the highlands and found only basalt-like rock beneath their landing pads. The new map shows that the rocks on the Phoebe and Alpha Regio plateaus are lighter in colour and look old compared to the majority of the planet. On Earth, such light-coloured rocks are usually granite and form continents.
Granite is formed when ancient rocks, made of basalt, are driven down into the planet by shifting continents, a process known as plate tectonics. The water combines with the basalt to form granite and the mixture is reborn through volcanic eruptions.
"If there is granite on Venus, there must have been an ocean and plate tectonics in the past," says Müller.
Müller points out that the only way to know for sure whether the highland plateaus are continents is to send a lander there. Over time, Venus's water has been lost to space, but there might still be volcanic activity. The infrared observations are very sensitive to temperature. But in all images they saw only variations of between 3-20°C, instead of the kind of temperature difference they would expect from active lava flows.
Although Venus Express did not see any evidence of ongoing volcanic activity this time this time around, Müller does not rule it out. "Venus is a big planet, being heated by radioactive elements in its interior. It should have as much volcanic activity as Earth," he says. Indeed, some areas do appear to be composed of darker rock, which hints at relatively recent volcanic flows.
The new map gives astronomers another tool in their quest to understand why Venus is so similar in size to Earth and yet has evolved so differently.
Adapted from materials provided by European Space Agency.

Turbulence Responsible For Black Holes' Balancing Act

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ScienceDaily (July 14, 2009) — We live in a hierarchical Universe where small structures join into larger ones. Earth is a planet in our Solar System, the Solar System resides in the Milky Way Galaxy, and galaxies combine into groups and clusters. Clusters are the largest structures in the Universe, but sadly our knowledge of them is not proportional to their size.

Researchers have long known that the gas in the centers of some galaxy clusters is rapidly cooling and condensing, but were puzzled why this condensed gas did not form into stars. Until recently, no model existed that successfully explained how this was possible.
Evan Scannapieco, a theoretical astrophysicist, has spent much of his career studying the evolution of galaxies and clusters. "There are two types of clusters: cool-core clusters and non-cool core clusters," he explains. "Non-cool core clusters haven't been around long enough to cool, whereas cool-core clusters are rapidly cooling, although by our standards they are still very hot."
Scannapieco is an assistant professor in Arizona State University's School of Earth and Space Exploration in the College of Liberal Arts and Sciences.
X-ray telescopes have revolutionized our understanding of the activity occurring within cool-core clusters. Although these clusters can contain hundreds or even thousands of galaxies, they are mostly made up of a diffuse, but very hot gas known as the intracluster medium. This intergalactic gas is only visible to X-ray telescopes, which are able to map out its temperature and structure. These observations show that the diffuse gas is rapidly cooling into the centers of cool-core clusters.
At the core of each of these clusters is a black hole, billions of times more massive than the Sun. Some of the cooling medium makes its way down to a dense disk surrounding this black hole, some of it goes into the black hole itself, and some of it is shot outward. X-ray images clearly show jet-like bursts of ejected material, which occur in regular cycles.
But why were these outbursts so regular, and why did the cooling gas never drop to colder temperatures that lead to the formation of stars? Some unknown mechanism was creating an impressive balancing act.
"It looked like the jets coming from black holes were somehow responsible for stopping the cooling," says Scannapieco, "but until now no one was able to determine exactly how."
Scannapieco and Marcus Brüggen, a professor at Jacobs University in Bremen, Germany, used the powerful supercomputers at ASU to develop their own three-dimensional simulation of the galaxy cluster surrounding one of the Universe's biggest black holes. By adapting an approach developed by Guy Dimonte at Los Alamos National Laboratory and Robert Tipton at Lawrence Livermore National Laboratory, Scannapieco and Brüggen added the component of turbulence to the simulations, which was never accounted for in the past.
That was the key ingredient.
Turbulence works in partnership with the black hole to maintain the balance. Without the turbulence, the jets coming from around black hole would grow stronger and stronger, and the gas would cool catastrophically into a swarm of new stars. When turbulence is accounted for, the black hole not only balances the cooling, but goes through regular cycles of activity.
"When you have turbulent flow, you have random motions on all scales," explains Brüggen. "Each jet of material ejected from the disk creates turbulence that mixes everything together."
Scannapieco and Brüggen's results, to be published in the journal Monthly Notices of the Royal Astronomical Society, reveal that turbulence acts to effectively mix the heated region with its surroundings so that the cool gas can't make it down to the black hole, thus preventing star formation.
Every time some cool gas reaches the black hole, it is shot out in a jet. This generates turbulence that mixes the hot gas with the cold gas. This mixture becomes so hot that it doesn't accrete onto the black hole. The jet stops and there is nothing to drive the turbulence so it fades away. At that point, the hot gas no longer mixes with the cold gas, so the center of the cluster cools, and more gas makes its way down to the black hole.
Before long, another jet forms and the gas is once again mixed together.
"We improved our simulations so that they could capture those tiny turbulent motions," explains Scannapieco. "Even though we can't see them, we can estimate what they would do. The time it takes for the turbulence to decay away is exactly the same amount of time observed between the outbursts."
Adapted from materials provided by Arizona State University, via EurekAlert!, a service of AAAS.

Herschel has carried out the first test observations with all its instruments, with spectacular results.

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ScienceDaily (July 13, 2009) — Herschel has carried out the first test observations with all its instruments, with spectacular results. Galaxies, star-forming regions and dying stars comprised the telescope’s first targets. The instruments provided spectacular data at their first attempt, finding water, carbon and revealing dozens of distant galaxies.

These observations show that Herschel’s instruments are working beyond expectations. They promise a mission of rich discoveries for waiting astronomers.
SPIRE surprises with power
On 24 June, Herschel’s Spectral and Photometric Imaging Receiver (SPIRE) was trained on two galaxies for its first look at the Universe. The galaxies showed up prominently, providing astronomers with their best images yet at these wavelengths, and revealing other more distant galaxies in the background of the images.
The pictures show galaxies M66 and M74 at a wavelength of 250 microns, longer than any previous infrared space observatory, but still the shortest SPIRE wavelength.
SPIRE is designed to look at star formation in our own Galaxy and in nearby galaxies. It will also search for star-forming galaxies in the very distant Universe. Because these galaxies are so far away, their light has taken a very long time to reach us, so by detecting them we are looking into the past and learning how and when galaxies like our own were formed.
Herschel’s primary mirror is 3.5 m in diameter, nearly four times larger than any previous infrared space telescope. These images prove that it represents a giant leap forward in our ability to study celestial objects at far infrared wavelengths.
Spitzer primarily observes shorter infrared wavelengths than Herschel, so the two telescopes complement each other.
These observations were all made on the first day that SPIRE was used. They clearly show that the main scientific studies planned with the instrument are going to work extremely well.
Water-hunter HIFI scores at first try
Scientists used Herschel’s Heterodyne Instrument for the Far-Infrared (HIFI) on 22 June to look for warm molecular gas heated by newborn massive stars in the DR21 star-forming region in Cygnus.
HIFI provided excellent data in two different observing modes, returning information on the composition of the region with unprecedented accuracy and resolution. It works by ‘zooming in’ on specific wavelengths, revealing different spectral ‘lines’ that represent the fingerprints of atoms and molecules and even the physical conditions of the object observed. This makes it a powerful tool to study the role of gas and dust in the formation of stars and planets and the evolution of galaxies.
Using HIFI, scientists observed ionised carbon, carbon monoxide, and water in DR21. These different molecular lines add their pieces to a more complete understanding of what is happening.
The high quality of these first observations promises great new insights into the process of star formation.
PACS stares into the Cat’s Eye
The first observation with the Photodetector Array Camera and Spectrometer (PACS) instrument was carried out on 23 June.
The first target was the dying star known as the Cat's Eye Nebula. Discovered by William Herschel in 1786, this nebula consists of a complex shell of gas thrown off by a dying star. Dying stars create spectacular nebulae, enriching the interstellar medium with heavy chemical elements. But how does an initially spherical star produce such a complex nebula? To solve this question we need to look at the processes close to the star, where the matter is ejected.
With the PACS spectrometer it is now possible for the first time to make images in spectral lines for on the sky, and see how the wind from the star shapes the nebula in three dimensions. The PACS spectrometer was used to look into the Cat’s eye. This mode records the composition and condition of celestial objects at precisely defined wavelengths.
PACS observed the nebula in two spectral lines from ionised nitrogen and oxygen. For better orientation, the PACS photometer took a small map of the Cat’s Eye Nebula in its 70 micron band, showing the structure of a dust ring with an opening on one side.
Following these first light images, Herschel is now in the performance verification phase, where the instruments will be further tested and calibrated. This phase will last until the end of November, after which the mission will begin its routine science phase. These images show that there is a lot of science to look forward to.
Adapted from materials provided by European Space Agency.

Antimatter Positrons Explain Gamma Ray Mystery In Milky Way Galaxy

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ScienceDaily (July 8, 2009) — A team of astrophysicists has solved a mystery that led some scientists to speculate that the distribution of certain gamma rays in our Milky Way galaxy was evidence of a form of undetectable “dark matter” believed to make up much of the mass of the universe.

In two separate scientific papers, the most recent of which appears in the July 10 issue of the journal Physical Review Letters, the astrophysicists show that this distribution of gamma rays can be explained by the way “antimatter positrons” from the radioactive decay of elements, created by massive star explosions in the galaxy, propagate through the galaxy. Thus, the scientists said, the observed distribution of gamma rays is not evidence for dark matter.
“There is no great mystery,” said Richard Lingenfelter, a research scientist at UC San Diego’s Center for Astrophysics and Space Sciences who conducted the studies with Richard Rothschild, a research scientist also at UCSD, and James Higdon, a physics professor at the Claremont Colleges. “The observed distribution of gamma rays is in fact quite consistent with the standard picture.”
Over the past five years, gamma ray measurements from the European satellite INTEGRAL have perplexed astronomers, leading some to argue that a “great mystery” existed because the distribution of these gamma rays across different parts of the Milky Way galaxy was not as expected.
To explain the source of this mystery, some astronomers had hypothesized the existence of various forms of dark matter, which astronomers suspect exists—from the unusual gravitational effects on visible matter such as stars and galaxies—but have not yet found.
What is known for certain is that our galaxy—and others—are filled with tiny subatomic particles known as positrons, the antimatter counterpart of typical, everyday electrons. When an electron and positron encounter each other in space, the two particles annihilate and their energy is released as gamma rays. That is, the electron and positron disappear and two or three gamma rays appear.
”These positrons are born at nearly the speed of light, and travel thousands of light years before they slow down enough in dense clouds of gas to have a chance of joining with an electron to annihilate in a dance of death,” explains Higdon. “Their slowing down occurs from the drag of other particles during their journey through space. Their journey is also impeded by the many fluctuations in the galactic magnetic field that scatter them back and forth as they move along. All of this must be taken into account in calculating the average distance the positrons would travel from their birthplaces in supernova explosions.”
”Some positrons head towards the center of the Galaxy, some towards the outer reaches of the Milky Way known as the galactic halo, and some are caught in the spiral arms,” said Rothschild. “While calculating this in detail is still far beyond the fastest supercomputers, we were able to use what we know about how electrons travel throughout the solar system and what can be inferred about their travel elsewhere to estimate how their anti-matter counterparts permeate the galaxy.”
The scientists calculated that most of the gamma rays should be concentrated in the inner regions of the galaxy, just as was observed by the satellite data, the team reported in a paper published last month in the Astrophysical Journal.
“The observed distribution of gamma rays is consistent with the standard picture where the source of positrons is the radioactive decay of isotopes of nickel, titanium and aluminum produced in supernova explosions of stars more massive than the Sun,” said Rothschild.
In their companion paper in this week’s issue of Physical Review Letters, the scientists point out that a basic assumption of one of the more exotic explanations for the purported mystery—dark matter decays or annihilations—is flawed, because it assumes that the positrons annihilate very close to the exploding stars from which they originated.
“We clearly demonstrated this was not the case, and that the distribution of the gamma rays observed by the gamma ray satellite was not a detection or indication of a ‘dark matter signal’,” said Lingenfelter.
The scientists were supported in their studies by grants from the National Aeronautics and Space Administration.
Adapted from materials provided by University of California/San Diego.

Dozens Of Newly Discovered Pulsars Probed By NASA's Fermi Gamma-ray Space Telescope

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ScienceDaily (July 7, 2009) — With NASA's Fermi Gamma-ray Space Telescope, astronomers now are getting their best look at those whirling stellar cinders known as pulsars. In two studies published in the July 2 edition of Science Express, international teams have analyzed gamma-rays from two dozen pulsars, including 16 discovered by Fermi. Fermi is the first spacecraft able to identify pulsars by their gamma-ray emission alone.

A pulsar is the rapidly spinning and highly magnetized core left behind when a massive star explodes. Most of the 1,800 cataloged pulsars were found through their periodic radio emissions. Astronomers believe these pulses are caused by narrow, lighthouse-like radio beams emanating from the pulsar's magnetic poles.
"Fermi has truly unprecedented power for discovering and studying gamma-ray pulsars," said Paul Ray of the Naval Research Laboratory in Washington. "Since the demise of the Compton Gamma Ray Observatory a decade ago, we've wondered about the nature of unidentified gamma-ray sources it detected in our galaxy. These studies from Fermi lift the veil on many of them."
The Vela pulsar, which spins 11 times a second, is the brightest persistent source of gamma rays in the sky. Yet gamma rays -- the most energetic form of light -- are few and far between. Even Fermi's Large Area Telescope sees only about one gamma-ray photon from Vela every two minutes.
"That's about one photon for every thousand Vela rotations," said Marcus Ziegler, a member of the team reporting on the new pulsars at the University of California, Santa Cruz. "From the faintest pulsar we studied, we see only two gamma-ray photons a day."
Radio telescopes on Earth can detect a pulsar easily only if one of the narrow radio beams happens to swing our way. If not, the pulsar can remain hidden.
A pulsar's radio beams represent only a few parts per million of its total power, whereas its gamma rays account for 10 percent or more. Somehow, pulsars are able to accelerate particles to speeds near that of light. These particles emit a broad beam of gamma rays as they arc along curved magnetic field lines.
The new pulsars were discovered as part of a comprehensive search for periodic gamma-ray fluctuations using five months of Fermi Large Area Telescope data and new computational techniques.
"Before launch, some predicted Fermi might uncover a handful of new pulsars during its mission," Ziegler added. "To discover 16 in its first five months of operation is really beyond our wildest dreams."
Like spinning tops, pulsars slow down as they lose energy. Eventually, they spin too slowly to power their characteristic emissions and become undetectable.
But pair a slowed dormant pulsar with a normal star, and a stream of stellar matter from the companion can spill onto the pulsar and increase its spin. At rotation periods between 100 and 1,000 times a second, ancient pulsars can resume the activity of their youth. In the second study, Fermi scientists examined gamma rays from eight of these "born-again" pulsars, all of which were previously discovered at radio wavelengths.
"Before Fermi launched, it wasn't clear that pulsars with millisecond periods could emit gamma rays at all," said Lucas Guillemot at the Center for Nuclear Studies in Gradignan, near Bordeaux, France. "Now we know they do. It's also clear that, despite their differences, both normal and millisecond pulsars share similar mechanisms for emitting gamma rays."
NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.
Adapted from materials provided by NASA/Goddard Space Flight Center.

International Space Hotel Envisioned

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ScienceDaily (July 6, 2009) — Plans for a new international space hotel have been unveiled by students this month as part of a project for their Masters degree in Innovation Design Engineering (IDE).

Students from the course have developed plans for a hotel that could be built in space and fitted to the International Space Station, which is currently orbiting the Earth. The Masters in IDE is run jointly by Imperial College London and the Royal College of Art.
On June 26, the students unveiled a 12 metre-long replica of the hotel interior, together with animated computer designs that showed what the inside of the space hotel would look and feel like for tourists.
For the project, students had to grapple with the challenges of designing that could function in a zero gravity environment. They worked with visiting lecturer and space architecture expert Daniele Bedini, who has worked for the National Aeronautical Space Agency (NASA) and the European Space Agency (ESA) on projects for a Moon base and new missions to Mars.
“Designing a building that is floating hundreds of miles above Earth throws up all kinds of engineering challenges,” said Bedini. “From personal hygiene to sleeping in zero gravity, we encouraged the students to be completely creative with their solutions so that the living conditions in the world’s most isolated hotel could be as comfortable as possible.”
The students designed smaller toilets that would save space and that would also have the suction power of a vacuum, to counteract zero gravity and help human muscles to remove waste more effectively. In addition, they devised a shower nozzle that could spit out water when it was pressed on the skin and then suck the water back up again after it had been used for washing. This would stop the water from being left floating as globules in zero gravity.
The students were tasked with creating new fashions that space tourists could wear. IDE student Katrin Baumgarten was part of a team that had to develop new fashion concepts that were comfortable, stylish and practical. She said:
“There are no washing machines or tumble dryers in space so we had to design clothes that enabled the skin to breathe, which reduces sweating, smells and the need for clothes to be washed. We achieved this by using natural fibres that breathe and we also made small chest flaps, which let the air in to keep the body cool and comfortable.”
The students were also challenged with finding new bedding for people sleeping in zero gravity, which could restrain the body without making the sleeper feel claustrophobic. The students designed single and double sleeping bags that were large warm cocoons, with soft elastic covers that could restrain the sleepers, so that people could be comfortable without feeling like they were hemmed in.
The students created a novel solution for tourists wanting to record their trip, designing a 'floating camera' that would be able to move independently in space, to automatically follow the space tourist and document their life on board. The students believe this would be an important aspect of the experience for tourists who would wish to capture their trip for posterity and show it to friends and family on Earth.
Adapted from materials provided by Imperial College London.

Fireworks Display In The Helix Nebula

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ScienceDaily (July 5, 2009) — The Helix Nebula, NGC 7293, is not only one of the most interesting and beautiful planetary nebulae; it is also one of the closest nebulae to Earth, at a distance of only 710 light years away. A new image, taken with an infrared camera on the Subaru Telescope in Hawaii, shows tens of thousands of previously unseen comet-shaped knots inside the nebula. The sheer number of knots -- more than have ever been seen before -- looks like a massive fireworks display in space.

The Helix Nebula was the first planetary nebula in which knots were seen, and their presence may provide clues to what planetary material may survive at the end of a star’s life. Planetary nebulae are the final stages in the lives of low-mass stars, such as our Sun. As they reach the ends of their lives they throw off large amounts of material into space. Although the nebula looks like a fireworks display, the process of developing a nebula is neither explosive nor instantaneous; it takes place slowly, over a period of about 10,000 to 1,000,000 years. This gradual process creates these nebulae by exposing their inner cores, where nuclear burning once took place and from which bright ultraviolet radiation illuminates the ejected material.
Astronomers from the National Astronomical Observatory of Japan (NAOJ), from London, Manchester and Kent universities in the UK and from a university in Missouri in the USA studied the emissions from hydrogen molecules in the infrared and found that knots are found throughout the entire nebula. Although these molecules are often destroyed by ultraviolet radiation in space, they have survived in these knots, shielded by dust and gas that can be seen in optical images. The comet-like shape of these knots results from the steady evaporation of gas from the knots, produced by the strong winds and ultraviolet radiation from the dying star in the center of the nebula.
Unlike previous optical images of the Helix Nebula knots, the infrared image shows thousands of clearly resolved knots, extending out from the central star at greater distances than previously observed. The extent of the cometary tails varies with the distance from the central star, just as Solar System comets have larger tails when they are closer to the Sun and when wind and radiation are stronger. “This research shows how the central star slowly destroys the knots and highlights the places where molecular and atomic material can be found in space,”says lead astronomer Dr. Mikako Matsuura, previously at NAOJ and now from University College London.
These images enable astronomers to estimate that there may be as many as 40,000 knots in the entire nebula, each of which are billions of kilometers/miles across. Their total mass may be as much as 30,000 Earths, or one-tenth the mass of our Sun. The origin of the knots is currently unknown. Are they remnants of the star's planetary system or are they material ejected from the star at some stage in its life? Either answer will help astronomers answer important questions about the lives of stars and planetary systems.
The innovative technology of the Subaru Telescope with its near-infrared camera, MOIRCS, enabled researchers to produce such impressive images. Mounted on one of the largest infrared optical telescopes in the world, MOIRCS (Multi-object Infrared Camera and Spectrograph) has a large (4 arcmin by 7 arcmin) field of view, allowing it to capture, with a single shot, such detailed features in a large PN.
This paper will be published in the Astrophysical Journal in August 2009.
Adapted from materials provided by National Astronomical Observatory of Japan.

Fast Neutral Hydrogen Detected Coming From The Moon

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ScienceDaily (July 5, 2009) — NASA's Interstellar Boundary Explorer (IBEX) spacecraft has made the first observations of very fast hydrogen atoms coming from the moon, following decades of speculation and searching for their existence.

During spacecraft commissioning, the IBEX team turned on the IBEX-Hi instrument, built primarily by Southwest Research Institute (SwRI) and the Los Alamos National Laboratory, which measures atoms with speeds from about half a million to 2.5 million miles per hour. Its companion sensor, IBEX-Lo, built by Lockheed Martin, the University of New Hampshire, NASA Goddard Space Flight Center, and the University of Bern in Switzerland, measures atoms with speeds from about one hundred thousand to 1.5 million mph.
"Just after we got IBEX-Hi turned on, the moon happened to pass right through its field of view, and there they were," says Dr. David J. McComas, IBEX principal investigator and assistant vice president of the SwRI Space Science and Engineering Division. "The instrument lit up with a clear signal of the neutral atoms being detected as they backscattered from the moon."
The solar wind, the supersonic stream of charged particles that flows out from the sun, moves out into space in every direction at speeds of about a million mph. The Earth's strong magnetic field shields our planet from the solar wind. The moon, with its relatively weak magnetic field, has no such protection, causing the solar wind to slam onto the moon's sunward side.
From its vantage point in space, IBEX sees about half of the moon -- one quarter of it is dark and faces the nightside (away from the sun), while the other quarter faces the dayside (toward the sun). Solar wind particles impact only the dayside, where most of them are embedded in the lunar surface, while some scatter off in different directions. The scattered ones mostly become neutral atoms in this reflection process by picking up electrons from the lunar surface.
The IBEX team estimates that only about 10 percent of the solar wind ions reflect off the sunward side of the moon as neutral atoms, while the remaining 90 percent are embedded in the lunar surface. Characteristics of the lunar surface, such as dust, craters and rocks, play a role in determining the percentage of particles that become embedded and the percentage of neutral particles, as well as their direction of travel, that scatter.
McComas says the results also shed light on the "recycling" process undertaken by particles throughout the solar system and beyond. The solar wind and other charged particles impact dust and larger objects as they travel through space, where they backscatter and are reprocessed as neutral atoms. These atoms can travel long distances before they are stripped of their electrons and become ions and the complicated process begins again.
The combined scattering and neutralization processes now observed at the moon have implications for interactions with objects across the solar system, such as asteroids, Kuiper Belt objects and other moons. The plasma-surface interactions occurring within protostellar nebula, the region of space that forms around planets and stars -- as well as exoplanets, planets around other stars -- also can be inferred.
IBEX's primary mission is to observe and map the complex interactions occurring at the edge of the solar system, where the million miles per hour solar wind runs into the interstellar material from the rest of the galaxy. The spacecraft carries the most sensitive neutral atom detectors ever flown in space, enabling researchers to not only measure particle energy, but also to make precise images of where they are coming from.
Around the end of the summer, the team will release the spacecraft's first all-sky map showing the energetic processes occurring at the edge of the solar system. The team will not comment until the image is complete, but McComas hints, "It doesn't look like any of the models."
IBEX is the latest in NASA's series of low-cost, rapidly developed Small Explorers spacecraft. The IBEX mission was developed by SwRI with a national and international team of partners. NASA's Goddard Space Flight Center manages the Explorers Program for NASA's Science Mission Directorate.
Journal reference:
McComas, F. Allegrini, P. Bochsler, P. Frisch, H.O. Funsten, M. Gruntman, P.H. Janzen, H. Kucharek, E. Moebius, D.B. Reisenfeld, and N.A. Schwadron. Lunar Backscatter and Neutralization of the Solar Wind: First Observations of Neutral Atoms from the Moon. Geophysical Research Letters, 2009 DOI: 10.1029/2009GL038794
Adapted from materials provided by Southwest Research Institute.

Coolest Spacecraft Ever In Orbit (-273 Degrees Celsius)

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ScienceDaily (July 4, 2009) — On July 2 the detectors of Planck's High Frequency Instrument reached their amazingly low operational temperature of -273°C, making them the coldest known objects in space. The spacecraft has also just entered its final orbit around the second Lagrange point of the Sun-Earth system, L2. Planck is equipped with a passive cooling system that brings its temperature down to about -230°C by radiating heat into space. Three active coolers take over from there, and bring the temperature down further to an amazing low of -273.05°C, only 0.1°C above absolute zero - the coldest temperature theoretically possible in our Universe.

Such low temperatures are necessary for Planck’s detectors to study the Cosmic Microwave Background (CMB), the first light released by the universe only 380 000 yrs after the Big Bang, by measuring its temperature across the sky.
Like measuring the heat of a rabbit on the Moon
The detectors will look for variations in the temperature of the CMB that are about a million times smaller than one degree – this is comparable to measuring from Earth the heat produced by a rabbit sitting on the Moon. This is why the detectors must be cooled to temperatures close to absolute zero (–273.15°C, or zero Kelvin, 0K).
Details on the different stages of the cool-down process are available via the 'Planck in depth' link at right.
Arriving at L2
Starting at 13:15 CEST July 2, the Planck Mission Control Team conducted a crucial orbit insertion manoeuvre designed to place the satellite into its final orbit about L2.
Once commanded, the burn was auto-controlled by Planck, with the thrusters operating for between 12 and 24 hours. The manoeuvre directed the satellite into its final operational orbit around the second Lagrange point of the Sun-Earth system, L2.
The thruster burn was planned to deliberately under-perform by a small margin, necessitating a small 'touch up' manoeuvre in the coming days to bring the satellite fully onto its planned trajectory.
"While this manoeuvre itself is routine, it represents the final major step in the long voyage to L2, and everyone here is quite happy to see Planck getting into its operational orbit," said Chris Watson, Spacecraft Operations Manager, speaking in the mission's Dedicated Control Room at ESA’s European Space Operations Centre, Darmstadt, Germany.
The manoeuvre was planned to change the satellite’s speed by 211.6 km/hour, ending with a final speed of 1010 Km/hour with respect to the ground. Together with Earth and the virtual point L2, Planck will then be orbiting the Sun at a speed of 106 254 km/hour (29.5 km/second).
At the start of yesterday’s manoeuvre, Planck was located 1.43 million km from Earth.
Science operations to begin soon
All commissioning activities are on schedule, and this phase of the mission is practically complete. Over the next few weeks, the operation of the instruments will be fine-tuned for best performance.
Planck will begin to survey the sky in mid-August.
Adapted from materials provided by European Space Agency.

Super-energetic Bursts Discovered Near Giant Black Hole

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ScienceDaily (July 4, 2009) — Using a worldwide combination of diverse telescopes, astronomers have discovered that a giant galaxy's bursts of very high energy gamma rays are coming from a region very close to the supermassive black hole at its core. The discovery provides important new information about the mysterious workings of the powerful "engines" in the centers of innumerable galaxies throughout the Universe.

The galaxy M87, 50 million light-years from Earth, harbors at its center a black hole more than six billion times more massive than the Sun. Black holes are concentrations of matter so dense that not even light can escape their gravitational pull. The black hole is believed to draw material from its surroundings -- material that, as it falls toward the black hole, forms a tightly-rotating disk.
Processes near this "accretion disk," powered by the immense gravitational energy of the black hole, propel energetic material outward for thousands of light-years. This produces the "jets" seen emerging from many galaxies. In 1998, astronomers found that M87 also was emitting flares of gamma rays a trillion times more energetic than visible light.
However, the telescopes that discovered these bursts of very high energy gamma rays could not determine exactly where in the galaxy they originated. In 2007 and 2008, the astronomers using these gamma-ray telescopes combined forces with a team using the National Science Foundation's continent-wide Very Long Baseline Array (VLBA), a radio telescope with extremely high resolving power, or ability to see fine detail.
"Combining the gamma-ray observations with the supersharp radio 'vision' of the VLBA allowed us to see that the gamma rays are coming from a region very near the black hole itself," said Craig Walker, of the National Radio Astronomy Observatory (NRAO).
"Pinning down this location addresses what was an open question and provides important clues for understanding how such highly energetic emissions are produced in the jets of active galaxies," said Matthias Beilicke, of Washington University in St. Louis, MO.
The gamma-ray flares from the galaxy were monitored by systems of large telescopes designed to detect faint flashes of blue light that result when gamma rays enter the Earth's atmosphere. Data from sensitive cameras in these systems can allow astronomers to infer the energy of the gamma rays and the direction from which they came. Their directional information, however, is not precise enough to narrow down the gamma-ray-emitting region within the galaxy.
The VLBA offered a millionfold improvement in resolving power, allowing the scientists to determine that the gamma rays are coming from the immediate vicinity of the black hole. Though gamma rays are the most energetic form of electromagnetic radiation and radio waves the least energetic, both often arise from the same regions. This was shown clearly when M87's most energetic gamma-ray flares were accompanied by the largest flare of radio waves seen from that galaxy by the VLBA.
The radio flare began at about the time of the gamma-ray flares, but continued to increase in brightness for at least two months. "This tells us that energetic material burst out very close to the black hole, causing the gamma rays to be emitted and the radio flare to begin. As that material traveled down the jet, expanding and losing energy, the gamma-ray emission ceased, but the radio continued to increase in brightness," Walker explained. "The VLBA showed us with great precision where the radio emission came from, so we know the gamma rays came from closer in toward the black hole," he added.
M87 is the largest galaxy in the Virgo Cluster of galaxies, at the center of a supercluster of galaxies that includes the Local Group, of which our own Milky Way is a member. The black hole in M87 has an "event horizon," from which matter cannot escape, roughly twice the size of our Solar System, or a tiny fraction of the size of the entire galaxy. The new measurements indicate that the gamma rays are coming from an area no larger than 50 times the size of the event horizon.
The telescope systems that detected the gamma-ray flares are the VERITAS array in Arizona, the H.E.S.S. system in Namibia, Africa, and the MAGIC system on La Palma in the Canary Islands.
The VLBA is a system of ten radio-telescope antennas stretching from Hawaii to the Caribbean, operated by the NRAO from Socorro, New Mexico. The VLBA offers resolving power equal to the ability to read a newspaper in New York while standing in Los Angeles.
Walker and Beilicke worked with Fred Davies of NRAO and New Mexico Tech, Henric Krawczynski of Washington University, Phil Hardee of the University of Alabama, Bill Junor of Los Alamos National Laboratory, Chun Ly of UCLA, and large research teams from VERITAS, H.E.S.S., and MAGIC. The scientists reported their findings in the July 2 online edition of the journal Science.
Adapted from materials provided by National Radio Astronomy Observatory, via EurekAlert!, a service of AAAS.

Largest Ever Survey Of Very Distant Galaxy Clusters Completed

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ScienceDaily (July 3, 2009) — An international team of researchers led by a UC Riverside astronomer has completed the largest ever survey designed to find very distant clusters of galaxies.

Named the Spitzer Adaptation of the Red-sequence Cluster Survey, "SpARCS" detects galaxy clusters using deep ground-based optical observations from the CTIO 4m and CFHT 3.6m telescopes, combined with Spitzer Space Telescope infrared observations.
In a universe which astronomers believe to be 13.7 billion years old, SpARCS is designed to find clusters, snapped as they appeared long ago in time, when the universe was 6 billion years old or younger.
Clusters of galaxies are rare regions of the universe consisting of hundreds of galaxies containing trillions of stars, plus hot gas and mysterious dark matter. Most of the mass in clusters is actually in the form of invisible dark matter which astronomers are convinced exists because of its influence on the orbits of the visible galaxies.
An example of one of the most massive clusters found in the SpARCS survey is shown in the accompanying image. Seen when the universe was a mere 4.8 billion years old, this is also one of the most distant clusters ever discovered. Many similar-color red cluster galaxies can be seen in the image (the green blobs are stars in our own galaxy, The Milky Way).
"We are looking at massive structures very early in the universe's history," said Gillian Wilson, an associate professor of physics and astronomy who leads the SpARCS project.
The SpARCS survey has discovered about 200 new cluster candidates.
"It is very exciting to have discovered such a large sample of these rare objects," Wilson said. "Although we are catching these clusters at early times, we can tell by their red colors that many of the galaxies we are seeing are already quite old. We will be following up this new sample for years to come, to better understand how clusters and their galaxies form and evolve in the early universe."
A summary of the survey and additional images of newly discovered clusters may be found in two companion papers led by Wilson and Adam Muzzin of Yale University, published in the June 20 issue of The Astrophysical Journal.
The SpARCS team consists of Wilson, who joined UCR in 2007, Ricardo Demarco of UCR; Muzzin of Yale University, Conn.; H.K.C. Yee of the University of Toronto, Canada; Mark Lacy and Jason Surace of the Spitzer Science Center/California Institute of Technology; Henk Hoekstra of Leiden University; Michael Balogh and David Gilbank of the University of Waterloo, Canada; Kris Blindert of the Max Planck Institute for Astronomy, Germany; Subhabrata Majumdar of the Tata Institute of Fundamental Research, India; Jonathan P. Gardner of the Goddard Space Flight Center; Mike Gladders of the University of Chicago; and Carol Lonsdale of the North American ALMA Science Center; Douglas Burke of the Harvard-Smithsonian Center for Astrophysics; Shelly Bursick of the University of Arkansas; Michelle Doherty, Chris Lidman and Piero Rosati of ESO; Erica Ellingson of the University of Colorado; Amalia Hicks of Michigan State University; Alessandro Rettura of Johns Hopkins University; David Shupe of the Herscel Science Center/California Institute of Technology; Paolo Tozzi of the University of Trieste, Italy; Renbin Yan of the University of Toronto; and Tracy Webb of McGill University, Canada.
This work is based in part on archival data obtained with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This work is also based on observations obtained with The Cerro Tololo Inter-American Observatory, which is operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation; observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii; and by observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil) and SECYT (Argentina).
Support for this work was provided, in part, by awards issued by JPL/Caltech, and from Wilson's College of Natural and Agricultural Sciences start-up funds at UCR.
Adapted from materials provided by University of California - Riverside.

New Class Of Pulsars Solve Mystery Of Previously Unidentified Gamma-ray Sources

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ScienceDaily (July 3, 2009) — A new class of pulsars detected by NASA's Fermi Gamma-ray Space Telescope is solving the mystery of previously unidentified gamma-ray sources and helping scientists understand the mechanisms behind pulsar emissions.

A study to be published by an international team of scientists in the July 2 edition of Science Express describes 16 pulsars discovered by Fermi based on their pulsed emissions of high-energy gamma rays. A pulsar is a rapidly spinning neutron star, the dense core left behind after a supernova explosion. Most of the 1,800 known pulsars were found through their periodic radio emissions.
"These are the first pulsars ever detected by gamma rays alone, and already we've found 16," said coauthor Robert Johnson, professor of physics at the University of California, Santa Cruz. "The existence of a large population of radio-quiet pulsars was suspected prior to this, but until Fermi was launched, only one radio-quiet pulsar was known, and it was first detected in x-rays."
Johnson and other physicists at UCSC's Santa Cruz Institute for Particle Physics (SCIPP) identified the gamma-ray pulsars using computational techniques they developed to comb through data from Fermi's Large Area Telescope (LAT). Marcus Ziegler, a postdoctoral researcher at SCIPP and corresponding author of the paper, said detection of gamma-ray pulsations from a typical source requires weeks or months of data from the LAT.
"From the faintest pulsar we studied, the LAT sees only two gamma-ray photons a day," Ziegler said.
Of the 16 gamma-ray pulsars found by Fermi, 13 are associated with unidentified gamma-ray sources detected previously by the EGRET instrument on the Compton Gamma-ray Observatory. EGRET detected nearly 300 gamma-ray point sources, but was unable to detect pulsations from those sources, most of which have remained unidentified, said Pablo Saz Parkinson, also a SCIPP postdoctoral researcher and corresponding author of the paper.
"It's been a longstanding question what could be powering those unidentified sources, and the new Fermi results tell us that a lot of them are pulsars," Saz Parkinson said. "These findings are also giving us important clues about the mechanism of pulsar emissions."
A pulsar emits narrow beams of radio waves from the magnetic poles of the neutron star, and the beams sweep around like a lighthouse beacon because the magnetic poles are not aligned with the star's spin axis. If the radio beam misses the Earth, the pulsar cannot be detected by radio telescopes. Fermi's ability to detect so many radio-quiet gamma-ray pulsars indicates that the gamma-rays are emitted in a beam that is wider and more fan-like than the radio beam.
"This favors models in which the gamma rays are emitted from the outer magnetosphere of the pulsar, as opposed to the polar cap much closer to the surface of the star," Saz Parkinson said.
The very intense magnetic and electric fields of a pulsar accelerate charged particles to nearly the speed of light, and these particles are ultimately responsible for the gamma-ray emissions.
Because the rotation of the star powers the emissions, isolated pulsars slow down as they age and lose energy. But a binary companion star can feed material to a pulsar and spin it up to a rotation rate of 100 to 1,000 times a second. These are called millisecond pulsars, and Fermi scientists detected gamma-ray pulsations from eight millisecond pulsars that were previously discovered at radio wavelengths. Those results are reported in a second study also published in the July 2 edition of Science Express.
"Fermi has truly unprecedented power for discovering and studying gamma-ray pulsars," said Paul Ray of the Naval Research Laboratory in Washington. "Since the demise of the Compton Gamma Ray Observatory a decade ago, we've wondered about the nature of unidentified gamma-ray sources it detected in our galaxy. These studies from Fermi lift the veil on many of them."
The corresponding authors of the first paper include Ziegler, Saz Parkinson, Ray, and UCSC graduate student Michael Dormody. Nine of the paper's coauthors are affiliated with UCSC, including William Atwood, adjunct professor of physics, who came up with the original design concept for the LAT as well as the concept for the algorithm to find gamma-ray pulsars. Much of the computational work was carried out on the UCSC Astronomy Department's Pleiades supercomputer. The second paper also has nine coauthors affiliated with UCSC.
Adapted from materials provided by University of California - Santa Cruz.

Mars More Like Earth Than Earth Than Thought? New Details About History Of Water On Red Planet

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ScienceDaily (July 3, 2009) — Scientists offer new details about the history of water on Mars, gleaned from the 2008 NASA Phoenix Mars Mission that was operated from The University of Arizona.

Four papers on the topic have been published in the journal Science on June 3, 2009.
Peter H. Smith, a scientist with the UA Lunar and Planetary Laboratory is the mission's principal investigator. There are 35 co-authors from six countries on the paper. Smith and his group of scientists and students used the lander to investigate the role of water and ice on Mars, as well as the changing weather patterns.
The popular mission launched in early August 2007. In May, 2008, early 10 months later, its landing trajectory was spectacularly captured by the HiRISE camera onboard the Mars Reconnaissance Orbiter.
For the next five months, the UA Science Operations Center clattered with researchers gearing themselves to follow the Martian diurnal phases, which are about 40 minutes longer than day and night on Earth and enough to throw off human sleep schedules in short order.
The landing site was an ejecta field. A comet or asteroid that crashed into the surface melted the ice below creating a sheet of dust and water that flowed across a shallow valley. Smith said that event also covered any large rocks that could have interfered with the ability of the Phoenix to safely land.
Smith and his group found patterns in the ground near the lander, multi-sided shapes about three to ten meters in size. The shapes are created when the surface contracts and the ice cracks. Sand fills in the cracks before the ice expands and buckles the surface to make the distinctive patterns.
Smith used the Phoenix lander's robotic arm to dig a series of trenches to expose subsurface ice and found that the ice in the centers of the polygons was fairly shallow, only a couple of inches deep.
"But in the troughs in between, we went down as much as eight inches and never did find the ice underneath. We weren't able to dig further down because the robot arm was hitting against the side of the lander. It was not known ahead of time that there would be changes in the depth of the ice," he said.
"We wanted to know the origin of the ice," Smith said. "It could have been the remnant of a larger polar ice cap that shrank; could have been a frozen ocean; could have been a snowfall frozen into the ground," he said.
"The most likely theory is that water vapor from the atmosphere slowly diffused into the surface and froze at the level where the temperature matches the frost point. We expected that was probably the source of the ice, but some of what we found was surprising."
One of the surprises was finding perchlorate.
"Perchlorate was not predicted at this landing site and nobody had it on their list of likely chemicals. There was a very high concentration of it, higher than the salts we might have expected like sodium chloride (table salt). As an oxidized state of chlorine, it has interesting properties including a strong affinity for water. On Earth, microbes use it as a chemical energy source."
During the mission, Mars moved from summer to winter, giving Smith and others an unprecedented look at the planet's changing weather patterns, including frost and snow.
"Frost was predicted, but snowfall was quite a welcome surprise," Smith said. "In summer there was a lot of dust in the atmosphere. As we neared fall, the dust cleared, and all of a sudden there were water ice clouds forming at about 4 km (2.5 mi.) above the surface. We could see the clouds scud by, moving through the camera field, and once we saw snow coming out of the bottom of a cloud. It was very exciting to watch the daily weather changes. No one has ever had this experience."
Smith said there are clues that thin films of water modified the soil chemistry. Unlike Earth, Mars has an unstable spin axis, which currently is tilted at about 25 degrees from vertical. Perhaps five millions years ago, he said, it was tilted much more, which would have exposed the north pole to larger amounts of sunlight creating warmer, wetter conditions during summer.
"During that previous climate, you would expect huge increase in the amounts of water vapor coming off the polar cap. If the cap goes unstable, you can have as much as three hundred times as much water in the atmosphere," Smith said.
It would have been enough for snowdrifts. On hot summer days, melting snow could have formed thin films of water.
Not enough for a lake or a river, but he said this could have been a time when damp soil provided a growth period for any microbes that learned to survive those long periods of dryness.
"Who knows? Evolution is a powerful force. If life ever started on Mars, there are niches where still it could survive."
Journal reference:
P. H. Smith et al. H2O at the Phoenix Landing Site. Science, July 3, 2009; Vol. 325. no. 5936, pp. 58 - 61 DOI: 10.1126/science.1172339
Adapted from materials provided by University of Arizona.

Return To The Moon: First Images Kick Off Mapping Mission

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ScienceDaily (July 3, 2009) — NASA's Lunar Reconnaissance Orbiter Camera (LROC) has taken and received its first images of the Moon, kicking off the year-long mapping mission of Earth's nearest celestial neighbor. The LROC imaging system, under the watchful eyes of Arizona State University professor Mark Robison, the principal investigator, consists of two Narrow Angle Cameras (NACs) to provide high-resolution black-and-white images, a Wide Angle Camera (WAC) to provide images in seven color bands over a 60-kilometer (37.28-mile) swath, and a Sequence and Compressor System (SCS) supporting data acquisition for both cameras.

NASA reports that the Lunar Reconnaissance Orbiter, which launched June 18, is performing exceptionally well and spacecraft checkout is proceeding smoothly, so smoothly in fact that LROC was given an early, but short (two orbits) opportunity Tuesday evening to measure temperatures and background values while imaging. Since LRO is in a terminator orbit, much of the area photographed was in shadows, which is actually a good situation for performing engineering checks of camera settings, according to Robinson, with ASU's School of Earth and Space Exploration. Much to the delight of the LROC team, a few of the images captured dramatic views of the surface.
"Our first images were taken along the Moon's terminator – the dividing line between day and night – making us initially unsure of how they would turn out," says Robinson. "Because of the deep shadowing, subtle topography is exaggerated suggesting a craggy and inhospitable surface. In reality, the area is similar to the region where the Apollo 16 astronauts comfortably explored in 1972. Though these images are magnificent in their own right, the main message is that LROC is nearly ready to begin its mission."
LROC NAC: Two details from one of the first images
LRO was 70 kilometers (43.5 miles) above the lunar surface when the summed mode image was taken, resulting in a resolution of approximately 1.4-meters/pixel (34.4°S, 6.0°W). Incredible levels of detail are visible in these two (1000 pixel-by-1000 pixel) cutouts from the full image (2532 pixels-by-53,248 pixels). The NAC data shown has not been calibrated, and the pixel values were stretched to enhance contrast.
Along the terminator, there simply is not much light – the instrument is "photon-starved," resulting in suboptimal signal-to-noise ratios. Without summing, images taken in this circumstance would be underexposed. To compensate for low light levels, the pixels can effectively be made larger by summing adjacent pixels to increase the signal-to-noise ratio, making the image sharper, though with 2x lower resolution. At this resolution, features as small as three meters (9.8 feet) wide can be discerned.
The NAC image shows a starkly beautiful region a few kilometers east of Hell E crater, which is located on the floor of the ancient Imbrian-aged Deslandres impact structure in the lunar highlands south of Mare Nubium. Numerous small, secondary craters can be identified, including several small crater chains. Also identifiable are distinctive lineations made readily apparent by the extreme lighting, representing ejecta from a nearby impact. The quality of these early engineering test images gives the LROC science team confidence it can achieve its primary goals, including obtaining the data needed to support future human lunar exploration and utilization.
Once LRO finishes commissioning operations and enters its 50-kilometer x 50-kilometer (31 miles x 31 miles) mapping orbit, a maneuver currently scheduled for mid-August, the LROC NAC will take images of over 8 percent of the Moon at 50-cm/pixel.
LROC WAC: Seeing the colors of the Moon
The LROC WAC represents a very different type of imaging system than the NAC. The WAC sees the surface in seven colors, one after the other. Looking at the raw image is akin to looking through venetian blinds, which is a little confusing at first.
First you notice the five stair step-like visible bands, and then the two lower-resolution and barely visible ultraviolet bands. During processing, these seven bands are pulled apart and seven single-filter mosaics are created that can be combined in various combinations for scientific analysis.
The WAC is designed to help place the super-high-resolution NAC images into their proper geologic context, as well as discriminate color units on the surface to help geologists map rock types and identify resources. Acquired at the same time as the NAC image, more of the Deslandres region is visible because the WAC has a field of view 20 times wider than the NAC though with substantially lower resolution. For comparison, the width of the NAC image is shown as two vertical bars in the center of the image. The WAC image shown here has not been calibrated and the pixel values were stretched to enhance contrast.
LROC is scheduled for activation July 3 to formally begin its commissioning activities. The LROC Science Operations Center, part of the School of Earth and Space Exploration in the College of Liberal Arts and Sciences on ASU's Tempe campus plans to steadily release images of the lunar frontier as more data is collected and processed.
LRO will spend the next year gathering crucial data on the lunar environment that will help astronauts prepare for exploring the Moon and eventually leaving the Earth-Moon system for voyages to Mars and beyond.
Adapted from materials provided by Arizona State University.

New Class Of Black Holes Discovered

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ScienceDaily (July 2, 2009) — A new class of black hole, more than 500 times the mass of the Sun, has been discovered by an international team of astronomers.

The finding in a distant galaxy approximately 290 million light years from Earth is reported today in the journal Nature.
Until now, identified black holes have been either super-massive (several million to several billion times the mass of the Sun) in the centre of galaxies, or about the size of a typical star (between three and 20 Solar masses).
The new discovery is the first solid evidence of a new class of medium-sized black holes. The team, led by astrophysicists at the Centre d'Etude Spatiale des Rayonnements in France, detected the new black hole with the European Space Agency's XMM-Newton X-ray space telescope.
"While it is widely accepted that stellar mass black holes are created during the death throes of massive stars, it is still unknown how super-massive black holes are formed," says the lead author of the paper, Dr Sean Farrell, now based at the Department of Physics and Astronomy at the University of Leicester.
He added: "One theory is that super-massive black holes may be formed by the merger of a number of intermediate mass black holes. To ratify such a theory, however, you must first prove the existence of intermediate black holes.
"This is the best detection to date of such long sought after intermediate mass black holes. Such a detection is essential. While it is already known that stellar mass black holes are the remnants of massive stars, the formation mechanisms of supermassive black holes are still unknown."
"The identification of HLX-1 is therefore an important step towards a better understanding of the formation of the super-massive black holes that exist at the centre of the Milky Way and other galaxies."
A black hole is a remnant of a collapsed star with such a powerful gravitational field that it absorbs all the light that passes near it and reflects nothing.
It had been long believed by astrophysicists that there might be a third, intermediate class of black holes, with masses between a hundred and several hundred thousand times that of the Sun. However, such black holes had not been reliably detected until now.
This new source, dubbed HLX-1 (Hyper-Luminous X-ray source 1), lies towards the edge of the galaxy ESO 243-49. It is ultra-luminous in X-rays, with a maximum X-ray brightness of approximately 260 million times that of the Sun.
The X-ray signature of HLX-1 and the lack of a counterpart in optical images confirm that it is neither a foreground star nor a background galaxy, and its position indicates that it is not the central engine of the host galaxy.
Using XMM-Newton observations carried out on the 23rd November 2004 and the 28th November 2008, the team showed that HLX-1 displayed a variation in its X-ray signature. This indicated that it must be a single object and not a group of many fainter sources. The huge radiance observed can only be explained if HLX-1 contains a black hole more than 500 times the mass of the Sun. No other physical explanation can account for the data.
S.A.F acknowledges funding from the CNES. S.A.F. and O.G. acknowledge STFC funding. This work made use of the 2XMM Serendipitous Source Catalogue constructed by the XMM-Newton Survey Science Centre on behalf of ESA. We thank the Swift team for performing a TOO observation which provided justification for an additional observation with XMM-Newton. This work was based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.
Adapted from materials provided by University of Leicester, via EurekAlert!, a service of AAAS.

Astronomers Discover Pair Of Solar Systems In The Making

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ScienceDaily (July 2, 2009) — Two University of Hawai'i at Mānoa astronomers have found a binary star-disk system in which each star is surrounded by the kind of dust disk that is frequently the precursor of a planetary system. Doctoral student Rita Mann and Dr. Jonathan Williams used the Submillimeter Array on Mauna Kea, Hawaii to make the observations.

A binary star system consists of two stars bound together by gravity that orbit a common center of gravity. Most stars form as binaries, and if both stars are hospitable to planet formation, it increases the likelihood that scientists will discover Earth-like planets.
This binary system, 253-1536, stands out as the first known example of two optically visible stars, each surrounded by a disk with enough mass to form a planetary system like our own. It lies 1,300 light-years from Earth, in the famous Orion Nebula, the kind of rich cluster of stars that is a common birth environment for most stars in our Milky Way galaxy, including our sun.
One of the disks was discovered in an image taken with the Hubble Space Telescope, but the other disk was hidden in the glare of the star. Hubble saw only the disk shadow, so the amount of material and its capability for planet formation was unknown until the UH team made the SMA observations. "The SMA was able to image the binary system at almost the same level of detail as the Hubble Space Telescope, but in the extreme infrared, where we can see the glow from the dust, rather than its shadow," explained Mann.
The two stars are 400 times farther from each other than Earth is from the sun. They would take 4,500 years, or about the length of human recorded history, to complete one orbit around their common center. Both stars are only about a third the mass of our sun and are much cooler and redder in color. Viewed from a potential future planet, the stellar neighbor would appear as an intense point in the night sky, about one thousand times brighter than the brightest star in our night sky, Sirius. Planets around the other star would be visible only through telescopes, but they would be within reach of spacecraft from a civilization with the same level of technology as ours.
The larger disk in 253-1536 is also the most massive found in the Orion Nebula so far. The discovery of this massive disk and the binary disk system improve our understanding of how common planet formation is in our Galaxy and place our Solar System in context.
Journal reference:
Mann et al. Massive Protoplanetary Disks in Orion beyond the Trapezium Cluster. The Astrophysical Journal, 2009; 699 (1): L55 DOI: 10.1088/0004-637X/699/1/L55
Adapted from materials provided by University of Hawaii at Manoa, via EurekAlert!, a service of AAAS.

First Direct Evidence Of Lightning On Mars Detected

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ScienceDaily (July 1, 2009) — For the first time, direct evidence of lightning has been detected on Mars, say University of Michigan researchers who found signs of electrical discharges during dust storms on the Red Planet.

The bolts were dry lightning, says Chris Ruf, a professor in the departments of Atmospheric, Oceanic and Space Sciences and Electrical Engineering and Computer Sciences.
"What we saw on Mars was a series of huge and sudden electrical discharges caused by a large dust storm," Ruf said. "Clearly, there was no rain associated with the electrical discharges on Mars. However, the implied possibilities are exciting."
Electric activity in Martian dust storms has important implications for Mars science, the researchers say.
"It affects atmospheric chemistry, habitability and preparations for human exploration. It might even have implications for the origin of life, as suggested by experiments in the 1950s," said Nilton Renno, a professor in the Department of Atmospheric, Oceanic and Space Sciences.
The findings are based on observations made using an innovative microwave detector developed at the U-M Space Physics Research Laboratory. The kurtosis detector, which is capable of differentiating between thermal and non-thermal radiation, took measurements of microwave emissions from Mars for approximately five hours a day for 12 days between May 22 and June 16, 2006.
On June 8, 2006 both an unusual pattern of non-thermal radiation and an intense Martian dust storm occurred, the only time that non-thermal radiation was detected. Non-thermal radiation would suggest the presence of lightning.
The researchers reviewed the data to determine the strength, duration and frequency of the non-thermal activity, as well as the possibility of other sources. But each test led to the conclusion that the dust storm likely caused dry lightning.
This work confirms soil measurements from the Viking landers 30 years ago, and it challenges 2006 experiments that suggested otherwise.
Data from the Viking landers raised the possibility that Martian dust storms might be electrically active like Earth's thunderstorms and thus, might be a source of reactive chemistry. But the hypothesis was untestable. In 2006, using theoretical modeling, laboratory experiments and field studies on Earth, a group of planetary scientists suggested that there was no direct evidence that lightning occurred on Mars. This new research refutes those findings.
"Mars continues to amaze us. Every new look at the planet gives us new insights," said Michael Sanders, manager of the exploration systems and technology office at Jet Propulsion Laboratory and a researchers involved in this study.
The new finding will be published in an upcoming issue of Geophysical Research Letters. The paper is called "The Emission of Non-Thermal Microwave Radiation by a Martian Dust Storm." In addition to Ruf and Renno, other U-M authors include Jasper Kok, a recent Ph.D. graduate from the Department of Atmospheric, Oceanic and Space Sciences; Etienne Bandelier, a graduate student in the same department; and Steve Gross, a lead research engineer in the same department.
Adapted from materials provided by University of Michigan.

Intense Heat Killed The Universe's Would-be Galaxies, Researchers Say

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ScienceDaily (July 1, 2009) — Millions of would-be galaxies failed to develop after being exposed to intense heat from the first stars and black holes formed in the early Universe, according to new research. Our Milky Way galaxy only survived because it was already immersed in a large clump of dark matter which trapped gases inside it, scientists led by Durham University's Institute for Computational Cosmology (ICC) found.

The research, presented at an international conference on July 1, 2009 also forms a core part of a new ICC movie charting the evolution of the Milky Way to be shown at the Royal Society.
The researchers said that the early Milky Way, which had begun forming stars, held on to the raw gaseous material from which further stars would be made. This material would otherwise have been evaporated by the high temperatures generated by the "ignition" of the Universe about half-a-billion years after the Big Bang.
Tiny galaxies, inside small clumps of dark matter, were blasted away by the heat which reached approximate temperatures of between 20,000 and 100,000 degrees centigrade, the scientists, including experts at Japan's University of Tsukuba, said.
Dark matter is thought to make up 85 per cent of the Universe's mass and is believed to be one of the building blocks of galaxy formation.
Using computer simulations carried out by the international Virgo Consortium (which is led by Durham) the scientists examined why galaxies like the Milky Way have so few companion galaxies or satellites.
Astronomers have found a few dozen small satellites around the Milky Way, but the simulations revealed that hundreds of thousands of small clumps of dark matter should be orbiting our galaxy.
The scientists said the heat from the early stars and black holes rendered this dark matter barren and unable to support the development of satellite star systems.
The findings will be presented to The Unity of the Universe conference to be held at the Institute of Cosmology and Gravitation, at the University of Portsmouth on Wednesday, July 1. The work has been funded by the Science and Technology Facilities Council (STFC) and the Japanese Society for the Promotion of Science.
The simulations also form part of a new ICC movie – called Our Cosmic Origins – which combines ground-breaking simulations with observations of galaxies to track the evolution of the Milky Way over the 13-billion-year history of the Universe.
Joint lead investigator Professor Carlos Frenk, Director of the Institute for Computational Cosmology, at Durham University, said: "The validity of the standard model of our Universe hinges on finding a satisfactory explanation for why galaxies like the Milky Way have so few companions.
"The simulations show that hundreds of thousands of small dark matter clumps should be orbiting the Milky Way, but they didn't form galaxies.
"We can demonstrate that it was almost impossible for these potential galaxies to survive the extreme heat generated by the first stars and black holes.
"The heat evaporated gas from the small dark matter clumps, rendering them barren. Only a few dozen front-runners which had a head start on making stars before the Universe ignited managed to survive."
By providing a natural explanation for the origin of galaxies, the simulations support the view that cold dark matter is the best candidate for the mysterious material believed to make up the majority of our Universe, the scientists added.
It is now up to experimental physicists to either find this dark matter directly or to make it in a particle accelerator such as the Large Hadron Collider at CERN.
Professor Frenk, added: "Identifying the dark matter is not only one of the most pressing problems in science today, but also the key to understanding the formation of galaxies."
Joint lead investigator Dr Takashi Okamoto from the University of Tsukuba said: "These are still early days in trying to make realistic galaxies in a computer, but our results are very encouraging."
Presentations:
1. Constraining feedback in galaxy formation: cosmological simulations of satellite galaxy formation, Okamoto, T; Frenk CS; Jenkins A; and Theuns T, July 2009.
2. The origin of failed subhaloes and the common mass scale of the Milky Way satellite galaxies, Okamoto, T and Frenk CS, July 2009.
Adapted from materials provided by Durham University, via EurekAlert!, a service of AAAS.