Posted on by Fraser Cain

Radio Telescopes Around the World Combine in Real Time

European and US radio astronomers have demonstrated a new way of observing the Universe – through the Internet!

Using cutting-edge technology, the researchers have managed to observe a distant star by using the world’s research networks to create a giant virtual telescope. The process has allowed them to image the object with unprecedented detail, in real-time; something which only a few years ago would have been impossible. The star chosen for this remarkable demonstration, called IRC+10420, is one of the most unusual in the sky. Surrounded by clouds of dusty gas and emitting strongly in radio waves, the object is poised at the end of its life, heading toward a cataclysmic explosion known as a ‘supernova’.

These new observations give an exciting glimpse of the future of radio astronomy. Using research networks, not only will radio astronomers be able to see deeper into the distant Universe, they’ll be able to capture unpredictable, transient events as they happen, reliably and quickly.

Astronomers are always seeking to maximise the resolution of their telescopes. Resolution is a measure of the amount of detail it can pick out. The bigger the telescope, the better the resolution. VLBI (or Very Long Baseline Interferometry) is a technique used by radio astronomers to image the sky in supreme detail. Instead of using a single radio dish, arrays of telescopes are linked together across whole countries or even continents. When the signals are combined in a specialised computer, the resulting image has a resolution equal to that of a telescope as large as the maximum antenna separation.

In the past, the VLBI technique was severely hampered because the data had to be recorded onto tape and then shipped to a central processing facility for analysis. Consequently, radio astronomers were unable to judge the success of their endeavours until many weeks, even months, after the observations were made. The solution, to link the telescopes electronically in real-time, enables astronomers to analyse the data as it happens. The technique, naturally called e-VLBI, is only possible now that high-bandwidth network connectivity is a reality.

The recent 20-hour long observations, performed on 22nd September using the European VLBI Network (EVN), involved radio telescopes in the UK, Sweden, the Netherlands, Poland and Puerto Rico. The maximum separation of the antennas was 8200 km, giving a resolution of at least 20 milliarcseconds (mas); this is about 5 times better than the Hubble Space Telescope (HST). This level of detail is equivalent to picking out a small building on the surface of the moon! The inclusion of the antenna at Arecibo, in Puerto Rico, also increased the sensitivity of the telescope array by a factor of 10. Even so, observing at a frequency of 1612 MHz, the signal from the distant star was more than a billion billion times weaker than a typical mobile phone handset!

Each telescope was connected to its country’s National Research and Education Network (NREN), and the data routed at 32 Mbits/second per telescope through GEANT, the pan-European research network, to SURFnet, the Dutch network. The data were then delivered to the Joint Institute for VLBI in Europe (JIVE), the central processing facility for the EVN in the Netherlands. There, the 9 Terabits of data were fed in real-time into a specialised supercomputer, called a ‘correlator’, and combined. The same research networks were then used to deliver the final data product directly to the astronomers who formed the image. Until the network infrastructure provided GEANT became available, astronomers were unable to transfer the huge amounts of data required for e-VLBI across the Internet. In a very real sense, the Internet itself acts like a telescope, performing the same job as the curved surfaces of the individual radio dishes. Dai Davies, General Manager of DANTE who operate GEANT, said “e-VLBI performed successfully on an intercontinental basis demonstrates in the clearest possible terms the importance of data communications networks to modern science. Research networking is fundamental to this new radio astronomy technique and it is very satisfying indeed to see the benefits that are now resulting from it”.

Although the scientific goals of the experiment were modest, these e-VLBI observations of IRC+10420 open up the possibility of watching the structures of astrophysical objects as they change. IRC+10420 is a supergiant star in the constellation of Aquila. It has a mass about 10 times that of our own Sun and lies about 15,000 light years from Earth. One of the brightest infrared sources in the sky, it is surrounded by a thick shell of dust and gas thrown out from the surface of the star at a rate of about 200 times the mass of the Earth every year. Radio astronomers are able to image the dust and gas surrounding IRC+10420 because one of the component molecules, hydroxyl (OH), reveals itself by means of strong ‘maser’ emission. Essentially, the astronomers see clumps of gas where radio emission is strongly amplified by special conditions. With the zoom lens provided by e-VLBI, astronomers can make images with great detail and watch the clumps of gas move, watch masers being born and die on timescales of weeks to months, and study the changing magnetic fields that permeate the shell. The results show that the gas is moving at about 40 km/s and was ejected from the star about 900 years ago. As Prof. Phil Diamond, one of the research team at Jodrell Bank Observatory (UK), explained, “the material we’re seeing in this image left the surface of the star at around the time of the Norman Conquest of England”.

It is believed IRC+10420 is rapidly evolving toward the end of its life. At some point, maybe thousands of years from now, maybe tomorrow, the star is expected to blow itself apart in one of the most energetic phenomena known in the Universe – a ‘supernova’. The resulting cloud of material will eventually form a new generation of stars and planetary systems. Radio astronomers are now poised, with the incredible power of e-VLBI, to catch the details as they happen and study the physical processes that are so important to the structure of our Galaxy and to life itself.

The emergent technology of e-VLBI is set to revolutionise radio astronomy. As network bandwidths increase, so too will the sensitivity of e-VLBI arrays, allowing clearer views of the furthest and faintest regions of space. Dr Mike Garrett, JIVE Director, commented, “These results provide a glimpse of the enormous potential of e-VLBI. The rapid progress in global communications networks should permit us to connect together the largest radio telescopes in the world at speeds exceeding tens of Gigabits per second over the next few years. The death throes of the first massive stars in the Universe, the emerging jets of matter from the central black-holes of the first galaxies, will be revealed in exquisite detail.”

Original Source: Jodrell Bank News Release

Posted on by Fraser Cain

Rovers Still Turning Up Water Evidence

NASA’s Spirit and Opportunity have been exploring Mars about three times as long as originally scheduled. The more they look, the more evidence of past liquid water on Mars these robots discover. Team members reported the new findings at a news briefing today.

About six months ago, Opportunity established that its exploration area was wet a long time ago. The area was wet before it dried and eroded into a wide plain. The team’s new findings suggest some rocks there may have gotten wet a second time, after an impact excavated a stadium sized crater.

Evidence of this exciting possibility has been identified in a flat rock dubbed “Escher” and in some neighboring rocks near the bottom of the crater. These plate-like rocks bear networks of cracks dividing the surface into patterns of polygons, somewhat similar in appearance to cracked mud after the water has dried up here on Earth.

Alternative histories, such as fracturing by the force of the crater-causing impact, or the final desiccation of the original wet environment that formed the rocks, might also explain the polygonal cracks. Rover scientists hope a lumpy boulder nicknamed “Wopmay,” Opportunity’s next target for inspection, may help narrow the list of possible explanations.

“When we saw these polygonal crack patterns, right away we thought of a secondary water event significantly later than the episode that created the rocks,” said Dr. John Grotzinger. He is a rover-team geologist from the Massachusetts Institute of Technology, Cambridge, Mass. Finding geological evidence about watery periods in Mars’ past is the rover project’s main goal, because such persistently wet environments may have been hospitable to life.

“Did these cracks form after the crater was created? We don’t really know yet,” Grotzinger said.

If they did, one possible source of moisture could be accumulations of frost partially melting during climate changes, as Mars wobbled on its axis of rotation, in cycles of tens of thousands of years. According to Grotzinger, another possibility could be the melting of underground ice or release of underground water in large enough quantity to pool a little lake within the crater.

One type of evidence Wopmay could add to the case for wet conditions after the crater formed would be a crust of water-soluble minerals. After examining that rock, the rover team’s plans for Opportunity are to get a close look at a tall stack of layers nicknamed “Burns Cliff” from the base of the cliff. The rover will then climb out of the crater and head south to the spacecraft’s original heat shield and nearby rugged terrain, where deeper rock layers may be exposed.

Halfway around Mars, Spirit is climbing higher into the “Columbia Hills.” Spirit drove more than three kilometers (approximately two miles) across a plain to reach them. After finding bedrock that had been extensively altered by water, scientists used the rover to look for relatively unchanged rock as a comparison for understanding the area’s full range of environmental changes. Instead, even the freshest-looking rocks examined by Spirit in the Columbia Hills have shown signs of pervasive water alteration.

“We haven’t seen a single unaltered volcanic rock, since we crossed the boundary from the plains into the hills, and I’m beginning to suspect we never will,” said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the science payload on both rovers. “All the rocks in the hills have been altered significantly by water. We’re having a wonderful time trying to work out exactly what happened here.”

More clues to deciphering the environmental history of the hills could lie in layered rock outcrops farther upslope, Spirit’s next targets. “Just as we worked our way deeper into the Endurance crater with Opportunity, we’ll work our way higher and higher into the hills with Spirit, looking at layered rocks and constructing a plausible geologic history,” Squyres said.

Jim Erickson, rover project manager at JPL, said, “Both Spirit and Opportunity have only minor problems, and there is really no way of knowing how much longer they will keep operating. However we are optimistic about their conditions, and we have just been given a new lease on life for them, a six-month extended mission that began Oct. 1. The solar power situation is better than expected, but these machines are already well past their design life. While they’re healthy, we’ll keep them working as hard as possible.”

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

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Motion of Material in the Early Universe

Cosmologists from the California Institute of Technology have used observations probing back to the remote epoch of the universe when atoms were first forming to detect movements among the seeds that gave rise to clusters of galaxies. The new results show the motion of primordial matter on its way to forming galaxy clusters and superclusters. The observations were obtained with an instrument high in the Chilean Andes known as the Cosmic Background Imager (CBI), and they provide new confidence in the accuracy of the standard model of the early universe in which rapid inflation occurred a brief instant after the Big Bang.

The novel feature of these polarization observations is that they reveal directly the seeds of galaxy clusters and their motions as they proceeded to form the first clusters of galaxies.

Reporting in the October 7 online edition of Science Express, Caltech’s Rawn Professor of Astronomy, and principal investigator on the CBI project, Anthony Readhead and his team say the new polarization results provide strong support for the standard model of the universe as a place in which dark matter and dark energy are much more prevalent than everyday matter as we know it, which poses a major problem for physics. A companion paper describing early polarization observations with the CBI has been submitted to the Astrophysical Journal.

The cosmic background observed by the CBI originates from the era just 400,000 years after the Big Bang and provides a wealth of information on the nature of the universe. At this remote epoch none of the familiar structures of the universe existed–there were no galaxies, stars, or planets. Instead there were only tiny density fluctuations, and these were the seeds out of which galaxies and stars formed under the hand of gravity.

Instruments prior to the CBI had detected fluctuations on large angular scales, corresponding to masses much larger than superclusters of galaxies. The high resolution of the CBI allowed the seeds of the structures we observe around us in the universe today to be observed for the first time in January 2000.

The expanding universe cooled and by 400,000 years after the Big Bang it was cool enough for electrons and protons to combine to form atoms. Prior to this time photons could not travel far before colliding with an electron, and the universe was like a dense fog, but at this point the universe became transparent and since that time the photons have streamed freely across the universe to reach our telescopes today, 13.8 billion years later. Thus observations of the microwave background provide a snapshot of the universe as it was just 400,000 years after the Big Bang–long before the formation of the first galaxies, stars, and planets.

The new data were collected by the CBI between September 2002 and May 2004, and cover four patches of sky, encompassing a total area three hundred times the size of the moon and showing fine details only a fraction of the size of the moon. The new results are based on a property of light called polarization. This is a property that can be demonstrated easily with a pair of polarizing sunglasses. If one looks at light reflected off a pond through such sunglasses and then rotates the sunglasses, one sees the reflected light varying in brightness. This is because the reflected light is polarized, and the polarizing sunglasses only transmit light whose polarization is properly aligned with the glasses. The CBI likewise picks out the polarized light, and it is the details of this light that reveal the motion of the seeds of galaxy clusters.

In the total intensity we see a series of peaks and valleys, where the peaks are successive harmonics of a fundamental “tone.” In the polarized emission we also see a series of peaks and valleys, but the peaks in the polarized emission coincide with the valleys in the total intensity, and vice versa. In other words, the polarized emission is exactly out of step with the total intensity. This property of the polarized emission being out of step with the total intensity indicates that the polarized emission arises from the motion of the material.

The first detection of polarized emission by the Degree Angular Scale Interferometer (DASI), the sister project of the CBI, in 2002 provided dramatic evidence of motion in the early universe, as did the measurements by the Wilkinson Microwave Anisotropy Probe (WMAP) in 2003. The CBI results announced today significantly augment these earlier findings by demonstrating directly, and on the small scales corresponding to galaxy clusters, that the polarized emission is out of step with the total intensity.

Other data on the cosmic microwave background polarization were released just two weeks ago by the DASI team, whose three years of results show further compelling evidence that the polarization is indeed due to the cosmic background and is not contaminated by radiation from the Milky Way. The results of these two sister projects therefore complement each other beautifully, as was the intention of Readhead and John Carlstrom, the principal investigator of DASI and a coauthor on the CBI paper, when they planned these two instruments a decade ago.

According to Readhead, “Physics has no satisfactory explanation for the dark energy which dominates the universe. This problem presents the most serious challenge to fundamental physics since the quantum and relativistic revolutions of a century ago. The successes of these polarization experiments give confidence in our ability to probe fine details of the polarized cosmic background, which will eventually throw light on the nature of this dark energy.”

“The success of these polarization experiments has opened a new window for exploring the universe which may allow us to probe the first instants of the universe through observations of gravitational waves from the epoch of inflation,” says Carlstrom.

The analysis of the CBI data is carried out in collaboration with groups at the National Radio Astronomy Observatory (NRAO) and at the Canadian Institute for Theoretical Astrophysics (CITA).

“This is truly an exciting time in cosmological research, with a remarkable convergence of theory and observation, a universe full of mysteries such as dark matter and dark energy, and a fantastic array of new technology–there is tremendous potential for fundamental discoveries here” says Steve Myers of the NRAO, a coauthor and key member of the CBI team from its inception.

According to Richard Bond, director of CITA and a coauthor of the paper, “As a theorist in the early eighties, when we were first showing that the magnitude of the cosmic microwave background polarization would likely be a factor of a hundred down in power from the minute temperature variations that were themselves a heroic effort to discover, it seemed wishful thinking that even in some far distant future such minute signals would be revealed. With these polarization detections, the wished-for has become reality, thanks to remarkable technological advances in experiments such as CBI. It has been our privilege at CITA to be fully engaged as members of the CBI team in unveiling these signals and interpreting their cosmological significance for what has emerged as the standard model of cosmic structure formation and evolution.”

The next step for Readhead and his CBI team will be to refine these polarization observations significantly by taking more data, and to test whether or not the polarized emission is exactly out of step with the total intensity with the goal of finding some clues to the nature of the dark matter and dark energy.

The CBI is a microwave telescope array comprising 13 separate antennas, each about three feet in diameter and operating in 10 frequency channels, set up in concert so that the entire instruments acts as a set of 780 interferometers. The CBI is located at Llano de Chajnantor, a high plateau in Chile at 16,800 feet, making it by far the most sophisticated scientific instrument ever used at such high altitudes. The telescope is so high, in fact, that members of the scientific team must each carry bottled oxygen to do the work.

The upgrade of the CBI to polarization capability was supported by a generous grant from the Kavli Operating Institute, and the project is also the grateful recipient of continuing support from Barbara and Stanley Rawn Jr. The CBI is also supported by the National Science Foundation, the California Institute of Technology, and the Canadian Institute for Advanced Research, and has also received generous support from Maxine and Ronald Linde, Cecil and Sally Drinkward, and the Kavli Institute for Cosmological Physics at the University of Chicago.

In addition to the scientists mentioned above, today’s Science Express paper is coauthored by C. Contaldi and J. L. Sievers of CITA, J.K. Cartwright and S. Padin, both of Caltech and the University of Chicago; B. S. Mason and M. Pospieszalski of the NRAO; C. Achermann, P. Altamirano, L. Bronfman, S. Casassus, and J. May all of the University of Chile; C. Dickinson, J. Kovac, T. J. Pearson, and M. Shepherd of Caltech; W. L. Holzapfel of UC Berkeley; E. M. Leitch and C. Pryke of the University of Chicago; D. Pogosyan of the University of Toronto and the University of Alberta; and R. Bustos, R. Reeves, and S. Torres of the University of Concepci?n, Chile.

Original Source: Caltech News Release

Posted on by Fraser Cain

Antarctica Is Getting Ready to Really Heat Up

While Antarctica has mostly cooled over the last 30 years, the trend is likely to rapidly reverse, according to a computer model study by NASA researchers. The study indicates the South Polar Region is expected to warm during the next 50 years.

Findings from the study, conducted by researchers Drew Shindell and Gavin Schmidt of NASA’s Goddard Institute of Space Studies (GISS), New York, appeared in the Geophysical Research Letters. Shindell and Schmidt found depleted ozone levels and greenhouse gases are contributing to cooler South Pole temperatures.

Low ozone levels in the stratosphere and increasing greenhouse gases promote a positive phase of a shifting atmospheric climate pattern in the Southern Hemisphere, called the Southern Annular Mode (SAM). A positive SAM isolates colder air in the Antarctic interior.

In the coming decades, ozone levels are expected to recover due to international treaties that banned ozone-depleting chemicals. Higher ozone in the stratosphere protects Earth’s surface from harmful ultraviolet radiation. The study found higher ozone levels might have a reverse impact on the SAM, promoting a warming, negative phase. In this way, the effects of ozone and greenhouse gases on the SAM may cancel each other out in the future. This could nullify the SAM’s affects and cause Antarctica to warm.

“Antarctica has been cooling, and one could argue some regions could escape warming, but this study finds this is not very likely,” Shindell said. “Global warming is expected to dominate in future trends.”

The SAM, similar to the Arctic Oscillation or Northern Annular Mode in the Northern Hemisphere, is a seesaw in atmospheric pressure between the pole and the lower latitudes over the Southern Ocean and the tip of South America.

These pressure shifts between positive and negative phases speed-up and slow down the westerly winds that encircle Antarctica. Since the late 1960s, the SAM has more and more favored its positive phase, leading to stronger westerly winds. These stronger westerly winds act as a kind of wall that isolates cold Antarctic air from warmer air in the lower latitudes, which leads to cooler temperatures.

Greenhouse gases and ozone depletion both lower temperatures in the high latitude stratosphere. The cooling strengthens the stratospheric whirling of westerly winds, which in turn influences the westerly winds in the lower atmosphere. According to the study, greenhouse gases and ozone have contributed roughly equally in promoting a strong-wind, positive SAM phase in the troposphere, the lowest part of the atmosphere.

Shindell and Schmidt used the NASA GISS Climate Model to run three sets of tests, each three times. For each scenario, the three runs were averaged together. Scenarios included the individual effects of greenhouse gases and ozone on the SAM, and then a third run that examined the effects of the two together.

The model included interactions between the oceans and atmosphere. Each model run began in 1945 and extended through 2055. For the most part, the simulations matched well compared with past observations.

Model inputs of increasing greenhouse gases were based upon observations through 1999, and upon the Intergovernmental Panel on Climate Change mid-range estimates of future emissions. Stratospheric ozone changes were based on earlier NASA GISS model runs that were found to be in good agreement with past observations and similar to those found in other chemistry-climate models for the future.

Shindell said the biggest long-term danger of global warming in this region would be ice sheets melting and sliding into the ocean. “If Antarctica really does warm up like this, then we have to think seriously about what level of warming might cause the ice sheets to break free and greatly increase global sea levels,” he said.

In the Antarctic Peninsula, ice sheets as big as Rhode Island have already collapsed into the ocean due to warming. The warming in this area is at least partially a result of the strengthened westerly winds that pass at latitudes of about 60 to 65 degrees south. As the peninsula sticks out from the continent, these winds carry warm maritime air that heats the peninsula.

Original Source: NASA News Release

Posted on by Fraser Cain

Epsom Salts Could Be a Source of Martian Water

Epsom-like salts believed to be common on Mars may be a major source of water there, say geologists at Indiana University Bloomington and Los Alamos National Laboratory. In their report in this week’s Nature, the scientists also speculate that the salts will provide a chemical record of water on the Red Planet.

“The Mars Odyssey orbiter recently showed that there may be as much as 10 percent water hidden in the Martian near-surface,” said David Bish, Haydn Murray Chair of Applied Clay Mineralogy at IU and a co-author of the report. “We were able to show that under Mars-like conditions, magnesium sulfate salts can contain a great deal of water. Our findings also suggest that the kinds of sulfates we find on Mars could give us a lot of insight into the history of water and mineral formation there.”

The scientists learned that magnesium sulfate salts are extremely sensitive to changes in temperature, pressure and humidity. For that reason, the scientists argue that information contained in the salts could be easily lost if samples were brought back to Earth for study. Instead, they say, future missions to Mars should measure the properties of the salts on site.

The existence of magnesium sulfate salts on Mars was first suggested by the 1976 Viking missions and has since been confirmed by the Mars Exploration Rover as well as the Odyssey and Pathfinder missions. One way to quash remaining doubts that the salts are really there, however, would be to equip a Martian rover with an X-ray diffractometer — an instrument that analyzes the properties of crystals. Coincidentally, such a device could also be used to examine magnesium sulfate salts on Mars. Bish and collaborators from NASA Ames and Los Alamos are currently developing a miniaturized X-ray diffractometer with NASA funding.

Some magnesium sulfate salts trap more water than others. Epsomite, for example, has the most water in it — 51 percent by weight — while hexahydrite and kieserite have less (47 percent and 13 percent by weight, respectively). The proportion of water to magnesium sulfate affects the chemical properties of the different salts.

While varying temperature, pressure and humidity inside an experimental chamber, the scientists studied how the different magnesium salts transform over time.

When temperature and pressure inside an experimental chamber were lowered to Mars-like conditions (minus 64 degrees Fahrenheit, and less than 1 percent of Earth’s normal surface pressure), crystals of epsomite initially transformed into slightly less watery hexahydrite crystals and then became disorganized, but they still contained water. In contrast, “kieserite doesn’t let go of its water very easily, even at very low pressure and humidity or at elevated temperatures,” Bish said.

But when the scientists increased humidity inside the experimental chamber, they found that kieserite transformed into hexahydrite and then epsomite, which have more water.

Bish and his Los Alamos colleagues believe that the proportion and distribution of hexahydrite, kieserite and other magnesium sulfate salts on Mars may hold a record of past changes in climate and whether or not water once flowed there. However, kieserite might not be preserved through cycles of wetting and drying because of its ability to rehydrate to hexahydrite and epsomite, which can then become amorphous through drying.

Los Alamos National Laboratory geologists David Vaniman, Steve Chipera, Claire Fialips, William Carey and William Feldman also contributed to the study. It was funded by LANL Directed Research and Development Funding and NASA Mars Fundamental Research Program grants.

Original Source: Indiana University News Release

Posted on by Fraser Cain

New Mission Will Survey the Entire Sky in Infrared

A new NASA mission will scan the entire sky in infrared light in search of nearby cool stars, planetary construction zones and the brightest galaxies in the universe.

Called the Wide-field Infrared Survey Explorer, the mission has been approved to proceed into the preliminary design phase as the next in NASA’s Medium-class Explorer program of lower cost, highly focused, rapid-development scientific spacecraft. It is scheduled to launch in 2008.

Like a powerful set of night vision goggles, the new space-based telescope will survey the cosmos with infrared detectors up to 500,000 times more sensitive than previous survey missions. It will reveal hundreds of cool, or failed, stars, called brown dwarfs, some of which may lie closer to us than any known stars.

“Approximately two-thirds of nearby stars are too cool to be detected with visible light,” said Principal Investigator Dr. Edward Wright of the University of California, Los Angeles, who proposed the new mission to NASA. “The Wide-field Infrared Survey Explorer will see most of them.”

The telescope will also provide a complete inventory of dusty planet-forming discs around nearby stars, and find colliding galaxies that emit more light – specifically infrared light – than any other galaxies in the universe. In the end, the survey will consist of more than one million images, from which hundreds of millions of space objects will be catalogued.

“The mission will complete the basic reconnaissance of the universe in mid-infrared wavelengths, providing a vast storehouse of knowledge that will endure for decades,” said Dr. Peter Eisenhardt, project scientist for the mission at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “This catalogue of data will also provide NASA’s future James Webb Space Telescope with a comprehensive list of targets.”

JPL will manage the Wide-field Infrared Survey Explorer at a total cost to NASA of approximately $208 million. William Irace of JPL is the project manager. The cryogenic instrument will be built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft will be built by Ball Aerospace and Technologies Corporation, Boulder, Colorado. Science operations and data processing will take place at the JPL/Caltech Infrared Processing and Analysis Center, Pasadena. Calif. JPL is a division of Caltech.

More than 70 U.S. and cooperative international scientific space missions have been part of NASA’s Explorer program. The missions are characterized by relatively moderate cost, and by small- to medium-sized missions that are capable of being built, tested and launched in a short time interval compared to the large observatories. NASA Goddard Space Flight Center, Greenbelt, Md., manages the Explorer program for the Science Mission Directorate, NASA Headquarters, Washington.

For more information, visit http://ds9.ssl.berkeley.edu/wise/ or http://explorers.gsfc.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

It Gave Until it Couldn’t Give Any More

Astronomers using the Gemini North and Keck II telescopes have peered inside a violent binary star system to find that one of the interacting stars has lost so much mass to its partner that it has regressed to a strange, inert body resembling no known star type.

Unable to sustain nuclear fusion at its core and doomed to orbit with its much more energetic white dwarf partner for millions of years, the dead star is essentially a new, indeterminate type of stellar object.

“Like the classic line about the aggrieved partner in a romantic relationship, the smaller donor star gave, and gave, and gave some more until it had nothing left to give,” says Steve B. Howell, an astronomer with Wisconsin-Indiana-Yale-NOAO (WIYN) telescope and the National Optical Astronomy Observatory, Tucson, AZ. “Now the donor star has reached a dead end – it is far too massive to be considered a super-planet, its composition does not match known brown dwarfs, and it is far too low in mass to be a star. There’s no true category for an object in such limbo.”

The binary system, known as EF Eridanus (abbreviated EF Eri), is located 300 light-years from Earth in the constellation Eridanus. EF Eri consists of a faint white dwarf star with about 60 percent of the mass of the Sun and the donor object of unknown type, which has an estimated bulk of only 1/20th of a solar mass.

Howell and Thomas E. Harrison of New Mexico State University made high-precision infrared measurements of the binary star system using the spectrographic capabilities of the Near Infrared Imager (NIRI) on the Gemini North telescope and NIRSPEC on Keck II both on Mauna Kea in December 2002 and September 2003, respectively. Supporting observations were made with the 2.1-meter telescope at Kitt Peak National Observatory near Tucson in September 2002.

EF Eri is a type of binary star system known as magnetic cataclysmic variables. This class of systems may produce many more of these ‘dead’ objects than scientists have realized, says Harrison, co-author of a paper on the discovery to be published in the October 20 issue of the Astrophysical Journal. “These types of systems are not generally accounted for within the usual census figures of star systems in a typical galaxy,” Harrison says. “They certainly should be considered more carefully.”

The white dwarf in EF Eri is a compressed, burnt-out remnant of a solar-type star that is now about the same diameter as the Earth, though it still emits copious amounts of visible light. Howell and Harrison observed EF Eri in the infrared because infrared light from the pair is naturally dominated by heat and longer wavelength emissions from the secondary object.

The scientific detective work to deduce the components of this binary system was complicated greatly by the cyclotron radiation emitted as free electrons spiral down the powerful magnetic field lines of the white dwarf. The white dwarf’s magnetic field is about 14 million times as powerful as the Sun’s. The resulting cyclotron radiation is emitted primarily in the infrared part of the spectrum.

“In our initial spectroscopy of EF Eri, we noted that some parts of the infrared continuum light became about 2-3 times brighter for a time period, then went away. This brightening repeated every orbit, and thus had to have an origin within the binary,” Howell explains. “We first thought the brightness change resulted from the difference between a heated side and a cooler side of the donor object, but further observations with Gemini and Keck instead pointed to cyclotron radiation. We ‘see’ this additional infrared component at the phases which occur when the radiation is beamed in our direction, and we do not see it when the beaming points in other directions.”

The 81-minute orbital period of the two objects was probably four or five hours when the mass transfer process began about five billion years ago. Originally, the secondary object may also have been similar in size to the Sun, with perhaps 50-100 percent of a solar mass.

“When this interactive process of mass transfer from the secondary star to the white dwarf begin, and why it stopped, both remain unknown to us,” Howell says. During this process, repeated outbursts and novae explosions were very likely. The physics of the process also caused the two objects to spiral closer to each other. Today, the two objects orbit each other at about the same separation as the distance from the Earth to the Moon. The donor object has regressed to a body with a diameter roughly equal to the planet Jupiter.

The combined observing power of the Gemini 8-meter and Keck 10-meter telescopes and their large primary mirrors, which were essential to this research, Howell says, makes it clear that neither spectral features of the donor nor its composition match any known type of brown dwarf or planet.

Derek Homeier University of Georgia created a series of computer models that attempt to replicate the conditions at EF Eri, but even the best of these do not match perfectly.

The shape of the spectra indicate a very cool object (about 1,700 degrees Kelvin, equivalent to a cool brown dwarf), yet they do not have the same detailed shape or key features of brown dwarf spectra. The coolest normal stars (very low mass M-type stars) are about 2,500 degrees K, and Jupiter is 124 degrees K. The close-in “hot Jupiter” exoplanets detected indirectly by other astronomers using their gravitational effect on their parent stars are estimated to be 1,000-1,600 degrees K.

There is a small chance that the EF Eri system could have originally consisted of the progenitor of the present-day white dwarf star and some sort of “super-planet” that survived the evolution of the white dwarf to result in the system observed now, but this is considered unlikely.

“There are about 15 other known binary systems out there that may be similar to EF Eri, but none has been studied enough to tell,” Howell says. “We are working on some of them right now, and trying to improve our models to better match the infrared spectra.”

Co-authors of this paper on EF Eri are Paula Szkody of the University of Washington in Seattle, and Joni Johnson and Heather Osborne of New Mexico State.

The WIYN 3.5-meter telescope is located at Kitt Peak National Observatory, 55 miles southwest of Tucson, AZ. Kitt Peak National Observatory is part of the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under a cooperative agreement with the National Science Foundation (NSF).

The national research agencies that form the Gemini Observatory partnership include: the US National Science Foundation (NSF), the UK Particle Physics and Astronomy Research Council (PPARC), the Canadian National Research Council (NRC), the Chilean Comisi?n Nacional de Investigaci?n Cientifica y Tecnol?gica (CONICYT), the Australian Research Council (ARC), the Argentinean Consejo Nacional de Investigaciones Cient?ficas y T?cnicas (CONICET) and the Brazilian Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq). The Observatory is managed by AURA under a cooperative agreement with the NSF.

The W.M. Keck Observatory is operated by the California Association for Research in Astronomy (CARA), a scientific partnership of the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration.

Original Source: Gemini News Release

Posted on by Fraser Cain

Rover’s Wheels Acting Up

Engineers on NASA’s Mars Exploration Rover team are investigating possible causes and remedies for a problem affecting the steering on Spirit.

The relay for steering actuators on Spirit’s right-front and left-rear wheels did not operate as commanded on Oct. 1. Each of the front and rear wheels on the rover has a steering actuator, or motor, that adjusts the direction in which the wheels are headed independently from the motor that makes the wheels roll. When the actuators are not in use, electric relays are closed and the motor acts as a brake to prevent unintended changes in direction.

Engineers received results from Spirit today from a first set of diagnostic tests on the relay. “We are interpreting the data and planning additional tests,” said Rick Welch, rover mission manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We hope to determine the best work-around if the problem does persist.”

Spirit and its twin, Opportunity, successfully completed their three-month primary missions in April and five-month mission extensions in September. They began second extensions of their missions on Oct. 1. Spirit has driven more than 3.6 kilometers (2.2 miles), six times the distance set as a goal for mission success. It is climbing into uplands called the “Columbia Hills.”

JPL’s Jim Erickson, rover project manager, said, “If we do not identify other remedies, the brakes could be released by a command to blow the fuse controlling the relay, though that would make those two brakes unavailable for the rest of the mission.” Without the steering-actuator brakes, small bumps or dips that a wheel hits during a drive might twist the wheel away from the intended drive direction.

“If we do need to disable the brakes, errors in drive direction could increase. However, the errors might be minimized by continuing to use the brakes on the left-front and right-rear wheels, by driving in smaller segments, and by adding a software patch to reset the direction periodically during a drive,” Erickson said. Engineers believe the steering-brake issue is not related to excessive friction detected during the summer in the drive motor for Spirit’s right-front wheel, because the steering actuator is a different motor.

Meanwhile, the team continues to use Spirit’s robotic arm and camera mast to study rocks and soils around the rover, without moving the vehicle until the cause of the anomaly is understood and corrective measures can be implemented.

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

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

The Great Observatories Examine Kepler’s Supernova

Four hundred years ago, sky watchers, including the famous astronomer Johannes Kepler, best known as the discoverer of the laws of planetary motion, were startled by the sudden appearance of a “new star” in the western sky, rivaling the brilliance of the nearby planets.

Modern astronomers, using NASA’s three orbiting Great Observatories, are unraveling the mysteries of the expanding remains of Kepler’s supernova, the last such object seen to explode in our Milky Way galaxy.

When a new star appeared Oct. 9, 1604, observers could use only their eyes to study it. The telescope would not be invented for another four years. A team of modern astronomers has the combined abilities of NASA’s Great Observatories, the Spitzer Space Telescope, Hubble Space Telescope and Chandra X-ray Observatory, to analyze the remains in infrared radiation, visible light, and X-rays. Ravi Sankrit and William Blair of the Johns Hopkins University in Baltimore lead the team.

The combined image unveils a bubble-shaped shroud of gas and dust, 14 light-years wide and expanding at 6 million kilometers per hour (4 million mph). Observations from each telescope highlight distinct features of the supernova, a fast-moving shell of iron-rich material, surrounded by an expanding shock wave sweeping up interstellar gas and dust.

“Multi-wavelength studies are absolutely essential for putting together a complete picture of how supernova remnants evolve,” Sankrit said. Sankrit is an associate research scientist, Center for Astrophysical Sciences at Hopkins and lead for Hubble astronomer observations.

“For instance, the infrared data are dominated by heated interstellar dust, while optical and X-ray observations sample different temperatures of gas,” Blair added. Blair is a research professor, Physics and Astronomy Department at Hopkins and lead astronomer for Spitzer observations. “A range of observations is needed to help us understand the complex relationship that exists among the various components,” Blair said.

The explosion of a star is a catastrophic event. The blast rips the star apart and unleashes a roughly spherical shock wave that expands outward at more than 35 million kilometers per hour (22 million mph) like an interstellar tsunami. The shock wave spreads out into surrounding space, sweeping up any tenuous interstellar gas and dust into an expanding shell. The stellar ejecta from the explosion initially trail behind the shock wave. It eventually catches up with the inner edge of the shell and is heated to X-ray temperatures.

Visible-light images from Hubble’s Advanced Camera for Surveys reveal where the supernova shock wave is slamming into the densest regions of surrounding gas. The bright glowing knots are dense clumps that form behind the shock wave. Sankrit and Blair compared their Hubble observations with those taken with ground-based telescopes to obtain a more accurate distance to the supernova remnant of about 13,000 light-years.

The astronomers used Spitzer to probe for material that radiates in infrared light, which shows heated microscopic dust particles that have been swept up by the supernova shock wave. Spitzer is sensitive enough to detect both the densest regions seen by Hubble and the entire expanding shock wave, a spherical cloud of material. Instruments on Spitzer also reveal information about the chemical composition and physical environment of the expanding clouds of gas and dust ejected into space. This dust is similar to dust which was part of the cloud of dust and gas that formed the Sun and planets in our solar system.

The Chandra X-ray data show regions of very hot gas. The hottest gas, higher-energy X-rays, is located primarily in the regions directly behind the shock front. These regions also show up in the Hubble observations and also align with the faint rim of material seen in the Spitzer data. Cooler X-ray gas, lower-energy X-rays, resides in a thick interior shell and marks the location of the material expelled from the exploded star.

There have been six known supernovas in our Milky Way over the past 1,000 years. Kepler’s is the only one for which astronomers do not know what type of star exploded. By combining information from all three Great Observatories, astronomers may find the clues they need. “It’s really a situation where the total is greater than the sum of the parts,” Blair said. “When the analysis is complete, we will be able to answer several questions about this enigmatic object.”

Images and additional information are available at http://www.nasa.gov, http://hubblesite.org/news/2004/29, http://chandra.harvard.edu , http://spitzer.caltech.edu ,http://www.jhu.edu/news_info/news/, http://heritage.stsci.edu/2004/29 and http://www.nasa.gov/vision/universe/starsgalaxies/kepler.html.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Rocket Will Launch 50 Nanosatellites

Image credit: Arianespace
During this year’s International Astronautical Federation (IAF) Congress in Vancouver, Canada, Arianespace, the Russian Space Agency with the support of the Russian space industry and IAF, in partnership with the leading space agencies from around the world, are proposing to commemorate the first satellite launch in 1957, by orbiting a cluster of 50 nanosatellites, each representing a different country.

Each nanosat will weigh about one kilogram, and will be dedicated to a scientific experiment under the responsibility of researchers at universities or other organizations. Each nanosat will offer a design life of about two years. All 50 will be launched on a single Arianespace mission.

“Arianespace is very proud to be participating in this commemoration,” said Jean-Yves Le Gall, the company’s Chief Executive Officer. “Supporting science and research is an integral part of our assigned mission. We have already orbited some 40 auxiliary payloads of the same type we will launch in 2007. Just like 50 years ago, when the first man-made Earth satellite was launched, these nanosatellites will signal a new era for scientists worldwide.”

Original Source: Arianespace News Release