Posted on by Fraser Cain

Clearer Images of the Milky Way’s Centre

The center of our Milky Way galaxy captured by Keck Laser Guide Star. Image credit: W.M. Keck Observatory/UCLA Click to enlarge
UCLA astronomers and colleagues have taken the first clear picture of the center of our Milky Way galaxy, including the area surrounding the supermassive black hole, using a new laser virtual star at the W.M. Keck observatory in Hawaii.

“Everything is much clearer now,” said Andrea Ghez, UCLA professor of physics and astronomy, who headed the research team. “We used a laser to improve the telescope’s vision ? a spectacular breakthrough that will help us understand the black hole’s environment and physics. It’s like getting Lasik surgery for the eyes, and will revolutionize what we can do in astronomy.”

Astronomers are used to working with images that are blurred by the Earth’s atmosphere. However, a laser virtual star, launched from the Keck telescope, can be used to correct the atmosphere’s distortions and clear up the picture. This new technology, called Laser Guide Star adaptive optics, will lead to important advances for the study of planets in our solar system and outside of our solar system, as well as galaxies, black holes, and how the universe formed and evolved, Ghez said.

“We have worked for years on techniques for ‘beating the distortions in the atmosphere’ and producing high-resolution images,” she said. “We are pleased to report the first Laser Guide Star adaptive optics observations of the center of our galaxy.”

Ghez and her colleagues took “snapshots” of the center of the galaxy, targeting the supermassive black hole 26,000 light years away, at different wavelengths. This approach allowed them to study the infrared light emanating from very hot material just outside the black hole’s “event horizon,” about to be pulled through.

“We are learning the conditions of the infalling material and whether this plays a role in the growth of the supermassive black hole,” Ghez said. “The infrared light varies dramatically from week to week, day to day and even within a single hour.”

The research, federally funded by the National Science Foundation, will be published Dec. 20 in the Astrophysical Journal Letters.

The research was conducted using the 10-meter Keck II Telescope, which is the world’s first 10-meter telescope with a laser on it. Laser Guide Star allows astronomers to “generate an artificial bright star” exactly where they want it, which reveals the atmosphere’s distortions.

Since 1995, Ghez has been using the W.M. Keck Observatory to study the galactic center and the movement of 200 nearby stars.

Black holes are collapsed stars so dense that nothing can escape their gravitational pull, not even light. Black holes cannot be seen directly, but their influence on nearby stars is visible, and provides a signature, Ghez said. The supermassive black hole, with a mass more than 3 million times that of our sun, is in the constellation of Sagittarius. The galactic center is located due south in the summer sky.

The black hole came into existence billions of years ago, perhaps as very massive stars collapsed at the end of their life cycles and coalesced into a single, supermassive object, Ghez said.

Co-authors on the research include UCLA graduate students Seth Hornstein and Jessica Lu; the adaptive optics team at W. M. Keck Observatory: David Le Mignant, Marcos Van Dam and Peter Wizinowich; Antonin Bouchez (formerly with the W. M. Keck Observatory) and Keith Matthews at Caltech; Mark Morris, a UCLA professor of physics and astronomy; and Eric Becklin, a UCLA professor of physics and astronomy.

Ghez provides more information, and images of the galactic center, at http://www.astro.ucla.edu/research/galcenter/.

Original Source: UCLA News Release

Posted on by Fraser Cain

Alpha Centauri’s Sounds Measured

Alpha Centauri and the Southern Cross. Image credit: ESO Click to enlarge
Astronomers have used ESO’s Very Large Telescope in Chile and the Anglo-Australian Telescope in eastern Australia as a ‘stellar stethoscope’ to listen to the internal rumblings of a nearby star. The data collected with the VLT have a precision better than 1.5 cm/s, or less than 0.06 km per hour!

By observing the star with two telescopes at the same time, the astronomers have made the most precise and detailed measurements to date of pulsations in a star similar to our Sun. They measured the rate at which the star’s surface is pulsing in and out, giving clues to the density, temperature, chemical composition and rotation of its inner layers – information that could not be obtained in any other way.

The astronomers from Denmark, Australia, and the USA used Kueyen, one of the four 8.2-m Unit Telescopes of ESO’s Very Large Telescope (VLT) at Cerro Paranal in Chile, and the 3.9-m Anglo-Australian Telescope (AAT) in New South Wales (Australia), to study the star Alpha Centauri B, one of our closest neighbours in space, about 4.3 light-years away.

Alpha Centauri is the brighter of the two ‘Pointers’ to the Southern Cross. Alpha Centauri itself is a triple system and Alpha Centauri B is an orange star, a little cooler and a little less massive than the Sun.

Churning gas in the star’s outer layers creates low-frequency sound waves that bounce around the inside of the star, causing it to ring like a bell. This makes the star’s surface pulsate in and out by very tiny amounts – only a dozen metres or so every four minutes. Astronomers can detect these changes by measuring the small, associated wavelength shifts.

The researchers sampled the light from Alpha Centauri B for seven nights in a row, making more than 5 000 observations in all. At the VLT, 3379 spectra were obtained with typical exposure times of 4 seconds and a median cadence of one exposure every 32 seconds! At the AAT 1642 spectra were collected, with typical exposures of 10 s, taken every 90 s.

“From this unique dataset, we were able to determine as many as 37 different patterns (or modes) of oscillation”, says Hans Kjeldsen, from University of Aarhus (Denmark) and lead author of the paper describing the results.

The astronomers also measured the mode lifetimes (how long the oscillations last), the frequencies of the modes, and their amplitudes (how far the surface of the star moves in and out). Such measurements are a huge technical challenge. Indeed, the star’ surface moves slowly, at the tortoise-like speed of 9 cm a second, or about 300 metre an hour. The astronomers borrowed their high-precision measurement technique from the planet-hunters, who also look for slight Doppler shifts in starlight.

“So much of what we think we know about the universe rests on the ages and properties of stars,” said Tim Bedding, from the University of Sydney and co-author of the study. “But there is still a great deal we don’t know about them.”

By using two telescopes at different sites the astronomers were able to observe the Alpha Centauri B as continuously as possible.

“That’s a huge advantage, because gaps in the data introduce ambiguity,” said Bedding. “The success of the observations also depended on the very stable spectrographs attached to the two telescopes – UVES at the VLT and UCLES at the AAT – which analysed the star’s light.”

Original Source: ESO News Release

Posted on by Fraser Cain

Greenland is Melting Faster

Decreasing levels of ice thickness from Greenland. Image credit: NASA/JPL. Click to enlarge.
In the first direct, comprehensive mass survey of the entire Greenland ice sheet, scientists using data from the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (Grace) have measured a significant decrease in the mass of the Greenland ice cap. Grace is a satellite mission that measures movement in Earth’s mass.

In an update to findings published in the journal Geophysical Research Letters, a team led by Dr. Isabella Velicogna of the University of Colorado, Boulder, found that Greenland’s ice sheet decreased by 162 (plus or minus 22) cubic kilometers a year between 2002 and 2005. This is higher than all previously published estimates, and it represents a change of about 0.4 millimeters (.016 inches) per year to global sea level rise.

“Greenland hosts the largest reservoir of freshwater in the northern hemisphere, and any substantial changes in the mass of its ice sheet will affect global sea level, ocean circulation and climate,” said Velicogna. “These results demonstrate Grace’s ability to measure monthly mass changes for an entire ice sheet ? a breakthrough in our ability to monitor such changes.”

Other recent Grace-related research includes measurements of seasonal changes in the Antarctic Circumpolar Current, Earth’s strongest ocean current system and a very significant force in global climate change. The Grace science team borrowed techniques from meteorologists who use atmospheric pressure to estimate winds. The team used Grace to estimate seasonal differences in ocean bottom pressure in order to estimate the intensity of the deep currents that move dense, cold water away from the Antarctic. This is the first study of seasonal variability along the full length of the Antarctic Circumpolar Current, which links the Atlantic, Pacific and Indian Oceans.

Dr. Victor Zlotnicki, an oceanographer at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., called the technique a first step in global satellite monitoring of deep ocean circulation, which moves heat and salt between ocean basins. This exchange of heat and salt links sea ice, sea surface temperature and other polar ocean properties with weather and climate-related phenomena such as El Ninos. Some scientific studies indicate that deep ocean circulation plays a significant role in global climate change.

The identical twin Grace satellites track minute changes in Earth’s gravity field resulting from regional changes in Earth’s mass. Masses of ice, air, water and solid Earth can be moved by weather patterns, seasonal change, climate change and even tectonic events, such as this past December’s Sumatra earthquake. To track these changes, Grace measures micron-scale changes in the 220-kilometer (137-mile) separation between the two satellites, which fly in formation. To limit degradation of Grace’s satellite antennas due to atomic oxygen exposure and thereby preserve mission life, a series of maneuvers was performed earlier this month to swap the satellites’ relative positions in orbit.

In a demonstration of the satellites’ sensitivity to minute changes in Earth’s mass, the Grace science team reported that the satellites were able to measure the deformation of the Earth’s crust caused by the December 2004 Sumatra earthquake. That quake changed Earth’s gravity by one part in a billion.

Dr. Byron Tapley, Grace principal investigator at the University of Texas at Austin, said that the detection of the Sumatra earthquake gravity signal illustrates Grace’s ability to measure changes on and within Earth’s surface. “Grace’s measurements will add a global perspective to studies of large earthquakes and their impacts,” said Tapley.

Grace is managed for NASA by JPL. The University of Texas Center for Space Research has overall mission responsibility. GeoForschungsZentrum Potsdam, or GFZ, Potsdam, Germany, is responsible for German mission elements. Science data processing, distribution, archiving and product verification are managed jointly by JPL, the University of Texas and GFZ.

Imagery related to these latest Grace findings may be viewed at: http://www.nasa.gov/vision/earth/lookingatearth/grace-images-20051220.html .

For more information on Grace, visit: http://www.csr.utexas.edu/grace or http://www.gfz-potsdam.de/grace .

Original Source: NASA News Release

Posted on by Fraser Cain

Pluto Mission is Around the Corner

NASA’s New Horizons spacecraft. Image credit: NASA/KSC Click to enlarge
NASA is preparing to launch the first spacecraft to distant Pluto and its moon Charon. The January 2006 launch of New Horizons will complete the initial reconnaissance of the planets in the solar system.

“New Horizons will study a unique world, and we can only imagine what we may learn. This is a prime example of scientific missions that complement the Vision for Space Exploration,” said Mary Cleave, associate administrator for NASA’s Science Mission Directorate.

The Vision for Space Exploration is a bold new course into the cosmos, a journey that will return the space shuttle safely to flight, complete the construction of the International Space Station, take humans back to the moon and eventually to Mars and beyond.

The National Academy of Sciences has ranked the exploration of Pluto-Charon and the Kuiper Belt among the highest priorities for space exploration, citing the fundamental scientific importance of these bodies to advancing understanding of our solar system.

Different than the inner, rocky planets (like Earth) or the outer gas giants, Pluto is a different type of planet known as an “ice dwarf,” commonly found in the Kuiper Belt region billions of miles from the sun.

“Exploring Pluto and the Kuiper Belt is like conducting an archeological dig into the history of the outer solar system, a place where we can peek into the ancient era of planetary formation,” said Alan Stern, New Horizons principal investigator, Southwest Research Institute Department of Space Studies, Boulder, Colo.

Designed and built at the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., pending launch approval, New Horizons is set to launch from Cape Canaveral Air Force Station, Fla., no earlier than Jan. 17, 2006. The launch window extends until Feb. 14, 2006.

The compact, 1,050-pound piano-sized probe will launch aboard an Atlas V expendable launch vehicle, followed by a boost from a kick-stage solid propellant motor. New Horizons will be the fastest spacecraft ever launched, reaching lunar orbit distance in just nine hours and passing Jupiter 13 months later.

Launch before Feb. 3 allows New Horizons to fly past Jupiter in early 2007 and use the planet’s gravity as a slingshot toward Pluto. The Jupiter flyby trims the trip to Pluto by five years and provides opportunities to test the spacecraft’s instruments and flyby capabilities on the Jupiter system.

The New Horizons science payload, developed under direction of Southwest Research Institute, includes imaging infrared and ultraviolet spectrometers, a multi-color camera, a long-range telescopic camera, two particle spectrometers, a space-dust detector and a radio science experiment. The dust counter was designed and built by students at the University of Colorado, Boulder.

Depending on its launch date, New Horizons could reach the Pluto system as early as mid-2015, conducting a five-month-long study possible only from the close-up vantage of a spacecraft. It will characterize the global geology and geomorphology of Pluto and Charon, map their surface compositions and temperatures, and examine Pluto’s atmospheric composition and structure. New Horizons also will study the small moons recently discovered in the Pluto system.

The spacecraft will “sleep” in electronic hibernation for much of the cruise to Pluto. Operators will turn off all but the most critical electronic systems and monitor the spacecraft once a year to check out critical systems, calibrate instruments and perform course corrections, if necessary.

The spacecraft will send back a beacon signal each week to give operators an instant read on spacecraft health. The entire spacecraft, drawing electricity from a single radioisotope thermoelectric generator, operates on less power than a pair of 100-watt household light bulbs.

For more information about NASA and the New Horizons mission on the Web, visit: http://www.nasa.gov/newhorizons

Original Source: NASA News Release

Update: Is Pluto still a planet? No.

Posted on by Fraser Cain

Have the Constants of Physics Remained Unchanged?

The Robert C. Byrd Green Bank Telescope. Image credit: NRAO Click to enlarge
An international team of astronomers has looked at something very big — a distant galaxy — to study the behavior of things very small — atoms and molecules — to gain vital clues about the fundamental nature of our entire Universe. The team used the National Science Foundation’s Robert C. Byrd Green Bank Telescope (GBT) to test whether the laws of nature have changed over vast spans of cosmic time.

“The fundamental constants of physics are expected to remain fixed across space and time; that’s why they’re called constants! Now, however, new theoretical models for the basic structure of matter indicate that they may change. We’re testing these predictions.” said Nissim Kanekar, an astronomer at the National Radio Astronomy Observatory (NRAO), in Socorro, New Mexico.

So far, the scientists’ measurements show no change in the constants. “We’ve put the most stringent limits yet on some changes in these constants, but that’s not the end of the story,” said Christopher Carilli, another NRAO astronomer.

“This is the exciting frontier where astronomy meets particle physics,” Carilli explained. The research can help answer fundamental questions about whether the basic components of matter are tiny particles or tiny vibrating strings, how many dimensions the Universe has, and the nature of “dark energy.”

The astronomers were looking for changes in two quantities: the ratio of the masses of the electron and the proton, and a number physicists call the fine structure constant, a combination of the electron charge, the speed of light and the Planck constant.

These values, considered fundamental physical constants, once were “taken as time independent, with values given once and forever” said German particle physicist Christof Wetterich. However, Wetterich explained, “the viewpoint of modern particle theory has changed in recent years,” with ideas such as superstring theory and extra dimensions in spacetime calling for the “constants” to change over time, he said.

The astronomers used the GBT to detect and study radio emissions at four specific frequencies between 1612 MHz and 1720 MHz coming from hydroxyl (OH) molecules in a galaxy more than 6 billion light-years from Earth, seen as it was at roughly half the Universe’s current age. Each of the four frequencies represents a specific change in the energy level of the molecule.

The exact frequency emitted or absorbed when the molecule undergoes a transition from one energy level to another depends on the values of the fundamental physical constants. However, each of the four frequencies studied in the OH molecule will react differently to a change in the constants. That difference is what the astronomers sought to detect using the GBT, which, Kanekar explained, is the ideal telescope for this work because of its technical capabilities and its location in the National Radio Quiet Zone, where radio interference is at a minimum.

“We can place very tight limits on changes in the physical constants by studying the behavior of these OH molecules at a time when the Universe was only about half its current age, and comparing this result to how the molecules behave today in the laboratory,” said Karl Menten of the Max-Planck Institute for Radioastronomy in Germany.

Wetterich, a theorist, welcomes the new capability, saying the observational method “seems very promising to obtain perhaps the most accurate values for such possible time changes of the constants.” He pointed out that, while some theoretical models call for the constants to change only in the early moments after the Big Bang, models of the recently-discovered, mysterious “dark energy” that seems to be accelerating the Universe’s expansion call for changes “even in the last couple of billion years.”

“Only observations can tell,” he said.

This research ties together the theoretical and observational work of Wetterich and Carilli, this year’s winners of the prestigious Max Planck Research Award of the Alexander von Humboldt Foundation and the Max Planck Society in Germany. Menten and Carilli have collaborated on research in this area for years, and Kanekar has pioneered the OH molecular technique.

Kanekar, Carilli and Menten worked with Glen Langston of NRAO, Graca Rocha of the Cavendish Laboratory in the UK, Francoise Combes of the Paris Observatory, Ravi Subrahmanyan of the Australia Telescope National Facility (ATNF), John Stocke of the University of Colorado, Frank Briggs of the ATNF and the Australian National University, and Tommy Wiklind of the Space Telescope Science Institute in Sweden. The scientists reported their findings in the December 31 edition of the scientific journal Physical Review Letters.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Original Source: NRAO News Release

Posted on by Mark Mortimer

Book Review: Women in Space

Being female makes for some basic biological differences. But as proven time and again, women have proven themselves capable to undertake and satisfactorily complete the same tasks as done by men. Given that piloting vehicles is less about strength and more about coordination and intuition, some would happily wager that women should excel in this role. However, because flight grew up as a tool of war and war has been a strictly male domain, women have always been at the periphery looking in. The insipient space industry also arose from a military foundation, hence, again men made decisions and prepared designs for themselves. Thus, though many women had the capability and desire to contribute, few opportunities arose for their participation in space.

Even though much could be said on the participation, or lack thereof, of women in space, Shayler and Moule’s book focuses solely on the achievements. The little seagull, Valentina Tereshkova, was the first woman to fly into space, but predecessors abounded. In acknowledging this, Shayler and Moule take the reader on a history lesson. They go to the 1700’s, when women astronomers were making their mark by flying in Montgolfier styled balloons. Parachuting, gliding and powered flight quickly succumbed to their skills. As most of these accomplishments could be achieved by an individual, women could and did do as they wished. This history review, though brief, amply demonstrates the ability of women.

In a juxtaposition, the book shows how, once society’s morality came into play, women were no longer equal players. That is, they were involved because of their sex, principally shown by the USSR in their program. The authors, however, stay with the facts by noting cosmonaut selection and training. After providing the backgrounds of many of these hopefuls, and the successful Valentina herself, Shayler and Moule switch back to the program of the United States. In an attempt to be broadly inclusive or perhaps to fill in a sorry lack of participation, they broaden their extent of achievements. There’s the female computers doing orbital trajectories as well as seamstresses who sewed flight suits and Skylab’s reflector. However, in using old phone books for identification, the authors let slip the narration and in consequence the book transposes into a series of lists rather than a discussion of accomplishments.

For example, much is made of Nichelle Nichols, better known as Uhura of Star Trek fame. True, she was prominent in early outreach programs for females but she did not directly contribute. There’s also description of the families and spouses of male astronauts. It wasn’t until the space shuttle era that women entered the mainstream. Sadly, here again, the authors trivialize their work by filling up much of the remainder of the book with data sheets. Using NASA Query Book and Press Kit factoids, they list every female who has flown on the space shuttle (or Soyuz), their technical background and their mission tasks. They go so far as identifying which shuttle seat they occupied during launch and return. Listing of minor roles, such as organizing flight shirts, clearly shows that the authors let NASA’s dogma dictate the contents. They neglect their own narrative abilities, which they ably showed in the earlier chapters.

By staying narrowly focussed on achievements, the author’s missed writing a great book rather than the good book they did write. They should have surmised on the precepts of a society that kept females in support roles while men achieved the glory. They alluded to but did not support the premise that shuttle crews would no longer include females so society would grieve less should another disaster occur. Does this mean men are more expendable? Sadly, their book never rises to this occasion.

There is no doubt that in most fields women are every bit as capable as men. The aerospace frontier is no exception. Women in Space by David Shayler and Ian Moule lists the women and their achievements as they and space flight increased in capability. From flying in balloons to piloting the space shuttle, they’re all in this book with great praise to their contributions.

Review by Mark Mortimer

Read more reviews online, or purchase a copy from Amazon.com.

Posted on by Fraser Cain

Rhea Hiding Behind the Rings

Saturn’s icy F ring. Image credit: NASA/JPL/SSI Click to enlarge
The searing arc of light seen here is Saturn’s icy F ring, seen nearly edge-on. In the background, Rhea (1,528 kilometers, or 949 miles across) is lit by reflected light from Saturn and the rings, with only the slightest sliver of light at its bottom being from direct sunlight.

The faint material surrounding the F ring likely lies in the planet’s equatorial plane, extending radially farther out and in from the main F ring core. A smaller fraction of this material could be vertically extended, and Cassini’s investigations should help to clarify this.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 30, 2005, at a distance of approximately 689,000 kilometers (428,000 miles) from Saturn. The image scale is approximately 4 kilometers (2 miles) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo. For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Enceladus is Creating one of Saturn’s Rings

Enceladus plume. Image credit: NASA/JPL/UA Click to enlarge
Cassini observations by several instruments have revealed the source of Saturn’s broadest and faintest ring. Recent observations show that tiny particles of frozen water ice are streaming outward into space from the south polar region of the moon Enceladus.

The source of geological activity on Enceladus is a mystery. “We’re amazed to see ice geysers on this little world that was thought to be cold and dead long ago,” commented Dr. Dale Cruikshank of NASA Ames Research center, a member of the visual and infrared mapping spectrometer team. “Some unexpected process is vigorously heating the interior of Enceladus, especially the south polar region, and causing the ejection of the plumes of ice particles.”

As the icy plumes jet out from the moon, the larger particles probably follow paths that mostly bring them back to the surface, while the smaller particles are nudged by sunlight into orbits around Saturn.

“Most of these small particles probably re-impact the moon, but the smallest ones eventually disperse as a result of radiation (light) pressure and interactions with Saturn’s magnetosphere to form the broad E ring,” said Dr. Mark Showalter of the SETI Institute, Mountain View, Calif. Thus, the E ring is currently being regenerated by some kind of geological activity in the interior of Enceladus.

During the Cassini spacecraft’s flyby on Nov. 26, the visual and infrared mapping spectrometer instrument measured the spectrum of the polar plumes of Enceladus. “We see a very clear signature of small ice particles in the plume data, in the form of a strong absorption band at 2.9 microns in an otherwise featureless spectrum,” said Dr. Phil Nicholson, professor of astronomy at Cornell University, Ithaca, N.Y. Nicholson is a member of the visual and infrared mapping spectrometer science team.

The visual and infrared mapping spectrometer images of Enceladus show not only the plume over the south pole, but also the dark side of the moon, silhouetted against a foggy background of light from the E Ring. Measurements of the spectrum show a very similar signature of small ice particles to that in the plumes, confirming earlier expectations that Enceladus is indeed the source of the E ring.

Preliminary analyses suggest that the average size of the particles in the plume is about 10 microns (1/100,000 of a meter), whereas the particles in the E ring are about three times smaller. The sunlit surface of Enceladus itself is also composed of water ice, but with a much larger grain size than the plume.

Original Source: NASA/JPL/SSI News Release