 PASADENA - Saturn's moon Titan might be in for some wild weather as it heads into its spring and summer, if two new models are correct. Scientists think that as the seasons change in Titan's northern hemisphere, waves could ripple across the moon's hydrocarbon seas, and hurricanes could begin to swirl over these areas, too. The model predicting waves tries to explain data from the moon obtained so far by NASA's Cassini spacecraft. Both models help mission team members plan when and where to look for unusual atmospheric disturbances as Titan summer approaches.
 |
| This image shows the first flash of sunlight reflected off a lake on Saturn's moon Titan. Image credit: NASA/JPL/University of Arizona/DLR |
"If you think being a weather forecaster on Earth is difficult, it can be even more challenging at Titan," said Scott Edgington, Cassini's deputy project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We know there are weather processes similar to Earth's at work on this strange world, but differences arise due to the presence of unfamiliar liquids like methane. We can't wait for Cassini to tell us whether our forecasts are right as it continues its tour through Titan spring into the start of northern summer." Titan's north polar region, which is bejeweled with sprawling hydrocarbon seas and lakes, was dark when Cassini first arrived at the Saturn system in 2004. But sunlight has been creeping up Titan's northern hemisphere since August 2009, when the sun's light crossed the equatorial plane at equinox. Titan's seasons take about seven Earth years to change. By 2017, the end of Cassini's mission, Titan will be approaching northern solstice, the height of summer. Given the wind-sculpted dunes Cassini has seen on Titan, scientists were baffled about why they hadn't yet seen wind-driven waves on the lakes and seas. A team led by Alex Hayes, a member of Cassini's radar team who is based at Cornell University, Ithaca, N.Y., set out to look for how much wind would be required to generate waves. Their new model, just published in the journal Icarus, improves upon previous ones by simultaneously accounting for Titan's gravity; the viscosity and surface tension of the hydrocarbon liquid in the lakes; and the air-to-liquid density ratio. “We now know that the wind speeds predicted during the times Cassini has observed Titan have been below the threshold necessary to generate waves," Hayes said. "What is exciting, however, is that the wind speeds predicted during northern spring and summer approach those necessary to generate wind waves in liquid ethane and/or methane. It may soon be possible to catch a wave in one of the solar system’s most exotic locations.” The new model found that winds of 1 to 2 mph (2 to 3 kilometers per hour) are needed to generate waves on Titan lakes, a speed that has not yet been reached during Titan's currently calm period. But as Titan's northern hemisphere approaches spring and summer, other models predict the winds may increase to 2 mph (3 kilometers per hour) or faster. Depending on the composition of the lakes, winds of that speed could be enough to produce waves 0.5 foot (0.15 meter) high. The other model about hurricanes, recently published in Icarus, predicts that the warming of the northern hemisphere could also bring hurricanes, also known as tropical cyclones. Tropical cyclones on Earth gain their energy from the build-up of heat from seawater evaporation and miniature versions have been seen over big lakes such as Lake Huron. The new modeling work, led by Tetsuya Tokano of the University of Cologne, Germany, shows that the same processes could be at work on Titan as well, except that it is methane rather than water that evaporates from the seas. The most likely season for these hurricanes would be Titan's northern summer solstice, when the sea surface gets warmer and the flow of the air near the surface becomes more turbulent. The humid air would swirl in a counterclockwise direction over the surface of one of the northern seas and increase the surface wind over the seas to possibly 45 mph (about 70 kilometers per hour). "For these hurricanes to develop at Titan, there needs to be the right mix of hydrocarbons in these seas, and we still don't know their exact composition," Tokano said. "If we see hurricanes, that would be one good indicator that there is enough methane in these lakes to support this kind of activity. So far, scientists haven't yet been able to detect methane directly." The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. The mission is managed by JPL for NASA's Science Mission Directorate, Washington. JPL is a division of the California Institute of Technology in Pasadena, Calif. |  PASADENA - Kepler Status Report - Following the apparent failure of reaction wheel 4 on May 11, 2013, engineers were successful at transitioning the spacecraft from a Thruster-Controlled Safe Mode to Point Rest State at approximately 3:30 p.m. PDT on Wednesday, May 15, 2013. The spacecraft has remained safe and stable in this attitude and is no longer considered to be in a critical situation.
As part of a normal spacecraft response to a pointing error, redundant electronics were automatically powered off to isolate them as a possible cause. However, once the team recovered the spacecraft to Point Rest State (PRS) and exonerated those systems, they were turned back on, providing full redundancy to the spacecraft. The reaction wheels remain offline. The photometer, which was turned off to reduce the power load, will be turned back on in the near future to keep thermal conditions of the spacecraft within nominal operating parameters. Kepler is not in science data collection.
PRS was developed in order to preserve fuel for an eventual recovery effort once a second wheel failed. This state uses thrusters to control the pointing of the spacecraft, tipping it towards the sun and letting the solar pressure tip it back away, resembling the motion of a pendulum. This is a very fuel-efficient mode, and it also provides an on-demand telemetry link to allow engineers to monitor and command the spacecraft. With nearly a week of PRS operations, the fuel usage appears to be on the low end of our estimates, allowing time for recovery planning.
The operations staff at Ball Aerospace did a wonderful job at developing and implementing PRS. As a result, the spacecraft is not in an emergency condition, and work can be conducted at a more deliberate pace. For the next week or so, we will contact the spacecraft on a daily basis to ensure PRS continues to operate as expected.
Over the coming weeks, an anomaly response team (ART) will evaluate wheel recovery options. The ART includes members from NASA Ames, Ball Aerospace, the Jet Propulsion Laboratory and UTC, the wheel manufacturer. This team has access to a broader reach of experts throughout NASA and industry, and will manage the wheel recovery efforts.
The team will continue to analyze recent telemetry received from the spacecraft. This analysis, and any planned recovery actions, will take time, and will likely be on the order of weeks, possibly months. Any planned commanding will first be vetted on the spacecraft test bed to validate command operability.
For now, PRS is working very well and keeping Kepler safe. We will provide updates on significant changes as the plan develops.
We are grateful to all our followers for their well wishes and support!
|  PASADENA - Scientists have created the first global topographic map of Saturn's moon Titan, giving researchers a valuable tool for learning more about one of the most Earth-like and interesting worlds in the solar system. The map was just published as part of a paper in the journal Icarus. Titan is Saturn's largest moon - with a radius of about 1,600 miles (2,574 kilometers), it's bigger than planet Mercury - and is the second–largest moon in the solar system. Scientists care about Titan because it's the only moon in the solar system known to have clouds, surface liquids and a mysterious, thick atmosphere. The cold atmosphere is mostly nitrogen, like Earth's, but the organic compound methane on Titan acts the way water vapor does on Earth, forming clouds and falling as rain and carving the surface with rivers. Organic chemicals, derived from methane, are present in Titan's atmosphere, lakes and rivers and may offer clues about the origins of life.
 |
| Using data from NASA's Cassini spacecraft, scientists have created the first global topographic map of Saturn's moon Titan, giving researchers a 3-D tool for learning more about one of the most Earthlike and interesting worlds in the solar system. Credit: NASA JPL |
"Titan has so much interesting activity – like flowing liquids and moving sand dunes – but to understand these processes it's useful to know how the terrain slopes," said Ralph Lorenz, a member of the Cassini radar team based at the Johns Hopkins University Applied Physics Laboratory, Laurel, Md., who led the map-design team. "It's especially helpful to those studying hydrology and modeling Titan's climate and weather, who need to know whether there is high ground or low ground driving their models." Titan's thick haze scatters light in ways that make it very hard for remote cameras to "see" landscape shapes and shadows, the usual approach to measuring topography on planetary bodies. Virtually all the data we have on Titan comes from NASA's Saturn-orbiting Cassini spacecraft, which has flown past the moon nearly 100 times over the past decade. On many of those flybys, Cassini has used a radar imager, which can peer through the haze, and the radar data can be used to estimate the surface height. "With this new topographic map, one of the most fascinating and dynamic worlds in our solar system now pops out in 3-D," said Steve Wall, the deputy team lead of Cassini's radar team, based at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "On Earth, rivers, volcanoes and even weather are closely related to heights of surfaces – we're now eager to see what we can learn from them on Titan." There are challenges, however. "Cassini isn't orbiting Titan," Lorenz said. "We have only imaged about half of Titan's surface, and multiple 'looks' or special observations are needed to estimate the surface heights. If you divided Titan into 1-degree by 1-degree [latitude and longitude] squares, only 11 percent of those squares have topography data in them." Lorenz's team used a mathematical process called splining – effectively using smooth, curved surfaces to "join" the areas between grids of existing data. "You can take a spot where there is no data, look how close it is to the nearest data, and use various approaches of averaging and estimating to calculate your best guess," he said. "If you pick a point, and all the nearby points are high altitude, you'd need a special reason for thinking that point would be lower. We're mathematically papering over the gaps in our coverage." The estimations fit with current knowledge of the moon – that its polar regions are "lower" than areas around the equator, for example – but connecting those points allows scientists to add new layers to their studies of Titan's surface, especially those modeling how and where Titan's rivers flow, and the seasonal distribution of its methane rainfall. "The movement of sands and the flow of liquids are influenced by slopes, and mountains can trigger cloud formation and therefore rainfall. This global product now gives modelers a convenient description of this key factor in Titan's dynamic climate system," Lorenz said. The most recent data used to compile the map is from 2012; Lorenz says it could be worth revising when the Cassini mission ends in 2017, when more data will have accumulated, filling some of the gaps in present coverage. "We felt we couldn't wait and should release an interim product," he says. "The community has been hoping to get this for a while. I think it will stimulate a lot of interesting work." The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries. |  PASADENA, Calif. -- NASA's senior Mars rover, Opportunity, is driving to a new study area after a dramatic finish to 20 months on "Cape York" with examination of a rock intensely altered by water.
The fractured rock, called "Esperance," provides evidence about a wet ancient environment possibly favorable for life. The mission's principal investigator, Steve Squyres of Cornell University, Ithaca, N.Y., said, "Esperance was so important, we committed several weeks to getting this one measurement of it, even though we knew the clock was ticking."
The mission's engineers at NASA's Jet Propulsion Laboratory, Pasadena, Calif., had set this week as a deadline for starting a drive toward "Solander Point," where the team plans to keep Opportunity working during its next Martian winter.
 |
| The pale rock in the upper center of this image, about the size of a human forearm, includes a target called "Esperance," which was inspected by NASA's Mars Exploration Rover Opportunity. Data from the rover's alpha particle X-ray spectrometer (APXS) indicate that Esperance's composition is higher in aluminum and silica, and lower in calcium and iron, than other rocks Opportunity has examined in more than nine years on Mars. Preliminary interpretation points to clay mineral content due to intensive alteration by water. Image Credit: NASA/JPL-Caltech/Cornell/Arizona State Univ. |
"What's so special about Esperance is that there was enough water not only for reactions that produced clay minerals, but also enough to flush out ions set loose by those reactions, so that Opportunity can clearly see the alteration," said Scott McLennan of the State University of New York, Stony Brook, a long-term planner for Opportunity's science team.
This rock's composition is unlike any other Opportunity has investigated during nine years on Mars -- higher in aluminum and silica, lower in calcium and iron.
The next destination, Solander Point, and the area Opportunity is leaving, Cape York, both are segments of the rim of Endeavour Crater, which spans 14 miles (22 kilometers) across. The planned driving route to Solander Point is about 1.4 miles (2.2 kilometers). Cape York has been Opportunity's home since the rover arrived at the western edge of Endeavour in mid-2011 after a two-year trek from a smaller crater.
"Based on our current solar-array dust models, we intend to reach an area of 15 degrees northerly tilt before Opportunity's sixth Martian winter," said JPL's Scott Lever, mission manager. "Solander Point gives us that tilt and may allow us to move around quite a bit for winter science observations."
Northerly tilt increases output from the rover's solar panels during southern-hemisphere winter. Daily sunshine for Opportunity will reach winter minimum in February 2014. The rover needs to be on a favorable slope well before then.
The first drive away from Esperance covered 81.7 feet (24.9 meters) on May 14. Three days earlier, Opportunity finished exposing a patch of the rock's interior with the rock abrasion tool. The team used a camera and spectrometer on the robotic arm to examine Esperance.
The team identified Esperance while exploring a portion of Cape York where the Compact Reconnaissance Spectrometer for Mars (CRISM) on NASA's Mars Reconnaissance Orbiter had detected a clay mineral. Clays typically form in wet environments that are not harshly acidic. For years, Opportunity had been finding evidence for ancient wet environments that were very acidic. The CRISM findings prompted the rover team to investigate the area where clay had been detected from orbit. There, they found an outcrop called "Whitewater Lake," containing a small amount of clay from alteration by exposure to water.
"There appears to have been extensive, but weak, alteration of Whitewater Lake, but intense alteration of Esperance along fractures that provided conduits for fluid flow," Squyres said. "Water that moved through fractures during this rock's history would have provided more favorable conditions for biology than any other wet environment recorded in rocks Opportunity has seen."
NASA's Mars Exploration Rover Project launched Opportunity to Mars on July 7, 2003, about a month after its twin rover, Spirit. Both were sent for three-month prime missions to study the history of wet environments on ancient Mars and continued working in extended missions. Spirit ceased operations in 2010.
JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project for NASA's Science Mission Directorate. For more about Opportunity, visit: http://www.nasa.gov/rovers and http://marsrovers.jpl.nasa.gov . You can follow the project on Twitter and on Facebook at: http://twitter.com/MarsRovers and http://www.facebook.com/mars.rovers . |  GREENBELT, MD - NASA's first mission to sample an asteroid is moving ahead into development and testing in preparation for its launch in 2016.
The Origins-Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx) passed a confirmation review Wednesday called Key Decision Point (KDP)-C. NASA officials reviewed a series of detailed project assessments and authorized the spacecraft's continuation into the development phase.
OSIRIS-REx will rendezvous with the asteroid Bennu in 2018 and return a sample of it to Earth in 2023.
 |
| Artist's rendering of OSIRIS-REx compared to a human. Photo Credit: NASA |
"Successfully passing KDP-C is a major milestone for the project," said Mike Donnelly, OSIRIS-REx project manager at NASA's Goddard Space Flight Center in Greenbelt, Md. "This means NASA believes we have an executable plan to return a sample from Bennu. It now falls on the project and its development team members to execute that plan."
Bennu could hold clues to the origin of the solar system. OSIRIS-REx will map the asteroid's global properties, measure non-gravitational forces and provide observations that can be compared with data obtained by telescope observations from Earth. OSIRIS-REx will collect a minimum of 2 ounces (60 grams) of surface material.
"The entire OSIRIS-REx team has worked very hard to get to this point," said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona in Tucson. "We have a long way to go before we arrive at Bennu, but I have every confidence when we do, we will have built a supremely capable system to return a sample of this primitive asteroid."
The mission will be a vital part of NASA's plans to find, study, capture and relocate an asteroid for exploration by astronauts. NASA recently announced an asteroid initiative proposing a strategy to leverage human and robotic activities for the first human mission to an asteroid while also accelerating efforts to improve detection and characterization of asteroids.
NASA's Goddard Space Flight Center in Greenbelt, Md., will provide overall mission management, systems engineering and safety and mission assurance. The University of Arizona in Tucson is the principal investigator institution. Lockheed Martin Space Systems of Denver will build the spacecraft. OSIRIS-REx is the third mission in NASA's New Frontiers Program. NASA's Marshall Space Flight Center in Huntsville, Ala., manages New Frontiers for NASA's Science Mission Directorate in Washington.
| PASADENA - Kepler Status Report - At our semi-weekly contact on Tuesday, May 14, 2013, we found the Kepler spacecraft once again in safe mode. As was the case earlier this month, this was a Thruster-Controlled Safe Mode. The root cause is not yet known, however the proximate cause appears to be an attitude error. The spacecraft was oriented with the solar panels facing the sun, slowly spinning about the sun-line. The communication link comes and goes as the spacecraft spins.
We attempted to return to reaction wheel control as the spacecraft rotated into communication, and commanded a stop rotation. Initially, it appeared that all three wheels responded and that rotation had been successfully stopped, but reaction wheel 4 remained at full torque while the spin rate dropped to zero. This is a clear indication that there has been an internal failure within the reaction wheel, likely a structural failure of the wheel bearing. The spacecraft was then transitioned back to Thruster-Controlled Safe Mode.
An Anomaly Review Board concurred that the data appear to unambiguously indicate a wheel 4 failure, and that the team’s priority is to complete preparations to enter Point Rest State. Point Rest State is a loosely-pointed, thruster-controlled state that minimizes fuels usage while providing a continuous X-band communication downlink. The software to execute that state was loaded to the spacecraft last week, and last night the team completed the upload of the parameters the software will use.
The spacecraft is stable and safe, if still burning fuel. Our fuel budget is sufficient that we can take due caution while we finish our planning. In its current mode, our fuel will last for several months. Point Rest State would extend that period to years.
We have requested and received additional NASA Deep Space Network communication coverage, and this morning the Anomaly Review Board approved the transition to Point Rest State later today. Because this is a new operating mode of the spacecraft, the team will closely monitor the spacecraft, but no other immediate actions are planned. We will take the next several days and weeks to assess our options and develop new command products. These options are likely to include steps to attempt to recover wheel functionality and to investigate the utility of a hybrid mode, using both wheels and thrusters.
With the failure of a second reaction wheel, it's unlikely that the spacecraft will be able to return to the high pointing accuracy that enables its high-precision photometry. However, no decision has been made to end data collection.
Kepler had successfully completed its primary three-and-a-half year mission and entered an extended mission phase in November 2012.
Even if data collection were to end, the mission has substantial quantities of data on the ground yet to be fully analyzed, and the string of scientific discoveries is expected to continue for years to come. SOURCE: NASA |  GREENBELT. MD - NASA's Hubble Space Telescope has found the building blocks for Earth-sized planets in an unlikely place-- the atmospheres of a pair of burned-out stars called white dwarfs.
These dead stars are located 150 light-years from Earth in a relatively young star cluster, Hyades, in the constellation Taurus. The star cluster is only 625 million years old. The white dwarfs are being polluted by asteroid-like debris falling onto them.
 |
| This is an artist’s impression of a white dwarf (burned-out) star accreting rocky debris left behind by the star’s surviving planetary system. It was observed by Hubble in the Hyades star cluster. At lower right, an asteroid can be seen falling toward a Saturn-like disk of dust that is encircling the dead star. Infalling asteroids pollute the white dwarf’s atmosphere with silicon. Credit: NASA, ESA, and G. Bacon (STScI) |
Hubble's Cosmic Origins Spectrograph observed silicon and only low levels of carbon in the white dwarfs' atmospheres. Silicon is a major ingredient of the rocky material that constitutes Earth and other solid planets in our solar system. Carbon, which helps determine properties and origin of planetary debris, generally is depleted or absent in rocky, Earth-like material.
"We have identified chemical evidence for the building blocks of rocky planets," said Jay Farihi of the University of Cambridge in England. He is lead author of a new study appearing in the Monthly Notices of the Royal Astronomical Society. "When these stars were born, they built planets, and there's a good chance they currently retain some of them. The material we are seeing is evidence of this. The debris is at least as rocky as the most primitive terrestrial bodies in our solar system."
This discovery suggests rocky planet assembly is common around stars, and it offers insight into what will happen in our own solar system when our sun burns out 5 billion years from now.
Farihi's research suggests asteroids less than 100 miles (160 kilometers) wide probably were torn apart by the white dwarfs' strong gravitational forces. Asteroids are thought to consist of the same materials that form terrestrial planets, and seeing evidence of asteroids points to the possibility of Earth-sized planets in the same system.
The pulverized material may have been pulled into a ring around the stars and eventually funneled onto the dead stars. The silicon may have come from asteroids that were shredded by the white dwarfs' gravity when they veered too close to the dead stars.
"It's difficult to imagine another mechanism than gravity that causes material to get close enough to rain down onto the star," Farihi said.
By the same token, when our sun burns out, the balance of gravitational forces between the sun and Jupiter will change, disrupting the main asteroid belt. Asteroids that veer too close to the sun will be broken up, and the debris could be pulled into a ring around the dead sun.
According to Farihi, using Hubble to analyze the atmospheres of white dwarfs is the best method for finding the signatures of solid planet chemistry and determining their composition.
"Normally, white dwarfs are like blank pieces of paper, containing only the light elements hydrogen and helium,"Farihi said. "Heavy elements like silicon and carbon sink to the core. The one thing the white dwarf pollution technique gives us that we just won't get with any other planet-detection technique is the chemistry of solid planets."
The two "polluted" Hyades white dwarfs are part of the team's search of planetary debris around more than 100 white dwarfs, led by Boris Gansicke of the University of Warwick in England. Team member Detlev Koester of the University of Kiel in Germany is using sophisticated computer models of white dwarf atmospheres to determine the abundances of various elements that can be traced to planets in the Hubble spectrograph data.
Fahiri's team plans to analyze more white dwarfs using the same technique to identify not only the rocks' composition, but also their parent bodies.
|  WASHINGTON - Gone are the days of being able to count the number of known planets on your fingers. Today, there are more than 800 confirmed exoplanets -- planets that orbit stars beyond our sun -- and more than 2,700 other candidates. What are these exotic planets made of? Unfortunately, you cannot stack them in a jar like marbles and take a closer look. Instead, researchers are coming up with advanced techniques for probing the planets' makeup. One breakthrough to come in recent years is direct imaging of exoplanets. Ground-based telescopes have begun taking infrared pictures of the planets posing near their stars in family portraits. But to astronomers, a picture is worth even more than a thousand words if its light can be broken apart into a rainbow of different wavelengths.
 |
| This image shows the HR 8799 planets with starlight optically suppressed and data processing conducted to remove residual starlight. The star is at the center of the blackened circle in the image. The four spots indicated with the letters b through e are the planets. Image courtesy of Project 1640 |
Those wishes are coming true as researchers are beginning to install infrared cameras on ground-based telescopes equipped with spectrographs. Spectrographs are instruments that spread an object's light apart, revealing signatures of molecules. Project 1640, partly funded by NASA's Jet Propulsion Laboratory, Pasadena, Calif., recently accomplished this goal using the Palomar Observatory near San Diego. "In just one hour, we were able to get precise composition information about four planets around one overwhelmingly bright star," said Gautam Vasisht of JPL, co-author of the new study appearing in the Astrophysical Journal. "The star is a hundred thousand times as bright as the planets, so we've developed ways to remove that starlight and isolate the extremely faint light of the planets." Along with ground-based infrared imaging, other strategies for combing through the atmospheres of giant planets are being actively pursued as well. For example, NASA's Spitzer and Hubble space telescopes monitor planets as they cross in front of their stars, and then disappear behind. NASA's upcoming James Webb Space Telescope will use a comparable strategy to study the atmospheres of planets only slightly larger than Earth. In the new study, the researchers examined HR 8799, a large star orbited by at least four known giant, red planets. Three of the planets were among the first ever directly imaged around a star, thanks to observations from the Gemini and Keck telescopes on Mauna Kea, Hawaii, in 2008. The fourth planet, the closest to the star and the hardest to see, was revealed in images taken by the Keck telescope in 2010. That alone was a tremendous feat considering that all planet discoveries up until then had been made through indirect means, for example by looking for the wobble of a star induced by the tug of planets. Those images weren't enough, however, to reveal any information about the planets' chemical composition. That's where spectrographs are needed -- to expose the "fingerprints" of molecules in a planet's atmosphere. Capturing a distant world's spectrum requires gathering even more planet light, and that means further blocking the glare of the star. Project 1640 accomplished this with a collection of instruments, which the team installs on the ground-based telescopes each time they go on "observing runs." The instrument suite includes a coronagraph to mask out the starlight; an advanced adaptive optics system, which removes the blur of our moving atmosphere by making millions of tiny adjustments to two deformable telescope mirrors; an imaging spectrograph that records 30 images in a rainbow of infrared colors simultaneously; and a state-of-the-art wave front sensor that further adjusts the mirrors to compensate for scattered starlight. "It's like taking a single picture of the Empire State Building from an airplane that reveals a bump on the sidewalk next to it that is as high as an ant," said Ben R. Oppenheimer, lead author of the new study and associate curator and chair of the Astrophysics Department at the American Museum of Natural History, N.Y., N.Y. Their results revealed that all four planets, though nearly the same in temperature, have different compositions. Some, unexpectedly, do not have methane in them, and there may be hints of ammonia or other compounds that would also be surprising. Further theoretical modeling will help to understand the chemistry of these planets. Meanwhile, the quest to obtain more and better spectra of exoplanets continues. Other researchers have used the Keck telescope and the Large Binocular Telescope near Tucson, Ariz., to study the emission of individual planets in the HR8799 system. In addition to the HR 8799 system, only two others have yielded images of exoplanets. The next step is to find more planets ripe for giving up their chemical secrets. Several ground-based telescopes are being prepared for the hunt, including Keck, Gemini, Palomar and Japan's Subaru Telescope on Mauna Kea, Hawaii. Ideally, the researchers want to find young planets that still have enough heat left over from their formation, and thus more infrared light for the spectrographs to see. They also want to find planets located far from their stars, and out of the blinding starlight. NASA's infrared Spitzer and Wide-field Infrared Survey Explorer (WISE) missions, and its ultraviolet Galaxy Evolution Explorer, now led by the California Institute of Technology, Pasadena, have helped identify candidate young stars that may host planets meeting these criteria. "We're looking for super-Jupiter planets located faraway from their star," said Vasisht. "As our technique develops, we hope to be able to acquire molecular compositions of smaller, and slightly older, gas planets." Still lower-mass planets, down to the size of Saturn, will be targets for imaging studies by the James Webb Space Telescope. "Rocky Earth-like planets are too small and close to their stars for the current technology, or even for James Webb to detect. The feat of cracking the chemical compositions of true Earth analogs will come from a future space mission such as the proposed Terrestrial Planet Finder," said Charles Beichman, a co-author of the P1640 result and executive director of NASA's Exoplanet Science Institute at Caltech. Though the larger, gas planets are not hospitable to life, the current studies are teaching astronomers how the smaller, rocky ones form. "The outer giant planets dictate the fate of rocky ones like Earth. Giant planets can migrate in toward a star, and in the process, tug the smaller, rocky planets around or even kick them out of the system. We're looking at hot Jupiters before they migrate in, and hope to understand more about how and when they might influence the destiny of the rocky, inner planets," said Vasisht. NASA's Exoplanet Science Institute manages time allocation on the Keck telescope for NASA. JPL manages NASA's Exoplanet Exploration program office. Caltech manages JPL for NASA. A visualization from the American Museum of Natural History showing where the HR 8799 system is in relation to our solar system is online at http://www.youtube.com/watch?v=yDNAk0bwLrU . More information about exoplanets and NASA's planet-finding program is at http://planetquest.jpl.nasa.gov . |  PARIS - ESA’s Herschel space observatory has made detailed observations of surprisingly hot molecular gas that may be orbiting or falling towards the supermassive black hole lurking at the centre of our Milky Way galaxy. Our local black hole is located in a region known as Sagittarius A* – Sgr A* – after a nearby radio source. It has a mass about four million times that of our Sun and lies around 26 000 light-years away from the Solar System. Even at that distance, it is a few hundred times closer to us than any other galaxy with an active black hole at its centre, making it the ideal natural laboratory to study the environment around these enigmatic objects.
 |
|
The environment at the centre of our Milky Way Galaxy. The Galactic Centre hosts a supermassive black hole in the region known as Sagittarius A*, or Sgr A*, with a mass of about four million times that of our Sun.
A dense torus of molecular gas and dust surrounds the Galactic Centre and occupies the innermost 15 light-years of our Galaxy. Enshrouded within the disc is a central cavity, with a radius of a few light-years, filled with warm dust and lower density gas.Part of this gas is being heated by the strong ultraviolet radiation from massive stars that closely orbit the central black hole. Heating also likely results from strong shocks, generated as gas orbits around or flows towards Sgr A*, in collisions between gas clouds or in material flowing at high velocity from stars and protostars. Credit: ESA
|
Vast amounts of dust lie in the plane of the Milky Way between here and its centre, obscuring our view at visible wavelengths. But at far-infrared wavelengths, it is possible to peer through the dust, affording Herschel’s scientists the chance to study the turbulent innermost region of our Galaxy in great detail. Herschel has detected a great variety of simple molecules at the Milky Way’s heart, including carbon monoxide, water vapour and hydrogen cyanide. By analysing the signature from these molecules, astronomers have been able to probe some of the fundamental properties of the interstellar gas surrounding the black hole. “Herschel has resolved the far-infrared emission within just 1 light-year of the black hole, making it possible for the first time at these wavelengths to separate emission due to the central cavity from that of the surrounding dense molecular disc,” says Javier Goicoechea of the Centro de Astrobiología, Spain, and lead author of the paper reporting the results. The biggest surprise was quite how hot the molecular gas in the innermost central region of the Galaxy gets. At least some of it is around 1000ºC, much hotter than typical interstellar clouds, which are usually only a few tens of degrees above the –273ºC of absolute zero. While some of the heating is down to the fierce ultraviolet radiation pouring from a cluster of massive stars that live very close to the Galactic Centre, they are not enough to explain the high temperatures alone. In addition to the stellar radiation, Dr Goicoechea’s team hypothesise that emission from strong shocks in highly-magnetised gas in the region may be a significant contributor to the high temperatures. Such shocks can be generated in collisions between gas clouds, or in material flowing at high speed from stars and protostars. “The observations are also consistent with streamers of hot gas speeding towards Sgr A*, falling towards the very centre of the Galaxy,” says Dr Goicoechea. “Our Galaxy’s black hole may be cooking its dinner right in front of Herschel’s eyes.” |  PASADENA - Our galaxy is teeming with a wild variety of planets. In addition to our solar system's eight near-and-dear planets, there are more than 800 so-called exoplanets known to circle stars beyond our sun. One of the first "species" of exoplanets to be discovered is the hot Jupiters, also known as roasters. These are gas giants like Jupiters, but they orbit closely to their stars, blistering under the heat. Thanks to NASA's Spitzer Space Telescope, researchers are beginning to dissect this exotic class of planets, revealing raging winds and other aspects of their turbulent nature. A twist to come out of the recent research is the planets' wide range of climates. Some are covered with a haze, while others are clear. Their temperature profiles, chemistries and densities differ as well.
 |
| Artist's rendering of a Hot Jupiter. Photo Credit: NASA |
"The hot Jupiters are beasts to handle. They are not fitting neatly into our models and are more diverse than we thought," said Nikole Lewis of the Massachusetts Institute of Technology, Cambridge, lead author of a new Spitzer paper in the Astrophysical Journal examining one such hot Jupiter called HAT-P-2b. "We are just starting to put together the puzzle pieces of what's happening with these planets, and we still don't know what the final picture will be." The very first exoplanet discovered around a sun-like star was, in fact, a hot Jupiter, called 51 Pegasi b. It was detected in 1995 by Swiss astronomers using the radial velocity technique, which measures the wobble of a star caused by the tug of a planet. Because hot Jupiters are heavy and whip around their stars quickly, they are the easiest to find using this strategy. Dozens of hot Jupiter discoveries soon followed. At first, researchers thought they might represent a more common configuration for other planetary systems in our galaxy beyond our own solar system. But new research, including that from NASA's Kepler space telescope, has shown that they are relatively rare. In 2005, scientists were thrilled when Spitzer became the first telescope to detect light emitted by an exoplanet. Spitzer monitored the infrared light coming from a star and its planet -- a hot Jupiter -- as the planet disappeared behind the star in an event known as a secondary eclipse. Once again, this technique works best for hot Jupiters, because they are the biggest and hottest planets. In addition to watching hot Jupiters slip behind their stars, researchers also use Spitzer to monitor the planets as they orbit all the way around a star. This allows them to create global climate maps, revealing how the planets' atmospheres vary from their hot, sun-facing sides to their cooler, night sides, due in part to fierce winds. (Hot Jupiters are frequently tidally locked, with one side always facing the star, just as our moon is locked to Earth.) Since that first observation, Spitzer has probed the atmospheres of dozens of hot Jupiters, and some even smaller planets, uncovering clues about their composition and climate. "When Spitzer launched in 2003, we had no idea it would prove to be a giant in the field of exoplanet science," said Michael Werner, the Spitzer project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Now, we're moving farther into the field of comparative planetary science, where we can look at these objects as a class, and not just as individuals." In the new study, Lewis and colleagues made the longest Spitzer observation yet of a hot Jupiter. The infrared telescope stared at the HAT-P-2 system continuously for six days, watching it cross in front of its star, slip behind, and then reappear on the other side, making a full orbit. What makes the observation even more exciting to scientists is that the planet has a comet-like eccentric orbit, carrying it as close as 2.8 million miles (4.5 million kilometers) to the star and out to as far as 9.3 million miles (15 million kilometers). For reference, Mercury is about 28.5 million miles from our sun. "It's as if nature has given us a perfect lab experiment with this system," said Heather Knutson, a co-author of the new paper at the California Institute of Technology, Pasadena, Calif. "Because the planet's distance to the sun changes, we can watch how fast it takes to heat up and cool down. It's as though we're turning the heat knob up on our planet and watching what happens." Knutson led the first team to create a global "weather" map of a hot Jupiter, called HD 189733 b, in 2007. The new HAT-P-2b study is also one of the first to use multiple wavelengths of infrared light, instead of just one, while watching a full orbit of a hot Jupiter. This enables the scientists to peer down into different layers of the planet. The results reveal that HAT-P-2b takes about a day to heat up as it approaches the hottest part of its orbit, and four to five days to cool down as it swings away. It also exhibits a temperature inversion -- a hotter, upper layer of gas -- when it is closest to its star. What's more, the carbon chemistry of the planet seems to be behaving in unexpected ways, which the astronomers are still trying to understand. "These planets are much hotter and more dynamic than our own Jupiter, which is sluggish by comparison. Strong winds are churning material up from below, and the chemistry is always changing," said Lewis. Another challenge in understanding hot Jupiters lies in parsing through the data. Lewis said her team's six-day Spitzer observation left them with 2 million data points to map out while carefully removing instrument noise. "Theories are being shot down right and left," said Nick Cowan of Northwestern University, Evanston, Ill., a co-author of the HAT-P-2b study. "Right now, it's like the wild, wild west." NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. |
|