International Space Station Crews Enter Columbus Laboratory

Daily Science Journal (Feb. 13, 2008) — The 24th shuttle flight to the International Space Station, STS-122, delivers Columbus, the European Space Agency's new laboratory. Columbus will be installed on Harmony Node 2.

European astronaut and station flight engineer Leopold Eyharts photographs the inside of the new Columbus laboratory. In the foreground is European astronaut and mission specialist Hans Schlegel. (Credit: NASA TV)

European astronaut and station flight engineer Leopold Eyharts got a look inside the new Columbus laboratory around 9 a.m. EST February 12. Official ingress is scheduled to occur at 2:55 p.m after preliminary outfitting of the new lab.

Supplies and equipment will be transferred into the European Space Agency’s Columbus laboratory. Three of the laboratory module’s five payload racks also are scheduled for relocation Feb. 12. Expedition 16 crew members Leopold Eyharts and Peggy Whitson will be the first to enter Columbus.

Later in the day, STS-122 Mission Specialists Rex Walheim and Hans Schlegel will camp out in the station’s Quest Airlock in preparation for the Feb. 13 spacewalk, scheduled for 9:35 a.m. EST.

On Feb 11, astronauts used the station’s robotic arm to connect Columbus to the orbital outpost and Walheim and Mission Specialist Stanley Love conducted the first of three scheduled STS-122 spacewalks. Among other tasks, the spacewalkers prepared the new module for its installation.

Adapted from materials provided by National Aeronautics And Space Adminstration.

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Particle Accelerator May Reveal Shape Of Alternate Dimensions

Daily Science Journal (Feb. 6, 2008) — When the world's most powerful particle accelerator starts up later this year, exotic new particles may offer a glimpse of the existence and shapes of extra dimensions.

A new particle accelerator, the Large Hadron Collider, is scheduled to begin operating later this year near Geneva, Switzerland. (Credit: CERN)

Researchers from the University of Wisconsin-Madison and the University of California-Berkeley say that the telltale signatures left by a new class of particles could distinguish between possible shapes of the extra spatial dimensions predicted by string theory.

String theory, which describes the fundamental particles of the universe as tiny vibrating strings of energy, suggests the existence of six or seven unseen spatial dimensions in addition to the time and three space dimensions that we normally see.

Much as the shape of a musical instrument determines its sound, the shape of these dimensions determines the properties and behavior of our four-dimensional universe, says Gary Shiu, lead author of a paper appearing in the Jan. 25 issue of Physical Review Letters.

"The shape of the dimensions is crucial because, in string theory, the way the string vibrates determines the pattern of particle masses and the forces that we feel," says the UW-Madison physics professor.

Zeroing in on that shape should further our understanding and predictions of our four-dimensional world, Shiu says. "There are myriad possibilities for the shapes of the extra dimensions out there. It would be useful to know a way to distinguish one from another and perhaps use experimental data to narrow down the set of possibilities."

Such experimental evidence could appear in data from a new particle accelerator, the Large Hadron Collider, scheduled to begin operating later this year near Geneva, Switzerland.

In an accelerator, smashing atomic nuclei head-on at nearly the speed of light can briefly create new high-energy and highly unstable particles, which quickly decay into a shower of detectable lower energy ones. Characteristic patterns of decay serve as fingerprints of the fleeting exotic particles and, possibly, the shape of the unseen dimensions.

With colleagues Bret Underwood and Kathryn Zurek at UW-Madison and Devin Walker at UC-Berkeley, Shiu shows in the new study that the signature patterns from particles called Kaluza-Klein (KK) gravitons can distinguish between different proposed extra-dimensional geometries.

How" Shiu compares the effect to a darkened room in which patterns of sound resonating off the walls can reveal the shape of the room. Similarly, KK gravitons are sensitive to the extra-dimensional shape and, through their behavior and decay, may reveal clues to that shape.

The current study shows that, in simulations, even small geometric variations lead to visible differences in KK graviton signatures, Underwood says.

Based on these results, Shiu says, "At least in principle, one may be able to use experimental data to test and constrain the geometry of our universe."

Last year, Shiu and Underwood reported that clues to dimensional geometries might also be visible in patterns of cosmic radiation left over from the Big Bang. The new work complements the previous approach, they say.

"The more hints we get, the better idea we have about the underlying physics," says Shiu.

Adds Underwood, "If the cosmology and particle physics data agree, it's an indication we're on the right track."

The work was supported by the National Science Foundation, the U.S. Department of Energy, the Research Corporation, and a University of California Presidential Fellowship.

Adapted from materials provided by University of Wisconsin-Madison.

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NASA To Beam Beatles' 'Across The Universe' Into Space

Daily Science Journal (Feb. 5, 2008) — For the first time ever, NASA will beam a song -- The Beatles' "Across the Universe" -- directly into deep space at 7 p.m. EST on Feb. 4.

An estimated 10,000 galaxies are revealed in humankind's deepest portrait of the visible universe ever from the Hubble Space Telescope. (Credit: Image courtesy of NASA)

The transmission over NASA's Deep Space Network will commemorate the 40th anniversary of the day The Beatles recorded the song, as well as the 50th anniversary of NASA's founding and the group's beginnings. Two other anniversaries also are being honored: The launch 50 years ago this week of Explorer 1, the first U.S. satellite, and the founding 45 years ago of the Deep Space Network, an international network of antennas that supports missions to explore the universe.

The transmission is being aimed at the North Star, Polaris, which is located 431 light years away from Earth. The song will travel across the universe at a speed of 186,000 miles per second. Former Beatle Sir Paul McCartney expressed excitement that the tune, which was principally written by fellow Beatle John Lennon, was being beamed into the cosmos.

"Amazing! Well done, NASA!" McCartney said in a message to the space agency. "Send my love to the aliens. All the best, Paul."

Lennon's widow, Yoko Ono, characterized the song's transmission as a significant event.

"I see that this is the beginning of the new age in which we will communicate with billions of planets across the universe," she said.

It is not the first time Beatles music has been used by NASA; in November 2005, McCartney performed the song "Good Day Sunshine" during a concert that was transmitted to the International Space Station. "Here Comes the Sun," "Ticket to Ride" and "A Hard Day's Night" are among other Beatles' songs that have been played to wake astronaut crews in orbit.

Feb. 4 has been declared "Across The Universe Day" by Beatles fans to commemorate the anniversaries. As part of the celebration, the public around the world has been invited to participate in the event by simultaneously playing the song at the same time it is transmitted by NASA. Many of the senior NASA scientists and engineers involved in the effort are among the group's biggest fans.

"I've been a Beatles fan for 45 years – as long as the Deep Space Network has been around," said Dr. Barry Geldzahler, the network's program executive at NASA Headquarters, Washington. "What a joy, especially considering that 'Across the Universe' is my personal favorite Beatles song."

Adapted from materials provided by National Aeronautics and Space Administration.

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Dark Fluid: Dark Matter And Dark Energy May Be Two Faces Of Same Coin

Daily Science Journal (Feb. 5, 2008) — Astronomers at the University of St Andrews believe they can "simplify the dark side of the universe" by shedding new light on two of its mysterious constituents.

The magnificent spiral arms of the nearby galaxy Messier 81. Astronomers believe that both the universe and galaxies are held together by the gravitational attraction of a huge amount of unseen material, now commonly referred to as dark matter. (Credit: NASA/JPL/Caltech/Harvard-Smithsonian Center for Astrophysics)

Dr HongSheng Zhao, of the University's School of Physics and Astronomy, has shown that the puzzling dark matter and its counterpart dark energy may be more closely linked than was previously thought.

Only 4% of the universe is made of known material - the other 96% is traditionally labelled into two sectors, dark matter and dark energy.

A British astrophysicist and Advanced Fellow of the UK's Science and Technology Facilities Council, Dr Zhao points out, "Both dark matter and dark energy could be two faces of the same coin.

"As astronomers gain understanding of the subtle effects of dark energy in galaxies in the future, we will solve the mystery of astronomical dark matter at the same time. "

Astronomers believe that both the universe and galaxies are held together by the gravitational attraction of a huge amount of unseen material, first noted by the Swiss astronomer Fritz Zwicky in 1933, and now commonly referred to as dark matter.

Dr Zhao reports that, "Dark energy has already revealed its presence by masking as dark matter 60 years ago if we accept that dark matter and dark energy are linked phenomena that share a common origin."

In Dr Zhao's model, dark energy and dark matter are simply different manifestations of the same thing, which he has considered as a 'dark fluid'. On the scale of galaxies, this dark fluid behaves like matter and on the scale of the Universe overall as dark energy, driving the expansion of the Universe. Importantly, his model, unlike some similar work, is detailed enough to produce the same 3:1 ratio of dark energy to dark matter as is predicted by cosmologists.

Efforts are currently underway to hunt for very massive dark-matter particles with a variety of experiments. The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) in Geneva is a particle accelerator that amongst other objectives, could potentially detect dark matter particles.

According to Dr Zhao, these efforts could turn out to be fruitless. He said, "In this simpler picture of universe, the dark matter would be at a surprisingly low energy scale, too low to be probed by upcoming Large Hadron Collider.

"The search for dark-matter particles so far has concentrated on highly-energetic particles. If dark matter however is a twin phenomenon of dark energy, it will not show up at instruments like the LHC, but has been seen over and over again in galaxies by astronomers."

However, the Universe might be absent of dark-matter particles at all. The findings of Dr Zhao are also compatible with an interpretation of the dark component as a modification of the law of gravity rather than particles or energy.

Dr Zhao concluded. "No matter what dark matter and dark energy are, these two phenomena are likely not independent of each other."

Background

Theories of the physics of gravity were first developed by Isaac Newton in 1687 and refined by Albert Einstein’s theory of General Relativity in 1905 which stated that the speed of gravity is equal to the speed of light. However, Einstein was never fully decided on whether his equation should add an omnipresent constant source, now called dark energy in general.

Astronomers following Fred Zwicky have also speculated additional sources to Einstein's equation in the form of non-light emitting material, called dark matter in general. Apart from very light neutrinos neither dark sources have been confirmed experimentally.

Dr Zhao and his collaborators' findings have recently been published by Astrophysical Journal Letters in December 2007, and Physics Review D. 2007.

Adapted from materials provided by Science and Technology Facilities Council.

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White Dwarf Pulses Like A Pulsar

Daily Science Journal (Jan. 3, 2008) — New observations from Suzaku, a joint Japanese Aerospace Exploration Agency (JAXA) and NASA X-ray observatory, have challenged scientists’ conventional understanding of white dwarfs. Observers had believed white dwarfs were inert stellar corpses that slowly cool and fade away, but the new data tell a completely different story.

The white dwarf in the AE Aquarii system is the first star of its type known to give off pulsar-like pulsations that are powered by its rotation and particle acceleration. (Credit: Casey Reed)

At least one white dwarf, known as AE Aquarii, emits pulses of high-energy (hard) X-rays as it whirls around on its axis. "We’re seeing behavior like the pulsar in the Crab Nebula, but we’re seeing it in a white dwarf," says Koji Mukai of NASA Goddard Space Flight Center in Greenbelt, Md. The Crab Nebula is the shattered remnant of a massive star that ended its life in a supernova explosion. "This is the first time such pulsar-like behavior has ever been observed in a white dwarf." Mukai is co-author of a paper presented at a Suzaku science conference in San Diego, Calif., in December.

White dwarfs and pulsars represent distinct classes of compact objects that are born in the wake of stellar death. A white dwarf forms when a star similar in mass to our sun runs out of nuclear fuel. As the outer layers puff off into space, the core gravitationally contracts into a sphere about the size of Earth, but with roughly the mass of our sun. The white dwarf starts off scorching hot from the star’s residual heat. But with nothing to sustain nuclear reactions, it slowly cools over billions of years, eventually fading to near invisibility as a black dwarf.

A pulsar is a type of neutron star, a collapsed core of an extremely massive star that exploded in a supernova. Whereas white dwarfs have incredibly high densities by earthly standards, neutron stars are even denser, cramming roughly 1.3 solar masses into a city-sized sphere. Pulsars give off radio and X-ray pulsations in lighthouse-like beams.

The discovery team, led by Yukikatsu Terada of the Institute of Physical and Chemical Research (RIKEN) in Wako, Japan, was not expecting to find a white dwarf mimicking a pulsar. Instead, the astronomers were hoping to find out if white dwarfs could accelerate charged subatomic particles to near-light speed, meaning they could be responsible for many of the cosmic rays that zip through our galaxy and occasionally strike Earth.

Some white dwarfs, including AE Aquarii, spin very rapidly and have magnetic fields millions of times stronger than Earth’s. These characteristics give them the energy to generate cosmic rays.

To find out if this is happening, Terada and his colleagues targeted AE Aquarii with Suzaku in October 2005 and October 2006. The white dwarf resides in a binary system with a normal companion star. Gas from the star spirals toward the white dwarf and heats up, giving off a glow of low-energy (soft) X-rays. But Suzaku also detected sharp pulses of hard X-rays. After analyzing the data, the team realized that the hard X-ray pulses match the white dwarf’s spin period of once every 33 seconds.

The hard X-ray pulsations are very similar to those of the pulsar in the center of the Crab Nebula. In both objects, the pulses appear to be radiated like a lighthouse beam, and a rotating magnetic field is thought to be controlling the beam. Astronomers think that the extremely powerful magnetic fields are trapping charged particles and then flinging them outward at near-light speed. When the particles interact with the magnetic field, they radiate X-rays.

"AE Aquarii seems to be a white dwarf equivalent of a pulsar," says Terada. "Since pulsars are known to be sources of cosmic rays, this means that white dwarfs should be quiet but numerous particle accelerators, contributing many of the low-energy cosmic rays in our galaxy."

Launched in 2005, Suzaku is the fifth in a series of Japanese satellites devoted to studying celestial X-ray sources. Managed by JAXA, this mission is a collaborative effort between Japanese universities and institutions and Goddard.

Adapted from materials provided by NASA/Goddard Space Flight Center.

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Supernova Surprise: Black Holes May Pull Apart, Reignite White Dwarf Stars

Daily Science Journal (Feb. 2, 2008) — A strange and violent fate awaits a white dwarf star that wanders too close to a moderately massive black hole. According to a new study, the black hole's gravitational pull on the white dwarf would cause tidal forces sufficient to disrupt the stellar remnant and reignite nuclear burning in it, giving rise to a supernova explosion with an unusual appearance. Observations of such supernovae could confirm the existence of intermediate-mass black holes, currently the subject of much debate among astronomers.

This series of images shows the interaction of a white dwarf star with a black hole. As it passes the black hole, the white dwarf becomes strongly compressed and heated (top left), triggering an explosion. Most of the stellar mass is ejected into space (the "bubble" in the upper right part of the debris in the top right image), while the rest (the cusp-like part of the image) falls toward the black hole. While the ejected matter expands rapidly, the infalling matter builds a violent, thick accretion disk around the black hole. (Credit: Image courtesy of University of California - Santa Cruz)

"Our supercomputer simulations show a peculiar supernova that would be a unique signature of an intermediate-mass black hole," said Enrico Ramirez-Ruiz, assistant professor of astronomy and astrophysics at the University of California, Santa Cruz.

Ramirez-Ruiz and his collaborators--Stephan Rosswog of Jacobs University in Bremen, Germany, and William Hix of Oak Ridge National Laboratory--used detailed computer simulations to follow the entire process of tidal disruption of a white dwarf by a black hole. Their simulations included gas dynamics, gravity, and nuclear physics, requiring weeks of computer time to simulate events that would take place in a fraction of a second.

"Every star that is not too massive ends up as a white dwarf, so they are very common. We were interested in whether tidal disruption can bring this stellar corpse to life again," said Rosswog, the first author of the paper.

A white dwarf can explode as a "type Ia" supernova if it accumulates enough mass by siphoning matter away from a companion star. When it reaches a critical mass (about 1.4 times the mass of the Sun), the white dwarf collapses and explodes. Astronomers use these type Ia supernovae as "standard candles" for cosmic distance measurements because their brightness evolves over time in a predictable manner.

The new paper* describes a distinctly different mechanism for igniting a white dwarf, in which tidal disruption by a black hole causes drastic compression of the stellar material. The white dwarf is flattened into a pancake shape aligned in the plane of its orbit around the black hole. As each section of the star is squeezed through a point of maximum compression, the extreme pressure causes a sharp increase in temperatures, which triggers explosive burning.

The explosion ejects more than half of the debris from the disrupted star, while the rest of the stellar material falls into the black hole. The infalling material forms a luminous accretion disk that emits x-rays and should be detectable by the Chandra X-ray Observatory, the researchers said.

"This is a new mechanism for ignition of a white dwarf that results in a very different type of supernova than the standard type Ia, and it is followed by an x-ray source," Ramirez-Ruiz said.

He estimated that this type of event would occur about 100 times less frequently than the standard type Ia supernovae, but should be detectable by future surveys designed to observe large numbers of supernovae. The Large Synoptic Survey Telescope (LSST), planned for completion in 2013, is expected to discover hundreds of thousands of type Ia supernovae per year.

"These exotic creatures will start showing up in the data from the LSST," Ramirez-Ruiz said. "We want to predict the light curves so we can look for them in the survey data."

The mechanism described in the paper requires a black hole that is neither too small nor too big. Such intermediate-mass black holes (500 to 1,000 times the mass of the Sun) may reside in some globular star clusters, but there is much less evidence for their existence than there is for the relatively small stellar black holes (tens of times the mass of the Sun) or for supermassive black holes (a few million times the mass of the Sun), found at the centers of galaxies.

The new paper describes in detail the disruption of a white dwarf with two-tenths the mass of the Sun by a black hole 1,000 times the mass of the Sun. The researchers also found that they can vary the mass of the white dwarf and still get the same outcome--tidal disruption and ignition of the white dwarf.

"We can ignite the whole mass range of white dwarfs if they get close enough to the black hole," Rosswog said.

*A paper describing their results has been accepted for publication in Astrophysical Journal Letters, and a preprint is currently available online.

This research was supported by the Department of Energy's Program for Scientific Discovery through Advanced Computing.

Adapted from materials provided by University of California - Santa Cruz.

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'The Spider' On Mercury: MESSENGER Spacecraft Streams Back Surprises

Daily Science Journal (Feb. 2, 2008) — The recent flyby of Mercury by NASA's MESSENGER spacecraft has given scientists an entirely new look at a planet once thought to have characteristics similar to those of Earth's moon. Researchers are amazed by the wealth of images and data that show a unique world with a diversity of geological processes and a very different magnetosphere from the one discovered and sampled more than 30 years ago.

The Spider: MESSENGER obtained high-resolution images of the floor of the Caloris basin on January 14, 2008. Near the center of the basin, this remarkable feature -- nicknamed "the spider" by the science team -- was revealed. A set of troughs radiating outward are interpreted to be the result of the breaking apart of the floor materials that filled the Caloris basin after its formation. Other troughs near the center form a polygonal pattern. An impact crater about 40 km (~25 miles) in diameter appears to be centered on "the spider." (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

After a journey of more than 2 billion miles and three and a half years, NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft made its first flyby on Jan. 14. MESSENGER is the first mission sent to orbit the planet closest to our sun. The spacecraft's cameras and other sophisticated, high-technology instruments collected more than 1,200 images and made other science observations. Data included the first up-close measurements of Mercury since the Mariner 10 spacecraft's third and final flyby on March 16, 1975.

"This flyby allowed us to see a part of the planet never before viewed by spacecraft, and our little craft has returned a gold mine of exciting data," said Sean Solomon, MESSENGER's principal investigator, Carnegie Institution of Washington. "From the perspectives of spacecraft performance and maneuver accuracy, this encounter was near-perfect, and we are delighted that all of the science data are now on the ground."

Unlike the moon, MESSENGER showed that Mercury has huge cliffs with structures snaking up hundreds of miles across the planet's face. These cliffs preserve a record of patterns of fault activity from early in the planet's history. The spacecraft also revealed impact craters that appear very different from lunar craters.

Instruments provided a topographic profile of craters and other geological features on the night side of Mercury. The spacecraft also discovered a unique feature that scientists dubbed "The Spider." This formation never has been seen on Mercury before and nothing like it has been observed on the moon. It lies in the middle of a large impact crater called the Caloris basin and consists of more than one hundred narrow, flat-floored troughs radiating from a complex central region.

"The Spider has a crater near its center, but whether that crater is related to the original formation or came later is not clear at this time," said James Head, science team co-investigator at Brown University, Providence, R.I.

Now that MESSENGER has shown scientists the full extent of the Caloris basin, its diameter has been revised upward from the Mariner 10 estimate of 800 miles to perhaps as large as 960 miles from rim to rim. The plains inside the Caloris basin are distinctive and more reflective than the exterior plains. Impact basins on the moon have opposite characteristics.

The magnetosphere and magnetic field of Mercury during the MESSENGER flyby appeared to be different from the Mariner 10 observations. MESSENGER found the planet's magnetic field was generally quiet but showed several signatures indicating significant pressure within the magnetosphere.

Magnetic fields like Earth's and their resulting magnetospheres are generated by electrical dynamos in the form of a liquid metallic outer core deep in the planet's center. Of the four terrestrial planets, only Mercury and Earth exhibit such a phenomenon. The magnetic field deflects the solar wind from the sun, producing a protective bubble around Earth that shields the surface of our planet from those energetic particles and other sources farther out in the galaxy. Similar variations are expected for Mercury's magnetic field, but the precise nature of its field and the time scales for internal changes are unknown. The next two flybys and the yearlong orbital phase will shed more light on these processes.

MESSENGER's suite of instruments also has provided insight into the mineral makeup of the surface terrain and detected ultraviolet emissions from sodium, calcium and hydrogen in Mercury's exosphere. The spacecraft explored the sodium-rich exospheric "tail," which extends more than 25,000 miles from the planet.

"We should keep this treasure trove of data in perspective. With two flybys to come and an intensive orbital mission to follow, we are just getting started to go where no one has been before," said project scientist Ralph McNutt of the Applied Physics Laboratory, Laurel, Md.

Adapted from materials provided by National Aeronautics and Space Administration.

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Nova Finding Challenges Thinking On Powerful Stellar Explosions

Daily Science Journal (Feb. 2, 2008) — First results from a new NASA-funded scientific instrument at the W. M. Keck Observatory in Hawaii are helping scientists overturn long-standing assumptions about powerful explosions called novae and have produced the first unified model for a nearby nova called RS Ophiuchi.

This artist rendering depicts the RS Ophiuchi binary system shortly after the white dwarf (right) has exploded as a nova. The other star is a red giant. Note the spiral dust lanes. (Credit: Casey Reed; Courtesy of NASA/Goddard Space Flight Center)

"We were getting ready for a routine engineering run when all of a sudden the nova went off. It was very bright and easy to observe, so we took this opportunity and turned it into gold," says team member Marc Kuchner of NASA's Goddard Space Flight Center in Greenbelt, Md.

Kuchner and his colleagues used the "nulling" mode of the Keck Interferometer, which is part of the NASA-funded Keck Interferometer. This state-of-the-art instrument combines starlight using two 10-meter (33 feet) telescopes. In the nulling mode, the interferometer suppresses the blinding light of a star so researchers can study the surrounding environment. The instrument helps researchers observe very faint objects near bright sources and produces ten times more resolving power than a single Keck telescope working alone. It is the only instrument of its kind in operation.

The Keck Nuller was undergoing tests on February 12, 2006, when a nova flared up in the constellation Ophiuchus. The system, known as RS Ophiuchi, consists of a white dwarf and a red giant. The red giant is gradually shedding its massive gaseous outer layers, and the white dwarf is sweeping up much of this wind, growing in mass over time. As the matter builds up on the white dwarf's surface it eventually reaches a critical temperature that ignites a thermonuclear explosion that causes the system to brighten 600-fold. RS Ophiuchi was previously seen to blow its stack in 1898, 1933, 1958, 1967, and 1985, so astronomers were eagerly anticipating the 2006 eruption.

Just 3.8 days after the nova was detected, the group observed the explosion with the Keck Nuller. The team set the instrument to cancel out the nova's light, allowing the group to see the much fainter surrounding material. The group next adjusted the nuller to observe the extremely bright blast zone.

The instrument's versatility was key to a surprising discovery. The nuller saw no dust in the bright zone, presumably because the nova's blast wave vaporized dust particles. But farther from the white dwarf, at distances starting around 20 times the Earth-Sun distance, the nuller recorded the spectral signature of silicate dust. The blast wave had not yet reached this zone, so the dust must have pre-dated the explosion.

"This flies in the face of what we expected. Astronomers had previously thought that nova explosions actually create dust," says Richard Barry of NASA Goddard, lead author of a paper on the Keck observations that will be published in the Astrophysical Journal.

The team thinks the dust is created as the white dwarf plows through the red giant's wind, creating a pinwheel pattern of higher-density regions that is reminiscent of galaxy spiral arms. Inside these spiral arms, atoms reach low enough temperatures and high enough densities to allow atoms to stick together to form dust particles. The nova's blast wave has since destroyed RS Ophiuchi's pinwheel pattern, but it should re-form over the next few years, and future Spitzer Space Telescope observations could see it.

Most studies of RS Ophiuchi have relied on spectroscopic models, but those methods have not been able to distinguish various nova components with as much detail as the interferometer. The Keck Nuller measured one component of the RS Ophiuchi system to an accuracy of just 4 milliarcseconds, or about the size of a basketball seen 7,500 miles away.

Barry is also coauthor of a paper based on Spitzer observations of RS Ophiuchi. This paper reports independent evidence for silicate dust that predates the 2006 explosion.

"The RS Ophiuchi observations are just a small taste of the power and potential we expect from the Keck Nuller," says coauthor William Danchi of NASA Goddard. "But ultimately we want to launch a nulling interferometer into space to image extrasolar planets. These Keck results are a technological and scientific pathfinder toward that future."

Adapted from materials provided by NASA/Goddard Space Flight Center.

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Could An Asteroid Hit Planet Earth, Again?

Daily Science Journal (Feb. 1, 2008) — Earth dodged a bullet today, when asteroid TU24 passed within 540,000 kilometers of our planet, which is just down the street on a galactic scale. Tomorrow, another asteroid – 2007 WD5 – will zip past Mars at a distance of only 26,000 kilometers away. Will we dodge the bullet the next time a near-Earth object (NEO) hurtles dangerously close to our home planet?

Asteroid impact on early Earth. Some scientists believe that impacts such as this during the Late Heavy Bombardment period, 4 billion years ago, may have delivered primitive life to Earth. (Credit: Copyright Don Davis)

To mark the 100th anniversary of the Tunguska event, when an exploding asteroid leveled 2000 square kilometers of Siberian forest, The Planetary Society today kicked off a year-long focus on Target Earth. The asteroid believed responsible for the cataclysm on June 30, 1908 became a fireball from the sky and knocked pine trees over like matchsticks near the Podkamennaya Tunguska River in Russia. Such an explosion today over more populated areas could lay waste an entire city.

“The solar system is a busy place,” said Louis Friedman, Executive Director of The Planetary Society. “In fact, we live in a dangerous neighborhood, and keeping track of NEOs is like organizing a Neighborhood Watch in our corner of space.”

Earth has been hit by NEOs many times in the past; ancient craters are still visible in landforms around the world. The famed Meteor Crater in Arizona and Canada’s Lake Manicouagan are only two examples.

Target Earth will focus on a variety of NEO projects supported by The Planetary Society, including the Apophis Mission Design Competition, the Gene Shoemaker Near Earth Object Grants, NEO mission advocacy, and a one-hour HD TV “Daily Planet” special on asteroids being produced by Discovery Canada.

In mid-to late February, the Society will announce the winners of the Apophis Mission Design Competition, which invited participants to compete for $50,000 in prizes by designing a mission to rendezvous with and "tag" a potentially dangerous near-Earth asteroid. The competition received 37 mission proposals from 19 countries on 6 continents.

Tagging may be necessary to track an asteroid accurately enough to determine whether it will impact Earth, thus helping space agencies to decide whether to mount a deflection mission to alter its orbit. Apophis is an approximately 400-meter NEO, which will come closer to Earth in 2029 than the orbit of our geostationary satellites – close enough to be visible to the naked eye. If Apophis passes through a several hundred-meter wide "keyhole" in 2029, it will impact Earth in 2036. While current estimates rate the probability of impact as very low, Apophis is being used as an example to enable design of a broader type of mission to any potentially dangerous asteroid.

"Target Earth encompasses The Planetary Society’s three-pronged approach to NEO research,” said Director of Projects Bruce Betts. "We fund researchers who discover and track asteroids, advocate greater NEO research funding by the government, and help spur the development of possible ways to avert disaster should a potentially dangerous asteroid be discovered."

The Society will call for another round of Shoemaker grant proposals in the summer of 2008. One past grant recipient, Roy Tucker from Arizona, co-discovered Apophis. Many other past recipients from around the world continue to discover, track, and characterize NEOs.

NASA currently has no plans to study methods of asteroid deflection, or how to tag an asteroid for precise tracking. NASA and the European Space Agency (ESA) have co-sponsored the Society’s Apophis competition and will study the best mission designs offered.

The $50,000 in prize money for the Apophis Mission Design competition was contributed by The Planetary Society's Chairman of the Board, Dan Geraci, together with donations from Planetary Society members around the world. Funding for the Gene Shoemaker NEO Grant program comes from Planetary Society members.

Adapted from materials provided by Planetary Society.

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Scientists Propose Test Of String Theory Based On Neutral Hydrogen Absorption

Daily Science Journal (Feb. 1, 2008) — Ancient light absorbed by neutral hydrogen atoms could be used to test certain predictions of string theory, say cosmologists at the University of Illinois. Making the measurements, however, would require a gigantic array of radio telescopes to be built on Earth, in space or on the moon.

This image reveals the first galaxies to emerge from the so-called "dark ages," the time shortly after the big bang when the first stars reheated the cold, dark universe. A network of strings is predicted by string theory to have been produced in the early universe. (Credit: NASA/ESA/S. Beckwith(STScI) and The HUDF Team)

String theory -- a theory whose fundamental building blocks are tiny one-dimensional filaments called strings -- is the leading contender for a "theory of everything." Such a theory would unify all four fundamental forces of nature (the strong and weak nuclear forces, electromagnetism, and gravity). But finding ways to test string theory has been difficult.

Now, cosmologists at the U. of I. say absorption features in the 21-centimeter spectrum of neutral hydrogen atoms could be used for such a test.

"High-redshift, 21-centimeter observations provide a rare observational window in which to test string theory, constrain its parameters and show whether or not it makes sense to embed a type of inflation -- called brane inflation -- into string theory," said Benjamin Wandelt, a professor of physics and of astronomy at the U. of I.

"If we embed brane inflation into string theory, a network of cosmic strings is predicted to form," Wandelt said. "We can test this prediction by looking for the impact this cosmic string network would have on the density of neutral hydrogen in the universe."

Wandelt and graduate student Rishi Khatri describe their proposed test in a paper accepted for publication in the journal Physical Review Letters.

About 400,000 years after the Big Bang, the universe consisted of a thick shell of neutral hydrogen atoms (each composed of a single proton orbited by a single electron) illuminated by what became known as the cosmic microwave background.

Because neutral hydrogen atoms readily absorb electromagnetic radiation with a wavelength of 21 centimeters, the cosmic microwave background carries a signature of density perturbations in the hydrogen shell, which should be observable today, Wandelt said.

Cosmic strings are filaments of infinite length. Their composition can be loosely compared to the boundaries of ice crystals in frozen water.

When water in a bowl begins to freeze, ice crystals will grow at different points in the bowl, with random orientations. When the ice crystals meet, they usually will not be aligned to one another. The boundary between two such misaligned crystals is called a discontinuity or a defect.

Cosmic strings are defects in space. A network of strings is predicted by string theory (and also by other supersymmetric theories known as Grand Unified Theories, which aspire to unify all known forces of nature except gravity) to have been produced in the early universe, but has not been detected so far. Cosmic strings produce characteristic fluctuations in the gas density through which they move, a signature of which will be imprinted on the 21-centimeter radiation.

The cosmic string network predicted to occur with brane inflation could be tested by looking for the corresponding fluctuations in the 21-centimeter radiation.

Like the cosmic microwave background, the cosmological 21-centimeter radiation has been stretched as the universe has expanded. Today, this relic radiation has a wavelength closer to 21 meters, putting it in the long-wavelength radio portion of the electromagnetic spectrum.

To precisely measure perturbations in the spectra would require an array of radio telescopes with a collective area of more than 1,000 square kilometers. Such an array could be built using current technology, Wandelt said, but would be prohibitively expensive.

If such an enormous array were eventually constructed, measurements of perturbations in the density of neutral hydrogen atoms could also reveal the value of string tension, a fundamental parameter in string theory, Wandelt said. "And that would tell us about the energy scale at which quantum gravity begins to become important."

Funding was provided by the Alexander von Humboldt Foundation.

Adapted from materials provided by University of Illinois at Urbana-Champaign.

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New Discovery On Magnetic Reconnection To Impact Future Space Missions ; Magnetic Fields Get Reconnected In Turbulent Plasma Too, Cluster Reveals

Daily Science Journal (Jan. 31, 2008) — ESA’s Cluster mission has, for the first time, observed the extent of the region that triggers magnetic reconnection, and it is much larger than previously thought. This gives future space missions a much better chance of studying it.

In a plasma (a gas of charged particles), during magnetic reconnection, magnetic field lines of opposite direction break and then reconnect, forming an X-line magnetic topology. The newly reconnected field lines accelerate the plasma away from the X-line. (Credit: Center for Visual computing, Univ. of California Riverside)

Space is filled with plasma (a gas composed of ions and electrons, globally neutral) and is threaded by magnetic fields. These magnetic fields store energy which can be released explosively, in a process called magnetic reconnection.

This process plays a key role in numerous astrophysical phenomena: star formation, solar flares and intense aurorae, to name a few. On Earth, magnetic reconnection prevents the efficient production of electricity in controlled fusion reactors, potential sources of electricity for the future.

Schematic of magnetic field lines during reconnection

At the heart of magnetic reconnection is the ‘electron diffusion region’, where reconnection is thought to be triggered. Here, a kink in newly-reconnected magnetic field lines produces large-scale high-velocity jets of plasma.

“Understanding the structure of the diffusion region and its role in controlling the rate at which magnetic energy is converted into particle energy remains a key scientific challenge,” says Dr Michael Shay, University of Delaware, USA.

Until recently, theoretical scientists believed that the electron diffusion region was relatively tiny (width about 2 km, length about 10 km). In the vastness of space, the chance of a spacecraft encountering this region would therefore be exceedingly small.

With increased computational power, simulations showed electron diffusion regions that were a lot more elongated than those seen earlier. It was not possible to judge whether the new finding was real because the length of the region increased with more powerful simulations. Nor it was known whether such a layer would be stable in the real, 3D world.

Comparison between observations and simulation

On 14 January 2003, the four Cluster satellites were crossing the magnetosheath, a turbulent plasma region located just outside Earth’s magnetosphere, when they encountered an electron diffusion region. The length of the observed region measured 3000 km, 300 times longer than the earlier theoretical expectations and four times longer than seen in recent simulations. Nevertheless, the observations strongly support new simulations.

“These Cluster observations are very significant since they are the first measurements of the length of the electron diffusion region in the space environment. The finding drastically changes the way we understand the physics of reconnection,” noted Dr James Drake, University of Maryland, USA.

“This discovery of a large electron diffusion region gives future ESA and NASA missions a much better chance to study it,” said Tai Phan at the University of California at Berkeley, USA, lead author of the paper on the findings.

Magnetic reconnection simulation

Cluster was able to detect the region based on its high-resolution magnetic field, electric field and ion measurements. But to understand the fundamental physics of the electron diffusion region responsible for reconnection, higher time resolution measurements are needed to resolve the layer.

The four spacecraft of NASA’s Magnetospheric Multi-Scale mission, planned for launch in 2014, are being designed for such measurements. Cross-scale, a mission under study at ESA in collaboration with other space agencies, would use 12 spacecraft to probe the diffusion region, whilst simultaneously measuring the consequences of energy released by reconnection in the surrounding environment.

“With the higher probability of encountering the electron diffusion region, we can be confident that future missions will be able to fully understand magnetic reconnection,” said Dr Philippe Escoubet, ESA’s Cluster and Double Star Project Scientist and Cross-scale Study Scientist.

The findings appear in, ‘Evidence for an elongated (> 60 ion skin depths) electron diffusion region during fast magnetic reconnection,’ by T. Phan, J. Drake, M. Shay, F. Mozer and J. Eastwood, published in the Physical Review Letters, on 21 December 2007.

Adapted from materials provided by European Space Agency.

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Magnetic Fields Get Reconnected In Turbulent Plasma Too, Cluster Reveals

Using measurements of the four ESA's Cluster satellites, a study published in Nature Physics shows pioneering experimental evidence of magnetic reconnection also in turbulent 'plasma' around Earth.

This image provides a model of magnetic fields at the Sun's surface using SOHO data, showing irregular magnetic fields (the 'magnetic carpet') in the solar corona (top layer of the Sun's atmosphere). Small-scale current sheets are likely to form in such turbulent environment and reconnection may occur in similar fashion as in Earth's magnetosheath. This can be relevant to a better understanding of the heating of solar corona. (Credit: Stanford-Lockheed Inst. for Space Research/NASA GSFC)

Magnetic reconnection – a phenomenon by which magnetic fields lines get interconnected and reconfigure themselves - is a universal process in space that plays a key role in various astrophysical phenomena such as star formation, solar explosions or the entry of solar material within the Earth's environment. Reconnection has been observed at large-scale boundaries between different plasma environments such as the boundary between Earth and interplanetary space. Plasma is a gas composed of charged particles.

An irregular behaviour of particle flows and magnetic fields causes plasma turbulence within which many small-scale boundaries can form, where reconnection has been predicted via modelling. However, thanks to Cluster this was the first time that this could be directly observed, opening up new perspectives to help us better understand the behaviour of turbulent plasma.

Our first line of defence against the incessant flow of solar particles, the Earth's magnetic field deflects most of this material around the Earth's magnetosphere. This is marked by a boundary layer called the magnetopause. As for any other planet which has a planetary magnetic field (for example Jupiter and Saturn), solar wind is decelerated from supersonic to subsonic speeds by a shock wave (called the 'bow shock') located in front of the magnetopause. The region between the bow shock and the magnetopause is called the magnetosheath.

One of the most turbulent environments in the near-Earth space, the terrestrial magnetosheath is an accessible laboratory to study in-situ turbulence, unlike the solar atmosphere or accretion disks. Characterising the properties of the magnetic turbulence in this region is of prime importance to understand its role in fundamental processes such as energy dissipation and particle acceleration.

Observing reconnection at small-scale boundaries in space requires simultaneous measurements by at least four spacecraft flying in close formation. With an inter-spacecraft distance of only 100 kilometres, on 27 March 2002 the four Cluster satellites observed reconnection within a very thin current 'sheet' embedded in the turbulent plasma with a typical size of about 100 kilometres.

A challenge for the instruments onboard, the observations show that the turbulent plasma is accelerated and heated during the reconnection process. This newly observed type of small-scale reconnection seems also to be associated with the acceleration of particles to energies much higher than their average which could explain, in part, the creation of high energy particles by the Sun.

To quote Alessandro Retinò, lead author of this study and PhD student at the Swedish Institute of Space Physics, Uppsala, Sweden, "we found reconnection in one single current sheet, so that in such an environment of irregular magnetic fields one may think that reconnection is sporadic, but this is not the case. For this particular magnetosheath crossing, a very large number of other thin current sheets was found where reconnection is very likely to occur, a subject currently under investigation by our team."

This discovery of reconnection in turbulent plasma has significant implications for the study of laboratory and astrophysical plasmas, where both turbulence and reconnection develop and thus where turbulent reconnection is very likely to occur. Possible applications range from the dissipation of magnetic energy in fusion devices on Earth to the understanding of the acceleration of high energy particles in solar explosions called solar flares.

"Magnetic reconnection, turbulence and shocks are three fundamental ingredients of the plasma Universe," says Philippe Escoubet Cluster and Double Star project scientist at ESA. "The detailed understanding of these key processes and their associated multi-scale physics is a challenge for the future of space physics. One of the lessons learned from Cluster is the need for new space missions equipped with instruments of higher sensitivity and better time resolution together with a larger number of satellites."

Adapted from materials provided by European Space Agency.

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Traces Of The Martian Past In The Terby Crater, Europe's Eye On Mars: First Spectacular Results From Mars Express

Daily Science Journal (Jan. 31, 2008) — The High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express has returned striking scenes of the Terby crater on Mars. The region is of great scientific interest as it holds information on the role of water in the history of the planet.

This false-colour image of Terby crater on Mars was derived from three HRSC colour channels and the nadir channel of the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express orbiter. (Credit: ESA/DLR/FU Berlin (G. Neukum))

The image data was obtained on 13 April 2007 during orbit 4199, with a ground resolution of approximately 13 m/pixel. The Sun illuminates the scene from the west (from above in the image).

Terby crater lies at approximately 27° south and 74° east, at the northern edge of the Hellas Planitia impact basin in the southern hemisphere of Mars.

The crater, named after the Belgian astronomer Francois J. Terby (1846 – 1911), has a diameter of approximately 170 km. The scene shows a section of a second impact crater in the north.

Eye-catching finger-shaped plateaux extend in the north-south direction. They rise up to 2000 m above the surrounding terrain. The relatively old crater was filled with sediments in the past, which formed plateaux on erosion.

The flanks of the plateaux clearly exhibit layering of different-coloured material. Differences in colour usually indicate changes in the composition of the material and such layering is called ‘bedding’. Bedding structures are typical of sedimentary rock, which has been deposited either by wind or water. Different rock layers erode differently, forming terraces.

The valleys exhibit gullies, or channels cut in the ground by running liquid, mainly in the northern part of the image. These gullies and the rock-bedding structure indicate that the region has been affected by water.

The sediments in this region are interesting to study because they contain information on the role of water in the history of the planet. This is one of the reasons why Terby crater was originally short listed as one of 33 possible landing sites for NASA’s Mars Science Laboratory mission, planned for launch in 2009.

The colour scenes have been derived from the three HRSC colour channels and the nadir channel. The perspective views have been calculated from the digital terrain model derived from the HRSC stereo channels. The 3D anaglyph image was calculated from the nadir channel and one stereo channel, stereoscopic glasses are required for viewing.

Adapted from materials provided by European Space Agency.

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Europe's Eye On Mars: First Spectacular Results From Mars Express

ESA's Mars Express, successfully inserted into orbit around Mars on 25 December 2003, is about to reach its final operating orbit above the poles of the Red Planet. The scientific investigation has just started and the first results already look very promising, as this first close-up image shows.

Picture taken by the High Resolution Stereo Camera (HRSC) on board ESA’s Mars Express orbiter on 14 January 2004 under the responsibility of the Principal Investigator Prof. Gerhard Neukum. It was processed by the Institute for Planetary Research of the German Aerospace Centre (DLR), also involved in the development of the camera, and by the Institute of Geosciences of the Freie Universität Berlin.

Although the seven scientific instruments on board Mars Express are still undergoing a thorough calibration phase, they have already started collecting amazing results. The first high-resolution images and spectra of Mars have already been acquired.

This first spectacular stereoscopic colour picture was taken on 14 January 2004 by ESA's Mars Express satellite from 275 km above the surface of Mars by the High Resolution Stereo Camera (HRSC). This image is available on the ESA Portal at: http://mars.esa.int

The picture shows a portion of a 1700 km long and 65 km wide swath which was taken in south-north direction across the Grand Canyon of Mars (Valles Marineris). It is the first image of this size that shows the surface of Mars in high resolution (12 metres per pixel), in colour, and in 3D. The total area of the image on the Martian surface (top left corner) corresponds to 120 000 km². The lower part of the picture shows the same region in perspective view as if seen from a low-flying aircraft. This perspective view was generated on a computer from the original image data. One looks at a landscape which has been predominantly shaped by the erosional action of water. Millions of cubic kilometres of rock have been removed, and the surface features seen now such as mountain ranges, valleys, and mesas, have been formed.

The HRSC is just one of the instruments to have collected exciting data. To learn more about the very promising beginning to ESA's scientific exploration of Mars, media representatives are invited to attend a press conference on Friday, 23 January 2004, at 11:00 CET at ESA's Space Operations Centre in Darmstadt, Germany, and in video-conference with the other ESA centres.

There, under the auspices of ESA Council Chair, Germany's Minister for Education and Research, Mrs Edelgard Bulmahn, ESA's Director of the Scientific Programme, Prof. David Southwood and the Principal Investigators of all instruments on board Mars Express will present the first data and preliminary results.

Also a spectacular, three-dimensional video sequence, featuring famous landmarks on the surface of Mars 'as seen through European eyes' will be unveiled for the first time on Friday 23 January.

Adapted from materials provided by European Space Agency.

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Mercury's Magnetosphere Fends Off Solar Wind

Daily Science Journal (Jan. 31, 2008) — The planet Mercury's magnetic field appears to be strong enough to fend off the harsh solar wind from most of its surface, according to data gathered in part by a University of Michigan instrument onboard NASA's MESSENGER spacecraft.

Departing shots: The top left image was taken when MESSENGER was about 34,000 kilometers (21,000 miles) from Mercury, and the bottom right image was snapped from a distance of about 400,000 kilometers (250,000 miles). Mercury and Earth are the only two terrestrial planets in the solar system with magnetospheres produced by an intrinsic magnetic field. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington)

U-M's Fast Imaging Plasma Spectrometer (FIPS) on Jan. 14 took the first direct measurements of Mercury's magnetosphere to determine how the planet interacts with the space environment and the Sun.

The solar wind, a stream of charged particles, fills the entire solar system. It interacts with all planets, but bears down on Mercury, 2/3 closer than the Earth to the Sun.

Earth's magnetosphere is strong enough to protect us from the solar wind's radiation, but Mercury's magnetic field is comparatively weaker.

"From our magnetic measurements, we can tell that Mercury is managing to stand up to a lot of the solar wind and protect the surface of the planet, at least in some spots. Even though the magnetic field was weak, it was enough," said Thomas Zurbuchen, FIPS instrument project leader and a professor in the U-M Department of Atmospheric, Oceanic and Space Science.

Zurbuchen said scientists can tell Mercury is putting up a good fight because instruments detected a layer of much slower-moving magentospheric plasma around the planet.

It's possible that the magnetosphere shield has holes. Scientists found ions in the magnetosphere that may have been knocked off the surface by the solar wind at the poles, for example. The source and chemical composition of the ions is still unclear, Zurbuchen said. The particles could also be from the planet's thin atmosphere.

"Mercury's magnetosphere is more similar to Earth's than we might have thought," Zurbuchen said.

The spacecraft did find one major difference. Mercury has no Van Allen Belts, wing-shaped regions of energetic particles trapped by Earth's magnetic field.

"We flew through the region they would be in and they just weren't there," Zurbuchen said. "It could be that they're intermittent, but when we were there, they weren't."

Mercury and Earth are the only two terrestrial planets in the solar system with magnetospheres produced by an intrinsic magnetic field.

This was the first of three planned flybys of Mercury. MESSENGER is scheduled to enter orbit in 2011.

Adapted from materials provided by University of Michigan.

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Astronomers Prepare To Obtain Close Images Of A Near-Earth Asteroid

Daily Science Journal (Jan. 27, 2008) — The Arecibo Observatory in Arecibo, Puerto Rico will observe a newly discovered asteroid on Jan. 27-28, as the object called 2007 TU24 passes within 1.4 lunar distances, or 334,000 miles, from Earth.

The asteroid, estimated at between 150 and 600 meters in diameter -- about 500 feet to 1,900 feet, or the size of a football field, at 360 feet, to the size of Chicago's 110-story Sears Tower, at 1,454 feet -- was discovered by the University of Arizona's Catalina Sky Survey in October 2007. It poses no threat to Earth, but its near approach gives Arecibo astronomers a golden opportunity to learn more about potentially hazardous near-Earth objects.

"We don't yet know anything about this asteroid," said Mike Nolan, head of radar astronomy at the Puerto Rico observatory. Such objects pass near Earth with relative frequency, he said -- approximately one every five years or so -- but it's rare that astronomers have enough advance notice to plan for rigorous observing.

"Because it's coming so close, we'll get our highest quality imaging," said Nolan.

Using Arecibo's powerful radar, which is the most sensitive in the world, researchers will gauge the object's size, observe its speed and measure its spin. Switching then to imaging mode, which will offer resolution to 7.5 meters -- three times more precise than NASA's Goldstone telescope, the only other radar telescope in the world -- the researchers hope to map the object's surface in detail. The Robert C. Byrd Green Bank Telescope, Green Bank, W.Va., will receive Arecibo's echo from the asteroid and transmit its data back to Arecibo.

TU2 is one of an estimated 7,000 near-Earth objects, its size or larger -- most have never been closely studied.

"We have good images of a couple dozen objects like this, and for about one in 10, we see something we've never seen before," said Nolan. "We really haven't sampled the population enough to know what's out there."

Arecibo's radar is vital for continuing to classify and understand such objects, said Cornell University assistant professor of astronomy Jean-Luc Margot. "Arecibo does a fantastic job at getting images, discovering the shape, spin and reflection properties of such an object . . . all these things that are important to know."

The telescope will be trained on TU24 Jan. 27-28 and again Feb. 1-4. Goldstone's planetary radar observed it Jan. 23-24.

Steven Ostro, astronomer at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., is principal investigator for the project; also contributing are Lance Benner and Jon Giorgini at JPL and Greg Black of the University of Virginia. Their research is funded by NASA.

The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, a national research center operated by Cornell for the National Science Foundation. The Green Bank Telescope is operated by National Radio Astronomy Observatory for the National Science Foundation.

Adapted from materials provided by Cornell University.

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Asteroid To Make Rare Close Flyby Of Earth January 29

Daily Science Journal (Jan. 25, 2008) — Scientists are monitoring the orbit of asteroid 2007 TU24. The asteroid, believed to be between 150 meters (500 feet) and 610 meters (2,000 feet) in size, is expected to fly past Earth on Jan. 29, with its closest distance being about 537,500 kilometers (334,000 miles) at 12:33 a.m. Pacific time (3:33 a.m. Eastern time). It should be observable that night by amateur astronomers with modest-sized telescopes.

The illustration from an amateur astronomer shows the asteroid's track on the sky for 3 days near the time of the close Earth approach as seen from the city of Philadelphia. (Credit: Dr. Dale Ireland, Silverdale, WA)

Asteroid 2007 TU24 was discovered by the NASA-sponsored Catalina Sky Survey on Oct. 11, 2007. Scientists at NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif., have determined that there is no possibility of an impact with Earth in the foreseeable future.

"This will be the closest approach by a known asteroid of this size or larger until 2027," said Don Yeomans, manager of the Near Earth Object Program Office at JPL. "As its closest approach is about one-and-a-half times the distance of Earth to the moon, there is no reason for concern. On the contrary, Mother Nature is providing us an excellent opportunity to perform scientific observations."

Asteroid 2007 TU24 will reach an approximate apparent magnitude 10.3 on Jan. 29-30 before quickly becoming fainter as it moves farther from Earth. On that night, the asteroid will be observable in dark and clear skies through amateur telescopes with apertures of at least 7.6 centimeters (3 inches). An object with a magnitude of 10.3 is about 50 times fainter than an object just visible to the naked eye in a clear, dark sky.

NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called "Spaceguard," discovers, characterizes and computes trajectories for these objects to determine if any could be potentially hazardous to our planet.

Adapted from materials provided by NASA/Jet Propulsion Laboratory.

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Flyby Of Mercury Coming Up In NASA's Messenger Mission

Daily Science Journal (Jan. 11, 2008) — NASA will point a power-packed $8.7 million University of Colorado at Boulder space instrument at some of the last unexplored terrain in the inner solar system when the MESSENGER spacecraft whips within 125 miles of Mercury's surface Jan. 14 at a mind-boggling 141,000 miles per hour.

Artist's concept of the NASA's MESSENGER spaceraft at Mercury. (Credit: NASA)

Launched in August 2004, MESSENGER has already flown by Venus twice and will make the first of three flybys of Mercury next week before finally settling into orbit around Mercury in 2011. The only other time Mercury was visited by a spacecraft was in 1974 and 1975, when NASA's Mariner 10 spacecraft made three flybys and mapped roughly 45 percent of the bizarre planet's hot, rocky surface, according to NASA.

The car-sized MESSENGER spacecraft is carrying seven instruments -- a camera, a magnetometer, an altimeter and four spectrometers. The Mercury Atmospheric and Surface Composition Spectrometer, or MASCS, built by CU-Boulder's Laboratory for Atmospheric and Space Physics, was miniaturized to weigh less than seven pounds.

During the flyby, the probe’s instruments will gather data essential to planning the MESSENGER mission’s orbital phase. MESSENGER’s scientific instruments will begin to address the mission goals of:

• mapping the elemental and mineralogical composition of Mercury’s surface;
• imaging globally the surface at a resolution of hundreds of meters or better;
• determining the structure of the planet’s magnetic field;
• measuring the planet’s gravitational field structure; and
• characterizing exospheric neutral particles and magnetospheric ions and electrons.

The instrument will make measurements of Mercury's surface and tenuous atmosphere, said LASP Senior Research Associate William McClintock, a MESSENGER co-investigator who led the MASCS instrument development team. MASCS breaks up light like a prism, and since each element and compound in the universe has a unique spectral "signature," scientists can determine the distribution and abundance of various minerals and gases on the planet's surface and its atmosphere.

"Believe it or not, scientists have only a vague idea today about the composition of Mercury's surface," said McClintock. "The instrument will make ultraviolet, visible and near infrared observations of the surface of Mercury, which together should tell us a lot more about the planet's composition, formation and evolution."

MESSENGER is slated to zip by Mercury at about 11:25 a.m. MST on Jan. 14 and take data and images for about 90 minutes, said LASP's Mark Lankton, program manager for MASCS. The data will be sent via NASA's Deep Space Network to the Applied Physics Laboratory at Johns Hopkins University -- which is managing the mission for NASA -- where mission scientists, including researchers and students at LASP's Space Technology Building at the CU Research Park, will access it electronically, he said.

The circuitous, 4.9 billion-mile-journey to Mercury requires more than seven years and 13 loops around the sun to guide it closer to Mercury's orbit. The craft is equipped with a large sunshade and heat-resistant ceramic fabric to protect it from the sun. More than half of the weight of the 1.2-ton spacecraft consists of propellant and helium.

"The LASP team is really spun up for this flyby," said Lankton. "It's very exciting, because this is the beginning of the science phase of the MESSENGER mission. It's a chance for us to make observations that have never been made before."

MASCS will scan Mercury's thin atmosphere -- known as the exosphere -- to determine its composition, and the spacecraft will fly through a comet-shaped cloud of sodium enveloping the planet during the flyby, said McClintock. "We will fly it right down the cloud's tail," he said. "Understanding how the cloud is replenished with sodium is one of the many pieces of this giant puzzle at Mercury we hope to solve."

LASP Director Daniel Baker, also a co-investigator on the MESSENGER mission, will be studying Mercury's magnetic field and its interaction with the solar wind, including violent "sub-storms" that occur in the planet's vicinity. The strong magnetic field on Mercury indicates it most likely has a liquid or molten core like that on Earth, Baker said.

Mercury is about two-thirds of the way nearer to the sun than Earth and is bombarded with 10 times the solar radiation, said Baker. Sandwiched by the sun and Mercury -- which has daytime temperatures of about 800 degrees Fahrenheit -- the MESSENGER spacecraft will "essentially be on a huge rotisserie," he said.

LASP's vast experience in space during the last several decades should serve the team well. "We are the only space lab in the world to design and build instruments that are either on the way to or have visited every planet in the solar system," Baker said. "Because of our successes, I view our scientists, engineers and support staff and students like a Super Bowl team. We have star players at every position."

Dozens of undergraduates and graduate students will be involved in analyzing data as information and images begin pouring back to Earth from MESSENGER, dubbed "the little spacecraft that could" by LASP scientists. "This mission is going to be a field day for students, not only at CU-Boulder, but for students all over the world," said Baker.

Adapted from materials provided by University of Colorado at Boulder.

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Astronomers Monitor Asteroid To Pass Near Mars

Daily Science Journal (Dec. 21, 2007) — Astronomers funded by NASA are monitoring the trajectory of an asteroid estimated to be 50 meters (164 feet) wide that is expected to cross Mars' orbital path early next year. Observations provided by the astronomers and analyzed by NASA's Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif., indicate the object may pass within 30,000 miles of Mars at about 6 a.m. EST (3 a.m. PST) on Jan. 30, 2008.

This artist rendering uses an arrow to show the predicted path of the asteroid on Jan. 30, 2008, and the orange swath indicates the area it is expected to pass through. Mars may or may not be in its path. (Credit: NASA/JPL)

"Right now asteroid 2007 WD5 is about half-way between Earth and Mars and closing the distance at a speed of about 27,900 miles per hour," said Don Yeomans, manager of the Near Earth Object Office at JPL. "Over the next five weeks, we hope to gather more information from observatories so we can further refine the asteroid's trajectory."

NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called "Spaceguard," plots the orbits of these objects to determine if any could be potentially hazardous to our planet.

Asteroid 2007 WD5 was first discovered on Nov. 20, 2007, by the NASA-funded Catalina Sky Survey and put on a "watch list" because its orbit passes near Earth. Further observations from both the NASA-funded Spacewatch at Kitt Peak, Ariz., and the Magdalena Ridge Observatory in New Mexico gave scientists enough data to determine that the asteroid was not a danger to Earth, but could potentially impact Mars. This makes it a member of an interesting class of small objects that are both near Earth objects and "Mars crossers."

Because of current uncertainties about the asteroid's exact orbit, there is a 1-in-75 chance of 2007 WD5 impacting Mars. If this unlikely event were to occur, it would be somewhere within a broad swath across the planet north of where the Opportunity rover is located.

"We estimate such impacts occur on Mars every thousand years or so," said Steve Chesley, a scientist at JPL. "If 2007 WD5 were to thump Mars on Jan. 30, we calculate it would hit at about 30,000 miles per hour and might create a crater more than half-a-mile wide." The Mars Rover Opportunity is exploring a crater approximately this size right now.

Such a collision could release about three megatons of energy. Scientists believe an event of comparable magnitude occurred here on Earth in 1908 in Tunguska, Siberia, but no crater was created. The object was disintegrated by Earth's thicker atmosphere before it hit the ground, although the air blast devastated a large area of unpopulated forest.

NASA and its partners will continue to track asteroid 2007 WD5 and will provide an update in January when further information is available. For more information on the Near Earth Object program, visit: http://neo.jpl.nasa.gov/.

Adapted from materials provided by NASA/Jet Propulsion Laboratory.

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Astronomers Discover How White Dwarf Stars Get Their 'Kicks'

Daily Science Journal (Dec. 5, 2007) — University of British Columbia astronomer Harvey Richer and UBC graduate student Saul Davis have discovered that white dwarf stars are born with a natal kick, explaining why these smoldering embers of Sun-like stars are found on the edge rather than at the centre of globular star clusters.

These images show young and old white dwarf stars — the burned-out relics of normal stars — in the ancient globular star cluster NGC 6397. The image at left shows the dense swarm of hundreds of thousands of stars that make up the globular cluster. The image at top, right reveals young white dwarfs less than 800 million years old and older white dwarfs between 1.4 and 3.5 billion years old. The blue squares pinpoint the young white dwarfs; the red circles outline the older white dwarfs. (Credit: D. Verschatse (Antilhue Observatory, Chile), NASA, ESA, and H. Richer (University of British Columbia))

White dwarfs represent the third major stage of a star's evolution. Like the Sun, each star begins its life with a long stable state where nuclear reactions take place in the core supplying the energy. After the core fuel is depleted, it swells up and turns into a huge red giant. Later, the red giant ejects its outer atmosphere and its core becomes a white dwarf that slowly cools over time and radiates its stored thermal heat into space.

Using NASA's Hubble telescope, Richer and his team looked at the position of white dwarfs in NGC 6397, one of the globular star clusters closest to Earth. Globular clusters are dense swarms of hundreds of thousands of stars. About 150 of these clusters exist in the Milky Way, each containing between 100,000 and one million stars.

"The distribution of young white dwarfs is the exact opposite of what we expected," says Prof. Richer, whose study will appear in the Monthly Notices of the Royal Astronomical Society Letters in January 2008.

Richer explains that globular clusters sort out stars according to their mass, governed by a gravitational billiard-ball game among stars. Heavier stars slow down and sink to the cluster's core, while lighter stars pick up speed and move across the cluster to its outskirts. The team found that the older white dwarfs were behaving as expected; they were scattered throughout the cluster according to weight.

"Newly-minted white dwarfs should be near the center, but they are not," says Richer. "Our idea is that when these white dwarfs were born, they were given a small kick of 7,000 to 11,000 miles an hour (three to five kilometers a second), which rocketed them to the outer reaches of the cluster."

Using computer simulations, Richer and his team showed that when white dwarfs were born, their own mass acts like "rocket fuel" propelling them forward.

"If more of this mass is ejected in one direction, it could propel the emerging white dwarf through space, just as exhaust from a rocket engine thrusts it from the launch pad," says Richer.

The researchers studied 22 young white dwarfs up to about 800 million years old and 62 older white dwarfs between 1.4 and 3.5 billion years old. They distinguished the younger from the older white dwarfs based on their color and brightness. The younger ones are hotter, and therefore bluer and brighter than the older ones.

Study co-authors are: I. King, University of Washington; J.Anderson, Space Telescope Science Institute; J. Coffey, UBC, G. Fahlman, National Research Council of Canada's Herzberg Institute of Astrophysics; J Hurley. Swinburne, University of Technology; and J. Kalirai, University of California, Santa Cruz.

Adapted from materials provided by University of British Columbia, via EurekAlert!, a service of AAAS.

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