Thursday, July 31, 2014

NASA Telescopes Help Solve Ancient Supernova Mystery

NASA Telescopes Help Solve Ancient Supernova Mystery:

All Eyes on Oldest Recorded Supernova
This image combines data from four different space telescopes to create a multi-wavelength view of all that remains of the oldest documented example of a supernova, called RCW 86.

› Full image and caption


October 24, 2011

PASADENA, Calif. -- A mystery that began nearly 2,000 years ago, when Chinese astronomers witnessed what would turn out to be an exploding star in the sky, has been solved. New infrared observations from NASA's Spitzer Space Telescope and Wide-field Infrared Survey Explorer, or WISE, reveal how the first supernova ever recorded occurred and how its shattered remains ultimately spread out to great distances.


The findings show that the stellar explosion took place in a hollowed-out cavity, allowing material expelled by the star to travel much faster and farther than it would have otherwise.


"This supernova remnant got really big, really fast," said Brian J. Williams, an astronomer at North Carolina State University in Raleigh. Williams is lead author of a new study detailing the findings online in the Astrophysical Journal. "It's two to three times bigger than we would expect for a supernova that was witnessed exploding nearly 2,000 years ago. Now, we've been able to finally pinpoint the cause."


A new image of the supernova, known as RCW 86, is online at http://go.nasa.gov/pnv6Oy .


In 185 A.D., Chinese astronomers noted a "guest star" that mysteriously appeared in the sky and stayed for about 8 months. By the 1960s, scientists had determined that the mysterious object was the first documented supernova. Later, they pinpointed RCW 86 as a supernova remnant located about 8,000 light-years away. But a puzzle persisted. The star's spherical remains are larger than expected. If they could be seen in the sky today in infrared light, they'd take up more space than our full moon.


The solution arrived through new infrared observations made with Spitzer and WISE, and previous data from NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton Observatory.


The findings reveal that the event is a "Type Ia" supernova, created by the relatively peaceful death of a star like our sun, which then shrank into a dense star called a white dwarf. The white dwarf is thought to have later blown up in a supernova after siphoning matter, or fuel, from a nearby star.


"A white dwarf is like a smoking cinder from a burnt-out fire," Williams said. "If you pour gasoline on it, it will explode."


The observations also show for the first time that a white dwarf can create a cavity around it before blowing up in a Type Ia event. A cavity would explain why the remains of RCW 86 are so big. When the explosion occurred, the ejected material would have traveled unimpeded by gas and dust and spread out quickly.


Spitzer and WISE allowed the team to measure the temperature of the dust making up the RCW 86 remnant at about minus 325 degrees Fahrenheit, or minus 200 degrees Celsius. They then calculated how much gas must be present within the remnant to heat the dust to those temperatures. The results point to a low-density environment for much of the life of the remnant, essentially a cavity.


Scientists initially suspected that RCW 86 was the result of a core-collapse supernova, the most powerful type of stellar blast. They had seen hints of a cavity around the remnant, and, at that time, such cavities were only associated with core-collapse supernovae. In those events, massive stars blow material away from them before they blow up, carving out holes around them.


But other evidence argued against a core-collapse supernova. X-ray data from Chandra and XMM-Newton indicated that the object consisted of high amounts of iron, a telltale sign of a Type Ia blast. Together with the infrared observations, a picture of a Type Ia explosion into a cavity emerged.


"Modern astronomers unveiled one secret of a two-millennia-old cosmic mystery only to reveal another," said Bill Danchi, Spitzer and WISE program scientist at NASA Headquarters in Washington. "Now, with multiple observatories extending our senses in space, we can fully appreciate the remarkable physics behind this star's death throes, yet still be as in awe of the cosmos as the ancient astronomers."


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. Caltech manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu/ and http://www.nasa.gov/spitzer .


JPL manages, and operated, WISE for NASA's Science Mission Directorate. The spacecraft was put into hibernation mode after it scanned the entire sky twice, completing its main objectives. Edward Wright is the principal investigator and is at UCLA. The mission was selected competitively under NASA's Explorers Program managed by the agency's Goddard Space Flight Center in Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory in Logan. The spacecraft was built by Ball Aerospace & Technologies Corp. in Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. More information is online at http://www.nasa.gov/wise and http://wise.astro.ucla.edu and http://www.jpl.nasa.gov/wise .

Whitney Clavin 818-354-4673

Jet Propulsion Laboratory, Pasadena, Calif.

whitney.clavin@jpl.nasa.gov


Trent J. Perrotto 202-358-0321

NASA Headquarters, Washington                                                                

trent.j.perrotto@nasa.gov


2011-329

NASA's Cassini Makes a New Pass at Enceladus

NASA's Cassini Makes a New Pass at Enceladus:

Enceladus 'E-16' Flyby: Radar Looks at Enceladus
The primary goal of this flyby is to obtain the first detailed radar observation of Enceladus. This will be the first close radar pass of an icy moon besides Titan; the results will enable a comparison of the radar properties of a moon with a known composition (Enceladus) with that of Titan.
› Larger image


November 03, 2011

NASA's Cassini spacecraft will acquire the first detailed radar images of Saturn's moon Enceladus during a flyby on Sunday, Nov. 6. These will be the first high-resolution radar observations made of an icy moon other than Titan. The results will provide new information about the surface of Enceladus and enable researchers to compare its geological features as seen by radar with those of Titan.


The spacecraft will fly past Enceladus at a distance of about 300 miles (500 kilometers) at its closest point. During the encounter, Cassini's synthetic aperture radar will sweep across a long, narrow swath of the surface just north of the moon's south pole. Cassini will use other radar techniques to map much more of the surface of Enceladus at lower resolutions and determine some of the surface's physical properties as the spacecraft approaches and then speeds away from the icy body. 


During this flyby, the mission's visible-light cameras will take images of Enceladus and its famous jets, and the composite infrared spectrometer will make new measurements of hot spots from which the jets emerge. Cassini's ultraviolet imaging spectrograph will also make distant observations of Saturn's moon Dione and its environment.


The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL.


For more information about the Cassini-Huygens mission visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov/ .

Rosemary Sullivant 818-354-0850

Jet Propulsion Laboratory, Pasadena, Calif.

rosemary.sullivant@jpl.nasa.gov

2011-340

Voyager 2 to Switch to Backup Thruster Set

Voyager 2 to Switch to Backup Thruster Set:

This artist's concept shows NASA's two Voyager spacecraft exploring a turbulent region of space known as the heliosheath
This artist's concept shows NASA's two Voyager spacecraft exploring a turbulent region of space known as the heliosheath, the outer shell of the bubble of charged particles around our sun. Image credit: NASA/JPL-Caltech
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November 05, 2011

Voyager Mission Status Report

NASA's Deep Space Network personnel sent commands to the Voyager 2 spacecraft Nov. 4 to switch to the backup set of thrusters that controls the roll of the spacecraft. Confirmation was received today that the spacecraft accepted the commands. The change will allow the 34-year-old spacecraft to reduce the amount of power it requires to operate and use previously unused thrusters as it continues its journey toward interstellar space, beyond our solar system.


Launched in 1977, Voyager 1 and Voyager 2 are each equipped with six sets, or pairs, of thrusters to control their movement. These include three pairs of primary thrusters and three backup, or redundant, pairs. Voyager 2 is currently using the two pairs of backup thrusters that control the pitch and yaw motion of the spacecraft. Switching to the backup thruster pair that controls roll motion will allow engineers to turn off the heater that keeps the fuel line to the primary thruster warm. This will save about 12 watts of power. The spacecraft's power supply now provides about 270 watts of electricity. By reducing its power usage, the spacecraft can continue to operate for another decade even as its available power continues to decline.


The thrusters involved in this switch have fired more than 318,000 times. The backup pair has not been used in flight. Voyager 1 changed to the backup for this same component after 353,000 pulses in 2004 and is now using all three sets of its backup thrusters.


Voyager 2 will relay the results of the switch back to Earth on Nov. 13. The signal will arrive on Earth on Nov. 14. Voyager 2 is currently located about 9 billion miles (14 billion kilometers) from Earth in the "heliosheath" -- the outermost layer of the heliosphere where the solar wind, which streams out from the sun, is slowed by the pressure of interstellar gas.




The Voyagers were built by NASA's Jet Propulsion Laboratory in Pasadena, Calif., which continues to operate both spacecraft. JPL is a division of the California Institute of Technology in Pasadena. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate. For more information about the Voyager spacecraft, visit: http://www.nasa.gov/voyager .




Rosemary Sullivant 818-354-0880

Jet Propulsion Laboratory, Pasadena, Calif.

Rosemary.sullivant@jpl.nasa.gov


2011-341

NASA's Voyager Hits New Region at Solar System Edge

NASA's Voyager Hits New Region at Solar System Edge:

Artist concept of Voyager 1 encountering a stagnation region
Artist concept of Voyager 1 encountering a stagnation region. Image credit: NASA/JPL-Caltech
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December 05, 2011

PASADENA, Calif. -- NASA's Voyager 1 spacecraft has entered a new region between our solar system and interstellar space. Data obtained from Voyager over the last year reveal this new region to be a kind of cosmic purgatory. In it, the wind of charged particles streaming out from our sun has calmed, our solar system's magnetic field is piled up, and higher-energy particles from inside our solar system appear to be leaking out into interstellar space.

"Voyager tells us now that we're in a stagnation region in the outermost layer of the bubble around our solar system," said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. "Voyager is showing that what is outside is pushing back. We shouldn't have long to wait to find out what the space between stars is really like."

Although Voyager 1 is about 11 billion miles (18 billion kilometers) from the sun, it is not yet in interstellar space. In the latest data, the direction of the magnetic field lines has not changed, indicating Voyager is still within the heliosphere, the bubble of charged particles the sun blows around itself. The data do not reveal exactly when Voyager 1 will make it past the edge of the solar atmosphere into interstellar space, but suggest it will be in a few months to a few years.

The latest findings, described today at the American Geophysical Union's fall meeting in San Francisco, come from Voyager's Low Energy Charged Particle instrument, Cosmic Ray Subsystem and Magnetometer.

Scientists previously reported the outward speed of the solar wind had diminished to zero in April 2010, marking the start of the new region. Mission managers rolled the spacecraft several times this spring and summer to help scientists discern whether the solar wind was blowing strongly in another direction. It was not. Voyager 1 is plying the celestial seas in a region similar to Earth's doldrums, where there is very little wind.

During this past year, Voyager's magnetometer also detected a doubling in the intensity of the magnetic field in the stagnation region. Like cars piling up at a clogged freeway off-ramp, the increased intensity of the magnetic field shows that inward pressure from interstellar space is compacting it.

Voyager has been measuring energetic particles that originate from inside and outside our solar system. Until mid-2010, the intensity of particles originating from inside our solar system had been holding steady. But during the past year, the intensity of these energetic particles has been declining, as though they are leaking out into interstellar space. The particles are now half as abundant as they were during the previous five years.

At the same time, Voyager has detected a 100-fold increase in the intensity of high-energy electrons from elsewhere in the galaxy diffusing into our solar system from outside, which is another indication of the approaching boundary.

"We've been using the flow of energetic charged particles at Voyager 1 as a kind of wind sock to estimate the solar wind velocity," said Rob Decker, a Voyager Low-Energy Charged Particle Instrument co-investigator at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "We've found that the wind speeds are low in this region and gust erratically. For the first time, the wind even blows back at us. We are evidently traveling in completely new territory. Scientists had suggested previously that there might be a stagnation layer, but we weren't sure it existed until now."

Launched in 1977, Voyager 1 and 2 are in good health. Voyager 2 is 9 billion miles (15 billion kilometers) away from the sun.

The Voyager spacecraft were built by NASA's Jet Propulsion Laboratory in Pasadena, Calif., which continues to operate both. JPL is a division of the California Institute of Technology. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington. For more information about the Voyager spacecraft, visit: http://www.nasa.gov/voyager .

For more information about NASA media events at the American Geophysical Union meeting, visit: http://www.nasa.gov/agu .

Jia-Rui C. Cook/Alan Buis 818-354-0850/818-653-8339

Jet Propulsion Laboratory, Pasadena, Calif.

jccook@jpl.nasa.gov/alan.d.buis@jpl.nasa.gov

Steve Cole 202-358-0918

NASA Headquarters, Washington                                                             

stephen.e.cole@nasa.gov

2011-372

Portraits of Moons Captured by Cassini

Portraits of Moons Captured by Cassini:

NASA's Cassini spacecraft obtained this unprocessed image  on  Dec. 12, 2011
NASA's Cassini spacecraft obtained this unprocessed image on Dec. 12, 2011. The camera was pointing toward Saturn's moon Dione from approximately 69,989 miles (112,636 kilometers) away. Image credit: NASA/JPL-Caltech/SSI

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December 12, 2011

NASA's Cassini spacecraft successfully completed its closest-ever pass over Saturn's moon Dione on Monday, Dec. 12, slaloming its way through the Saturn system on its way to tomorrow's close flyby of Titan. Cassini is expected to glide about 2,200 miles (3,600 kilometers) over the Titan surface on Dec. 13.


In the selection of the raw images obtained during the Cassini Dione flyby, Dione is sometimes joined by other moons. Mimas appears just beyond the dark side of Dione in one view. In another view, Epimetheus and Pandora appear together, along with Saturn's rings.


This Dione encounter was intended primarily for Cassini's composite infrared spectrometer and radio science subsystem. However, the imaging team did capture views of the distinctive, wispy fractures on the side of Dione that always trails in its orbit around Saturn. It also obtained images of a ridge called Janiculum Dorsa on the hemisphere of Dione that always leads in its orbit around Saturn. While other flybys produced more detailed views of the surface, the best resolved images from this flyby have scales ranging from about 1,100 feet (350 meters) to about 1,600 feet (500 meters) per pixel. Janiculum Dorsa will be imaged by Cassini at higher resolution in May 2012.


All of Cassini's raw images can be seen at http://saturn.jpl.nasa.gov/photos/raw/ .


The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory in Pasadena manages the mission for the agency's Science Mission Directorate in Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations team is based at the Space Science Institute in Boulder, Colo. JPL is a division of Caltech.


For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini .

Jia-Rui Cook 818-354-0850

Jet Propulsion Laboratory, Pasadena, Calif.

jccook@jpl.nasa.gov


2011-385
NASA's Cassini spacecraft obtained this unprocessed image on Dec. 12, 2011

NASA's Cassini spacecraft obtained this unprocessed image on Dec. 12, 2011. The camera was pointing toward Saturn's moon Dione from approximately 48,236 miles (77,682 kilometers) away. Image credit: NASA/JPL-Caltech/SSI

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enlarge image

NASA's Cassini spacecraft obtained this unprocessed image on Dec. 12, 2011

NASA's Cassini spacecraft obtained this unprocessed image on Dec. 12, 2011. The camera was pointing toward Saturn's moon Dione from approximately 76,344 miles (122,864 kilometers) away. Image credit: NASA/JPL-Caltech/SSI

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enlarge image




Black Hole Caught Red-Handed in a Stellar Homicide

Black Hole Caught Red-Handed in a Stellar Homicide:

Computer-simulated image shows gas from a tidally shredded star
This computer-simulated image shows gas from a tidally shredded star
falling into a black hole. Image credit: NASA/JPL-Caltech/JHU/UCSC

› Full image and caption May 02, 2012

PASADENA, Calif. - Astronomers have gathered the most direct evidence yet of a supermassive black hole shredding a star that wandered too close. NASA's Galaxy Evolution Explorer, a space-based observatory, and the Pan-STARRS1 telescope on the summit of Haleakala in Hawaii were among the first to help identify the stellar remains.


Supermassive black holes, weighing millions to billions times more than the sun, lurk in the centers of most galaxies. These hefty monsters lie quietly until an unsuspecting victim, such as a star, wanders close enough to get ripped apart by their powerful gravitational clutches.


Astronomers had spotted these stellar homicides before, but this is the first time they have identified the victim. Using several ground- and space-based telescopes, a team of astronomers led by Suvi Gezari of the Johns Hopkins University, Baltimore, Md., identified the victim as a star rich in helium gas. The star resides in a galaxy 2.7 billion light-years away. The team's results appear in today's online edition of the journal Nature.


"When the star is ripped apart by the gravitational forces of the black hole, some part of the star's remains falls into the black hole, while the rest is ejected at high speeds," Gezari said. "We are seeing the glow from the stellar gas falling into the black hole over time. We're also witnessing the spectral signature of the ejected gas, which we find to be mostly helium. It is like we are gathering evidence from a crime scene. Because there is very little hydrogen and mostly helium in the gas, we detect from the carnage that the slaughtered star had to have been the helium-rich core of a stripped star."


This observation yields insights about the harsh environment around black holes and the types of stars swirling around them. It is not the first time the unlucky star had a brush with the behemoth black hole.


The team believes the star's hydrogen-filled envelope surrounding the core was lifted off a long time ago by the same black hole. The star may have been near the end of its life. After consuming most of its hydrogen fuel, it had probably ballooned in size, becoming a red giant. Astronomers think the bloated star was looping around the black hole in a highly elliptical orbit, similar to a comet's elongated orbit around the sun. On one of its close approaches, the star was stripped of its puffed-up atmosphere by the black hole's powerful gravity. The stellar remains continued its journey around the center, until it ventured even closer to the black hole to face its ultimate demise.


Astronomers predict stripped stars circle the central black hole of our Milky Way galaxy. These close encounters are rare, occurring roughly every 100,000 years. To find this event, Gezari's team monitored hundreds of thousands of galaxies in ultraviolet light with the Galaxy Evolution Explorer, and in visible light with Pan-STARRS1. Pan-STARRS, short for Panoramic Survey Telescope and Rapid Response System, scans the entire night sky for all kinds of transient phenomena, including supernovae.


The team was looking for a bright flare in ultraviolet light from the nucleus of a galaxy with a previously dormant black hole. Both telescopes spotted one in June 2010. Astronomers continued to monitor the flare as it reached peak brightness a month later and slowly faded during the next 12 months. The brightening event was similar to the explosive energy unleashed by a supernova, but the rise to the peak was much slower, taking nearly one-and-a-half months.


"The longer the event lasted, the more excited we got, because we realized this is either a very unusual supernova or an entirely different type of event, such as a star being ripped apart by a black hole," said team member Armin Rest of the Space Telescope Science Institute in Baltimore.


By measuring the increase in brightness, the astronomers calculated the black hole's mass to be several million suns, which is comparable to the size of our Milky Way's black hole.


Spectroscopic observations with the Multiple Meter Telescope Observatory on Mount Hopkins in Arizona showed the black hole was swallowing lots of helium. Spectroscopy divides light into its rainbow colors, which yields an object's characteristics, such as its temperature and gaseous makeup.


To completely rule out the possibility of an active nucleus flaring up in the galaxy, the team used NASA's Chandra X-ray Observatory to study the hot gas. Chandra showed that the characteristics of the gas didn't match those from an active galactic nucleus.


For images, video and more information about this study, visit: http://hubblesite.org/news/2012/18 .


For graphics and information about the Galaxy Evolution Explorer, visit: http://www.nasa.gov/galex and http://www.galex.caltech.edu .



Whitney Clavin 818-354-4673

Jet Propulsion Laboratory, Pasadena, Calif.

Whitney.clavin@jpl.nasa.gov

J.D. Harrington 202-358-0321

Headquarters, Washington

j.d.harrington@nasa.gov

2012-122

NASA's Spitzer Sees the Light of Alien 'Super Earth'

NASA's Spitzer Sees the Light of Alien 'Super Earth':

How to See a Super Earth
NASA's Spitzer Space Telescope was able to detect a super Earth's direct light for the first time using its sensitive heat-seeking infrared vision. Super Earth's are more massive than Earth but lighter than gas giants like Neptune. As this artist's concept shows, in visible light, a planet is lost in the glare of its star (top view). When viewed in infrared, the planet becomes brighter relative to its star. This is largely due to the fact that the planet's scorching heat blazes with infrared light. Even on our own bodies emanate more infrared light than visible due to our heat. Image credit: NASA/JPL-Caltech
› Full image and caption





May 08, 2012

PASADENA, Calif. - NASA's Spitzer Space Telescope has detected light emanating from a "super-Earth" planet beyond our solar system for the first time. While the planet is not habitable, the detection is a historic step toward the eventual search for signs of life on other planets.

"Spitzer has amazed us yet again," said Bill Danchi, Spitzer program scientist at NASA Headquarters in Washington. "The spacecraft is pioneering the study of atmospheres of distant planets and paving the way for NASA's upcoming James Webb Space Telescope to apply a similar technique on potentially habitable planets."

The planet, called 55 Cancri e, falls into a class of planets termed super Earths, which are more massive than our home world but lighter than giant planets like Neptune. The planet is about twice as big and eight times as massive as Earth. It orbits a bright star, called 55 Cancri, in a mere 18 hours.

Previously, Spitzer and other telescopes were able to study the planet by analyzing how the light from 55 Cancri changed as the planet passed in front of the star. In the new study, Spitzer measured how much infrared light comes from the planet itself. The results reveal the planet is likely dark, and its sun-facing side is more than 2,000 Kelvin (3,140 degrees Fahrenheit), hot enough to melt metal.

The new information is consistent with a prior theory that 55 Cancri e is a water world: a rocky core surrounded by a layer of water in a "supercritical" state where it is both liquid and gas, and topped by a blanket of steam.

"It could be very similar to Neptune, if you pulled Neptune in toward our sun and watched its atmosphere boil away," said Michaël Gillon of Université de Liège in Belgium, principal investigator of the research, which appears in the Astrophysical Journal. The lead author is Brice-Olivier Demory of the Massachusetts Institute of Technology in Cambridge.

The 55 Cancri system is relatively close to Earth, at 41 light-years away. It has five planets, with 55 Cancri e the closest to the star and tidally locked, so one side always faces the star. Spitzer discovered the sun-facing side is extremely hot, indicating the planet probably does not have a substantial atmosphere to carry the sun's heat to the unlit side.

NASA's James Webb Space Telescope, scheduled to launch in 2018, likely will be able to learn even more about the planet's composition. The telescope might be able to use a similar infrared method to Spitzer to search other potentially habitable planets for signs of molecules possibly related to life.

"When we conceived of Spitzer more than 40 years ago, exoplanets hadn't even been discovered," said Michael Werner, Spitzer project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Because Spitzer was built very well, it's been able to adapt to this new field and make historic advances such as this."

In 2005, Spitzer became the first telescope to detect light from a planet beyond our solar system. To the surprise of many, the observatory saw the infrared light of a "hot Jupiter," a gaseous planet much larger than the solid 55 Cancri e. Since then, other telescopes, including NASA's Hubble and Kepler space telescopes, have performed similar feats with gas giants using the same method.

In this method, a telescope gazes at a star as a planet circles behind it. When the planet disappears from view, the light from the star system dips ever so slightly, but enough that astronomers can determine how much light came from the planet itself. This information reveals the temperature of a planet, and, in some cases, its atmospheric components. Most other current planet-hunting methods obtain indirect measurements of a planet by observing its effects on the star.

During Spitzer's ongoing extended mission, steps were taken to enhance its unique ability to see exoplanets, including 55 Cancri e. Those steps, which included changing the cycling of a heater and using an instrument in a new way, led to improvements in how precisely the telescope points at targets.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology (Caltech) 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.

For more information about Spitzer, visit: http://www.nasa.gov/spitzer and http://spitzer.caltech.edu .

Whitney Clavin 818-354-4673

Jet Propulsion Laboratory, Pasadena, Calif.

Whitney.clavin@jpl.nasa.gov

J. D. Harrington 202-358-5241

NASA Headquarters, Washington

j.d.harrington@nasa.gov

2012-127

Cassini Sees Tropical Lakes on Saturn Moon

Cassini Sees Tropical Lakes on Saturn Moon:

Saturn's rings lie in the distance as the Cassini spacecraft looks toward Titan
Saturn's rings lie in the distance as the Cassini spacecraft looks toward Titan and its dark region called Shangri-La, east of the landing site of the Huygens Probe. Image Credit:
NASA/JPL-Caltech/Space Science Institute
› Full image and caption June 13, 2012

PASADENA, Calif. - NASA's Cassini spacecraft has spied long-standing methane lakes, or puddles, in the "tropics" of Saturn's moon Titan. One of the tropical lakes appears to be about half the size of Utah's Great Salt Lake, with a depth of at least 3 feet (1 meter).

The result, which is a new analysis of Cassini data, is unexpected because models had assumed the long-standing bodies of liquid would only exist at the poles. The findings appear in this week's issue of the journal Nature.

Where could the liquid for these lakes come from?  "A likely supplier is an underground aquifer," said Caitlin Griffith, the paper's lead author and a Cassini team associate at the University of Arizona, Tucson. "In essence, Titan may have oases."

Understanding how lakes or wetlands form on Titan helps scientists learn about the moon's weather. Like Earth's hydrological cycle, Titan has a "methane" cycle, with methane rather than water circulating. In Titan's atmosphere, ultraviolet light breaks apart methane, initiating a chain of complicated organic chemical reactions. But existing models haven't been able to account for the abundant supply of methane.

"An aquifer could explain one of the puzzling questions about the existence of methane, which is continually depleted," Griffith said. "Methane is a progenitor of Titan's organic chemistry, which likely produces interesting molecules like amino acids, the building blocks of life."

Global circulation models of Titan have theorized that liquid methane in the moon's equatorial region evaporates and is carried by wind to the north and south poles, where cooler temperatures cause methane to condense. When it falls to the surface, it forms the polar lakes. On Earth, water is similarly transported by the circulation, yet the oceans also transport water, thereby countering the atmospheric effects.

The latest results come from Cassini's visual and infrared mapping spectrometer, which detected the dark areas in the tropical region known as Shangri-La, near the spot where the European Space Agency's Huygens probe landed in 2005. When Huygens landed, the heat of the probe's lamp vaporized some methane from the ground, indicating it had landed in a damp area.

Areas appear dark to the visual and infrared mapping spectrometer when liquid ethane or methane are present. Some regions could be shallow, ankle-deep puddles. Cassini's radar mapper has seen lakes in the polar region, but hasn't detected any lakes at low latitudes.

The tropical lakes detected by the visual and infrared mapping spectrometer have remained since 2004. Only once has rain been detected falling and evaporating in the equatorial regions, and only during the recent expected rainy season. Scientists therefore deduce the lakes could not be substantively replenished by rain.

"We had thought that Titan simply had extensive dunes at the equator and lakes at the poles, but now we know that Titan is more complex than we previously thought," said Linda Spilker, the Cassini project scientist based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Cassini still has multiple opportunities to fly by this moon going forward, so we can't wait to see how the details of this story fill out."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory manages the mission for NASA's Science Mission Directorate, Washington. The visual and infrared mapping spectrometer team is based at the University of Arizona, Tucson.

For more information, visit http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Jia-Rui C. Cook 818-354-0850

Jet Propulsion Laboratory, Pasadena, Calif.

jccook@jpl.nasa.gov

Dwayne Brown 202-358-1726

NASA Headquarters

dwayne.c.brown@nasa.gov

Dawn has Departed the Giant Asteroid Vesta

Dawn has Departed the Giant Asteroid Vesta:

A Last Look Back at Vesta
This image is from the last sequence of images NASA's Dawn spacecraft
obtained of the giant asteroid Vesta, looking down at Vesta's north pole as it was departing. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

› Full image and caption


September 05, 2012

Dawn Mission Status Report



PASADENA, Calif. -- Mission controllers received confirmation today that NASA's Dawn spacecraft has escaped from the gentle gravitational grip of the giant asteroid Vesta. Dawn is now officially on its way to its second destination, the dwarf planet Ceres.

Dawn departed from Vesta at about 11:26 p.m. PDT on Sept. 4 (2:26 a.m. EDT on Sept. 5). Communications from the spacecraft via NASA's Deep Space Network confirmed the departure and that the spacecraft is now traveling toward Ceres.

"As we respectfully say goodbye to Vesta and reflect on the amazing discoveries over the past year, we eagerly look forward to the next phase of our adventure at Ceres, where even more exciting discoveries await," said Robert Mase, Dawn project manager, based at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Launched on Sept. 27, 2007, Dawn slipped into orbit around Vesta on July 15, 2011 PDT (July 16 EDT). Over the past year, Dawn has comprehensively mapped this previously uncharted world, revealing an exotic and diverse planetary building block. The findings are helping scientists unlock some of the secrets of how the solar system, including our own Earth, was formed.


A web video celebrating Dawn's "greatest hits" at Vesta is available at http://www.nasa.gov/multimedia/videogallery/index.html?media_id=151669301 . Two of Dawn's last looks at Vesta are also now available, revealing the creeping dawn over the north pole.


Dawn spiraled away from Vesta as gently as it arrived. It is expected to pull into its next port of call, Ceres, in early 2015.


Dawn's mission is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Va., designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team. The California Institute of Technology in Pasadena manages JPL for NASA.



For more information about Dawn, visit: http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov .

Jia-Rui C. Cook 818-354-0850

Jet Propulsion Laboratory, Pasadena, Calif.

Jia-Rui.C.Cook@jpl.nasa.gov


2012-277

First Planets Found Around Sun-Like Stars in a Cluster

First Planets Found Around Sun-Like Stars in a Cluster:

Starry Starry Skies (Artist's Concept)
Astronomers have discovered two gas giant planets orbiting stars in the Beehive cluster, a collection of about 1,000 tightly packed stars. Image credit: NASA/JPL-Caltech
› Full image and caption


September 14, 2012

PASADENA, Calif. -- NASA-funded astronomers have, for the first time, spotted planets orbiting sun-like stars in a crowded cluster of stars. The findings offer the best evidence yet that planets can sprout up in dense stellar environments. Although the newfound planets are not habitable, their skies would be starrier than what we see from Earth.

The starry-skied planets are two so-called hot Jupiters, which are massive, gaseous orbs that are boiling hot because they orbit tightly around their parent stars. Each hot Jupiter circles a different sun-like star in the Beehive Cluster, also called the Praesepe, a collection of roughly 1,000 stars that appear to be swarming around a common center.

The Beehive is an open cluster, or a grouping of stars born at about the same time and out of the same giant cloud of material. The stars therefore share a similar chemical composition. Unlike the majority of stars, which spread out shortly after birth, these young stars remain loosely bound together by mutual gravitational attraction.

"We are detecting more and more planets that can thrive in diverse and extreme environments like these nearby clusters," said Mario R. Perez, the NASA astrophysics program scientist in the Origins of Solar Systems Program. "Our galaxy contains more than 1,000 of these open clusters, which potentially can present the physical conditions for harboring many more of these giant planets."


The two new Beehive planets are called Pr0201b and Pr0211b. The star's name followed by a "b" is the standard naming convention for planets.


"These are the first 'b's' in the Beehive," said Sam Quinn, a graduate student in astronomy at Georgia State University in Atlanta and the lead author of the paper describing the results, which was published in the Astrophysical Journal Letters.


Quinn and his team, in collaboration with David Latham at the Harvard-Smithsonian Center for Astrophysics, discovered the planets by using the 1.5-meter Tillinghast telescope at the Smithsonian Astrophysical Observatory's Fred Lawrence Whipple Observatory near Amado, Arizona to measure the slight gravitational wobble the orbiting planets induce upon their host stars. Previous searches of clusters had turned up two planets around massive stars but none had been found around stars like our sun until now.


"This has been a big puzzle for planet hunters," Quinn said. "We know that most stars form in clustered environments like the Orion nebula, so unless this dense environment inhibits planet formation, at least some sun-like stars in open clusters should have planets. Now, we finally know they are indeed there."


The results also are of interest to theorists who are trying to understand how hot Jupiters wind up so close to their stars. Most theories contend these blistering worlds start out much cooler and farther from their stars before migrating inward.


"The relatively young age of the Beehive cluster makes these planets among the youngest known," said Russel White, the principal investigator on the NASA Origins of Solar Systems grant that funded this study. "And that's important because it sets a constraint on how quickly giant planets migrate inward -- and knowing how quickly they migrate is the first step to figuring out how they migrate."


The research team suspects planets were turned up in the Beehive cluster because it is rich in metals. Stars in the Beehive have more heavy elements such as iron than the sun has.


According to White, "Searches for planets around nearby stars suggest that these metals act like a 'planet fertilizer,' leading to an abundant crop of gas giant planets. Our results suggest this may be true in clusters as well."


NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages NASA's Exoplanet Exploration Program office. More information about exoplanets and NASA's planet-finding program is available at: http://planetquest.jpl.nasa.gov .

Whitney Clavin 818-354-4673

Jet Propulsion Laboratory, Pasadena, Calif.

whitney.clavin@jpl.nasa.gov


J.D. Harrington 202-358-5241

Headquarters, Washington

j.d.harrington@nasa.gov


2012-289

Juno's Two Deep Space Maneuvers are 'Back-To-Back Home Runs'

Juno's Two Deep Space Maneuvers are 'Back-To-Back Home Runs':

Juno Main Engine Firing
A computer-generated image depicts NASA's Juno spacecraft firing its main engine. Image credit: NASA/JPL-Caltech

› Full image and caption


September 17, 2012

PASADENA, Calif. - NASA's Juno spacecraft successfully executed a second Deep Space Maneuver, called DSM-2 last Friday, Sept. 14. The 30 minute firing of its main engine refined the Jupiter-bound spacecraft's trajectory, setting the stage for a gravity assist from a flyby of Earth on Oct 9, 2013. Juno will arrive at Jupiter on July 4, 2016.


The maneuver began at 3:30 p.m. PDT (6:30 p.m. EDT), when the Leros-1b main engine began to fire. The burn ended at 4 p.m. PDT (7 p.m. EDT). Based on telemetry, the Juno project team believes the burn was accurate, changing the spacecraft's velocity by about 867 mph (388 meters a second) while consuming about 829 pounds (376 kilograms) of fuel.


The burn occurred when Juno was more than 298 million miles (480 million kilometers) from Earth.


Juno executed its first deep space maneuver (DSM-1), one of comparable duration and velocity change, on Aug. 30. Together, both maneuvers placed Juno on course for its Earth flyby, which will occur as the spacecraft is completing one elliptical orbit around the sun. The Earth flyby will boost Juno's velocity by 16,330 mph (about 7.3 kilometers per second), placing the spacecraft on its final flight path for Jupiter. The closest approach to Earth, on Oct. 9, 2013, will occur when Juno is at an altitude of about 348 miles (560 kilometers).


"It feels like we hit back-to-back home runs here with the near-flawless propulsion system performance seen during both DSM-1 and DSM-2." said Juno Project Manager Rick Nybakken of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "These successes move us closer to being ready for our most critical mission event, the Jupiter Orbit Insertion main engine burn in July 2016. We're not in the playoffs yet, as that will come in 2016 when we arrive at Jupiter, but it does feel fantastic to have hit both of these DSMs out of the park."


Juno was launched on Aug. 5, 2011. Once in orbit, the spacecraft will circle Jupiter 33 times, from pole to pole, and use its collection of eight science instruments to probe beneath the gas giant's obscuring cloud cover. Juno's science team will learn about Jupiter's origins, structure, atmosphere and magnetosphere, and look for a potential solid planetary core.


Juno's name comes from Greek and Roman mythology. The god Jupiter drew a veil of clouds around himself to hide his mischief, and his wife, the goddess Juno, was able to peer through the clouds and reveal Jupiter's true nature.


NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. The Juno mission is part of the New Frontiers Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems, Denver, built the spacecraft. JPL is a division of the California Institute of Technology in Pasadena.


More information about Juno is online at http://www.nasa.gov/juno and http://missionjuno.swri.edu .





DC Agle 818-393-9011

Jet Propulsion Laboratory, Pasadena, Calif.

agle@jpl.nasa.gov




Maria Martinez 210-522-3305

Southwest Research Institute, San Antonio


maria.martinez@swri.org


2012-291

NASA Telescopes Spy Ultra-Distant Galaxy

NASA Telescopes Spy Ultra-Distant Galaxy:

A Glimmer From a Dark Cosmic Era
In the big image at left, the many galaxies of a massive cluster called MACS J1149+2223 dominate the scene. Gravitational lensing by the giant cluster brightened the light from the newfound galaxy, known as MACS 1149-JD, some 15 times. At upper right, a partial zoom-in shows MACS 1149-JD in more detail, and a deeper zoom appears to the lower right.. Image credit: NASA/ESA/STScI/JHU
› Full image and caption


September 19, 2012

PASADENA, Calif. -- With the combined power of NASA's Spitzer and Hubble space telescopes, as well as a cosmic magnification effect, astronomers have spotted what could be the most distant galaxy ever seen. Light from the young galaxy captured by the orbiting observatories first shone when our 13.7-billion-year-old universe was just 500 million years old.

The far-off galaxy existed within an important era when the universe began to transit from the so-called cosmic dark ages. During this period, the universe went from a dark, starless expanse to a recognizable cosmos full of galaxies. The discovery of the faint, small galaxy opens a window onto the deepest, most remote epochs of cosmic history.

"This galaxy is the most distant object we have ever observed with high confidence," said Wei Zheng, a principal research scientist in the department of physics and astronomy at Johns Hopkins University in Baltimore who is lead author of a new paper appearing in Nature. "Future work involving this galaxy, as well as others like it that we hope to find, will allow us to study the universe's earliest objects and how the dark ages ended."

Light from the primordial galaxy traveled approximately 13.2 billion light-years before reaching NASA's telescopes. In other words, the starlight snagged by Hubble and Spitzer left the galaxy when the universe was just 3.6 percent of its present age. Technically speaking, the galaxy has a redshift, or "z," of 9.6. The term redshift refers to how much an object's light has shifted into longer wavelengths as a result of the expansion of the universe. Astronomers use redshift to describe cosmic distances.


Unlike previous detections of galaxy candidates in this age range, which were only glimpsed in a single color, or waveband, this newfound galaxy has been seen in five different wavebands. As part of the Cluster Lensing And Supernova Survey with Hubble Program, the Hubble Space Telescope registered the newly described, far-flung galaxy in four visible and infrared wavelength bands. Spitzer measured it in a fifth, longer-wavelength infrared band, placing the discovery on firmer ground.


Objects at these extreme distances are mostly beyond the detection sensitivity of today's largest telescopes. To catch sight of these early, distant galaxies, astronomers rely on gravitational lensing. In this phenomenon, predicted by Albert Einstein a century ago, the gravity of foreground objects warps and magnifies the light from background objects. A massive galaxy cluster situated between our galaxy and the newfound galaxy magnified the newfound galaxy's light, brightening the remote object some 15 times and bringing it into view.


Based on the Hubble and Spitzer observations, astronomers think the distant galaxy was less than 200 million years old when it was viewed. It also is small and compact, containing only about 1 percent of the Milky Way's mass. According to leading cosmological theories, the first galaxies indeed should have started out tiny. They then progressively merged, eventually accumulating into the sizable galaxies of the more modern universe.



These first galaxies likely played the dominant role in the epoch of reionization, the event that signaled the demise of the universe's dark ages. This epoch began about 400,000 years after the Big Bang when neutral hydrogen gas formed from cooling particles. The first luminous stars and their host galaxies emerged a few hundred million years later. The energy released by these earliest galaxies is thought to have caused the neutral hydrogen strewn throughout the universe to ionize, or lose an electron, a state that the gas has remained in since that time.


"In essence, during the epoch of reionization, the lights came on in the universe," said paper co-author Leonidas Moustakas, a research scientist at NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif.


Astronomers plan to study the rise of the first stars and galaxies and the epoch of reionization with the successor to both Hubble and Spitzer, NASA's James Webb Telescope, which is scheduled for launch in 2018. The newly described distant galaxy will likely be a prime target.


For more information about Spitzer, visit http://www.nasa.gov/spitzer . For more information about Hubble, visit: http://www.nasa.gov/hubble .

Whitney Clavin 818-354-4673

Jet Propulsion Laboratory, Pasadena, Calif.

whitney.clavin@jpl.nasa.gov


J.D. Harrington 202-358-5241

NASA Headquarters, Washington                                                      

j.d.harrington@nasa.gov


2012-294

NuSTAR Celebrates First 100 Days

NuSTAR Celebrates First 100 Days:

100 Days, 100 Nights in Space
NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, celebrates 100 days in orbit on Sept. 21, 2012. The black-hole spying telescope was blasted into orbit around Earth's equator on June 13, 2012. The mission's goal is to measure high-energy X-ray light from the most extreme objects in the universe, including black holes, neutron stars and supernovae. Image credit: NASA/JPL-Caltech
› Full image and caption


September 20, 2012

Tomorrow, Sept. 21, 2012, will mark 100 days since NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, launched into space from the L-1011 "Stargazer" aircraft. Since completing its 30-day checkout, the telescope has been busy making its first observations of black holes, super-dense dead stars and the glowing remains of exploded stars.

In this early mission phase, the NuSTAR team has been getting to know their telescope better and learning how to point it precisely at targets of interest. NuSTAR has the longest mast of any astronomical telescope ever launched. The 33-foot (10-meter) flexible structure is part of the mission's innovative design, allowing NuSTAR to focus high-energy X-rays into sharp images for the first time. The team has been spending time understanding the mast's mechanics and how they affect the telescope's pointing.

In addition, NuSTAR has continued to team up with other observatories, including NASA's Chandra and Swift telescopes, to make coordinated observations. These joint observations allow astronomers to interpret data from their telescopes more precisely, and to gain a better overall understanding of some of the most extreme events in the cosmos.


As its journey continues, NuSTAR will explore many more targets in our galaxy and beyond.

NuSTAR is a Small Explorer mission led by the California Institute of Technology in Pasadena and managed by NASA's Jet Propulsion Laboratory, also in Pasadena, for NASA's Science Mission Directorate in Washington. The spacecraft was built by Orbital Sciences Corporation, Dulles, Va. Its instrument was built by a consortium including Caltech; JPL; the University of California, Berkeley; Columbia University, New York; NASA's Goddard Space Flight Center, Greenbelt, Md.; the Danish Technical University in Denmark; Lawrence Livermore National Laboratory, Livermore, Calif.; and ATK Aerospace Systems, Goleta, Calif. NuSTAR's mission operations center is at UC Berkeley, with the Italian Space Agency providing its equatorial ground station located at Malindi, Kenya. The mission's outreach program is based at Sonoma State University, Rohnert Park, Calif. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.


For more information, visit http://www.nasa.gov/nustar and http://www.nustar.caltech.edu/ .

Whitney Clavin 818-354-4673

Jet Propulsion Laboratory, Pasadena, Calif.

whitney.clavin@jpl.nasa.gov



2012-298

Bounce, Skid, Wobble: How Huygens Landed on Titan

Bounce, Skid, Wobble: How Huygens Landed on Titan:

Artist concept showing the descent and landing of Huygens.
Artist concept showing the descent and landing of Huygens. Image credit: NASA/JPL/ESA

› Full image and caption


October 11, 2012

The European Space Agency's Huygens probe, ferried to Saturn's moon Titan by NASA's Cassini spacecraft, bounced, slid and wobbled its way to rest in the 10 seconds after touching down on Titan in January 2005, a new analysis reveals. The moon's surface is more complex than previously thought.


Scientists reconstructed the chain of events by analyzing data from a variety of instruments that were active during the impact, in particular changes in the acceleration. The instrument data were compared with results from computer simulations and a drop test using a model of Huygens designed to replicate the landing.


The analysis reveals that, on first contact with Titan's surface, Huygens made a dent 4.7 inches (12 centimeters) deep, before bouncing out onto a flat surface. The Huygens probe, which had a mass of about 400 pounds (200 kilograms), hit the ground with an impact speed that was similar to dropping a ball on Earth from a height of about 3 feet (one meter). The probe, tilted by about 10 degrees in the direction of motion, then slid 12 to 16 inches (30 to 40 centimeters) across the surface. It slowed due to friction with the surface and, upon coming to its final resting place, wobbled back and forth five times. Each wobble was about half as large as the previous one. Huygens' sensors continued to detect small vibrations for another two seconds, until motion subsided nearly 10 seconds after touchdown.


"A spike in the acceleration data suggests that during the first wobble, the probe likely encountered a pebble protruding by around an inch [2 centimeters] from the surface of Titan, and may have even pushed it into the ground, suggesting that the surface had a consistency of soft, damp sand," said Stefan Schröder of the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany, lead author of the paper reporting the results in the journal Planetary and Space Science.


Previous work measured the firmness of Titan's surface during the Huygens impact. Those results found the surface to be quite soft. The new work goes one step farther to demonstrate that if something put little pressure on the surface, the surface was hard, but if an object put more pressure on the surface, it sank in significantly.


"It is like snow that has been frozen on top," said Erich Karkoschka, a co-author at the University of Arizona, Tucson. "If you walk carefully, you can walk as on a solid surface, but if you step on the snow a little too hard, you break in very deeply."


Had the probe impacted a wet, mud-like substance, its instruments would have recorded a "splat" with no further indication of bouncing or sliding. The surface must have therefore been soft enough to allow the probe to make a sizeable depression, but hard enough to support Huygens rocking back and forth.


"We also see in the Huygens landing data evidence of a 'fluffy' dust-like material - most likely organic aerosols that are known to drizzle out of the Titan atmosphere - being thrown up into the atmosphere and suspended there for around four seconds after the impact," said Schröder.


Since the dust was easily lifted, it was most likely dry, suggesting that there had not been any rain of liquid ethane or methane for some time prior to the landing.


"This study takes us back to the historical moment of Huygens touching down on the most remote alien world ever visited by a landing probe," added ESA's Cassini-Huygens project scientist, Nicolas Altobelli. "Huygens data, even years after mission completion, are providing us with a new dynamical 'feeling' for these crucial first seconds of landing."


A new animation of the landing can be seen here: http://www.esa.int/esaSC/SEMJP13S18H_index_0.html.


The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C.

Jia-Rui C. Cook 818-354-0850

Jet Propulsion Laboratory, Pasadena, Calif.

jccook@jpl.nasa.gov


Markus Bauer 011-31-71-565-6799

European Space Agency, Noordwijk, the Netherlands

markus.bauer@esa.int

2012-317

NASA's WISE Colors in Unknowns on Jupiter Asteroids

NASA's WISE Colors in Unknowns on Jupiter Asteroids:

Trojan Colors Revealed (Artist's Concept)
New results from NASA's Wide-field Infrared Explorer, or WISE, reveal that the Jovian Trojans -- asteroids that lap the sun in the same orbit as Jupiter -- are uniformly dark with a hint of burgundy color, and have matte surfaces that reflect little sunlight. Image credit: NASA/JPL-Caltech
› Full image and caption


October 15, 2012

Scientists using data from NASA's Wide-field Infrared Survey Explorer, or WISE, have uncovered new clues in the ongoing mystery of the Jovian Trojans -- asteroids that orbit the sun on the same path as Jupiter. Like racehorses, the asteroids travel in packs, with one group leading the way in front of the gas giant, and a second group trailing behind.


The observations are the first to get a detailed look at the Trojans' colors: both the leading and trailing packs are made up of predominantly dark, reddish rocks with a matte, non-reflecting surface. What's more, the data verify the previous suspicion that the leading pack of Trojans outnumbers the trailing bunch.



The new results offer clues in the puzzle of the asteroids' origins. Where did the Trojans come from? What are they made of? WISE has shown that the two packs of rocks are strikingly similar and do not harbor any "out-of-towners," or interlopers, from other parts of the solar system. The Trojans do not resemble the asteroids from the main belt between Mars and Jupiter, nor the Kuiper belt family of objects from the icier, outer regions near Pluto.



"Jupiter and Saturn are in calm, stable orbits today, but in their past, they rumbled around and disrupted any asteroids that were in orbit with these planets," said Tommy Grav, a WISE scientist from the Planetary Science Institute in Tucson, Ariz. "Later, Jupiter re-captured the Trojan asteroids, but we don't know where they came from. Our results suggest they may have been captured locally. If so, that's exciting because it means these asteroids could be made of primordial material from this particular part of the solar system, something we don't know much about." Grav is a member of the NEOWISE team, the asteroid-hunting portion of the WISE mission.



The first Trojan was discovered on Feb. 22, 1906, by German astronomer Max Wolf, who found the celestial object leading ahead of Jupiter. Christened "Achilles" by the astronomer, the roughly 81-mile-wide (130-kilometer-wide) chunk of space rock was the first of many asteroids detected to be traveling in front of the gas giant. Later, asteroids were also found trailing behind Jupiter. The asteroids were collectively named Trojans after a legend, in which Greek soldiers hid inside in a giant horse statue to launch a surprise attack on the Trojan people of the city of Troy.



"The two asteroid camps even have their own 'spy,'" said Grav. "After having discovered a handful of Trojans, astronomers decided to name the asteroid in the leading camp after the Greek heroes and the ones in the trailing after the heroes of Troy. But each of the camps already had an 'enemy' in their midst, with asteroid 'Hector' in the Greek camp and 'Patroclus' in the Trojan camp."



Other planets were later found to have Trojan asteroids riding along with them too, such as Mars, Neptune and even Earth, where WISE recently found the first known Earth Trojan: http://www.jpl.nasa.gov/news/news.php?release=2011-230 .



Before WISE, the main uncertainty defining the population of Jupiter Trojans was just how many individual chunks were in these clouds of space rock and ice leading Jupiter, and how many were trailing. It is believed that there are as many objects in these two swarms leading and trailing Jupiter as there are in the entirety of the main asteroid belt between Mars and Jupiter.



To put this and other theories to bed requires a well-coordinated, well-executed observational campaign. But there were many things in the way of accurate observations -- chiefly, Jupiter itself. The orientation of these Jovian asteroid clouds in the sky in the last few decades has been an impediment to observations. One cloud is predominantly in Earth's northern sky, while the other is in the southern, forcing ground-based optical surveys to use at least two different telescopes. The surveys generated results, but it was unclear whether a particular result was caused by the problems of having to observe the two clouds with different instruments, and at different times of the year.



Enter WISE, which roared into orbit on Dec. 14, 2009. The spacecraft's 16-inch (40-centimeter) telescope and infrared cameras scoured the entire sky looking for the glow of celestial heat sources. From January 2010 to February 2011, about 7,500 images were taken every day. The NEOWISE project used the data to catalogue more than 158,000 asteroids and comets throughout the solar system.



"By obtaining accurate diameter and surface reflectivity measurements on 1,750 Jupiter Trojans, we increased by an order of magnitude what we knew about these two gatherings of asteroids," said Grav. "With this information, we were able to more accurately than ever confirm there are indeed almost 40 percent more objects in the leading cloud."



Trying to understand the surface or interior of a Jovian Trojan is also difficult. The WISE suite of infrared detectors was sensitive to the thermal glow of the objects, unlike visible-light telescopes. This means WISE can provide better estimates of their surface reflectivity, or albedo, in addition to more details about their visible and infrared colors (in astronomy "colors" can refer to types of light beyond the visible spectrum).



"Seeing asteroids with WISE's many wavelengths is like the scene in 'The Wizard of Oz,' where Dorothy goes from her black-and-white world into the Technicolor land of Oz," said Amy Mainzer, the principal investigator of the NEOWISE project at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Because we can see farther into the infrared portion of the light spectrum, we can see more details of the asteroids' colors, or, in essence, more shades or hues."



The NEOWISE team has analyzed the colors of 400 Trojan asteroids so far, allowing many of these asteroids to be properly sorted according to asteroid classification schemes for the first time.



"We didn't see any ultra-red asteroids, typical of the main belt and Kuiper belt populations," said Grav. "Instead, we find a largely uniform population of what we call D-type asteroids, which are dark burgundy in color, with the rest being C- and P-type, which are more grey-bluish in color. More research is needed, but it's possible we are looking at the some of the oldest material known in the solar system."



Scientists have proposed a future space mission to the Jupiter Trojans that will gather the data needed to determine their age and origins.



The results were presented today at the 44th annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Reno, Nev. Two studies detailing this research are accepted for publication in the Astrophysical Journal.



JPL manages, and operated, WISE for NASA's Science Mission Directorate. The spacecraft was put into hibernation mode in 2011, after it scanned the entire sky twice, completing its main objectives. Edward Wright is the principal investigator and is at UCLA. The mission was selected competitively under NASA's Explorers Program managed by the agency's Goddard Space Flight Center in Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory in Logan, Utah. The spacecraft was built by Ball Aerospace & Technologies Corp. in 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. More information is online at http://www.nasa.gov/wise , http://wise.astro.ucla.edu and http://jpl.nasa.gov/wise .

Whitney Clavin 818-354-4673

Jet Propulsion Laboratory, Pasadena, Calif.

Whitney.clavin@jpl.nasa.gov


2012-322