Wednesday, July 31, 2013

NASA's Cassini Spacecraft Reveals Forces Controlling Saturn Moon Jets

This set of images from NASA's Cassini mission shows how the gravitational pull of Saturn affects the amount of spray coming from jets at the active moon Enceladus. Image Credit: NASA/JPL-Caltech/University of Arizona/Cornell/SSI. › Full image and caption
This set of images from NASA's Cassini mission shows the difference in the amount of spray emanating from Saturn's moon Enceladus.Image Credit: NASA/JPL-Caltech/University of Arizona/Cornell. › Full image and caption
Cassini imaging scientists used views like this one to help them identify the source locations for individual jets spurting ice particles, water vapor and trace organic compounds from the surface of Saturn's moon Enceladus. Image Credit: NASA/JPL/Space Science Institute.  › Full image and caption
Dramatic plumes, both large and small, spray water ice out from many locations along the famed "tiger stripes" near the south pole of Saturn's moon Enceladus. Image Credit: NASA/JPL/Space Science Institute. › Full image and caption
PASADENA, Calif. -- The intensity of the jets of water ice and organic particles that shoot out from Saturn's moon Enceladus depends on the moon's proximity to the ringed planet, according to data obtained by NASA's Cassini spacecraft.

The finding adds to evidence that a liquid water reservoir or ocean lurks under the icy surface of the moon. This is the first clear observation the bright plume emanating from Enceladus' south pole varies predictably. The findings are detailed in a scientific paper in this week's edition of Nature.

"The jets of Enceladus apparently work like adjustable garden hose nozzles," said Matt Hedman, the paper's lead author and a Cassini team scientist based at Cornell University in Ithaca, N.Y. "The nozzles are almost closed when Enceladus is closer to Saturn and are most open when the moon is farthest away. We think this has to do with how Saturn squeezes and releases the moon with its gravity."

Cassini, which has been orbiting Saturn since 2004, discovered the jets that form the plume in 2005. The water ice and organic particles spray out from several narrow fissures nicknamed "tiger stripes."

"The way the jets react so responsively to changing stresses on Enceladus suggests they have their origins in a large body of liquid water," said Christophe Sotin, a co-author and Cassini team member at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Liquid water was key to the development of life on Earth, so these discoveries whet the appetite to know whether life exists everywhere water is present."

For years scientists hypothesized the intensity of the jets likely varied over time, but no one had been able to show they changed in a recognizable pattern. Hedman and colleagues were able to see the changes by examining infrared data of the plume as a whole, obtained by Cassini's visual and infrared mapping spectrometer (VIMS), and looking at data gathered over a long period of time.

The VIMS instrument, which enables the analysis of a wide range of data including the hydrocarbon composition of the surface of another Saturnian moon, Titan, and the seismological signs of Saturn's vibrations in its rings, collected more than 200 images of the Enceladus plume from 2005 to 2012.

These data show the plume was dimmest when the moon was at the closest point in its orbit to Saturn. The plume gradually brightened until Enceladus was at the most distant point, where it was three to four times brighter than the dimmest detection. This is comparable to moving from a dim hallway into a brightly lit office.
Adding the brightness data to previous models of how Saturn squeezes Enceladus, the scientists deduced the stronger gravitational squeeze near the planet reduces the opening of the tiger stripes and the amount of material spraying out. They think the relaxing of Saturn's gravity farther away from planet allows the tiger stripes to be more open and for the spray to escape in larger quantities.

"Cassini's time at Saturn has shown us how active and kaleidoscopic this planet, its rings and its moons are," said Linda Spilker, Cassini project scientist at JPL. "We've come a long way from the placid-looking Saturn that Galileo first spied through his telescope. We hope to learn more about the forces at work here as a microcosm for how our solar system formed."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology, Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The VIMS team is based at the University of Arizona in Tucson.

For more information about the Cassini mission, visit: and .

Jia-Rui C. Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.

Dwayne Brown 202-358-1726
NASA Headquarters, Washington

This is Your Galaxy: New data help astronomers explore the hidden Milky Way

Today, astronomers with the Sloan Digital Sky Survey III (SDSS-III) released a new online public data set featuring 60,000 stars that are helping to tell the story of how our Milky Way galaxy formed.

The highlight of today's "Data Release 10" is a new set of high-resolution stellar spectra — measurements of the amount of light given off by a star at each wavelength — using infrared light, invisible to human eyes but able to penetrate the veil of dust that obscures the center of the Galaxy.

The data released today includes infrared spectra of these two stars, shown in the context of the Milky Way galaxy. 
The map shows an infrared view of the Milky Way as seen from Earth. Green circles show areas where Data Release 10 includes infrared spectroscopy data from the first year of APOGEE observations. The white boxes show the infrared spectra of two stars as seen by APOGEE; red lines show where these stars live in the Galaxy. The two spectra are from two stars: one in the galactic bulge that is rich in elements heavier than hydrogen, and one further out in the disk that has fewer such heavy elements.  
Credit: Peter Frinchaboy (Texas Christian University), Ricardo Schiavon (Liverpool John Moores University), and the SDSS-III Collaboration. Infrared sky image from 2MASS, IPAC/Caltech, and University of Massachusetts.   Other versions:    B/W  -  300 DPI color  -  300 DPI B/W 

"This is the most comprehensive collection of infrared stellar spectra ever made," said Steven Majewski of the University of Virginia, the lead scientist for the APOGEE project. "Sixty thousand stars is almost ten times more high-resolution infrared stellar spectra than have ever been measured before, by all the world's telescopes. Selected from all the different parts of our galaxy, from the nearly-empty outskirts to the dust-enshrouded center, these spectra are allowing us to peel back the curtain on the hidden Milky Way."

The new spectra are the first data released by the SDSS-III's Apache Point Observatory Galactic Evolution Experiment (APOGEE), an effort to create a comprehensive census of our Milky Way galaxy.

"A star's spectrum is a powerful tool for learning about the star — it tells us key details about the star's temperature and size, and what elements are in its atmosphere," said Jon Holtzman of New Mexico State University, who led the effort to prepare the APOGEE data for Data Release 10. "It's one of the best tools we have for learning about stars, like getting someone's fingerprints instead of just knowing their height and weight."

The question of how our Milky Way galaxy formed has been the subject of scientific speculation and debate for hundreds of years. APOGEE's three-dimensional map will provide key information for resolving central questions about how our galaxy formed over the many billions of years of its history.

The Milky Way currently has three main parts: a high-density oblong bulge in the center, the flat disk where we live, and a low-density spherical component called the "halo" extending out hundreds of thousands of light years. "Stars in these different regions have different ages and compositions, which means they formed at different times and under different conditions throughout the history of our galaxy," says Gail Zasowski, an NSF Postdoctoral Fellow at The Ohio State University who led the critical effort to maximize APOGEE's scientific potential by selecting the best possible sample of stars.

If you look up at the sky from a dark site, far away from the overwhelming glow of city lights, the Milky Way galaxy appears as a luminous band across the sky, overlaid with dark curtains. This band is the disk and bulge of our galaxy, and the curtains are the dust that blocks visible light from more distant parts of the Milky Way.

Because of this dust, previous studies of stars in the Milky Way have been limited in their ability to consistently measure stars toward the center of our galaxy. APOGEE's solution is to look in infrared light, which can pass through the dust. This ability to explore previously hidden regions of the Galaxy allows APOGEE to conduct the first comprehensive study of the Milky Way, from center to halo."

Observing tens of thousands of stars is a daunting, time-consuming task. To accomplish its goal of observing 100,000 stars in just three years, the APOGEE instrument observes up to 300 different stars at a time using fiber-optic cables plugged into a large aluminum plate with holes drilled to line up with each star. Light passes through each fiber into the APOGEE spectrograph, where a prism-like grating distributes the light by wavelength. "The grating is the first and largest of its kind deployed in an astronomy instrument," said John Wilson of the University of Virginia, who led APOGEE's instrument design team. "That technology is critical to APOGEE's success."

APOGEE's spectra of stars will help unlock the history of our galaxy, and the key is learning the compositions and motions of stars in each region. Because elements heavier than hydrogen and helium were produced in stars and spread through the Galaxy by exploding stars and stellar winds, astronomers know that stars with more of these heavy elements must have formed more recently, after previous generations of stars had time to create those heavy elements.

"By finding which parts of the Galaxy contain older versus newer stars, and by putting this together with how the stars are moving, we can write a detailed history of how the Galaxy formed, and how it evolved into what we see today," said Peter Frinchaboy of Texas Christian University, who coordinated all of the APOGEE observations.

APOGEE data also provide a rich context for investigating a wide range of questions about the stars themselves. Because APOGEE observes each target star several times, it can identify changes in each star's spectrum over time. This feature has enabled the APOGEE team to discover unusual types of rapidly variable stars, to pinpoint how many stars are actually binary stars with unseen companions, and even to detect the subtle stellar motions caused by orbiting planets.

Data Release 10 also publishes another 685,000 spectra from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). These new spectra come from galaxies and quasars as seen when our universe was much younger, just as the mysterious force of "dark energy" was beginning to influence the universe's expansion. The new BOSS spectra, and the additional spectra that the SDSS-III will continue to obtain in the final years of the survey, will help scientists in their quest to understand what dark energy might be.

SDSS-III is a six-year survey of nearby stars, the Milky Way galaxy, and the distant cosmos. The Sloan Foundation 2.5-meter telescope at Apache Point Observatory in New Mexico conducts observations every night that feed either the BOSS optical or APOGEE infrared spectrograph. "We've been putting out data releases since 2001, and we're not slowing down yet," said SDSS-III Spokesperson Michael Wood-Vasey of the University of Pittsburgh. "Public access to data has always been a key goal of our project, and we're proud to continue that tradition today with this new release rich with information about our own galaxy." All of these data are available to the public, free of charge, at

A photo of four SDSS-III scientists working on the APOGEE spectrograph.
Left to right: Garrett Ebelke (Apache Point Observatory), Gail Zasowski (The Ohio State University), Steven Majewski (University of Virginia) and John Wilson (University of Virginia). Majewski is actually standing across the room; he appears here as a reflection in a mirror that was being installed in the spectrograph.   
Credit: Dan Long (Apache Point Observatory). Other versions:    B/W  -  300 DPI color  -  300 DPI B/W


Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is .

SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.


  • Steven R. Majewski, University of Virginia,, 1-434-924-4893
  • Jon Holtzman, New Mexico State University,, 1-575-646-8181
  • Gail Zasowski, The Ohio State University,, 1-614-292-3099
  • John Wilson, University of Virginia,, 434-924-4907
  • Michael Wood-Vasey, SDSS-III Spokesperson, University of Pittsburgh,, 1-412-624-2751
  • Jordan Raddick, SDSS-III Public Information Officer, Johns Hopkins University,, 1-410-516-8889

Violent Sun

SWAP sees the Sun
The SWAP instrument on board ESA's Proba-2 sees the Sun, 30 July 2013, at 9:28:57.258 CEST. SWAP (Sun Watcher using Active Pixel System detector and Image Processing) is a small telescope that captures the solar corona at wavelengths corresponding to temperatures of about a million degrees (around 17.1 nanometers).  Credits: ESA/SWAP PROBA2 science centre.  Access the image

ESA’s Sun-watching Proba-2 satellite has been in orbit since November 2009, demonstrating a range of technologies and serving as a platform for scientific observations. 

The 130 kg satellite carries two solar monitors. One is SWAP (Sun Watcher using Active Pixel System detector and Image Processing), a small telescope that captures the solar corona at wavelengths corresponding to temperatures of about a million degrees. The image above shows the latest SWAP image, from 30 July. 

SWAP images are used to study the origin of solar phenomena, including solar flares and coronal mass ejections – massive eruptions of material into interplanetary space. Both are important sources of space weather, which profoundly affects the environmental conditions in Earth’s magnetosphere, ionosphere and thermosphere. 

Space weather is not only of academic interest. In Europe’s economy today, numerous sectors are potentially affected by space weather, ranging from space-based telecommunications, broadcasting, weather services and navigation through to power distribution and terrestrial communications, especially at northern latitudes. 

The satellite has been managed since 1 July by ESA’s Space Situational Awareness (SSA) programme, complementing support provided by ESA’s Science directorate for the Proba-2 Science Centre at the Royal Observatory Belgium

Proba-2 data are used directly by the SSA Space Weather Coordination Centre at SpacePole, Brussels, to generate space weather products and services to a growing number of customers such as satellite operators, telecom and navigation users, and government agencies and research institutes. 

Source: ESA

Tuesday, July 30, 2013

HD 189733: NASA's Chandra Sees Eclipsing Planet in X-rays for First Time

HD 189733b
Credit  X-ray: NASA/CXC/SAO/K.Poppenhaeger et al;

This graphic depicts HD 189733b, the first exoplanet caught passing in front of its parent star in X-rays. As described in our press release, NASA's Chandra X-ray Observatory and the European Space Agency's XMM Newton Observatory have been used to observe a dip in X-ray intensity as HD 189733b transits its parent star. 

The main figure is an artist’s impression showing the HD 189733 system, containing a Sun-like star orbited by HD 189733b, an exoplanet about the size of Jupiter . This "hot Jupiter" is over 30 times closer to its star than Earth is to the Sun and goes around the star once every 2.2 days, as determined from previous observations. Also in the illustration is a faint red companion star, which was detected for the first time in X-rays with these observations . This star orbits the main star about once every 3,200 years.

The inset contains the Chandra image of HD 189733. The source in the middle is the main star and the source in the lower right is the faint companion star. The source at the bottom of the image is a background object not contained in the HD 189733 system. 

The exoplanet itself cannot be seen in the Chandra image, as the transits involve measuring small decreases in X-ray emission from the main star. The authors estimate that the percentage decrease in X-ray light during the transits is about three times greater than the corresponding decrease in optical light. This tells them that the region blocking X-rays from the star is substantially larger than the region blocking optical light from the star, helping to determine the size of the planet's atmosphere. The extended atmosphere implied by these results is shown by the light blue color around the planet. Recent observations of HD 189733b with the Hubble Space Telescope have confirmed that the lower atmosphere of the planet has a deep blue color, due to the preferential scattering of blue light by silicate particles in its atmosphere. 

For about a decade astronomers have known that ultraviolet and X-ray radiation from the main star in HD 189733 are evaporating the atmosphere of its closely orbiting planet over time. The authors of the new study estimate that HD 189733b is losing between 100 million and 600 million kilograms per second. This rate is about 25% to 65% higher than it would be if the planet's atmosphere were not extended.

At a distance of just 63 light years, HD 189733b is the closest hot Jupiter to Earth, which makes it a prime target for astronomers who want to learn more about this type of exoplanet and the atmosphere around it.
Chandra was used to make observations of six transits by HD 189733b and the team also used archival data from XMM-Newton for one transit. These results are available online and will appear in a future issue of The Astrophysical Journal.

Fast Facts for HD 189733:

Scale:  Image is 1.5 arcmin across (about 0.02 light years)
Coordinates (J2000):  RA 20h 00m 43.70s | Dec +22 42 39.10
Constellation:  Vulpecula
Observation Date:  6 pointings between 5-23 July, 2011 
Observation Time:  33 hours 20 min Obs. ID:  12340-12345 
Instrument:  ACIS
References: Poppenhaeger, K. et al, 2013, ApJ (submitted); arXiv:1306.2311
Color Code:  X-ray (Purple)
Distance Estimate:  About 60 light years

Monday, July 29, 2013

Messier 100 — Grand Design Splendour

Credit: ESO

Spiral galaxies are usually very aesthetically appealing objects, and never more so than when they appear face-on. And this image is a particularly splendid example: it is the grand design spiral galaxy Messier 100, located in the southern part of the constellation of Coma Berenices, and lying about 55 million light-years from Earth.

While Messier 100 shows very well defined spiral arms, it also displays the faintest of bar-like structures in the centre, which classifies this as type SAB. Although it is not easily spotted in the image, scientists have been able to confirm the bar’s existence by observing it in other wavelengths.

This very detailed image shows the main features expected in a galaxy of this type: huge clouds of hydrogen gas, glowing in red patches when they re-emit the energy absorbed from newly born, massive stars; the uniform brightness of older, yellowish stars near the centre; and black shreds of dust weaving through the arms of the galaxy.

Messier 100 is one of the brightest members of the Virgo Cluster, which is the closest cluster of galaxies to our galaxy, the Milky Way, containing over 2000 galaxies, including spirals, ellipticals, and irregulars. This picture is a combination of images from the FORS instrument on ESO’s Very Large Telescope at Paranal Observatory in Chile, taken with red (R), green (V) and blue (B) filters.


Source:  ESO

WIYN/NOAO: M51, the Whirlpool Galaxy, seen with new ODI Camera on WIYN Telescope

Full frame image of Spiral Galaxy M51 (Image gallery page), demonstrating the wide field of view of the One Degree Imager (ODI) on the WIYN 3.5-m telescope on Kitt Peak. Image credit: K. Rhode, M. Young and WIYN/NOAO/AURA/NSF. 

Cropped view of Spiral Galaxy M51, demonstrating the excellent sharpness of the One Degree Imager (ODI) on the WIYN 3.5-m telescope on Kitt Peak. Image credit: K. Rhode, M. Young and WIYN/NOAO/AURA/NSF. 

Stars over the WIYN 3.5-meter telescope on Kitt Peak National Observatory. Image credit: P. Marenfeld/NOAO/AURA/NSF 

The Whirlpool Galaxy (Messier 51) has been a popular night sky target for astronomers for centuries. Charles Messier first identified it in 1773 and listed it as number 51 in his catalog. To him, it looked like a faint, fuzzy object that might be a comet. William Parsons, the 3rd Earl of Rosse, used his 72-inch telescope “Leviathan” to observe the Whirlpool in 1845. Since then, Messier 51 has likely been targeted by virtually every telescope in the northern hemisphere. It is found in the constellation Canes Venatici (the Hunting Dogs) and is a classic example of a spiral galaxy. 

Now, a new camera on the WIYN 3.5-meter telescope at Kitt Peak National Observatory has imaged the Whirlpool Galaxy anew. The wide field of the One Degree Imager (ODI) camera makes it possible to capture the entire galaxy and its companion in one pointing, something that even the Hubble Space Telescope cannot do. 

Indiana University (IU) astronomy professor Katherine Rhode led this effort as part of an imaging survey of spiral and elliptical galaxies. The survey is aimed at understanding how these so-called “giant galaxies” form and evolve. 

“The WIYN telescope is an ideal telescope for the survey because of its wide field and because it produces some of the sharpest, highest-quality images possible with a ground-based telescope”, explained Rhode. “WIYN’s 3.5-meter mirror is also very efficient at gathering light from astronomical objects, so it allows us to image faint objects, like individual star clusters within the galaxies.”

This new image, as well as over one thousand others, can be found on the National Optical Astronomy Observatory (NOAO) image gallery The gallery contains images taken with all the telescopes supported by NOAO, selected videos, and pictures of telescopes and instruments.

An important consideration for imaging with ground-based telescopes is what astronomers refer to as “seeing”, and most people think of as stars twinkling. Twinkling is caused by movement of air in the Earth’s atmosphere, and it can be minimized at a good telescope site, like on a mountaintop in a dry climate. As WIYN Interim Director Dr. Eric Hooper said, “The WIYN telescope on Kitt Peak is known for producing excellent, steady images with high resolution, or sharpness.”

The WIYN ODI camera spent about an hour observing M51 through three different filters: blue, green, and red. These digital images were later combined to construct a “true-color” image: redder objects in the image are cooler, emitting most of their light at longer optical wavelengths, while bluer objects in the image are bluer and hotter in reality. Objects that glow green are somewhere in between. Even though the galaxy is almost 30 million light years away, the image clearly shows clusters of young, hot stars that light up the spiral arms. Threaded through the arms are dark “dust lanes”, where sooty material left over from previous generations of stars has settled. More dust lanes can be seen in the bridge of luminous stars and gas that connects Messier 51 to its companion, the peculiar galaxy NGC 5195, in the upper part of the image. 

The images were taken by Dr. Rhode in May 2013 and then processed by the ODI Portal, Pipeline, and Archive (ODI-PPA) project team at IU. The ODI-PPA project is a collaboration between IU’s Pervasive Technology Institute (PTI), the Science Data Management group at NOAO, and WIYN. Arvind Gopu, ODI-PPA project manager, noted: “When requested by a pipeline operator, ODI data are processed and archived using NSF-funded cyberinfrastructure located at IU. In the case of the M51 images, our lead developer Michael Young ran the raw images through the calibration pipeline and used that data to make the final true-color images.”

The ODI camera is funded by the WIYN partners, and the National Science Foundation, through its Telescope System Instrumentation Program. The WIYN partners are University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatory (NOAO). NOAO is operated by Association of Universities for Research in Astronomy Inc. (AURA) under a cooperative agreement with the National Science Foundation.

Science Contact:

Dr. Katherine L. Rhode
Indiana University Dept. of Astronomy
Bloomington, IN 47405

NASA's WISE Finds Mysterious Centaurs May Be Comets

This artist's concept shows a centaur creature together with asteroids on the left and comets at right. Image Credit: NASA/JPL-Caltech. Full image and caption

PASADENA, Calf. -- The true identity of centaurs, the small celestial bodies orbiting the sun between Jupiter and Neptune, is one of the enduring mysteries of astrophysics. Are they asteroids or comets? A new study of observations from NASA's Wide-field Infrared Survey Explorer (WISE) finds most centaurs are comets.

Until now, astronomers were not certain whether centaurs are asteroids flung out from the inner solar system or comets traveling in toward the sun from afar. Because of their dual nature, they take their name from the creature in Greek mythology whose head and torso are human and legs are those of a horse.

"Just like the mythical creatures, the centaur objects seem to have a double life," said James Bauer of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Bauer is lead author of a paper published online July 22 in the Astrophysical Journal. "Our data point to a cometary origin for most of the objects, suggesting they are coming from deeper out in the solar system."

"Cometary origin" means an object likely is made from the same material as a comet, may have been an active comet in the past, and may be active again in the future.

The findings come from the largest infrared survey to date of centaurs and their more distant cousins, called scattered disk objects. NEOWISE, the asteroid-hunting portion of the WISE mission, gathered infrared images of 52 centaurs and scattered disk objects. Fifteen of the 52 are new discoveries. Centaurs and scattered disk objects orbit in an unstable belt. Ultimately, gravity from the giant planets will fling them either closer to the sun or farther away from their current locations.

Although astronomers previously observed some centaurs with dusty halos, a common feature of outgassing comets, and NASA's Spitzer Space Telescope also found some evidence for comets in the group, they had not been able to estimate the numbers of comets and asteroids.

Infrared data from NEOWISE provided information on the objects' albedos, or reflectivity, to help astronomers sort the population. NEOWISE can tell whether a centaur has a matte and dark surface or a shiny one that reflects more light. The puzzle pieces fell into place when astronomers combined the albedo information with what was already known about the colors of the objects. Visible-light observations have shown centaurs generally to be either blue-gray or reddish in hue. A blue-gray object could be an asteroid or comet. NEOWISE showed that most of the blue-gray objects are dark, a telltale sign of comets. A reddish object is more likely to be an asteroid.

"Comets have a dark, soot-like coating on their icy surfaces, making them darker than most asteroids," said the study's co-author, Tommy Grav of the Planetary Science Institute in Tucson, Ariz. "Comet surfaces tend to be more like charcoal, while asteroids are usually shinier like the moon."

The results indicate that roughly two-thirds of the centaur population are comets, which come from the frigid outer reaches of our solar system. It is not clear whether the rest are asteroids. The centaur bodies have not lost their mystique entirely, but future research from NEOWISE may reveal their secrets further.

The paper is available online at: .

JPL, managed by the California Institute of Technology in Pasadena, managed and operated WISE for NASA's Science Mission Directorate. The NEOWISE portion of the project was funded by NASA's Near Earth Object Observation Program. WISE completed its key mission objective, two scans of the entire sky, in 2011 and has been hibernating in space since then.

For more information about the WISE mission, visit: .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

J.D. Harrington 202-358-5241
Headquarters, Washington

Friday, July 26, 2013

Comet ISON
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

In this Hubble Space Telescope composite image taken in April 2013, the sun-approaching Comet ISON floats against a seemingly infinite backdrop of numerous galaxies and a handful of foreground stars. The icy visitor, with its long gossamer tail, appears to be swimming like a tadpole through a deep pond of celestial wonders.
In reality, the comet is much, much closer. The nearest star to the Sun is over 60,000 times farther away, and the nearest large galaxy to the Milky Way is over thirty billion times more distant. These vast dimensions are lost in this deep space Hubble exposure that visually combines our view of the universe from the very nearby to the extraordinarily far away.

This photo is one of the original images featured on ISONblog, a new online source offering unique analysis of Comet ISON by Hubble Space Telescope astronomers and staff at the Space Telescope Science Institute in Baltimore, Md. For more on ISONblog, visit:

Source: Hubble Site

A mysterious old spiral

Credit: ESA/Hubble & NASA
Acknowledgement: Judy Schmidt

This striking cosmic whirl is the centre of galaxy NGC 524, as seen with the NASA/ESA Hubble Space Telescope. This galaxy is located in the constellation of Pisces, some 90 million light-years from Earth.

NGC 524 is a lenticular galaxy. Lenticular galaxies are believed to be an intermediate state in galactic evolution — they are neither elliptical nor spiral. Spirals are middle-aged galaxies with vast, pinwheeling arms that contain millions of stars. Along with these stars are large clouds of gas and dust that, when dense enough, are the nurseries where new stars are born. When all the gas is either depleted or lost into space, the arms gradually fade away and the spiral shape begins to weaken. At the end of this process, what remains is a lenticular galaxy — a bright disc full of old, red stars surrounded by what little gas and dust the galaxy has managed to cling on to.

This image shows the shape of NGC 524 in detail, formed by the remaining gas surrounding the galaxy’s central bulge. Observations of this galaxy have revealed that it maintains some spiral-like motion, explaining its intricate structure.

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.

Thursday, July 25, 2013

CfA-Built Telescope on IRIS Sees First Light

This image from NASA's IRIS spacecraft shows the region around two sunspots - the dark areas at upper left and lower right. It shows emission from ionized silicon (Si IV) in the transition region at a temperature of about 116,000 degrees Fahrenheit, plus ultraviolet continuum from the chromosphere at a temperature of about 17,000 degrees F. The bright dots are short-lived, intense patches of Si IV emission. The role that these dynamic events have in heating the solar atmosphere is currently unknown. Credit: NASA.  High Resolution Image (jpg) - Low Resolution Image (jpg)
This image from NASA's Solar Dynamics Observatory shows a larger area around the two sunspots that were photographed by IRIS. Credit: NASA.  High Resolution Image (jpg) - Low Resolution Image (jpg)

Cambridge, MA - NASA's Interface Region Imaging Spectrograph (IRIS) observatory has produced its first images and spectra of a little understood region of the Sun through which the energy that supports the Sun's hot corona is transported. IRIS was launched on June 27, 2013, and the front cover of the IRIS telescope was opened on July 17. 
"Already, we're finding that IRIS has the capability to reveal a very dynamic and highly structured chromosphere and transition region," says astrophysicist Hui Tian of the Harvard-Smithsonian Center for Astrophysics (CfA). "Thin and elongated structures are clearly present in these first-light images, and they evolve quickly in time." 

Important goals of the IRIS mission are to understand how the Sun's million degree corona is heated and to reveal the genesis of the solar wind. By tracing the flow of energy and plasma through the transition region - between the solar surface and the solar corona - where most of the Sun's ultraviolet emissions are generated, IRIS data will allow scientists to study and model a region of the Sun that has yet to reveal its secrets. Ultimately, such understanding could enable scientists to provide forecasts for the Sun's destructive behavior, which can disable satellites, cause power grid failures and disrupt GPS services. IRIS will deliver near continuous solar observations throughout its two-year mission. 

IRIS takes images with four different filters in the ultraviolet wavelength range. It is the first time that images in these wavelengths have been taken with very high resolution (~150 miles) and at a cadence that can capture the rapid evolution of the chromosphere (every 10 seconds). 

IRIS also takes very high-resolution spectra in three ultraviolet wavelength ranges. The spectra are critical for providing physical measurements underlying the dynamics seen in the images. Through the analysis of high-spatial-resolution spectra, scientists can measure flow speeds, energy deposition, and wave properties and densities of the atmospheric plasma. 

The IRIS science instrument and spacecraft were built at the Lockheed Martin Advanced Technology Center (ATC) Solar and Astrophysics Laboratory in Palo Alto, Calif. The IRIS solar telescope was built by the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., which also assists in science operations and data analysis. 

"The IRIS mission has been from inception an enormous international collaborative development effort," says Dr. Alan Title, IRIS principal investigator and physicist at the Lockheed Martin ATC Solar and Astrophysics Laboratory. "Our IRIS team was formed to design the mission and prepare the initial proposal. We have worked together seamlessly ever since." 

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics

Stephen Cole
NASA Headquarters, Washington


Solar system’s youth gives clues to planet search

Caption: Modeling results show where the injected gas and dust ended ups only 34 years after being injected at the disk’s surface. It was injected 9 astronomical units from the central prostar and is now in the disk’s midplane. The outer edge shown is 10 astronomical units from the central prostar. Mixing and transport are still underway and the underlying spiral arms that drive the mixing and transport can be seen. Image courtesy of Alan Boss. A larger version is available here.

Washington, D.C. - Comets and meteorites contain clues to our solar system's earliest days. But some of the findings are puzzle pieces that don't seem to fit well together. A new set of theoretical models from Carnegie's Alan Boss shows how an outburst event in the Sun's formative years could explain some of this disparate evidence. His work could have implications for the hunt for habitable planets outside of our solar system. It is published by The Astrophysical Journal.

One way to study the solar system’s formative period is to look for samples of small crystalline particles that were formed at high temperatures but now exist in icy comets. Another is to analyze the traces of isotopes—versions of elements with the same number of protons, but a different number of neutrons—found in primitive meteorites. These isotopes decay and turn into different, so-called daughter, elements. The initial abundances of these isotopes tell researchers where the isotopes may have come from, and can give clues as to how they traveled around the early solar system.

Stars are surrounded by disks of rotating gas during the early stages of their lives. Observations of young stars that still have these gas disks demonstrate that sun-like stars undergo periodic bursts, lasting about 100 years each, during which mass is transferred from the disk to the young star.

But analysis of particles and isotopes from comets and meteorites present a mixed picture of solar system formation, more complicated than just a one-way movement of matter from the disk to the star.

The heat-formed crystalline grains found in icy comets imply significant mixing and outward movement of matter from close to the star to the outer edges of the solar system. Some isotopes, such as aluminum, support this view. However, isotopes of the element oxygen seem to paint a different picture.

Boss' new model demonstrates how a phase of marginal gravitational instability in the gas disk surrounding a proto-sun, leading to an outburst phase, can explain all of these findings. The results are applicable to stars with a variety of masses and disk sizes. According to the model, the instability can cause a relatively rapid transportation of matter between the star and the gas disk, where matter is moved both inward and outward. This accounts for the presence of heat-formed crystalline particles in comets from the solar system's outer reaches.

According to the model, the ratios of aluminum isotopes can be explained by the parent isotope having been injected in a one-time event into the planet-forming disk by a shock wave from an exploding star and then traveling both inward and outward in the disk. The reason oxygen isotopes are present in a different pattern is because they are derived from sustained chemical reactions occurring on the surface of the outer solar nebula, rather than from a one-time event.

"These results not only teach us about the formation of our own solar system, but also could aid us in the search for other stars orbited by habitable planets," Boss said. "Understanding the mixing and transport processes that occur around Sun-like stars could give us clues about which of their surrounding planets might have conditions similar to our own."
* * *

This work was supported by the NASA Origins of Solar Systems program and the NASA Astrobiology Institute. Some of the calculations were performed on the Carnegie Alpha Cluster, the purchase of which was partially supported by a NSF grant.

Wednesday, July 24, 2013

Starburst to Star Bust

Three-dimensional view of ALMA observations 
of the outflows from NGC 253

The starburst galaxy NGC 253 seen with the VISTA and ALMA

The galaxy NGC 253 in the constellation of Sculptor

Wide-field view of NGC 253 from the VLT Survey Telescope



Three-dimensional view of ALMA observations of the outflows from NGC 253
Three-dimensional view of ALMA observations  o
f the outflows from NGC 253 

Three-dimensional view of ALMA observations of the outflows from NGC 253
Three-dimensional view of ALMA observations 
of the outflows from NGC 253

ALMA Sheds Light on Mystery of Missing Massive Galaxies

New observations from the ALMA telescope in Chile have given astronomers the best view yet of how vigorous star formation can blast gas out of a galaxy and starve future generations of stars of the fuel they need to form and grow. The dramatic images show enormous outflows of molecular gas ejected by star-forming regions in the nearby Sculptor Galaxy. These new results help to explain the strange paucity of very massive galaxies in the Universe. The study is published in the journal Nature on 25 July 2013.

Galaxies — systems like our own Milky Way that contain up to hundreds of billions of stars — are the basic building blocks of the cosmos. One ambitious goal of contemporary astronomy is to understand the ways in which galaxies grow and evolve, a key question being star formation: what determines the number of new stars that will form in a galaxy?

The Sculptor Galaxy, also known as NGC 253, is a spiral galaxy located in the southern constellation of Sculptor. At a distance of around 11.5 million light-years from our Solar System it is one of our closer intergalactic neighbours, and one of the closest starburst galaxies [1] visible from the southern hemisphere. 

Using the Atacama Large Millimeter/submillimeter Array (ALMA) astronomers have discovered billowing columns of cold, dense gas fleeing from the centre of the galactic disc.

With ALMA’s superb resolution and sensitivity, we can clearly see for the first time massive concentrations of cold gas being jettisoned by expanding shells of intense pressure created by young stars,” said Alberto Bolatto of the University of Maryland, USA lead author of the paper. “The amount of gas we measure gives us very good evidence that some growing galaxies spew out more gas than they take in. We may be seeing a present-day example of a very common occurrence in the early Universe.”

These results may help to explain why astronomers have found surprisingly few high-mass galaxies throughout the cosmos. Computer models show that older, redder galaxies should have considerably more mass and a larger number of stars than we currently observe. It seems that the galactic winds or outflow of gas are so strong that they deprive the galaxy of the fuel for the formation of the next generation of stars [2].

These features trace an arc that is almost perfectly aligned with the edges of the previously observed hot, ionised gas outflow,” noted Fabian Walter, a lead investigator at the Max Planck Institute for Astronomy in Heidelberg, Germany, and a co-author of the paper. “We can now see the step-by-step progression of starburst to outflow.”

The researchers determined that vast quantities of molecular gas — nearly ten times the mass of our Sun each year and possibly much more — were being ejected from the galaxy at velocities between 150 000 and almost 1 000 000 kilometres per hour [3]. The total amount of gas ejected would add up to more gas than actually went into forming the galaxy’s stars in the same time. At this rate, the galaxy could run out of gas in as few as 60 million years.

For me, this is a prime example of how new instruments shape the future of astronomy. We have been studying the starburst region of NGC 253 and other nearby starburst galaxies for almost ten years. But before ALMA, we had no chance to see such details,” says Walter. The study used an early configuration of ALMA with only 16 antennas. “It’s exciting to think what the complete ALMA with 66 antennas will show for this kind of outflow!” Walter adds.

More studies with the full ALMA array will help determine the ultimate fate of the gas carried away by the wind, which will reveal whether the starburst-driven winds are recycling or truly removing star forming material.


[1] Starburst galaxies are producing stars at an exceptionally high rate. As NGC 253 is one of the closest such extreme objects it is an ideal target to study the effect of such growth frenzy on the galaxy hosting it.

[2] Previous observations had shown hotter, but much less dense, gas streaming away from NGC 253’s star-forming regions, but alone this would have little, if any, impact on the fate of the galaxy and its ability to form future generations of stars. This new ALMA data show the much more dense molecular gas getting its initial “kick” from the formation of new stars and then being swept along with the thin, hot gas on its way to the galactic halo.

[3] Although the velocities are high, they may not be high enough for the gas to be ejected from the galaxy. It would get trapped in the galactic halo for many millions of years, and could eventually rain back on the disk, causing new episodes of star formation.

More information

This research was presented in a paper “The Starburst-Driven Molecular Wind in NGC 253 and the Suppression of Star Formation”, by Alberto D. Bolatto et al., to appear in Nature on 25 July 2013.

The team is composed of A. D. Bolatto (Department of Astronomy, Laboratory for Millimeter-wave Astronomy, and Joint Space Institute, University of Maryland, USA), S. R. Warren (University of Maryland), A. K. Leroy (National Radio Astronomy Observatory, Charlottesville, USA), F. Walter (Max-Planck Institut für Astronomie, Heidelberg, Germany), S. Veilleux (University of Maryland), E. C. Ostriker (Department of Astrophysical Sciences, Princeton University, USA), J. Ott (National Radio Astronomy Observatory, New Mexico, USA), M. Zwaan (European Southern Observatory, Garching, Germany), D. B. Fisher (University of Maryland), A. Weiss (Max-Planck-Institut für Radioastronomie, Bonn, Germany), E. Rosolowsky (Department of Physics, University of Alberta, Canada) and J. Hodge (Max-Planck Institut für Astronomie, Heidelberg, Germany).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.



Alberto Bolatto
University of Maryland
Tel: +49 6221 528 493


Martin Zwaan
Garching bei München, Germany
Tel: +49 89 3200 6834

Fabian Walter
Max-Planck Institut für Astronomie
Heidelberg, Germany
Tel: +49 6221 528 225

Richard Hook
ESO, Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591

NASA's Spitzer Observes Gas Emission From Comet ISON

These images from NASA's Spitzer Space Telescope of C/2012 S1 (Comet ISON) were taken on June 13, when ISON was 310 million miles (about 500 million kilometers) from the sun. Image credit: NASA/JPL-Caltech/JHUAPL/UCF.  › Full image and caption

PASADENA, Calif. -- Astronomers using NASA's Spitzer Space Telescope have observed what most likely are strong carbon dioxide emissions from Comet ISON ahead of its anticipated pass through the inner solar system later this year.

Images captured June 13 with Spitzer's Infrared Array Camera indicate carbon dioxide is slowly and steadily "fizzing" away from the so-called "soda-pop comet," along with dust, in a tail about 186,400 miles (300,000 kilometers) long.

"We estimate ISON is emitting about 2.2 million pounds (1 million kilograms) of what is most likely carbon dioxide gas and about 120 million pounds (54.4 million kilograms) of dust every day," said Carey Lisse, leader of NASA's Comet ISON Observation Campaign and a senior research scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "Previous observations made by NASA's Hubble Space Telescope and the Swift Gamma-Ray Burst Mission and Deep Impact spacecraft gave us only upper limits for any gas emission from ISON. Thanks to Spitzer, we now know for sure the comet's distant activity has been powered by gas."

Comet ISON was about 312 million miles (502 million kilometers) from the sun, 3.35 times farther than Earth, when the observations were made.

"These fabulous observations of ISON are unique and set the stage for more observations and discoveries to follow as part of a comprehensive NASA campaign to observe the comet," said James L. Green, NASA's director of planetary science in Washington. "ISON is very exciting. We believe that data collected from this comet can help explain how and when the solar system first formed."

Comet ISON (officially known as C/2012 S1) is less than 3 miles (4.8 kilometers) in diameter, about the size of a small mountain, and weighs between 7 billion and 7 trillion pounds (3.2 billion and 3.2 trillion kilograms). Because the comet is still very far away, its true size and density have not been determined accurately. Like all comets, ISON is a dirty snowball made up of dust and frozen gases such as water, ammonia, methane and carbon dioxide. These are some of the fundamental building blocks, which scientists believe led to the formation of the planets 4.5 billion years ago.

Comet ISON is believed to be inbound on its first passage from the distant Oort Cloud, a roughly spherical collection of comets and comet-like structures that exists in a space between one-tenth light-year and 1 light-year from the sun. The comet will pass within 724,000 miles (1.16 million kilometers) of the sun on Nov. 28.

It is warming up gradually as it gets closer to the sun. In the process, different gases are heating up to the point of evaporation, revealing themselves to instruments in space and on the ground. Carbon dioxide is thought to be the gas that powers emission for most comets between the orbits of Saturn and the asteroids.

The comet was discovered Sept. 21, roughly between Jupiter and Saturn, by Vitali Nevski and Artyom Novichonok at the International Scientific Optical Network (ISON) near Kislovodsk, Russia. This counts as an early detection of a comet, and the strong carbon dioxide emissions may have made the detection possible.

"This observation gives us a good picture of part of the composition of ISON, and, by extension, of the proto-planetary disk from which the planets were formed," said Lisse. "Much of the carbon in the comet appears to be locked up in carbon dioxide ice. We will know even more in late July and August, when the comet begins to warm up near the water-ice line outside of the orbit of Mars, and we can detect the most abundant frozen gas, which is water, as it boils away from the comet."

NASA's Jet Propulsion Laboratory in Pasadena, Calif., 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 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: . Learn more about NASA's Comet ISON Observing Campaign: . NASA's Comet ISON Toolkit is at: .

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.

Geoffrey Brown 240-228-5618
Johns Hopkins Applied Physics Laboratory, Laurel, Md.

J.D. Harrington 202-358-5241
Headquarters, Washington

Tuesday, July 23, 2013

Mystery of the Missing Waves on Titan

One of the most shocking discoveries of the past 10 years is how much the landscape of Saturn's moon Titan resembles Earth.  Like our own blue planet, the surface of Titan is dotted with lakes and seas; it has river channels, islands, mud, rain clouds and maybe even rainbows.  The giant moon is undeniably wet. 

The "water" on Titan is not, however, H2O.  With a surface temperature dipping 290 degrees F below zero, Titan is far too cold for liquid water. Instead, researchers believe the fluid that sculpts Titan is an unknown mixture of methane, ethane, and other hard-to-freeze hydrocarbons.

A new ScienceCast video ponders the mystery of the missing waves on Titan. Play it

This glint of sunlight detected by Cassini in 2009 is widely thought to be a reflection from the mirror-like surface of one of Titan's northern lakes. More

The idea that Titan is a wet world with its own alien waters is widely accepted by planetary scientists. Nothing else can account for the observations: NASA's Cassini spacecraft has flown by Titan more than 90 times since 2004, pinging the Moon with radar and mapping its lakes and seas. ESA's Huygens probe parachuted to the surface of Titan in 2005, descending through humid clouds and actually landing in moist soil. 

Yet something has been bothering Alex Hayes, a planetary scientist on the Cassini radar team at Cornell University.

Researchers have toyed with several explanations.  Perhaps the lakes are frozen. Hayes thinks that is unlikely, however, "because we see evidence of rainfall and surface temperatures well above the melting point of methane."  Or maybe the lakes are covered with a tar-like substance that damps wave motion. "We can't yet rule that out," he adds. 

If Titan is really so wet, he wonders, "Where are all the waves?"

Here on Earth, bodies of water are rarely still.  Breezes blowing across the surface cause waves to ripple and break; raindrops striking sea surfaces also provide some roughness.  Yet on Titan, the lakes are eerily smooth, with no discernable wave action down to the millimeter scale, according to radar data from Cassini.
"We know there is wind on Titan," says Hayes. "The moon's magnificent sand dunes [prove] it."

Add to that the low gravity of Titan—only 1/7th that of Earth—which offers so little resistance to wave motion, and you have a real puzzle.

The answer might be found in the results of a study Hayes and colleagues published in the July 2013 online edition of the journal Icarus. Taking into account the gravity of Titan, the low viscosity of liquid hydrocarbons, the density of Titan's atmosphere, and other factors, they calculated how fast wind on Titan would have to blow to stir up waves: A walking-pace breeze of only 1 to 2 mph should do the trick. 

This suggests a third possibility: the winds just haven’t been blowing hard enough. Since Cassini reached Saturn in 2004, Titan’s northern hemisphere (where most of the lakes are located) has been locked in the grip of winter.  Cold heavy air barely stirs, and seldom reaches the threshold for wave-making.

But now the seasons are changing. In August 2009 the sun crossed Titan’s equator heading north. Summer is coming, bringing light, heat and wind to Titan's lake country. 

"According to [climate models], winds will pick up as we approach the solstice in 2017 and should be strong enough for waves," he says. 

If waves appear, Cassini should be able to detect them.  Radar reflections from wavy lake surfaces can tell researchers a great deal.  Wave dimensions, for instance, may reveal the viscosity of the underlying fluid and, thus, its chemical composition.  Also, wave speeds would track the speed of the overlying winds, providing an independent check of Titan climate models. 

Hayes is excited about "bringing oceanography to another world. All we need now," he says, "are some rough seas." 


Author and Production editor: Dr. Tony Phillips

Credit: Science@NASA