Tracking the Origins of Speedy Space Particles

NASA's Time History of Events and Macroscale Interaction during Substorms (THEMIS) spacecraft combined with computer models have helped track the origin of the energetic particles in Earth's magnetic atmosphere that appear during a kind of space weather called a substorm. Understanding the source of such particles and how they are shuttled through Earth's atmosphere is crucial to better understanding the Sun's complex space weather system and thus protect satellites or even humans in space.

The results show that these speedy electrons gain extra energy from changing magnetic fields far from the origin of the substorm that causes them. THEMIS, which consists of five orbiting satellites, helped provide these insights when three of the spacecraft traveled through a large substorm on February 15, 2008. This allowed scientists to track changes in particle energy over a large distance. The observations were consistent with numerical models showing an increase in energy due to changing magnetic fields, a process known as betatron acceleration.

"The origin of fast electrons in substorms has been a puzzle," says Maha Ashour-Abdalla, the lead author of a Nature Physics paper that appeared online on January 30, 2011 on the subject and a physicist at the University of California, Los Angeles. "It hasn't been clear until now if they got their burst of speed in the middle of the storm, or from some place further away."

Substorms originate opposite the sun on Earth's "night side," at a point about a third of the distance to the moon. At this point in space, energy and particles from the solar wind store up over time. This is also a point where the more orderly field lines near Earth -- where they look like two giant ears on either side of the globe, a shape known as a dipole since the lines bow down to touch Earth at the two poles – can distort into long lines and sometimes pull apart and "reconnect." During reconnection, the stored energy is released in explosions that send particles out in all directions. But reconnection is a magnetic phenomenon and scientists don't know the exact mechanism that creates speeding particles from that phenomenon.

"For thirty years, one of the questions about the magnetic environment around Earth has been, 'how do magnetic fields give rise to moving, energetic particles?'" says NASA scientist Melvyn Goldstein, chief of the Geospace Physics Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Md., and another author on the paper. "We need to know such things to help plan the next generation of reconnection research instruments such as the Magnetospheric MultiScale mission (MMS) due to launch in 2014. MMS needs to look in the right place and for the correct signatures of particle energization."

In the early 1980s, scientists hypothesized that the quick, high-energy particles might get their speed from rapidly changing magnetic fields. Changing magnetic fields can cause electrons to zoom along a corkscrew path by the betatron effect.

Indeed, electrons moving toward Earth from a substorm will naturally cross a host of changing magnetic fields as those long, stretched field lines far away from Earth relax back to the more familiar dipole field lines closer to Earth, a process called dipolarization. Betatron acceleration causes the particles to gain energy and speed much farther away from the initial reconnection site. But in the absence of observations that could simultaneously measure data near the reconnection site and closer to Earth, the hypothesis was hard to prove or contradict.

THEMIS, however, was specifically designed to study the formation of substorms. It launched with five spacecraft, which can be spread out over some 44,000 miles – a perfect tool for examining different areas of Earth's magnetic environment at the same time. Near midnight, on February 15, 2008, three of the satellites moving through Earth's magnetic tail, about 36,000 miles from Earth, traveled through a large substorm.

"I looked at the THEMIS data for that substorm," says Ashour-Abdalla, "and saw there was a direct correlation of the increased particle energy at the origin with the region of dipolarization nearer to Earth."

To examine the data, Ashour-Abdalla and a team of researchers from UCLA, Nanchang University in China, NASA Goddard Space Flight Center, and the University of Maryland, Baltimore, used their expertise with computer modeling to simulate the complex dynamics that occur in space. The team began with spacecraft data from an ESA mission called Cluster that was in the solar wind at the time of the substorm. Using these observations of the solar environment, they modeled large scale electric and magnetic fields in space around Earth. Then they modeled the future fate of the various particles observed.

When the team looked at their models they saw that electrons near the reconnection sites didn't gain much energy. But as they looked closer to Earth, where the THEMIS satellites were located, their model showed particles that had some ten times as much energy – just as THEMIS had in fact observed.

This is consistent with the betatron acceleration model. The electrons gain a small amount of energy from the reconnection and then travel toward Earth, crossing many changing magnetic field lines. These fields produce betatronic acceleration just as Kivelson predicted in the early 1980s, speeding the electrons up substantially.

"This research shows the great science that can be accomplished when modelers, theorists and observationalists join forces," says astrophysicist Larry Kepko, who is a deputy project scientist for the THEMIS mission at Goddard. "THEMIS continues to yield critical insights into the dynamic processes that produce the space weather that affects Earth."

Launched in 2007, THEMIS was NASA's first five-satellite mission launched aboard a single rocket. The unique constellation of satellites provided scientists with data to help resolve the mystery of how Earth's magnetosphere stores and releases energy from the sun by triggering geomagnetic substorms. Two of the satellites have been renamed ARTEMIS and are in the process of moving to a new orbit around the moon. They are due to reach their final lunar orbit in July 2011. The three remaining THEMIS satellites continue to study substorms.

THEMIS is managed by NASA's Goddard Space Flight Center for the agency's Science Mission Directorate. The Space Sciences Laboratory at the University of California, Berkeley, is responsible for project management, space and ground-based instruments, mission integration, mission operations and science. ATK (formerly Swales Aerospace), Beltsville, Md., built the THEMIS probes. THEMIS is an international project conducted in partnership with Germany, France, Austria, and Canada.

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NASA's New Lander Prototype Skates Through Integration and Testing

NASA engineers successfully integrated and completed system testing on a new robotic lander recently at Teledyne Brown Engineering’s facility in Huntsville in support of the Robotic Lunar Lander Project at NASA's Marshall Space Flight Center in Huntsville, Ala.

The lander prototype was placed on modified skateboards and a customized track system as a low-cost solution to control movement during final testing of the prototype’s sensors, onboard computer, and thrusters. The functional test focused on ensuring that all system components work seamlessly to sense, communicate, and command the lander's movements.

The prototype will be transported to the United States Army Redstone Arsenal Test Center in Huntsville this week to begin strap-down testing, which will lead to free-flying tests later this year.

The lander prototype will aid NASA’s development of a new generation of small, smart, versatile landers for airless bodies such as the moon and asteroids. The lander's design is based on cutting-edge technology, which allows precision landing in high-risk, but high-priority areas, enabling NASA to achieve scientific and exploration goals in previously unexplored locations.

Development of the lander prototype is a cooperative endeavor led by the Robotic Lunar Lander Development Project at the Marshall Center, Johns Hopkins Applied Physics Laboratory of Laurel, Md., and the Von Braun Center for Science and Innovation, which includes the Science Applications International Corporation, Dynetics Corp., Teledyne Brown Engineering Inc., and Millennium Engineering and Integration Company, all of Huntsville.

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NASA Comet Hunter Spots Its Valentine

NASA's Stardust spacecraft has downlinked its first images of comet Tempel 1, the target of a flyby planned for Valentine's Day, Feb. 14. The images were taken on Jan. 18 and 19 from a distance of 26.3 million kilometers (16.3 million miles), and 25.4 million kilometers (15.8 million miles) respectively. On Feb. 14, Stardust will fly within about 200 kilometers (124 miles) of the comet's nucleus.

"This is the first of many images to come of comet Tempel 1," said Joe Veverka, principal investigator of NASA's Stardust-NExT mission from Cornell University, Ithaca, N.Y. "Encountering something as small and fast as a comet in the vastness of space is always a challenge, but we are very pleased with how things are setting up for our Valentine's Day flyby."

The composite image is a combination of several images taken by Stardust's navigation camera. Future images will be used to help mission navigators refine Stardust's trajectory, or flight path, as it closes the distance between comet and spacecraft at a rate of about 950,000 kilometers (590,000 miles) a day. On the night of encounter, the navigation camera will be used to acquire 72 high-resolution images of the comet's surface features. Stardust-NExT mission scientists will use these images to see how surface features on comet Tempel 1 have changed over the past five-and-a-half years. (Tempel 1 had previously been visited and imaged in July of 2005 by NASA's Deep Impact mission).

Launched on Feb. 7, 1999, Stardust became the first spacecraft in history to collect samples from a comet (comet Wild 2), and return them to Earth for study. While its sample return capsule parachuted to Earth in January 2006, mission controllers were placing the still-viable spacecraft on a path that would allow NASA the opportunity to re-use the already-proven flight system if a target of opportunity presented itself. In January 2007, NASA re-christened the mission "Stardust-NExT" (New Exploration of Tempel), and the Stardust team began a four-and-a-half year journey for the spacecraft to comet Tempel 1. This will be the second exploration of Tempel 1 by a spacecraft (Deep Impact).

Along with the high-resolution images of the comet's surface, Stardust-NExT will also measure the composition, size distribution and flux of dust emitted into the coma, and provide important new information on how Jupiter-family comets evolve and how they formed 4.6 billion years ago.

Stardust-NExT is a low-cost mission that will expand the investigation of comet Tempel 1 initiated by NASA's Deep Impact spacecraft. JPL, a division of the California Institute of Technology in Pasadena, manages Stardust-NExT for the NASA Science Mission Directorate, Washington, D.C. Joe Veverka of Cornell University, Ithaca, N.Y., is the mission's principal investigator. Lockheed Martin Space Systems, Denver, built the spacecraft and manages day-to-day mission operations.

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NASA's Hubble Finds Most Distant Galaxy Candidate Ever Seen in Universe

Astronomers have pushed NASA's Hubble Space Telescope to its limits by finding what is likely to be the most distant object ever seen in the universe. The object's light traveled 13.2 billion years to reach Hubble, roughly 150 million years longer than the previous record holder. The age of the universe is approximately 13.7 billion years.

The tiny, dim object is a compact galaxy of blue stars that existed 480 million years after the big bang. More than 100 such mini-galaxies would be needed to make up our Milky Way. The new research offers surprising evidence that the rate of star birth in the early universe grew dramatically, increasing by about a factor of 10 from 480 million years to 650 million years after the big bang.

"NASA continues to reach for new heights, and this latest Hubble discovery will deepen our understanding of the universe and benefit generations to come,” said NASA Administrator Charles Bolden, who was the pilot of the space shuttle mission that carried Hubble to orbit. “We could only dream when we launched Hubble more than 20 years ago that it would have the ability to make these types of groundbreaking discoveries and rewrite textbooks.”

Astronomers don't know exactly when the first stars appeared in the universe, but every step farther from Earth takes them deeper into the early formative years when stars and galaxies began to emerge in the aftermath of the big bang.

"These observations provide us with our best insights yet into the earlier primeval objects that have yet to be found," said Rychard Bouwens of the University of Leiden in the Netherlands. Bouwens and Illingworth report the discovery in the Jan. 27 issue of the British science journal Nature.

This observation was made with the Wide Field Camera 3 starting just a few months after it was installed in the observatory in May 2009, during the last NASA space shuttle servicing mission to Hubble. After more than a year of detailed observations and analysis, the object was positively identified in the camera's Hubble Ultra Deep Field-Infrared data taken in the late summers of 2009 and 2010.

The object appears as a faint dot of starlight in the Hubble exposures. It is too young and too small to have the familiar spiral shape that is characteristic of galaxies in the local universe. Although its individual stars can't be resolved by Hubble, the evidence suggests this is a compact galaxy of hot stars formed more than 100-to-200 million years earlier from gas trapped in a pocket of dark matter.

"We're peering into an era where big changes are afoot," said Garth Illingworth of the University of California at Santa Cruz. "The rapid rate at which the star birth is changing tells us if we go a little further back in time we're going to see even more dramatic changes, closer to when the first galaxies were just starting to form."

The proto-galaxy is only visible at the farthest infrared wavelengths observable by Hubble. Observations of earlier times, when the first stars and galaxies were forming, will require Hubble’s successor, the James Webb Space Telescope (JWST).

The hypothesized hierarchical growth of galaxies -- from stellar clumps to majestic spirals and ellipticals -- didn't become evident until the Hubble deep field exposures. The first 500 million years of the universe's existence, from a z of 1000 to 10, is the missing chapter in the hierarchical growth of galaxies. It's not clear how the universe assembled structure out of a darkening, cooling fireball of the big bang. As with a developing embryo, astronomers know there must have been an early period of rapid changes that would set the initial conditions to make the universe of galaxies what it is today.

"After 20 years of opening our eyes to the universe around us, Hubble continues to awe and surprise astronomers," said Jon Morse, NASA's Astrophysics Division director at the agency's headquarters in Washington. "It now offers a tantalizing look at the very edge of the known universe -- a frontier NASA strives to explore."

Hubble is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.

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Runaway Star Plows Through Space

A massive star flung away from its former companion is plowing through space dust. The result is a brilliant bow shock, seen here as a yellow arc in a new image from NASA's Wide-field Infrared Survey Explorer, or WISE.

The star, named Zeta Ophiuchi, is huge, with a mass of about 20 times that of our sun. In this image, in which infrared light has been translated into visible colors we see with our eyes, the star appears as the blue dot inside the bow shock.

Zeta Ophiuchi once orbited around an even heftier star. But when that star exploded in a supernova, Zeta Ophiuchi shot away like a bullet. It's traveling at a whopping 54,000 miles per hour (or 24 kilometers per second), and heading toward the upper left area of the picture.

As the star tears through space, its powerful winds push gas and dust out of its way and into what is called a bow shock. The material in the bow shock is so compressed that it glows with infrared light that WISE can see. The effect is similar to what happens when a boat speeds through water, pushing a wave in front of it.

This bow shock is completely hidden in visible light. Infrared images like this one from WISE are therefore important for shedding new light on the region.

JPL manages and operates WISE for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by NASA's Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

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Cosmonauts Perform 27th Russian Space Station Spacewalk

Two Russian cosmonauts ventured outside the International Space Station on Jan. 21 to complete installation of a new high-speed data transmission system, remove an old plasma pulse experiment, install a camera for the new Rassvet docking module and retrieve a materials exposure package.

Expedition 26 Flight Engineers Dmitry Kondratyev and Oleg Skripochka began the five-hour, 23-minute excursion at 9:29 a.m. EST. Both spacewalkers wore Russian Orlan-MK spacesuits.

Kondratyev was designated as Extravehicular 1 (EV1), with a red stripe on his suit, and Skripochka is EV2, with a blue stripe on his suit. Skripochka also wore a NASA-provided wireless television camera system and helmet lights to provide live point-of-view video to Mission Control-Moscow, which provided ground support for the spacewalk. Mission Control-Houston monitored the spacewalk as well.

Before the spacewalk began, Commander Scott Kelly and Flight Engineer Alexander Kaleri climbed into their Soyuz 24 spacecraft, which is docked to the Poisk module on the opposite side of Zvezda from the airlock, and sealed the hatches between Zvezda and Poisk. This protected against the unlikely possibility of a sudden station depressurization and also allowed for the use of the forward portion of Zvezda as a backup airlock if necessary. Flight Engineers Cady Coleman and Paolo Nespoli were in the U.S. segment and had access to their Soyuz 25 spacecraft, which is docked to the Rassvet module adjacent to Pirs on the Zarya control module; therefore they did not need to be sequestered.

As a sunrise dawned on the station, Kondratyev and Skripochka opened the Pirs hatch and began exiting the Russian segment of the station. They took with them a spacewalk tool carrier, an antenna and cable reel for the data transmission system, and protective covers for the experiments they were to bring back inside the station. All was temporarily affixed to the Zvezda service module’s exterior for handy access near the respective work sites.

The first job was to deploy the antenna for the Radio Technical System for Information Transfer, an experimental system designed to enable large data files to be downlinked using radio technology at a speed of about 100 megabytes a second from the Russian segment of the station. The system is similar to the NASA system already in use. Later in the spacewalk, the crew also routed external cabling to connect the antenna to patch panels connecting it to the cabling and computer systems already installed inside the station. They also jettisoned the antenna’s hatbox-shaped cover and the cable reel.

Next, the spacewalkers removed a plasma pulse generator on the port side of Zvezda that was part of an experiment to investigate disturbances and changes in the ionosphere from space station impulse plasma flow. The generator, which failed early on, was covered, removed and returned inside the station. They also removed the commercial Expose-R experiment from the port side of Zvezda. The joint Russian and European Space Agency package contains a number of material samples that were left open to space conditions. They returned both to the Pirs airlock and stowed them there, along with a tool carrier that was needed for the tasks earlier in the spacewalk. The plasma generator eventually will be disposed of in a departing Progress resupply craft, while the Expose-R experiment’s three cassettes will be removed inside the station, sealed and returned to Earth for study on a returning Soyuz.

While in the airlock, they grabbed the new docking camera for the Rassvet module and carried it to the worksite on Rassvet. During Russian spacewalk 26 in November, the crew had trouble installing the camera due to interference with multi-layer insulation adjacent to the camera mount. So, once outside again, Kondratyev and Skripochka used a special cutter to rip the threads on some of the insulation material to allow full access to the camera mount. Once the camera was installed, they mated the camera’s cable to a pre-wired connector that will route the video into the station. The camera isn’t crucial to Soyuz and Progress dockings on Rassvet, but provides additional information and situational awareness for remote-control operations when necessary.

With all tasks complete, Kondratyev and Skripochka re-entered the Pirs airlock and ended their spacewalk at 2:52 p.m.

The duo also will conduct the next Russian spacewalk, planned for Feb. 16. That spacewalk will focus on installation of two more scientific experiments on the Zvezda module. The first is called Radiometria, and is designed to collect information useful in seismic forecasts and earthquake predictions. The second is Molniya-Gamma, which will look at gamma splashes and optical radiation during terrestrial lightning and thunderstorm conditions using three sensors.

They’ll also retrieve two Komplast panels from the exterior of the Zarya module, and deploy a small satellite named ARISSat-1. The panels contain materials exposed to space, and are part of a series of international experiments looking for the best materials to use in building long-duration spacecraft.

They’ll deploy ARISSat-1, the first of a series of educational satellites being developed in a partnership with the Radio Amateur Satellite Corp. (AMSAT), the NASA Office of Education ISS National Lab Project, the Amateur Radio on ISS (ARISS) working group and RSC-Energia. ARISSat satellites can carry up to five student experiments and the data from these experiments will be transmitted to the ground via an amateur radio link. In addition, ARISSat will transmit still frame video Earth views from four onboard cameras, commemorative greetings in native languages from students around the world, and a Morse code tracking beacon. ARISSat also will function as a world-wide space communications utility for use by amateur radio operators.

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WORF First Image Web Feature

A test photo of British Columbia's snow-capped west coast mountains is the first official image taken from the International Space Station's new Window Observational Research Facility, or WORF.

The image was taken to test the functionality of the control computer and camera associated with EarthKAM, an educational outreach project that allows Earth bound middle school students to take pictures of our home planet from the unique perspective of the space station, 220 miles above the Earth's surface. WORF was delivered to the station on the STS-131 mission of space shuttle Discovery in April 2010.

EarthKAM uses a Nikon D2X digital camera, and was set up in the WORF by Expedition 26 NASA flight engineer Cady Coleman on Jan. 17. EarthKAM ground controllers took the test photo. Expedition 26 also includes Commander Scott Kelly of NASA, European Space Agency astronaut Paolo Nespoli, and Russian cosmonauts Oleg Skripochka, Alexander Kaleri and Dmitry Kontratyev.

The test photo, designated ISS EarthKAM Image Winter 2011 #9362, is of an area of British Columbia, Canada, just north of Vancouver Island. The center point of the photo is 51 degrees, 48 minutes north and 127 degrees, 54 minutes west. Visible in the photo are Calvert and Hecate Islands on the Canadian coast and the southern portion of Hunter Island. Also visible are glaciers of the Ha-iltzuk Icefield near the 8,720-foot-tall -- 2,658-meter-tall -- Mount Somolenko. Mount Somolenko is a volcanic peak in southwestern British Columbia, that lies in a circular volcanic depression in the Pacific Ranges of the Coast Mountains called the Silverthrone Caldera.

While this isn't a particularly unique Earth observation image, it is notable that even though it was taken with a wider angle, 50mm lens and covers an area 124 miles/200 kilometers, by 83 miles/134 kilometers, it can be enlarged by more than 400 percent while keeping features in the photo identifiable. This is made possible by the high-quality optics of the Earth-facing window of the Destiny Laboratory, which was launched on Feb. 7, 2001.

The installation of WORF allowed removal of an internal "scratch pane" that has reduced the quality of images taken though the window. WORF also provides a highly stable mounting platform to hold cameras and sensors rock steady at the window, as well as the power, command, data, and cooling connections needed for their operation.

"With the WORF finally in place we can now for the first time make full use of the investment we made in having an optical quality window onboard the station for Earth science and observation," said former astronaut Mario Runco, who was part of the design and development teams for the Destiny window and WORF, and now serves as NASA's lead for Spacecraft Window Optics and Window/WORF Utilization at NASA's Johnson Space Center, Houston.

"We are very excited to have a new camera system that appears to be functional and taking incredible images," said Karen Flammer, who manages EarthKAM operations at the University of California, can Diego. "The first student images were taken by Parkview Montessori in the Jackson-Madison County (Tenn.) School System, and Public School 229 - Dyker in Brooklyn, N.Y., part of the New York City Department of Education.

Parkview teacher Vickie LeCroy's students plan to study landforms, such as islands, mountains and deserts in the image they took of Mexico, and Dyker teacher Camille Fratantoni’s students plan to enrich their studies of earth science and learn more about NASA missions.

In addition to their educational outreach role with EarthKAM, the combination of the window and WORF adds to the station's capabilities as an Earth science remote sensing platform for high-resolution cameras and multi and hyperspectral imagers. Images from space have many applications, such as in the study of climate and meteorology; oceanography; geology and volcanology; coastal, agricultural, ranch and forestry management; and disaster assessments and management.

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Swift Survey Finds 'Missing' Active Galaxies

Seen in X-rays, the entire sky is aglow. Even far away from bright sources, X-rays originating from beyond our galaxy provide a steady glow in every direction. Astronomers have long suspected that the chief contributors to this cosmic X-ray background were dust-swaddled black holes at the centers of active galaxies. The trouble was, too few of them were detected to do the job.

An international team of scientists using data from NASA's Swift satellite confirms the existence of a largely unseen population of black-hole-powered galaxies. Their X-ray emissions are so heavily absorbed that little more than a dozen are known. Yet astronomers say that despite the deeply dimmed X-rays, the sources may represent the tip of the iceberg, accounting for at least one-fifth of all active galaxies.

"These heavily shrouded black holes are all around us," said Neil Gehrels, the Swift principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Md., and a co-author of the new study. "But before Swift, they were just too faint and too obscured for us to see."

The findings appear in the Feb. 10 issue of The Astrophysical Journal.

Most large galaxies contain a giant central black hole, and those observed in the Swift study weigh in at about 100 million times the sun's mass. In an active galaxy, matter falling toward the supermassive black hole powers high-energy emissions so intense that two classes of active galaxies, quasars and blazars, rank as the most luminous objects in the universe.

The X-ray background led astronomers to suspect that active galaxies were undercounted. Astronomers could never be certain that they had detected most of even the closest active galaxies. Thick clouds of dust and gas surround the central black hole and screen out ultraviolet, optical and low-energy (or soft) X-ray light. While infrared radiation can make it through the material, it can be confused with warm dust in the galaxy's star-forming regions.

However, some of the black hole's more energetic X-rays do penetrate the shroud, and that's where Swift comes in.

Since 2004, Swift's Burst Alert Telescope (BAT), developed and operated at NASA Goddard, has been mapping the entire sky in hard X-rays with energies between 15,000 and 200,000 electron volts -- thousands of times the energy of visible light. Gradually building up its exposure year after year, the survey is now the largest, most sensitive and most complete census at these energies. It includes hundreds of active galaxies out to a distance of 650 million light-years.

From this sample, the researchers eliminated sources less than 15 degrees away from the dusty, crowded plane of our own galaxy. All active galaxies sporting an energetic particle jet were also not considered, leaving 199 galaxies.

Although there are many different types of active galaxy, astronomers explain the different observed properties based on how the galaxy angles into our line of sight. We view the brightest ones nearly face on, but as the angle increases, the surrounding ring of gas and dust absorbs increasing amounts of the black hole's emissions.

Astronomers assumed that there were many active galaxies oriented edgewise to us, but they just couldn't be detected because the disk of gas attenuates emissions too strongly.

"These extremely obscured active galaxies are very faint and difficult to find. Out of a sample of 199 sources, we detected only nine of them," said Davide Burlon, the lead author of the study and a graduate student at the Max Planck Institute for Extraterrestrial Physics in Munich.

"But even Swift's BAT has trouble finding these highly absorbed sources, and we know that the survey undercounts them," Burlon explained. "When we factored this in, we found that these shrouded active galaxies are very numerous, making up about 20 to 30 percent of the total."

"With Swift we have now quantified exactly how many active galaxies there are around us -- really, in our back yard," said Marco Ajello at the SLAC National Accelerator Laboratory, Menlo Park, Calif. "The number is large, and it agrees with models that say they are responsible for most of the X-ray background." If the numbers remain consistent at greater distances, when the universe was substantially younger, then there are enough supermassive black holes to account for the cosmic X-ray background.

The team then merged Swift BAT data with archived observations from its X-Ray Telescope in an effort to study how the intensity of the galaxies' emissions changed at different X-ray energies.

"This is the first time we could investigate the average spectrum of heavily absorbed active galaxies," said Ajello. "These galaxies are responsible for the shape of the cosmic X-ray background -- they create the peak of its energy."

All of this is consistent with the idea that the cosmic X-ray background is the result of emission from obscured supermassive black holes active when the universe was 7 billion years old, or about half its current age.

Swift, launched in November 2004, is managed by Goddard. It was built and is being operated in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico, and General Dynamics in Falls Church, Va.; the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom; Brera Observatory and the Italian Space Agency in Italy; plus additional partners in Germany and Japan.

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NASA Chat: The Moon's Earth-like Core

State-of-the-art seismological techniques applied to Apollo-era data suggest our moon has a core similar to Earth's. Uncovering details about the lunar core is critical for developing accurate models of the moon's formation. The data sheds light on the evolution of a lunar dynamo -- a natural process by which our moon may have generated and maintained its own strong magnetic field.

The team's findings suggest the moon possesses a solid, iron-rich inner core with a radius of nearly 150 miles and a fluid, primarily liquid-iron outer core with a radius of roughly 205 miles. Where it differs from Earth is a partially molten boundary layer around the core estimated to have a radius of nearly 300 miles. The research indicates the core contains a small percentage of light elements such as sulfur, echoing new seismology research on Earth that suggests the presence of light elements -- such as sulfur and oxygen -- in a layer around our own core.

The researchers used extensive data gathered during the Apollo-era moon missions. The Apollo Passive Seismic Experiment consisted of four seismometers deployed between 1969 and 1972, which recorded continuous lunar seismic activity until late-1977.

Live Web Chat

On Thursday, Jan. 20 from 3:00 to 4:00 EST, NASA planetary scientist Dr. Renee Weber will answer your questions about the inner workings of our nearest neighbor.

Joining the chat is easy! Simply return to this page a few minutes before 3:00 p.m. EST on Thursday, Jan. 20. The chat module will appear at the bottom of this page. After you log in, wait for the chat module to be activated, then ask your questions!

About Chat Expert Dr. Renee Weber

Dr. Renee Weber is a planetary scientist at NASA's Marshall Space Flight Center. She serves as the project scientist for the Lunar Mapping and Modeling Project, a software project designed to provide lunar maps and surface feature information to mission planners and other lunar researchers. Renee's scientific research focuses on planetary seismology, in particular the re-processing of seismic data from the Apollo missions. She is involved in several international efforts with goals of sending modern, broad-band seismometers to both the moon and Mars.

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NASA's Fermi Catches Thunderstorms Hurling Antimatter into Space

Scientists using NASA's Fermi Gamma-ray Space Telescope have detected beams of antimatter produced above thunderstorms on Earth, a phenomenon never seen before.

Scientists think the antimatter particles were formed in a terrestrial gamma-ray flash (TGF), a brief burst produced inside thunderstorms and shown to be associated with lightning. It is estimated that about 500 TGFs occur daily worldwide, but most go undetected.

"These signals are the first direct evidence that thunderstorms make antimatter particle beams," said Michael Briggs, a member of Fermi's Gamma-ray Burst Monitor (GBM) team at the University of Alabama in Huntsville (UAH). He presented the findings Monday, during a news briefing at the American Astronomical Society meeting in Seattle.

Fermi is designed to monitor gamma rays, the highest energy form of light. When antimatter striking Fermi collides with a particle of normal matter, both particles immediately are annihilated and transformed into gamma rays. The GBM has detected gamma rays with energies of 511,000 electron volts, a signal indicating an electron has met its antimatter counterpart, a positron.

Although Fermi's GBM is designed to observe high-energy events in the universe, it's also providing valuable insights into this strange phenomenon. The GBM constantly monitors the entire celestial sky above and the Earth below. The GBM team has identified 130 TGFs since Fermi's launch in 2008.

"In orbit for less than three years, the Fermi mission has proven to be an amazing tool to probe the universe. Now we learn that it can discover mysteries much, much closer to home," said Ilana Harrus, Fermi program scientist at NASA Headquarters in Washington.

The spacecraft was located immediately above a thunderstorm for most of the observed TGFs, but in four cases, storms were far from Fermi. In addition, lightning-generated radio signals detected by a global monitoring network indicated the only lightning at the time was hundreds or more miles away. During one TGF, which occurred on Dec. 14, 2009, Fermi was located over Egypt. But the active storm was in Zambia, some 2,800 miles to the south. The distant storm was below Fermi's horizon, so any gamma rays it produced could not have been detected.

"Even though Fermi couldn't see the storm, the spacecraft nevertheless was magnetically connected to it," said Joseph Dwyer at the Florida Institute of Technology in Melbourne, Fla. "The TGF produced high-speed electrons and positrons, which then rode up Earth's magnetic field to strike the spacecraft."

The beam continued past Fermi, reached a location, known as a mirror point, where its motion was reversed, and then hit the spacecraft a second time just 23 milliseconds later. Each time, positrons in the beam collided with electrons in the spacecraft. The particles annihilated each other, emitting gamma rays detected by Fermi's GBM.

Scientists long have suspected TGFs arise from the strong electric fields near the tops of thunderstorms. Under the right conditions, they say, the field becomes strong enough that it drives an upward avalanche of electrons. Reaching speeds nearly as fast as light, the high-energy electrons give off gamma rays when they're deflected by air molecules. Normally, these gamma rays are detected as a TGF.

But the cascading electrons produce so many gamma rays that they blast electrons and positrons clear out of the atmosphere. This happens when the gamma-ray energy transforms into a pair of particles: an electron and a positron. It's these particles that reach Fermi's orbit.

The detection of positrons shows many high-energy particles are being ejected from the atmosphere. In fact, scientists now think that all TGFs emit electron/positron beams. A paper on the findings has been accepted for publication in Geophysical Research Letters.

"The Fermi results put us a step closer to understanding how TGFs work," said Steven Cummer at Duke University. "We still have to figure out what is special about these storms and the precise role lightning plays in the process."

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership. It is managed by NASA's Goddard Space Flight Center in Greenbelt, Md. It was developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

The GBM Instrument Operations Center is located at the National Space Science Technology Center in Huntsville, Ala. The team includes a collaboration of scientists from UAH, NASA's Marshall Space Flight Center in Huntsville, the Max Planck Institute for Extraterrestrial Physics in Germany and other institutions.

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The Two-faced Whirlpool Galaxy

These images by NASA's Hubble Space Telescope show off two dramatically different face-on views of the spiral galaxy M51, dubbed the Whirlpool Galaxy.

The image at left, taken in visible light, highlights the attributes of a typical spiral galaxy, including graceful, curving arms, pink star-forming regions, and brilliant blue strands of star clusters.

In the image at right, most of the starlight has been removed, revealing the Whirlpool's skeletal dust structure, as seen in near-infrared light. This new image is the sharpest view of the dense dust in M51. The narrow lanes of dust revealed by Hubble reflect the galaxy's moniker, the Whirlpool Galaxy, as if they were swirling toward the galaxy's core.

To map the galaxy's dust structure, researchers collected the galaxy's starlight by combining images taken in visible and near-infrared light. The visible-light image captured only some of the light; the rest was obscured by dust. The near-infrared view, however, revealed more starlight because near-infrared light penetrates dust. The researchers then subtracted the total amount of starlight from both images to see the galaxy's dust structure.

The red color in the near-infrared image traces the dust, which is punctuated by hundreds of tiny clumps of stars, each about 65 light-years wide. These stars have never been seen before. The star clusters cannot be seen in visible light because dense dust enshrouds them. The image reveals details as small as 35 light-years across.

Astronomers expected to see large dust clouds, ranging from about 100 light-years to more than 300 light-years wide. Instead, most of the dust is tied up in smooth and diffuse dust lanes. An encounter with another galaxy may have prevented giant clouds from forming.

Probing a galaxy's dust structure serves as an important diagnostic tool for astronomers, providing invaluable information on how the gas and dust collapse to form stars. Although Hubble is providing incisive views of the internal structure of galaxies such as M51, the planned James Webb Space Telescope (JWST) is expected to produce even crisper images.

Researchers constructed the image by combining visible-light exposures from Jan. 18 to 22, 2005, with the Advanced Camera for Surveys (ACS), and near-infrared light pictures taken in December 2005 with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS).

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Partner Galaxies Wildly Different In New WISE Image

NASA's Wide-field Infrared Survey Explorer has captured a new view of two companion galaxies -- a somewhat tranquil spiral beauty and its rambunctious partner blazing with smoky star formation.

The unlikely pair, named Messier 81 and Messier 82, got to know each other a lot better during an encounter that occurred a few hundred million years ago. As they swept by each other, gravitational interactions triggered new bursts of star formation. In the case of Messier 82, also known as the Cigar galaxy, the encounter has likely triggered a tremendous wave of new star birth at its core. Intense radiation from newborn massive stars is blowing copious amounts of gas and smoky dust out of the galaxy, as seen in the WISE image in yellow hues.

"What's unique about the WISE view of this duo is that we can see both galaxies in one shot, and we can really see their differences," said Ned Wright of UCLA, the principal investigator of WISE. "Because the Cigar galaxy is bursting with star formation, it's really bright in the infrared, and looks dramatically different from its less active companion."

The WISE mission completed its main goal of mapping the sky in infrared light in October 2010, covering it one-and-one-half times before its frozen coolant ran out, as planned. During that time, it snapped pictures of hundreds of millions of objects, the first batch of which will be released to the astronomy community in April 2011. WISE is continuing its scan of the skies without coolant using two of its four infrared channels -- the two shorter-wavelength channels not affected by the warmer temperatures. The mission's ongoing survey is now focused primarily on asteroids and comets.

Because WISE has imaged the entire sky, it excels at producing large mosaics like this new picture of Messier 81 and Messier 82, which covers a patch of sky equivalent to three-by-three full moons, or 1.5 by 1.5 degrees.

It is likely these partner galaxies will continue to dance around each other, and eventually merge into a single entity. They are both spiral galaxies, but Messier 82 is seen from an edge-on perspective, and thus appears in visible light as a thin, cigar-like bar. When viewed in infrared light, Messier 82 is the brightest galaxy in the sky. It is what scientists refer to as a starburst galaxy because it is churning out large amounts of new stars.

"The WISE picture really shows how spectacular Messier 82 shines in the infrared even though it is relatively puny in both size and mass compared to its big brother, Messier 81," said Tom Jarrett, a member of the WISE team at the California Institute of Technology in Pasadena.

In this WISE view, infrared light has been color coded so that we can see it with our eyes. The shortest wavelengths (3.4 and 3.6 microns) are shown in blue and blue-green, or cyan, and the longer wavelengths (12 and 22 microns) are green and red. Messier 82 appears in yellow hues because its cocoon of dust gives off longer wavelengths of light (the yellow is a result of combining green and red). This dust is made primarily of polycyclic aromatic hydrocarbons, which are found on Earth as soot.

Messier 81, also known as Bode's galaxy, appears blue in the infrared image because it is not as dusty. The blue light is from stars in the galaxy. Knots of yellow seen dotting the spiral arms are dusty areas of recent star formation, most likely triggered by the galaxy's encounter with its rowdy partner.

"It's striking how the same event stimulated a classic spiral galaxy in Messier 81, and a raging starburst in Messier 82," said WISE Project Scientist Peter Eisenhardt of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "WISE is finding the most extreme starbursts across the whole sky, out to distances over a thousand times greater than Messier 82."

Messier 81 is one of the brightest galaxies in the sky in visible light. Both it and its partner can be seen with binoculars on a dark, clear night in the northern constellation of Ursa Major, which contains the Big Dipper. The galaxies are 12 million light-years away from Earth.

JPL manages WISE for NASA's Science Mission Directorate. The mission was competitively selected under NASA's Explorers Program, which NASA's Goddard Space Flight Center in Greenbelt, Md., manages. The Space Dynamics Laboratory in Logan, Utah, built the science instrument, and Ball Aerospace & Technologies Corp. of Boulder, Colo., built the spacecraft. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena.

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NASA Satellites Find High-Energy Surprises in 'Constant' Crab Nebula

The combined data from several NASA satellites has astonished astronomers by revealing unexpected changes in X-ray emission from the Crab Nebula, once thought to be the steadiest high-energy source in the sky.

"For 40 years, most astronomers regarded the Crab as a standard candle," said Colleen Wilson-Hodge, an astrophysicist at NASA's Marshall Space Flight Center in Huntsville, Ala., who presented the findings today at the American Astronomical Society meeting in Seattle. "Now, for the first time, we're clearly seeing how much our candle flickers."

The Crab Nebula is the wreckage of an exploded star whose light reached Earth in 1054. It is one of the most studied objects in the sky. At the heart of an expanding gas cloud lies what's left of the original star's core, a superdense neutron star that spins 30 times a second. All of the Crab's high-energy emissions are thought to be the result of physical processes that tap into this rapid spin.

For decades, astronomers have regarded the Crab's X-ray emissions as so stable that they've used it to calibrate space-borne instruments. They also customarily describe the emissions of other high-energy sources in "millicrabs," a unit derived from the nebula's output.

"The Crab Nebula is a cornerstone of high-energy astrophysics," said team member Mike Cherry at Louisiana State University in Baton Rouge, La. (LSU), "and this study shows us that our foundation is slightly askew." The story unfolded when Cherry and Gary Case, also at LSU, first noticed the Crab's dimming in observations by the Gamma-ray Burst Monitor (GBM) aboard NASA's Fermi Gamma-ray Space Telescope.

The team then analyzed GBM observations of the object from August 2008 to July 2010 and found an unexpected but steady decline of several percent at four different "hard" X-ray energies, from 12,000 to 500,000 electron volts (eV). For comparison, visible light has energies between 2 and 3 eV.

With the Crab's apparent constancy well established, the scientists needed to prove that the fadeout was real and was not an instrumental problem associated with the GBM. "If only one satellite instrument had reported this, no one would have believed it," Wilson-Hodge said.

So the team amassed data from the fleet of sensitive X-ray observatories now in orbit: NASA's Rossi X-Ray Timing Explorer (RXTE) and Swift satellites and the European Space Agency's International Gamma-Ray Astrophysics Laboratory (INTEGRAL). The results confirm a real intensity decline of about 7 percent at energies between 15,000 to 50,000 eV over two years. They also show that the Crab has brightened and faded by as much as 3.5 percent a year since 1999.

The scientists say that astronomers will need to find new ways to calibrate instruments in flight and to explore the possible effects of the inconstant Crab on past findings. A paper on the results will appear in the Feb. 1 issue of The Astrophysical Journal Letters.

Fermi's other instrument, the Large Area Telescope, has detected unprecedented gamma-ray flares from the Crab, showing that it is also surprisingly variable at much higher energies. A study of these events was published Thursday, Jan. 6, in Science Express.

The nebula's power comes from the central neutron star, which is also a pulsar that emits fast, regular radio and X-ray pulses. This pulsed emission exhibits no changes associated with the decline, so it cannot be the source. Instead, researchers suspect that the long-term changes probably occur in the nebula's central light-year, but observations with future telescopes will be needed to know for sure.

This region is dominated by four high-energy structures: an X-ray-emitting jet; an outflow of particles moving near the speed of light, called a "pulsar wind"; a disk of accumulating particles where the wind terminates; and a shock front where the wind abruptly slows.

"This environment is dominated by the pulsar's magnetic field, which we suspect is organized precariously," said Roger Blandford, who directs the Kavli Institute for Particle Astrophysics and Cosmology, jointly located at the Department of Energy's SLAC National Accelerator Laboratory and Stanford University. "The X-ray changes may involve some rearrangement of the magnetic field, but just where this happens is a mystery."

The Crab Nebula is a supernova remnant located 6,500 light-years away in the constellation Taurus.

NASA's Fermi is an astrophysics and particle physics partnership managed by NASA's Goddard Space Flight Center in Greenbelt, Md., and developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

The GBM Instrument Operations Center is located at the National Space Science Technology Center in Huntsville, Ala. The team includes a collaboration of scientists from UAH, NASA's Marshall Space Flight Center in Huntsville, the Max Planck Institute for Extraterrestrial Physics in Germany and other institutions.

NASA Goddard manages Swift, RXTE and a guest observer facility for U.S. participation in the European Space Agency's INTEGRAL mission.

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Planck Mission Peels Back Layers of the Universe

The Planck mission released a new data catalogue Tuesday from initial maps of the entire sky. The catalogue includes thousands of never-before-seen dusty cocoons where stars are forming, and some of the most massive clusters of galaxies ever observed. Planck is a European Space Agency mission with significant contributions from NASA.

"NASA is pleased to support this important mission, and we have eagerly awaited Planck's first discoveries," said Jon Morse, NASA's Astrophysics Division director at the agency's headquarters in Washington. "We look forward to continued collaboration with ESA and more outstanding science to come."

Planck launched in May 2009 on a mission to detect light from just a few hundred thousand years after the Big Bang, an explosive event at the dawn of the universe approximately 13.7 billion years ago. The spacecraft's state-of-the-art detectors ultimately will survey the whole sky at least four times, measuring the cosmic microwave background, or radiation left over from the Big Bang. The data will help scientists decipher clues about the evolution, fate and fabric of our universe. While these cosmology results won't be ready for another two years or so, early observations of specific objects in our Milky Way galaxy, as well as more distant galaxies, are being released.

"The data we're releasing now are from what lies between us and the cosmic microwave background," said Charles Lawrence, the U.S. project scientist for Planck at NASA's Jet Propulsion Laboratory in Pasadena, Calif. We ultimately will subtract these data out to get at our cosmic microwave background signal. But by themselves, these early observations offer up new information about objects in our universe -- both close and far away, and everything in between."

Planck observes the sky at nine wavelengths of light, ranging from infrared to radio waves. Its technology has greatly improved sensitivity and resolution over its predecessor missions, NASA's Cosmic Background Explorer and Wilkinson Microwave Anisotropy Probe.

The result is a windfall of data on known and never-before-seen cosmic objects. Planck has catalogued approximately 10,000 star-forming "cold cores," thousands of which are newly discovered. The cores are dark and dusty nurseries where baby stars are just beginning to take shape. They also are some of the coldest places in the universe. Planck's new catalogue includes some of the coldest cores ever seen, with temperatures as low as seven degrees above absolute zero, or minus 447 degrees Fahrenheit. In order to see the coldest gas and dust in the Milky Way, Planck's detectors were chilled to only 0.1 Kelvin.

The new catalogue also contains some of the most massive clusters of galaxies known, including a handful of newfound ones. The most massive of these holds the equivalent of a million billion suns worth of mass, making it one of the most massive galaxy clusters known.

Galaxies in our universe are bound together into these larger clusters, forming a lumpy network across the cosmos. Scientists study the clusters to learn more about the evolution of galaxies and dark matter and dark energy -- the exotic substances that constitute the majority of our universe.

"Because Planck is observing the whole sky, it is giving us a comprehensive look at how all the smaller structures of the universe are connected to the whole," said Jim Bartlett, a U.S. Planck team member at JPL and the Astroparticule et Cosmologie-Universite Paris Diderot in France.

Planck's new catalogue also includes unique data on the pools of hot gas that permeate roughly 14,000 smaller clusters of galaxies; the best data yet on the cosmic infrared background, which is made up of light from stars evolving in the early universe; and new observations of extremely energetic galaxies spewing radio jets. The catalogue covers about one-and-a-half sky scans.

Planck is a European Space Agency mission, with significant participation from NASA. NASA's Planck Project Office is based at JPL. JPL contributed mission-enabling technology for both of Planck's science instruments. European, Canadian and U.S. Planck scientists will work together to analyze the Planck data. JPL is managed for NASA by the California Institute of Technology in Pasadena.

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In Distant Galaxies, New Clues to Century-Old Molecule Mystery

Andromeda, shown here, is one of two distant galaxies where astronomers recently searched for diffuse interstellar bands (DIBs). If DIBs were found when looking in a straight line from Earth to a star in the galaxy, the star is circled. Bigger circles indicate stronger DIBs. An "x" means no DIBS were observed. The colors in the insets correspond to wavelengths of the spectrum: blue for UV, green for visible light, and red for infrared.

In a study that pushes the limits of observations currently possible from Earth, a team of NASA and European scientists recorded the "fingerprints" of mystery molecules in two distant galaxies, Andromeda and the Triangulum. Astronomers can count on one hand the number of galaxies examined so far for such fingerprints, which are thought to belong to large organic molecules, says the team's leader, Martin Cordiner of the Goddard Center for Astrobiology at NASA's Goddard Space Flight Center in Greenbelt, Md.

Figuring out exactly which molecules are leaving these clues, known as "diffuse interstellar bands" (DIBs), is a puzzle that initially seemed straightforward but has gone unsolved for nearly a hundred years. The answer is expected to help explain how stars, planets and life form, so settling the matter is as important to astronomers who specialize in chemistry and biology as determining the nature of dark matter is to the specialists in physics.

Cordiner is presenting the team's research at the American Astronomical Society meeting in Seattle, Wash., on Jan. 10, 2011, and the results from Andromeda were published in an Astrophysical Journal paper on Jan. 1. The findings provide some evidence against one of the top candidates on the list of suspects: polycyclic aromatic hydrocarbons (PAHs), a group of molecules that is widespread in space. The research also reveals that some of the signatures found in Andromeda and the Triangulum are similar to ones seen in our own Milky Way, despite some big differences between those galaxies and ours.

"We have studied DIBs in incredibly diverse environments. Some have low levels of UV radiation. Some have radiation levels thousands of times higher. Some have different amounts of 'ingredients' available for making stars and planets," Cordiner says. "And throughout all of these, we see DIBs."

Missing in action

Until now, only two galaxies beyond our own have been investigated in detail for DIBs. Those are our nearest neighbors, the Large and Small Magellanic Clouds, which lie 160,000 to 200,000 light years away. (Researchers have conducted selective studies elsewhere, however.)

Andromeda and the Triangulum are located much farther away, at about 2.5 to 3 million light years from Earth. "At those distances, individual stars are so faint that we need to push even the largest telescopes in the world to their limits in order to observe them," Cordiner says.

That statement might seem strange to anyone who has looked into the night sky and seen either of these galaxies with the naked eye. Under favorable conditions, the galaxies appear as smudges in the constellations that bear their respective names.

But to study DIBs, researchers need to do much more than see that the galaxy is there. They have to pick out individual stars within the galaxy, and only a few telescopes worldwide are powerful enough to gather sufficient light for that. (The team used the Gemini Observatory's telescope in Hawaii.) This is why most DIBs found so far have been in the Milky Way.

Whichever galaxy an astronomer chooses, though, it will be made up of tens to hundreds of billions of stars. "The first step is choosing which stars to observe," Cordiner explains.

Cordiner's colleagues at Queen's University in Belfast, U.K., took the lead on finding good targets. They picked blue supergiants—stars that are very large, very hot and very bright. Supergiants also burn very clean: unlike our sun and other cooler stars, they contribute little background clutter to the observations being made.

To look for DIBs, an astronomer points the telescope at a star and scans through a rainbow made up of thousands of wavelengths of light. This rainbow, or spectrum, is extended a bit beyond visible light, into the UV at the blue end and into the infrared at the red end.

DIBs are not defined by what astronomers see while doing this, but by what they don't see. The colors missing from the rainbow, marked by black stripes, are the ones of interest. Each one is a wavelength being absorbed by some kind of atom or molecule.

A DIB is one of these regions where the color is missing. But compared to the nice, neat "absorption lines" that are identified with atoms or simple molecules, a DIB is not well-behaved, which is why it stands out.

"Astronomers were used to seeing quite sharp, narrow bands where typical atoms and molecules absorb," says Cordiner. "But DIBs are broad; that's why they are called 'diffuse.' Some DIBs have simple shapes and are quite smooth, but others have bumps and wiggles and may even be lopsided."

The mystery deepens

Over time, astronomers have been building up catalogs to show exactly which wavelengths are absorbed by all kinds of atoms and molecules. Each molecule has its own unique pattern, which can be used like a fingerprint: if a pattern found during an astronomical observation matches a pattern in one of the catalogs, the molecule can be identified.

It's a pretty straightforward concept. So, early researchers "would surely not have thought that the solution to the diffuse band problem would still be so elusive," wrote Peter Sarre in a 2006 review article about DIBs. Sarre, a professor of chemistry and molecular astrophysics at the University of Nottingham, U.K., supervised Cordiner's graduate-school work on DIBs.

The significance of the first DIBs, recorded in 1922 in Mary Lea Heger's Ph.D. thesis, was not immediately recognized. But once astronomers began systematic studies, starting with a 1934 paper by P. W. Merrill, they had every reason to believe the problem could be solved within a decade or two.

No such luck

More than 400 DIBs have been documented since then. But not one has been identified with enough certainty for astronomers to consider its case closed.

"With this many diffuse bands, you'd think we astronomers would have enough clues to solve this problem," muses Joseph Nuth, a senior scientist with the Goddard Center for Astrobiology who was not involved in this work. "Instead, it's getting more mysterious as more data is gathered."

Detailed analyses of the bumps and wiggles of the DIBs, suggest that the molecules which give rise to DIBs—called "carriers"—are probably large.

But like beauty, "large" is in the eye of the beholder. In this case, it means the molecule has at least 20 atoms or more. This is quite small compared to, say, a protein but huge compared to a molecule of carbon monoxide, a very common molecule in space.

Recently, though, more interest has been focused on at least one small molecule, a chain made from three carbon atoms and two hydrogen atoms (C3H2). This was tentatively identified with a pattern of DIBs.

Tenacious D

On the list of DIB-related suspects, all molecules have one thing in common: they are organic, which means they are built largely from carbon.

Carbon is great for building large numbers of molecules because it is available almost everywhere. In space, only hydrogen, helium and oxygen are more plentiful. Here on Earth, we find carbon in the planet's crust, the oceans, the atmosphere and all forms of life.

Likewise, astronomers "see DIBs pretty much in any direction we look," says Jan Cami, an astronomer at the University of Western Ontario, Canada. He has collaborated with Cordiner before but was not involved in this study. "And we see lots of DIBs."

Carbon is also great for building molecules in all kinds of configurations—millions of carbon compounds have been identified—and especially for building very stable molecules.

DIB carriers also seem to be quite stable. They survive the harsh physical conditions in the interstellar medium—the material found in the space between the stars. They also hang tough in the Large Magellanic Cloud, where radiation levels are thousands of times stronger than in the Milky Way. In fact, says Cordiner, DIB carriers seem comfortable almost everywhere except in the clouds of dense gas where stars are born.

"The carriers are readily formed but not readily destroyed in a wide range of different environments," says Cordiner. "It's remarkable how tenacious these molecules really are."

In short, carriers are thought to be made of carbon, Cami says, "because it's a lot easier to build strong and stable molecules from carbon atoms than from other elements, such as silicon or sulfur. Using those elements rather than carbon would be like building a house from a bucket of sand while there's a huge pile of bricks at the construction site."

The top three carrier candidates are: chain-like molecules, like the one now tentatively associated with a pattern of DIBs; PAHs, which often come up in studies of how planets formed; and compounds related to fullerenes, the soccer-ball-shaped molecules also known as buckyballs.

"This list covers most types of carbon molecules," notes Cami. "Chains are essentially the one-dimensional carbon molecules, PAHs are the two-dimensional ones, and fullerene compounds are the three-dimensional ones."

Present and accounted for

In spite of the challenges of looking for DIBs in other galaxies, it's worth the effort to astronomers because they need to see what DIBs look like under different conditions.

Granted, conditions are not uniform everywhere within a galaxy. Some stars have planets near them; others don't. Between the stars, in the vast tracts of interstellar medium, the relative amounts of gas and dust floating around can be different from one region to the next. And the exact mixture of chemicals can vary a little from place to place.

"But being on Earth and looking at another object in the Milky Way is like being in the crowd at Times Square in New York City on New Year's Eve and trying to find your friend," explains Nuth. "It's much easier to spot the person if you are on a balcony rather than standing in the crowd yourself." Likewise, it's much easier to get a clear overview of a galaxy when you are outside of it.

In some respects, Andromeda and the Triangulum are similar to the Milky Way. All three are spiral galaxies that belong to a collection of more than 30 nearby galaxies called the Local Group. The Milky Way is the largest member of this group. Andromeda is the second-largest, and the Triangulum is third.

Like the Milky Way, Andromeda and the Triangulum are thought to be good places to synthesize large organic molecules, which is what DIBs carriers are thought to be. And yet, says Cordiner, "nobody knew until now whether DIBs actually existed in either galaxy."

The team found that, indeed, DIBs do exist in both places, and they are strong, which implies there are many carriers.

In the Milky Way, when researchers find strong DIBs, they tend to find a lot of dust, too. This makes sense, because whenever there's more raw material available to make DIBs carriers, there's also more available to make dust. The team found the same situation in Andromeda, Cordiner says.

Of greater interest in Andromeda was whether the strength of the DIBs was related to the amount of PAHs, which are high on the list of candidates for carriers. The researchers knew going into the study that PAHs are plentiful in Andromeda, as they are in the Milky Way.

"The details of the PAH population seem to be somewhat different in Andromeda, though," says Cami. "This makes it interesting to try and find out exactly what is different."

But after checking to see if the PAH levels were related to DIBs strength, "we didn't find any correlation between the two," Cordiner says. That finding doesn't rule out a connection, but it might shift more attention to chains of carbon atoms or to fullerene compounds.

The carriers are not pure, isolated fullerenes, says Cami, who led the team that first detected fullerenes in space. More likely, "atoms or molecules are either locked up in fullerene cages or attached to the outside surface, " he explains. "This might even hold for some of the other proposed molecules. For example, you could think of carbon chains dangling from other molecules or even from dust grains."

The more things change . . .

One big difference between the Milky Way and Andromeda is the number of massive young stars. The Milky Way has more than Andromeda. Because those young stars generate a lot of UV radiation, the Milky Way's interstellar medium has higher levels of this radiation than Andromeda's does.

More radiation means a harsher environment, so organic molecules should survive better in an environment with less radiation. In that sense, Andromeda should be more favorable for the carriers of DIBs and, in theory, should be able to boast more of them. But Cordiner and his colleagues found that the DIBs in Andromeda were only slightly stronger than those in the Milky Way, implying that Andromeda can only claim slightly more carriers.

The observations in the Triangulum add even more intrigue. There, the researchers found strong DIBs even though this galaxy differs in its metallicity, which is a measure of the availability of ingredients for making stars and planets.

The consistency from galaxy to galaxy is surprising, given how much the conditions are thought to vary among them. "But there are no detailed studies of Andromeda to tell us everything we want to know about conditions there," says Cordiner. "And even less is known about the Triangulum."

As is usually the case in cutting-edge astronomy, some assumptions had to be made, and a lot depends on how well those assumptions hold up as more information becomes available.

Meanwhile, researchers will try to learn everything they can about DIBs near and far and the organic molecules they represent. "If we're going to understand fully how interstellar chemistry works—how stars and planets form," says Cordiner, "then we need a full understanding of the ingredients they use."

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Under Pressure: Stormy Weather Sensor for Hurricane Forecasting

It’s hard to believe that, in this day and age, we don’t have a way to measure sea-level air pressure during hurricanes. NASA researchers, however, are working on a system that will improve forecasting of severe ocean weather by doing just that. The device measures sea-level air pressure, a critical component of hurricane formation – and one that has been extremely difficult to capture.

The Differential Absorption Barometric Radar (DIABAR) prototype is scheduled to make its second flight early this year.

DIABAR remotely senses barometric pressure at sea level, which is important in the prediction and forecasting of severe weather, especially hurricanes, over oceans.

But the ability to measure sea-level air pressure is a major missing link in storm observation, says Dr. Bing Lin, an atmospheric scientist at NASA Langley Research Center in Hampton, Va.

“Air pressure is a driving force of weather systems, especially under severe weather conditions like hurricanes,” he said. “For severe storms, the forecasts of the intensity and track can be significantly improved by pressure measurements.”

A Hurricane’s Life

A hurricane begins as a tropical wave, a westward-moving area of low air pressure. As warm, moist air over the ocean rises in the low air-pressure area, surrounding air replaces it, and circulation forms. This produces strong gusty winds, heavy rain and thunderclouds – a tropical disturbance.

As air pressure drops and winds sustain at 38 mph or more, the disturbance becomes a tropical depression, then a tropical storm, and finally a hurricane with sustained winds of over 73 mph.

Lin hopes eventually to be able to measure sea-level air pressure from aircraft flyovers and space-based satellites. The local coverage provide by flyovers, combined with a broad perspective from space, will provide enough information to significantly improve the ability of forecasters to determine how intense a hurricane is and where it’s headed.

“Large and frequent sea surface measurements are critically needed,” he said. “These measurements cannot be made from buoys and aircraft dropsondes. The only hope is from remote sensing using aircraft, unmanned aerial vehicles, and satellites.”

An effort to remotely sense barometric pressure at sea-surface level using microwaves was undertaken at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., in the 1980s. “JPL has extensive experience on spaceborne microwave sensors,” said Lin.

First Flight

DIABAR was first deployed on a Navy MH-60S helicopter in 2009 at Naval Air Station Patuxent River in Maryland.

“We flew it, got the results, and it looks great,” said Lin.

The next step is testing this year on a blimp called the Bullet™ Class 580, the world’s largest airship. E-Green Technologies Inc. in Alabama makes the aircraft.

The 235-foot long, 65-foot diameter lighter-than-air vehicle is designed to fly on algae-based biofuel at speeds up to 74 mph and altitudes up to 20,000 feet. It will be stationed in a hanger at Moffett Federal Airfield at NASA Ames Research Center in California.

DIABAR is a partnership between NASA Langley, Old Dominion University in Norfolk, Va., and the State University of New York at Albany.

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NASA Image Shows La Niña-Caused Woes Down Under

The current La Niña in the Pacific Ocean, one of the strongest in the past 50 years, continues to exert a powerful influence on weather around the world, affecting rainfall and temperatures in varying ways in different locations.

For Australia, La Niña typically means above-average rains, and the current La Niña is no exception. Heavy rains that began in late December led to the continent's worst flooding in nearly a half century, at its peak inundating an area the size of Germany and France combined. The Associated Press reports about 1,200 homes in 40 communities are underwater and about 11,000 others are damaged, resulting in thousands of evacuations and 10 deaths to date.

On Jan. 7, 2010, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft captured this image of the inundated city of Rockhampton, Queensland, Australia. With a population of 75,000, Rockhampton is the largest city affected by the current flooding. Torrential rains in northeastern Australia caused the Fitzroy River to overflow its banks and flood much of the city and surrounding agricultural lands. Both the airport and major highways are underwater, isolating the city.

In this natural color rendition, muddy water is brown, and shallow, clearer water is gray. Vegetation is depicted in various shades of green, and buildings and streets are white. The image is located at 23.3 degrees south latitude, 150.5 degrees east longitude, and covers an area of 22 by 28.1 kilometers (13.6 by 17.4 miles).

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