CIBER: Caltech rocket experiment finds surprising cosmic light

The entrance of the CIBER optics, showing two near-infrared wide-field cameras (top), an absolute spectrometer (lower left) and a Fraunhofer line spectrometer (lower right). 

Credit: Jamie Bock/Caltech

Using an experiment carried into space on a NASA suborbital rocket, astronomers at Caltech and their colleagues have detected a diffuse cosmic glow that appears to represent more light than that produced by known galaxies in the universe.

The researchers, including Caltech Professor of Physics Jamie Bock and Caltech Senior Postdoctoral Fellow Michael Zemcov, say that the best explanation is that the cosmic light originates from stars that were stripped away from their parent galaxies and flung out into space as those galaxies collided and merged with other galaxies.

This explanation is described in a paper published November 7 in the journal Science,

The discovery suggests that many such previously undetected stars permeate what had been thought to be dark spaces between galaxies, forming an interconnected sea of stars.

"Measuring such large fluctuations surprised us, but we carried out many tests to show the results are reliable," says Zemcov, who led the study.

Although they cannot be seen individually, "the total light produced by these stray stars is about equal to the background light we get from counting up individual galaxies," says Bock, also a senior research scientist at JPL.

Bock is the principal investigator of the rocket project, called the Cosmic Infrared Background Experiment (CIBER), which originated at Caltech and flew on four rocket flights from 2009 through 2013.

In earlier studies, NASA's Spitzer Space Telescope, which sees the universe at longer wavelengths, had observed a splotchy pattern of infrared light called the cosmic infrared background.

The splotches are much bigger than individual galaxies.

"We are measuring structures that are grand on a cosmic scale," says Zemcov, "and these sizes are associated with galaxies bunching together on a large-scale pattern."

Initially some researchers proposed that this light came from the very first galaxies to form and ignite stars after the Big Bang.

Others, however, have argued the light originated from stars stripped from galaxies in more recent times.

CIBER was designed to help settle the debate. "CIBER was born as a conversation with Asantha Cooray, a theoretical cosmologist at UC Irvine and at the time a postdoc at Caltech with [former professor] Marc Kamionkowski," Bock explains.

"Asantha developed an idea for studying galaxies by measuring their large-scale structure. Galaxies form in dark-matter halos, which are over-dense regions initially seeded in the early universe by inflation.

Furthermore, galaxies not only start out in these halos, they tend to cluster together as well. Asantha had the brilliant idea to measure this large-scale structure directly from maps.

Experimentally, it is much easier for us to make a map by taking a wide-field picture with a small camera, than going through and measuring faint galaxies one by one with a large telescope."

More information: On the Origin of Near-Infrared Extragalactic Background Light Anisotropy, Science, www.sciencemag.org/lookup/doi/… 1126/science.1258168

Black hole fireworks in nearby galaxy Messier 106

A galaxy about 23 million light-years away is the site of impressive, ongoing, fireworks. 

Rather than paper, powder, and fire, this galactic light show involves a giant black hole, shock waves, and vast reservoirs of gas. 

Credit: NASA /CXC /JPL-Caltech /STScI /NSF /NRAO /VLA

Celebrants this Fourth of July will enjoy the dazzling lights and booming shock waves from the explosions of fireworks.

A similarly styled event is taking place in the galaxy Messier 106 (NGC 4258), as seen by NASA's Spitzer Space Telescope, Chandra X-ray Observatory and the Herschel Space Observatory. Herschel is a European Space Agency mission with important NASA contributions.

Energetic jets, which blast from Messier 106's central black hole, are heating up material in the galaxy and thus making it glow, like the ingredients in a firework.

The jets also power shock waves that are driving gases out of the galaxy's interior.

Those gases constitute the fuel for churning out new stars. A new study estimates the shock waves have already warmed and ejected two-thirds of the gas from the center of Messier 106.

With a reduced ability to birth new stars, Messier 106 appears to be transitioning into a barren, so-called lenticular galaxy full of old, red stars. Lenticular galaxies are flat disks without prominent spiral arms.

"Jets from the supermassive black hole at the center of Messier 106 are having a profound influence on the available gas for making stars in this galaxy," said Patrick Ogle, an astrophysicist at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, and lead author of a new paper describing the results.

"This process may eventually transform the spiral galaxy Messier 106 into a lenticular galaxy, depriving it of the raw material to form stars."

Many galaxies contain a central black hole that actively "feeds" upon nearby gas.

Some of the material, as it draws toward the black hole, dramatically speeds up and violently spews out as twin jets near the black hole's poles.

As one of the Milky Way's closest galactic neighbors, Messier 106 offers a great opportunity for investigating these high-powered jets.

Messier 106 is 23.5 million light-years distant, and visible with binoculars in the constellation Canes Venatici.

For the new study, researchers used data obtained with the Spitzer infrared telescope before the observatory ran out of coolant in 2009, as planned.

The data amount to a map of the infrared light emitted by heated-up hydrogen molecules in Messier 106.

The warmed hydrogen is a signature of the jet from the central black hole energizing the surrounding disk of the galaxy.

NASA Cassini Image: Looking beyond Saturn to view Uranus

This view from NASA's Cassini spacecraft features a blue planet, but unlike the view from July 19, 2013 (PIA17172 The Day the Earth Smiled) that featured our home planet, this blue orb is Uranus, imaged by Cassini for the first time.

Credit: NASA /JPL-Caltech /Space Science Institute

Uranus is a pale blue in this natural colour image because its visible atmosphere contains methane gas and few aerosols or clouds.

Methane on Uranus and its sapphire-coloured sibling, Neptune, absorbs red wavelengths of incoming sunlight, but allows blue wavelengths to escape back into space, resulting in the predominantly bluish color seen here.

Cassini imaging scientists combined red, green and blue spectral filter images to create a final image that represents what human eyes might see from the vantage point of the spacecraft.

Uranus

Uranus has been brightened by a factor of 4.5 to make it more easily visible. The outer portion of Saturn's A ring, seen at bottom right, has been brightened by a factor of two.

The bright ring cutting across the image center is Saturn's narrow F ring.

Uranus was approximately 28.6 astronomical units from Cassini and Saturn when this view was obtained.

An astronomical unit is the average distance from Earth to the sun, equal to 93,000,000 miles (150,000,000 kilometers).

Neptune

The view was acquired by the Cassini narrow-angle camera at a distance of approximately 614,300 miles (988,600 kilometers) from Saturn on April 11, 2014.

Image scale at Uranus is approximately 16,000 miles (25,700 kilometers) per pixel.

Image scale at Saturn's rings is approximately 4 miles (6 kilometers) per pixel.

In the image, the disk of Uranus is just barely resolved.

The solar phase angle at Uranus, seen from Cassini, is 11.9 degrees.

Nasa Cassini: Saturn's moon Pan in the Encke gap in Saturn's rings

Credit: NASA /JPL-Caltech /Space Science Institute

Saturn's moon Pan, named for the Greek god of shepherds, rules over quite a different domain: the Encke gap in Saturn's rings.

Pan (17 miles, or 28 kilometers across) keeps the Encke gap open through its gravitational influence on the ring particles nearby.

This view looks toward the sunlit side of the rings from about 48 degrees above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Dec. 25, 2013.

The view was obtained at a distance of approximately 1.4 million miles (2.3 million kilometers) from Pan and at a Sun-Pan-spacecraft, or phase, angle of 87 degrees. Image scale is 9 miles (14 kilometers) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.

The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C.

The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL.

The imaging operations center is based at the Space Science Institute in Boulder, Colo.

NRL Scientists detect water around a hot Jupiter

This is an artist's conception of a hot Jupiter extrasolar planet orbiting a star similar to tau Boötis. 

Credit: David Aguilar, CfA, Harvard-Smithsonian Center for Astrophysics

Scientists at the Naval Research Laboratory (NRL) are part of a research team that has detected water vapour in the atmosphere of a planet outside our solar system.

The team, including scientists from California Institute of Technology (CalTech), Harvard-Smithsonian Center for Astrophysics, Pennsylvania State University, and University of Arizona, applied a sophisticated Doppler technique to the infrared to directly detect the planet and demonstrate the presence of water in its atmosphere.

The discovery is described in the March 10, 2014 issue of The Astrophysical Journal Letters.

The planet, named tau Boo b, orbits the nearby star tau Boötis and belongs to a class of exotic planets called "hot Jupiters" that are not found in our solar system.

A hot Jupiter is a massive extrasolar planet that orbits very close to its parent star. Unlike our Jupiter, which is fairly cold and has an orbital period of about 12 years, tau Boo b orbits its star every 3.3 days and is heated to extreme temperatures by its proximity to the star.

Under these conditions, water will exist as a high temperature steam.

While hot Jupiters are found to be relatively common in the Galaxy, the origin and nature of these planets remain the subject of intense research.

The research team studied data collected at the W.M. Keck Observatory in Hawaii, using the Near Infrared Echelle Spectrograph instrument.

Because a hot Jupiter is too close to its star to separate the planet's light from that of the star, the researchers adapted a Doppler technique previously used to detect low mass-ratio spectroscopic binary stars.

Application of this method to tau Boo b, however, posed a huge challenge, because the infrared radiation from the star is more than 10,000 times greater than that of the planet.

The analysis software to extract this minute planetary signal was developed by Chad Bender, a Penn State member of the team, while he was a National Research Council Associate at NRL.

By comparing the molecular signature of water to the combined light spectrum of the planet and star, the scientists were able to measure the motion of the planet as it orbits the star and establish the presence of water vapour in the planet's atmosphere.

The team also determined that the planet is six times more massive than Jupiter.

This work is ongoing, with plans to further examine the physical properties and composition of this hot Jupiter's atmosphere.

The research team is also applying this technique to search for water and other molecules in several other hot Jupiter exoplanets.

More Information: The Astrophysical Journal Letters "Near-IR Direct Detection of Water Vapor in tau Boötis b."

Keck Observatory's NIRSPEC: Water vapour detected in the atmosphere of a hot Jupiter

Simulated data showing the method used for detecting water vapor features detected around the hot Jupiter tau Boo b. 

In this example, the planetary signal has been increased in strength relative by several orders of magnitude relative to the actual signal. 

The dotted lines show the blue- and red-shifts of the planetary and stellar lines in the data, respectively, due to the orbital motion of two bodies in the system. 

Credit: Alexandra Lockwood (CalTech), Background Image David Aguilar (CFA).

California Institute of Technology (Caltech) astronomers using data gathered at the W. M. Keck Observatory have developed a new technique for planetary scientists that could provide insight into how many water planets like Earth exist within our universe.

The results have been published on February 24th by Astrophysical Letters.

Alexandra Lockwood

Scientists have detected water vapour on other planets in the past, but these detections could only take place under very specific circumstances, according to graduate student Alexandra Lockwood, the first author of the study.

"When a planet transits, or passes in orbit, in front of its host star, we can use information from this event to detect water vapour and other atmospheric compounds."

"Alternatively, if the planet is sufficiently far away from its host star, we can also learn about a planet's atmosphere by imaging it."

However, a significant portion of the population of extrasolar planets does not fit either of these criteria and there wasn't really a way to find information about the atmospheres of these planets.

Geoffrey Blake

Looking to resolve this problem, Lockwood and her advisor Geoffrey Blake, Caltech professor of cosmochemistry, planetary sciences and chemistry, were inspired by the recent detection of carbon monoxide in the extrasolar planet, 'Tau Boo b' and they wondered if they could detect water in a similar manner.

The method used to detect carbon monoxide utilized the radial velocity (RV) technique, a technique commonly used in the visible region of the spectrum, to which our eyes are sensitive, for discovering non-transiting exoplanets.

Using the Doppler effect, RV detection traditionally determines the motion of a star due to the gravitational pull of a companion planet; the star moves opposite that of the orbital motion of the planet, and stellar features shift in wavelength. A large planet or a planet closer to its host star provides a larger shift.

An artistic impression of extrasolar planet, 'Tau Boo b' 

The team used the carbon monoxide study as a guide to expand the RV technique into the infrared to determine the orbit of extrasolar planet, 'Tau Boo b' around its star, and added further analysis of the light shifts via spectroscopy, an analysis of the light's spectrum.

Since every molecule emits a different wavelength of light, this unique light signature allows the researchers to analyze molecules that comprise the planet's atmosphere.

Using data of extrasolar planet, 'Tau Boo b' collected with the Near Infrared Echelle Spectrograph (NIRSPEC) instrument at the W. M. Keck Observatory in Hawai'i, the researchers were able to compare the molecular signature of water to the light spectrum emitted by the planet, confirming that the atmosphere did indeed include water vapour.

"The readout we get from Keck Observatory's NIRSPEC is like listening to an orchestra performance; you hear all of the music together, but if you listen carefully, you can pick out a trumpet or a violin or a cello, and you know that those instruments are present," Lockwood said.

"The instrument allows you to pick out different pieces; like this wavelength of light means that there is sodium, or this one means that there's water."

More information: "Near-IR Direct Detection of Water Vapour in Tau Boo b." Alexandra C. Lockwood, John A. Johnson, Chad F. Bender, John S. Carr, Travis Barman, Alexander J.W. Richert, Geoffrey A. Blake. arXiv:1402.0846 [astro-ph.EP].

The Grand Tack model: 'Rogue' asteroids may be normal

Credit: NASA/JPL-Caltech

To get an idea of how the early solar system may have formed, scientists often look to asteroids.

These relics of rock and dust represent what today's planets may have been before they differentiated into bodies of core, mantle, and crust.

In the 1980s, scientists' view of the solar system's asteroids was essentially static: Asteroids that formed near the sun remained near the sun; those that formed farther out stayed on the outskirts.

But in the last decade, astronomers have detected asteroids with compositions unexpected for their locations in space: Those that looked like they formed in warmer environments were found further out in the solar system, and vice versa. Scientists considered these objects to be anomalous "rogue" asteroids.

But now, a new map developed by researchers from MIT and the Paris Observatory charts the size, composition, and location of more than 100,000 asteroids throughout the solar system, and shows that rogue asteroids are actually more common than previously thought.

Particularly in the solar system's main asteroid belt—between Mars and Jupiter—the researchers found a compositionally diverse mix of asteroids.

The new asteroid map suggests that the early solar system may have undergone dramatic changes before the planets assumed their current alignment.

For instance, Jupiter may have drifted closer to the sun, dragging with it a host of asteroids that originally formed in the colder edges of the solar system, before moving back out to its current position.

Jupiter's migration may have simultaneously knocked around more close-in asteroids, scattering them outward.

Francesca DeMeo

"It's like Jupiter bowled a strike through the asteroid belt," says Francesca DeMeo, who did much of the mapping as a postdoc in MIT's Department of Earth, Atmospheric and Planetary Sciences.

"Everything that was there moves, so you have this melting pot of material coming from all over the solar system."

DeMeo says the new map will help theorists flesh out such theories of how the solar system evolved early in its history.

She and Benoit Carry of the Paris Observatory have published details of the map in Nature.

The compositional diversity seen in this new asteroid map may add weight to a theory of planetary migration called the Grand Tack model.

This model lays out a scenario in which Jupiter, within the first few million years of the solar system's creation, migrated as close to the sun as Mars is today.

During its migration, Jupiter may have moved right through the asteroid belt, scattering its contents and repopulating it with asteroids from both the inner and outer solar system before moving back out to its current position—a picture that is very different from the traditional, static view of a solar system that formed and stayed essentially in place for the past 4.5 billion years.

"That [theory] has been completely turned on its head," DeMeo says. "Today we think the absolute opposite: Everything's been moved around a lot and the solar system has been very dynamic."

DeMeo adds that the early pinballing of asteroids around the solar system may have had big impacts on Earth.

For instance, colder asteroids that formed further out likely contained ice. When they were brought closer in by planetary migrations, they may have collided with Earth, leaving remnants of ice that eventually melted into water.

"The story of what the asteroid belt is telling us also relates to how Earth developed water, and how it stayed in this Goldilocks region of habitability today," DeMeo says.

More information: Paper: dx.doi.org/10.1038/nature12908

NASA Asteroid Robotic Retrieval Mission: Retrieving an asteroid - Tempel1

An image of the asteroid Tempel 1 taken during the Deep Impact visit. 

Tempel 1 is about five kilometers across. 

CfA astronomers have estimated the size of the smallest measured near Earth asteroid, 2009 BD, as only about three meters across, perhaps too small for it to be useful in NASA's planned asteroid recovery mission. 

Credit: NASA/JPL-Caltech/UMd

Asteroids (or comets) whose orbits bring them close to the earth's orbit are called near Earth objects.

Some of them are old, dating from the origins of the solar system about four and one-half billion years ago, and expected to be rich in primitive materials.

They are of great interest to scientists studying the young solar system. Others, of lower scientific priority, are thought to contain minerals of potential economic value.

NASA has announced its interest in sending a manned mission to a near Earth object. The NASA Asteroid Robotic Retrieval Mission concept involves the capture of an asteroid, and dragging it onto a new trajectory that traps it in the Earth–Moon system where it will be further investigated by astronauts.

The current mission design requires the target asteroid to have a diameter of seven to ten meters. The object NEO 2009BD is a prime candidate for this retrieval mission.

It was discovered on January 16, 2009, at a distance from the Earth of only 0.008 AU (one AU is the average distance of the Earth from the Sun).

Its orbit is very Earth–like, with a period of 400 days, and it will end up close to the Earth–Moon system again in late 2022 when the proposed capture would take place.

It seems to be a perfect candidate, with a time frame that allows for proper mission planning.

The problem is that the size of the NEO 2009BD is uncertain, and thus its density and composition are also uncertain, but first estimates are that it likely falls in the diameter range specified by the mission.

The uncertainty arises because it was detected at optical wavelengths; they measure reflected light, which is a combination of both an object's size and reflectivity (albedo).

For NASA mission planning to succeed, a more direct size measurement of 2009 BD is needed—and soon, before its increasing distance from the Earth makes such an observation a practical impossibility.

CfA astronomers Joe Hora, Howard Smith and Giovanni Fazio have been regularly using the IRAC camera on the Spitzer Space Telescope to measure the infrared emission of near Earth objects, and (with some modeling) deriving both the sizes and densities of these objects.

They received special observatory time to study NEO 2009BD, and in an upcoming issue of the Astrophysical Journal they and their colleagues report on their conclusions.

They did not detect the NEO 2009BD to a very low light level, implying that it is very small, probably only about 2.9 meters in diameter, and modeling suggests it has a rubble-pile composition.

This is the smallest object ever reported on by Spitzer; whether it is still suitable for a NASA mission is now something that the NASA Retrieval Mission team must determine.

More information: "Constraining the Physical Properties of The Near–Earth Object 2009 BD," M. Mommert,J. L. Hora,D. E. Trilling,S. R. Chesley and D. Farnocchia,D. Vokrouhlick´y, M. Mueller,A. W. Harris, H. A. Smith and G. G. Fazio, ApJ, 2013, in press.

NASA Mars Curiosity Rover: MMRTG likely cause of electronic short

This artist concept features NASA's Mars Science Laboratory Curiosity rover, a mobile robot for investigating Mars' past or present ability to sustain microbial life. 

In this picture, the mast, or rover's "head," rises to about 2.1 meters (6.9 feet) above ground level, about as tall as a basketball player.

This mast supports two remote-sensing instruments: the Mast Camera, or "eyes," for stereo color viewing of surrounding terrain and material collected by the arm; and, the ChemCam instrument, which is a laser that vaporizes material from rocks up to about 7 meters (23 feet) away and determines what elements the rocks are made of.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Science Laboratory Project for the NASA Science Mission Directorate, Washington.

NASA's Mars rover Curiosity resumed full science operations on Saturday, Nov. 23.

Activities over the weekend included use of Curiosity's robotic arm to deliver portions of powdered rock to a laboratory inside the rover.

The powder has been stored in the arm since the rover collected it by drilling into the target rock "Cumberland" six months ago.

Several portions of the powder have already been analyzed. The laboratory has flexibility for examining duplicate samples in different ways.

The decision to resume science activities resulted from the success of work to diagnose the likely root cause of a Nov. 17 change in voltage on the vehicle. The voltage change itself did not affect the rover safety or health.

The vehicle's electrical system has a "floating bus" design feature to tolerate a range of voltage differences between the vehicle's chassis—its mechanical frame—and the 32-volt power lines that deliver electricity throughout the rover. This protects the rover from electrical shorts.

"We made a list of potential causes, and then determined which we could cross off the list, one by one," said rover electrical engineer Rob Zimmerman of NASA's Jet Propulsion Laboratory, Pasadena, Calif. Science operations were suspended for six days while this analysis took priority.

The likely cause is an internal short in Curiosity's power source, the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG).

Due to resilience in design, this short does not affect operation of the power source or the rover.

Similar generators on other spacecraft, including NASA's Cassini at Saturn, have experienced shorts with no loss of capability.

Testing of another MMRTG over many years found no loss of capability in the presence of these types of internal shorts.

Following the decision to resume science activities, engineers learned early Nov. 23 that the rover had returned to its pre-Nov. 17 voltage level.

This reversal is consistent with their diagnosis of an internal short in the generator on Nov. 17, and the voltage could change again.

The analysis work to determine the cause of the voltage change gained an advantage from an automated response by the rover's onboard software when it detected the voltage change on Nov. 17.

The rover stepped up the rate at which it recorded electrical variables, to eight times per second from the usual once per minute, and transmitted that engineering data in its next communication with Earth. "That data was quite helpful," Zimmerman said.

NASA Chandra Image: Elephant Trunk Nebula

Credit: X-ray: NASA/CXC/PSU/Getman et al, Optical: DSS, Infrared: NASA/JPL-Caltech

When radiation and winds from massive young stars impact clouds of cool gas, they can trigger new generations of stars to form.

This is what may be happening in this object known as the Elephant Trunk Nebula (or its official name of IC 1396A). 

X-rays from Chandra (purple) have been combined with optical (red, green, and blue) and infrared (orange and cyan) to give a more complete picture of this source.

Carina Nebula Image: Spitzer Space Telescope 10 years old

The Carina Nebula. Credit: NASA/JPL-Caltech

The infrared observatory Spitzer has been at work for 10 years, revealing the cool dusty regions where stars and planets form, as well as shedding light on planets, exoplanets, stars and galaxies.

Spitzer data have brought a better understanding of the Milky Way's spiral arm structure, led to the discovery of Saturn's largest and faintest ring, and the observatory was the first to detect light from an exoplanet.

Spitzer has enabled astronomers to investigate the composition, dynamics and atmospheres of exoplanets.

This image shows the Carina Nebula, a region where dust and gas are shaped by winds and radiation from the massive star Eta Carinae (100 times the mass of the Sun).

Infrared wavelength radiation from the star destroys dust, leaving cavities within the nebula surrounded by higher density "spikes".

This Spitzer image, reprocessed as part of the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) project, uses Spitzer's infrared array camera, with emission from wavelengths of 3.6 µm shown in blue, 4.5 µm in green and 8.0 µm in red. In the composite image, the dust appears red and the hotter gas, green.

Spitzer was originally called the Space Infrared Telescope Facility, and was renamed after its launch in honour of the late astronomer Lyman Spitzer.

It is one of NASA's Great Observatories, together with the Hubble Space Telescope, the Chandra X-ray Observatory and the now-defunct Compton Gamma Ray Observatory.

Spitzer used up its coolant for longer-wavelength observations in 2009, and is now continuing to work in the "warm mission phase".

This image is published in the October 2013 issue of Astronomy & Geophysics.

NASA Deep Impact: Team attempts to restore communications

Artist's concept of NASA's Deep Impact spacecraft. 

Credit: NASA/JPL-Caltech

Ground controllers have been unable to communicate with NASA's long-lived Deep Impact spacecraft. Last communication with the spacecraft was on Aug. 8, 2013.

Deep Impact mission controllers will continue to uplink commands in an attempt to reestablish communications with the spacecraft.

Mission controllers postulate that there was an anomaly generated by the spacecraft's software which left the vehicle's computers in a condition where they are continuously rebooting themselves.

If this is the case, the computers would not continue to command the vehicle's thrusters to fire and hold attitude.

Lack of attitude hold makes attempts to reestablish communications more difficult because the orientation of the spacecraft's antennas is unknown.

It also brings into question the vehicle's electrical power status, as the spacecraft derives its power from a solar array that is fixed, with its cells pointing in one direction.

Deep Impact is history's most traveled deep-space comet hunter. It successfully completed its original mission and a subsequent extended mission.

Near-Earth asteroid is really a comet

The image displays Don Quixote's orbit. Credit: Josh Emery

Some things are not always what they seem—even in space. For 30 years, scientists believed a large near-Earth object was an asteroid.

Now, an international team including Joshua Emery, assistant professor of earth and planetary sciences at the University of Tennessee, Knoxville, has discovered it is actually a comet.

Called 3552 Don Quixote, the body is the third largest near-Earth object—mostly rocky bodies, or asteroids, that orbit the Sun in the vicinity of Earth.

About 5 percent of near-Earth objects are thought to be "dead" comets that have shed all the water and carbon dioxide in the form of ice that give them their coma—a cloud surrounding the comet nucleus—and tail.

The team found that Don Quixote is neither. It is, in fact, an active comet, thus likely containing water ice and not just rocks.

The finding will be presented at the European Planetary Science Congress 2013 in London, Sept. 10. The discovery could hold implications for the origin of water on Earth.

Joshua Emery

"Don Quixote has always been recognized as an oddball," said Emery. "Its orbit brings it close to Earth, but also takes it way out past Jupiter."

"Such a vast orbit is similar to a comet's, not an asteroid's, which tend to be more circular—so people thought it was one that had shed all its ice deposits."

Using the Spitzer Space Telescope operated by the Jet Propulsion Laboratory at the California Institute of Technology (CalTech) under contract with NASA, the team, led by Michael Mommert of Northern Arizona University, re-examined images of Don Quixote from 2009 when it was in the part of its orbit closest to the Sun, and found it had a coma and a faint tail.

Emery also reexamined images from 2004, when it was at its farthest distance from the sun, and determined that the surface is composed of silicate dust, which is similar to comet dust.

He also determined that Don Quixote did not have a coma or tail at this distance, which is common for comets because they need the sun's radiation to form the coma and the sun's charged particles to form the tail.

The researchers also confirmed Don Quixote's size and the low, comet-like reflectivity of its surface.

"The power of the Spitzer telescope allowed us to spot the coma and tail, which was not possible using optical telescopes on the ground," said Emery.

"We now think this body contains a lot of ice, including carbon dioxide and/or carbon monoxide ice, rather than just being rocky."

This discovery implies that carbon dioxide and water ice might be present within other near-Earth asteroids, as well.

It also may have implications for the origins of water on Earth as comets may be the source of at least some of it, and the amount on Don Quixote represents about 100 billion tons of water—roughly the same amount that can be found in Lake Tahoe, California's.

NASA GALEX: Galaxy Hunter Spacecraft Decommissions

This image from NASA's Galaxy Evolution Explorer (GALEX) shows Messier 94, also known as NGC 4736, in ultraviolet light. 

It is located 17 million light-years away in the constellation Canes Venatici. 

Image credit: NASA/JPL-Caltech

NASA has turned off its Galaxy Evolution Explorer (GALEX) after a decade of operations in which the venerable space telescope used its ultraviolet vision to study hundreds of millions of galaxies across 10 billion years of cosmic time.

"GALEX is a remarkable accomplishment," said Jeff Hayes, NASA's GALEX program executive in Washington.

"This small Explorer mission has mapped and studied galaxies in the ultraviolet, light we cannot see with our own eyes, across most of the sky."

Operators at Orbital Sciences Corporation in Dulles, Va., sent the signal to decommission GALEX at 12:09 p.m. PDT (3:09 p.m. EDT) Friday, June 28.

The spacecraft will remain in orbit for at least 65 years, then fall to Earth and burn up upon re-entering the atmosphere.

GALEX met its prime objectives and the mission was extended three times before being cancelled.

Highlights from the mission's decade of sky scans include:

• Discovering a gargantuan, comet-like tail behind a speeding star called Mira.
• Catching a black hole "red-handed" as it munched on a star.
• Finding giant rings of new stars around old, dead galaxies.
• Independently confirming the nature of dark energy.
• Discovering a missing link in galaxy evolution—the teenage galaxies transitioning from young to old.

The mission also captured a dazzling collection of snapshots, showing everything from ghostly nebulas to a spiral galaxy with huge, spidery arms.

In a first-of-a-kind move for NASA, the agency in May 2012 loaned GALEX to the California Institute of Technology (Caltech) in Pasadena, which used private funds to continue operating the satellite while NASA retained ownership.

Since then, investigators from around the world have used GALEX to study everything from stars in our own Milky Way galaxy to hundreds of thousands of galaxies 5 billion light-years away.

In the space telescope's last year, it scanned across large patches of sky, including the bustling, bright center of our Milky Way.

The telescope spent time staring at certain areas of the sky, finding exploded stars, called supernovae, and monitoring how objects, such as the centers of active galaxies, change over time.

GALEX also scanned the sky for massive, feeding black holes and shock waves from early supernova explosions.

David Schiminovich

"In the last few years, GALEX studied objects we never thought we'd be able to observe, from the Magellanic Clouds to bright nebulae and supernova remnants in the galactic plane," said David Schiminovich of Columbia University, N.Y., N.Y, a longtime GALEX team member who led science operations over the past year.

"Some of its most beautiful and scientifically compelling images are part of this last observation cycle."

Data from the last year of the mission will be made public in the coming year.

"GALEX, the mission, may be over, but its science discoveries will keep on going," said Kerry Erickson, the mission's project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

A slideshow showing some of the popular GALEX images is online at: go.nasa.gov/17xAVDd

NASA - Solar-Electric ION Engine Burns Blue

This image shows a cutting-edge solar-electric propulsion thruster in development at NASA's Jet Propulsion Laboratory, Pasadena, Calif., that uses xenon ions for propulsion. 

An earlier version of this solar-electric propulsion engine has been flying on NASA's Dawn mission to the asteroid belt.

This engine is being considered as part of the Asteroid Initiative, a proposal to robotically capture a small near-Earth asteroid and redirect it safely to a stable orbit in the Earth-moon system where astronauts can visit and explore it. 

This image was taken through a porthole in a vacuum chamber at JPL where the ion engine is being tested.

Image credit: NASA/JPL-Caltech

NASA Mars Rover Curiosity at 'Cumberland'

NASA's Mars rover Curiosity used its front left Hazard-Avoidance Camera for this image of the rover's arm over the drilling target "Cumberland" during the 275th Martian day, or sol, of the rover's work on Mars (May 15, 2013).

The rover team plans to use Curiosity's drill to collect a powdered sample from the interior of the rock for analysis by laboratory instruments inside the rover. 

This is the mission's second rock-drilling target.

The rover drove from its position beside the first drilling target, "John Klein," to its position beside Cumberland with drives of 121 inches (308 centimeters) on Sol 273 (May 13) and 26.6 inches (67.5 centimeters) on Sol 275. Curiosity's total odometry on Mars is now 2,385 feet (727 meters).

Image credit: NASA/JPL-Caltech

NASA Spitzer Image: Galaxy's Ring of Fire

How many rings do you see in this new image of the galaxy Messier 94, also known as NGC 4736? 

While at first glance one might see a number of them, astronomers believe there is just one. 

This image was captured in infrared light by NASA's Spitzer Space Telescope. 

Credit: NASA/JPL-Caltech

The singer Johnny Cash may have preferred this galaxy's burning ring of fire to the one he sang about falling into in his popular song.

The "starburst ring" seen at centre in red and yellow hues is not the product of love, as in the song, but is instead a frenetic region of star formation.

The galaxy, a spiral beauty called Messier 94, is located about 17 million light-years away. In this image from NASA's Spitzer Space Telescope, infrared light is represented in different colours, with blue having the shortest wavelengths and red, the longest.

Starburst rings like this can often be triggered by gravitational encounters with other galaxies but, in this case, may have instead been caused by the galaxy's oval shape.

Gas in the ring is being converted into hot, young stars, which then warm the dust, causing it to glow with infrared light.

The outer, faint blue ring around the galaxy might be an optical illusion. Astronomers think that two separate spiral arms appear as a single unbroken ring when viewed from our position in space.

NASA Curiosity Rover: Mars Mount Sharp Possibly Built by Wind, Not Water

Researchers based at Princeton University, the California Institute of Technology and Ashima Research suggest that Mars' roughly 3.5-mile high Mount Sharp (above) most likely emerged as strong winds carried dust and sand into Gale Crater where the mound sits. 

If correct, the research could dilute expectations that the mound is the remnant of a massive lake, which would have important implications for understanding Mars' past habitability. 

Credit: NASA/JPL-Caltech/MSSS

A roughly 3.5-mile high Martian mound that scientists suspect preserves evidence of a massive lake might actually have formed as a result of the Red Planet's famously dusty atmosphere, an analysis of the mound's features suggests.

They report in the journal Geology that air likely rises out of the massive Gale Crater when the Martian surface warms during the day, then sweeps back down its steep walls at night.

Though strong along the Gale Crater walls, these "slope winds" would have died down at the crater's center where the fine dust in the air settled and accumulated to eventually form Mount Sharp, which is close in size to Alaska's Mt. McKinley.

This dynamic counters the prevailing theory that Mount Sharp formed from layers of lakebed silt—and could mean that the mound contains less evidence of a past, Earth-like Martian climate than most scientists currently expect.

Evidence that Gale Crater once contained a lake in part determined the landing site for the NASA Mars rover Curiosity.

The rover touched down near Mount Sharp in August with the purpose of uncovering evidence of a habitable environment, and in December Curiosity found traces of clay, water molecules and organic compounds.

Determining the origin of these elements and how they relate to Mount Sharp will be a focus for Curiosity in the coming months.

But the mound itself was likely never under water, though a body of water could have existed in the moat around the base of Mount Sharp, said study co-author Kevin Lewis, a Princeton associate research scholar in geosciences and a participating scientist on the Curiosity rover mission, Mars Science Laboratory.

The quest to determine whether Mars could have at one time supported life might be better directed elsewhere, he said.

NASA Cassini Image captures Enceladus' Plume

Credit: NASA/JPL-Caltech/Space Science Institute

Like a proud peacock displaying its tail, Enceladus shows off its beautiful plume to the Cassini spacecraft's cameras.

Enceladus (313 miles, or 504 kilometers across) is seen here illuminated by light reflected off Saturn.

This view looks toward the Saturn-facing side of Enceladus.

North on Enceladus is up and rotated 45 degrees to the right.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 18, 2013.

The view was acquired at a distance of approximately 483,000 miles (777,000 kilometers) from Enceladus and at a Sun-Enceladus-spacecraft, or phase, angle of 173 degrees. Image scale is 3 miles (5 kilometers) per pixel.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency (ISA). 

NASA Spitzer Image: Heavenly Valentine

Generations of stars can be seen in this infrared portrait from NASA's Spitzer Space Telescope.

In this wispy star-forming region, called W5, the oldest stars can be seen as blue dots in the centers of the two hollow cavities (other blue dots are background and foreground stars not associated with the region).

Younger stars line the rims of the cavities, and some can be seen as pink dots at the tips of the elephant-trunk-like pillars. 

The white knotty areas are where the youngest stars are forming. Red shows heated dust that pervades the region's cavities, while green highlights dense clouds. 

Image Credit: NASA/JPL-Caltech/Harvard-Smithsonian