Hubble Shows Farthest Lensing Galaxy Yields Clues to Early Universe Gravitational Lensing by Galaxy in Cluster IRC 0218

Gravitational Lensing by Galaxy in Cluster IRC 0218

Credit: NASA, ESA, K.-V. Tran (Texas A&M University), 
and K. Wong (Academia Sinica Institute of Astronomy & Astrophysics). 
Release Images

Astronomers using NASA's Hubble Space Telescope have unexpectedly discovered the most distant cosmic magnifying glass, produced by a monster elliptical galaxy. Seen here as it looked 9.6 billion years ago, this monster elliptical galaxy breaks the previous record holder by 200 million years. These "lensing" galaxies are so massive that their gravity bends, magnifies, and distorts light from objects behind them, a phenomenon called gravitational lensing.

The object behind the cosmic lens is a tiny spiral galaxy undergoing a rapid burst of star formation. Its light has taken 10.7 billion years to arrive here. Seeing this chance alignment at such a great distance from Earth is a rare find.

Locating more of these distant lensing galaxies will offer insight into how young galaxies in the early universe built themselves up into the massive dark-matter-dominated galaxies of today. Dark matter cannot be seen, but it accounts for the bulk of the universe's matter.

"When you look more than 9 billion years ago in the early universe, you don't expect to find this type of galaxy-galaxy lensing at all," explained lead researcher Kim-Vy Tran of Texas A&M University in College Station. "It's very difficult to see an alignment between two galaxies in the early universe. Imagine holding a magnifying glass close to you and then moving it much farther away. When you look through a magnifying glass held at arm's length, the chances that you will see an enlarged object are high. But if you move the magnifying glass across the room, your chances of seeing the magnifying glass nearly perfectly aligned with another object beyond it diminishes."

Team members Kenneth Wong and Sherry Suyu of Academia Sinica Institute of Astronomy & Astrophysics (ASIAA) in Taipei, Taiwan, used the gravitational lensing from the chance alignment to measure the giant galaxy's total mass, including the amount of dark matter, by gauging the intensity of its lensing effects on the background galaxy's light. The giant foreground galaxy weighs 180 billion times more than our Sun and is a massive galaxy for its epoch. It is also one of the brightest members of a distant cluster of galaxies, called IRC 0218.

"There are hundreds of lens galaxies that we know about, but almost all of them are relatively nearby, in cosmic terms," said Wong, first author on the team's science paper. "To find a lens as far away as this one is a very special discovery because we can learn about the dark-matter content of galaxies in the distant past. 

By comparing our analysis of this lens galaxy to the more nearby lenses, we can start to understand how that dark-matter content has evolved over time."

Although the elliptical galaxy is hefty, it is not as massive as many of today's galaxies. Our Milky Way galaxy, for example, is three to four times more massive than the elliptical galaxy. Most of the Milky Way's mass is locked up in dark matter. The lensing galaxy, however, is underweight in terms of its dark-matter content.

"The unusually small amount of dark matter in this massive, elliptical, lensing galaxy is very surprising," Suyu said. "Other elliptical galaxies that are closer to us have much more dark matter and have inventories of stars that appear to be different from this super-distant lensing galaxy."

The team suspects that the lensing galaxy will continue to grow over the next 9 billion years, gaining stars and dark matter by cannibalizing neighboring galaxies. "Recent studies suggest that these massive galaxies gain more dark matter than stars as they continue to grow," Tran explained. "Astronomers had assumed that dark matter and normal matter build up equally in a galaxy over time. But now we know that the ratio of dark matter to normal matter changes with time. Our lensing galaxy will eventually become much more massive than the Milky Way and definitely will have more dark matter, too."

Tran and her team were studying star formation in two distant galaxy clusters, including IRC 0218, when they stumbled upon the gravitational lens. While analyzing spectrographic data from the W.M. Keck Observatory in Hawaii, Tran spotted a strong detection of hot hydrogen gas that appeared to arise from a massive, bright elliptical galaxy. The detection was surprising because hot hydrogen gas is a clear signature of star birth. Previous observations had shown that the giant elliptical was an old, sedate galaxy that had stopped making stars a long time ago. Another puzzling discovery was that the young stars were at a much farther distance than the massive elliptical. "I was very surprised and worried," Tran recalled. "I thought we had made a major mistake with our observations."

The astronomer soon realized she hadn't made a mistake when she looked at the Hubble images taken in blue wavelengths, which revealed the glow of fledgling stars. The images, taken by the Advanced Camera for Surveys and the Wide Field Camera 3, revealed a blue, eyebrow-shaped object next to a smeared blue dot around the big elliptical. Tran recognized the unusual features as the distorted, magnified images of a more distant galaxy behind the elliptical galaxy, the signature of a gravitational lens. But some team members were not convinced. They speculated that the two objects could be a nearby galaxy pair being shredded during a galaxy collision. Tran, however, only had a partial fingerprint; she needed conclusive evidence.

To confirm the gravitational-lens hypothesis, collaborator Ivelina Momcheva of Yale University, New Haven, Connecticut, analyzed Hubble spectroscopic data from the 3D-HST survey, a near-infrared spectroscopic survey taken with the Wide Field Camera 3. She compared that data with images from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), a large Hubble deep-sky program. To paint an even more detailed picture of the system, Momcheva also added archival Hubble observations of the galaxy cluster. The data turned up another fingerprint of hot gas connected to the more distant galaxy.

"We discovered that light from the lensing galaxy and from the background galaxy were blended in the ground-based data, which was confusing us," Momcheva said. "The Keck spectroscopic data hinted that something interesting was going on here, but only with Hubble's high-resolution spectroscopy were we able to separate the lensing galaxy from the more distant background galaxy and determine that the two were at different distances. The Hubble data also revealed the telltale look of the system, with the foreground lens in the middle, flanked by a bright arc on one side and a faint smudge on the other — both distorted images of the background galaxy. We needed the combination of imaging and spectroscopy to solve the puzzle."

The distant galaxy is too small and far away for Hubble to resolve its structure. Team members, therefore, reconstructed and analyzed the distribution of light in the object to infer its spiral shape. In addition, spiral galaxies are more plentiful during those early times. The Hubble images also reveal at least one bright compact region near the center. The team suspects that the bright region is due to a flurry of star formation and is most likely composed of hot hydrogen gas heated by massive young stars.

Team members calculated the lensing galaxy's mass, including its dark-matter content, by first measuring the amount of light emitted by its stars. From that measurement, the astronomers obtained the mass of all the stars, which equals the amount of normal matter. Next, the team estimated the total mass by measuring how much the galaxy's gravity bends and distorts light from the distant background galaxy. The astronomers then subtracted the stellar mass from the total mass to determine the amount of dark matter in the galaxy.

As Tran continues her star-formation study in galaxy clusters, she will be hunting for more signatures of gravitational lensing. "I'm definitely going to keep an eye out for more lensing galaxies, but they're so rare that you would normally have to survey hundreds of clusters for them," Tran said. "That's why finding this one in such a small area of space was a complete shock."

The team's results appeared in the July 10 issue of The Astrophysical Journal Letters.

CONTACT

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu

Source: HubbleSite

ALMA Finds Double Star with Weird and Wild Planet-forming Discs

R Image eso1423a

Artist’s impression of the discs around the young stars HK Tauri A and B

PR Image eso1423b

The young double star HK Tauri in the constellation of Taurus

PR Image eso1423c

Wide-field view of part of the Taurus star formation region

PR Image eso1423d

Composite views of HK Tauri from Hubble and ALMA

 

PR Image eso1423e

The motions of material in the discs around the young double star HK Tauri

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Videos

PR Video eso1423a

Zooming in on the young double star HK Tauri

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found wildly misaligned planet-forming gas discs around the two young stars in the binary system HK Tauri. These new ALMA observations provide the clearest picture ever of protoplanetary discs in a double star. The new result also helps to explain why so many exoplanets — unlike the planets in the Solar System — came to have strange, eccentric or inclined orbits. The results will appear in the journal Nature on 31 July 2014.

Unlike our solitary Sun, most stars form in binary pairs — two stars that are in orbit around each other. Binary stars are very common, but they pose a number of questions, including how and where planets form in such complex environments.

“ALMA has now given us the best view yet of a binary star system sporting protoplanetary discs  — and we find that the discs are mutually misaligned!” said Eric Jensen, an astronomer at Swarthmore College in Pennsylvania, USA.

The two stars in the HK Tauri system, which is located about 450 light-years from Earth in the constellation of Taurus (The Bull), are less than five million years old and separated by about 58 billion kilometres — this is 13 times the distance of Neptune from the Sun.

The fainter star, HK Tauri B, is surrounded by an edge-on protoplanetary disc that blocks the starlight. Because the glare of the star is suppressed, astronomers can easily get a good view of the disc by observing in visible light, or at near-infrared wavelengths.

The companion star, HK Tauri A, also has a disc, but in this case it does not block out the starlight. As a result the disc cannot be seen in visible light because its faint glow is swamped by the dazzling brightness of the star. But it does shine brightly in millimetre-wavelength light, which ALMA can readily detect.

Using ALMA, the team were not only able to see the disc around HK Tauri A, but they could also measure its rotation for the first time. This clearer picture enabled the astronomers to calculate that the two discs are out of alignment with each other by at least 60 degrees. So rather than being in the same plane as the orbits of the two stars at least one of the discs must be significantly misaligned.

“This clear misalignment has given us a remarkable look at a young binary star system,” said Rachel Akeson of the NASA Exoplanet Science Institute at the California Institute of Technology in the USA. “Although there have been earlier observations indicating that this type of misaligned system existed, the new ALMA observations of HK Tauri show much more clearly what is really going on in one of these systems.”

Stars and planets form out of vast clouds of dust and gas. As material in these clouds contracts under gravity, it begins to rotate until most of the dust and gas falls into a flattened protoplanetary disc swirling around a growing central protostar.

But in a binary system like HK Tauri things are much more complex. When the orbits of the stars and the protoplanetary discs are not roughly in the same plane any planets that may be forming can end up in highly eccentric and tilted orbits [1].

“Our results show that the necessary conditions exist to modify planetary orbits and that these conditions are present at the time of planet formation, apparently due to the formation process of a binary star system,” noted Jensen. “We can’t rule other theories out, but we can certainly rule in that a second star will do the job.”

Since ALMA can see the otherwise invisible dust and gas of protoplanetary discs, it allowed for never-before-seen views of this young binary system. “Because we’re seeing this in the early stages of formation with the protoplanetary discs still in place, we can see better how things are oriented,” explained Akeson.

Looking forward, the researchers want to determine if this type of system is typical or not. They note that this is a remarkable individual case, but additional surveys are needed to determine if this sort of arrangement is common throughout our home galaxy, the Milky Way.

Jensen concludes: “Although understanding this mechanism is a big step forward, it can’t explain all of the weird orbits of extrasolar planets — there just aren’t enough binary companions for this to be the whole answer. So that’s an interesting puzzle still to solve, too!”

Notes

[1] If the two stars and their discs are not all in the same plane, the gravitational pull of one star will perturb the other disc, making it wobble or precess, and vice versa. A planet forming in one of these discs will also be perturbed by the other star, which will tilt and deform its orbit.

More information

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Southern Observatory (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

This research was presented in a paper entitled “Misaligned Protoplanetary Disks in a Young Binary Star System”, by Eric Jensen and Rachel Akeson, to appear in the 31 July 2014 issue of the journal Nature.

The team is composed of Eric L. N. Jensen (Dept. of Physics & Astronomy, Swarthmore College, USA) and Rachel Akeson (NASA Exoplanet Science Institute, IPAC/Caltech, Pasadena, USA).

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”.

Links

• Research paper
• NRAO press release about HK Tauri results
• Image of HK Tauri from the NASA/ESA Hubble Space Telescope
• More about ALMA
• Photos of ALMA
• Videos of ALMA
• ALMA brochure
• The movie ALMA — In Search of our Cosmic Origins
• The ALMA Photo Book In Search of our Cosmic Origins – The Construction of the Atacama Large Millimeter/submillimeter Array
• More press releases with ALMA

Contacts

Eric L. N. Jensen
Lead Scientist, Swarthmore College
Philadelphia, USA
Tel: +1 610-328-8249
Email: ejensen1@swarthmore.edu

Rachel Akeson
NASA Exoplanet Science Institute, IPAC/Caltech
Pasadena, USA
Tel: +1 626-395-1812
Email: rla@ipac.caltech.edu

Charles E. Blue
Public Information Officer, National Radio Astronomy Observatory
Charlottesville, USA
Tel: + 1 434 296 0314
Cell: +1 202 236 6324
Email: cblue@nrao.edu

Richard Hook
Public Information Officer, ESO
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Source: ESO

Binary Stars in the Globular Cluster Messier 4

An image of the globular cluster Messier 4

New observations of M4 have studied the binary stars in this cluster.

Credit: ESO

A globular cluster is a roughly spherical ensemble of stars, as many as several million of them, gravitationally bound together in groups whose diameters can be as small as only tens of light-years. To sense the dramatic implications of this dense packing, consider that the nearest star to the Sun, Proxima Centauri, is about four light-years away. Messier 4 (M4) is the closest globular cluster to Earth at a distance of about six thousand light-years, and a puzzle to astronomers. Normal gravitational effects should, over time, redistribute the stars in a globular cluster until they are more numerous towards the center, but while M4 shows a central concentration of stars it does not show evidence for a steep central cusp even though astronomers think enough time has passed.

To understand what is going on in this globular cluster, and to help understand how these clusters evolve in general, CfA astronomer Maureen van den Berg and her collaborators have undertaken a large and unprecedented set of deep images of M4 with the Hubble Space Telescope to look for binary stars, that is stars with companions. The dynamical interactions between the densely crowded stars in a globular cluster should disrupt many such binaries, but for reasons that are not understood about fifteen percent of the stars in M4 are binaries, at least based on monitoring brightness variations (a more typical number is two percent). Whether or not this unusual abundance is connected to the lack of a central cusp in stellar density is also not understood.

The astronomers set out to use Hubble to study the binary star population in M4 looking at both brightness variations and stellar wobble (astrometric) variations, in particular due to binaries with a massive, faint, and evolved companion like a white dwarf or neutron star. The team was able to find and characterize a much more complete set of binaries, including thirty-six new variables. They note in passing that, as part of the search process, any stars with massive "hot Jupiter" exoplanet companions would probably also have been detected, but that none were. The extensive results are still being analyzed, but the improved statistics will make the conclusions much more reliable.

Reference(s):

 

"The M 4 Core Project with HST – III. Search for Variable Stars in the Primary Field," V. Nascimbeni, L. R. Bedin, D. C. Heggie, M. van den Berg, M. Giersz, G. Piotto, K. Brogaard, A. Bellini, A. P. Milone, R. M. Rich, D. Pooley, J. Anderson,, L. Ubeda, S. Ortolani, L. Malavolta, A. Cunial1, and A. Pietrinferni, MNRAS 442, 2381, 2014

Source: Smithsonian Astrophysical Observatory - SAO

NASA-funded X-ray Instrument Settles Interstellar Debate

Colors indicate the density of interstellar helium near Earth and its enhancement in a downstream cone as the neutral atoms respond to the sun's gravity (blue is low density, red is high). Also shown are the observing angles for DXL and ROSAT. Image Credit: NASA's Goddard Space Flight Center. Hi-Res Image

New findings from a NASA-funded instrument have resolved a decades-old puzzle about a fog of low-energy X-rays observed over the entire sky. Thanks to refurbished detectors first flown on a NASA sounding rocket in the 1970s, astronomers have now confirmed the long-held suspicion that much of this glow stems from a region of million-degree interstellar plasma known as the local hot bubble, or LHB.

At the same time, the study also establishes upper limits on the amount of low-energy, or soft, X-rays produced within our planetary system by the solar wind, a gusty outflow of charged particles emanating from the sun.

"Interactions between the solar wind and neutral atoms in comets, the outer atmospheres of planets, and even interstellar gas produce soft X-rays," explained team member Steve Snowden, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We need to account for these processes because the X-rays they produce complicate our observations of the wider universe."

Decades of mapping the sky in X-rays with energies around 250 electron volts -- about 100 times the energy of visible light -- revealed strong emission precisely where it shouldn't be. This glow, known as the soft X-ray diffuse background, is surprisingly bright in the gas-rich central plane of our galaxy, where it should be strongly absorbed. This suggested the background was a local phenomenon, arising from a bubble of hot gas extending out a few hundred light-years from the solar system in all directions. Improved measurements also made it increasingly clear that the sun resides in a region where interstellar gas is unusually sparse. Taken together, the evidence suggests our solar system is moving through a region that may have been blasted clear by one or more supernova explosions during the past 20 million years.

In the 1990s, a six-month all-sky survey by the German X-ray observatory ROSAT provided improved maps of the diffuse background, but it also revealed that comets were an unexpected source of soft X-rays. As scientists began to understand this process, called solar wind charge exchange, they realized it could occur anywhere neutral atoms interacted with solar wind ions.

This animation illustrates solar wind charge exchange in action. An atom of interstellar helium (blue) collides with a solar wind ion (red), losing one of its electrons (yellow) to the other particle. As it settles into a lower-energy state, the electron emits a soft X-ray. Image Credit: NASA's Goddard Space Flight Center. Download this video in HD formats from NASA Goddard's Scientific Visualization Studio

Within the last decade, some scientists have been challenging the LHB interpretation, suggesting that much of the soft X-ray diffuse background is a result of charge exchange," said F. Scott Porter, a Goddard astrophysicist also participating in the study. "The only way to check is to design an instrument and make measurements."

Led by Massimiliano Galeazzi, a professor of physics at the University of Miami in Coral Gables, Florida, an international collaboration developed a mission to do just that. The team includes scientists from NASA, the University of Wisconsin -- Madison, the University of Michigan at Ann Arbor, the University of Kansas at Lawrence, Johns Hopkins University in Baltimore, Maryland, the French National Center for Scientific Research (CNRS), headquartered in Paris, and other institutions.

Galeazzi and his colleagues rebuilt, tested, calibrated, and adapted X-ray detectors originally designed by the University of Wisconsin and flown on sounding rockets in the 1970s. Components from another instrument flown on space shuttle Endeavour in 1993 also were given new life. The mission was named DXL, for Diffuse X-ray emission from the Local Galaxy. 

On Dec. 12, 2012, DXL launched from White Sands Missile Range in New Mexico atop a NASA Black Brant IX sounding rocket, reaching a peak altitude of 160 miles (258 km) and spending five minutes above Earth's atmosphere. The mission design allowed the instrument to observe a worst-case scenario involving charge exchange with interstellar gas.

The solar system is currently passing through a small cloud of cold interstellar gas as it moves through the galaxy. The cloud’s neutral hydrogen and helium atoms stream through the planetary system at about 56,000 mph (90,000 km/h). While hydrogen atoms quickly ionize and respond to numerous forces, the helium atoms travel paths largely governed by the sun's gravity. This creates a "helium focusing cone" downstream from the sun that crosses Earth's orbit and is located high in the sky near midnight in early December.

"This helium focusing creates a region with a much greater density of neutral atoms and a correspondingly enhanced charge exchange rate," Snowden said.

The solar wind is accelerated in the sun's corona, the hottest part of its atmosphere, so its atoms have been ionized -- stripped of many of their electrons. When a neutral atom collides with a solar wind ion, one of its electrons often jumps to the charged particle. Once captured by the ion, the electron briefly remains in an excited state, then emits a soft X-ray and settles down at a lower energy. This is solar wind charge exchange in action.

To establish a baseline for the soft X-ray background, the researchers used data captured by the ROSAT mission in September 1990 in a direction looking along, rather than into, the helium focusing cone. The results, published online in the journal Nature on July 27, indicate that only about 40 percent of the soft X-ray background originates within the solar system.

"We now know that the emission comes from both sources but is dominated by the local hot bubble,” said Galeazzi. "This is a significant discovery. Specifically, the existence or nonexistence of the local bubble affects our understanding of the area of the galaxy close to the sun, and can, therefore, be used as a foundation for future models of the galaxy structure."

Galeazzi and his collaborators are already planning the next flight of DXL, which will include additional instruments to better characterize the emission. The launch is currently planned for December 2015.

"The DXL team is an extraordinary example of cross-disciplinary science, bringing together astrophysicists, planetary scientists, and heliophysicists," added Porter. "It’s unusual but very rewarding when scientists with such diverse interests come together to produce such groundbreaking results."

Related Links:

• Download HD video and additional images from NASA Goddard's Scientific Visualization Studio

• Paper: "The Origin of the Local 1/4-keV X-ray Flux in Both Charge Exchange and a Hot Bubble"

• Paper: "Pressure Equilibrium between the Local Interstellar Clouds and the Local Hot Bubble"

• DXL Launches Successfully (12.13.2012)

• Imagine the Universe! The Soft X-ray Diffuse Background

Francis Reddy
NASA's Goddard Space Flight Center, Greenbelt, Maryland

Looking in all the right places: the Sloan Digital Sky Survey extends its reach

Fig. 1: The Milky Way Galaxy as seen in infrared light. The pink shaded region is not visible from the Northern Hemisphere, so has not been studied previously by the SDSS. The new phase of the SDSS will see the entire galaxy. Credit: The SDSS collaboration, Galaxy image credit: Two Micron All Sky Survey / Infrared Processing and Analysis Center / Caltech & University of Massachusetts

Fig. 2: MaNGA galaxy plate, showing the holes for the MaNGA IFUs and sky fibers. (credit: D.R. Law)

Fig. 3: SDSS images of the galaxies observed during the March 2014 MaNGA commissioning run at the Apache Point Observatory. (credit: K. Bundy) 

At the beginning of July, the Sloan Digital Sky Survey started a new phase with three major new programmes. eBOSS will work to extend precision cosmological measurements to a critical early phase of cosmic history; APOGEE-2 will expand the survey of the Galaxy across both the northern and southern hemispheres, and MaNGA (with participation of the Max Planck Institute for Astrophysics) will for the first time be using the Sloan spectrographs to make spatially resolved maps of individual galaxies. SDSS-IV will run from 2014 to 2020. 

Building on its past successes, the Sloan Digital Sky Survey (SDSS) has launched a major new program that will expand its census of the Universe into new areas it had been unable to explore before: 

- Exploring the compositions and motions of stars across the entire Milky Way in unprecedented detail, using a telescope in Chile.

- Making detailed maps of the internal structure of thousands of nearby galaxies to determine how they have grown and changed over billions of years, using a cutting-edge measurement device.

-Measuring the expansion of the Universe in a poorly-understood five-billion-year period of the Universe's history, using a new set of galaxies and quasars 

The new survey is a collaboration of more than 200 astronomers at more than 40 institutions on four continents, and incorporates telescopes in both the Northern and Southern Hemispheres. With these two telescopes, the SDSS will be able to see the entire sky for the first time. 

This new phase of the SDSS will provide a vast new database of observations that will significantly expand our understanding of the nature of the Universe at all scales, from our own galaxy to the distant universe. In our galaxy, the new SDSS will see hundreds of thousands of individual stars, including stars that were born at the birth of the Milky Way and stars that were born yesterday. Measuring the compositions, positions, and motions of individual stars will reveal how the Galaxy evolved from the distant past to today. 

In addition to the Sloan Foundation 2.5-meter Telescope in New Mexico, SDSS-IV will use the 2.5-meter Irenee du Pont Telescope at Las Campanas Observatory in La Serena, high in the Chilean Andes and home to the clearest skies on the planet. In addition to providing a 360-degree view of the Milky Way, the new telescope will also observe stars in the nearby Magellanic Clouds, giving astronomers a better understanding of the Milky Way's celestial environment.

But the Milky Way is far from the only galaxy that the new SDSS will examine. The new survey will employ innovative new technology to make detailed maps of thousands of nearby galaxies. Unlike nearly all previous astronomy surveys, which looked only at small areas in the centers of other galaxies, the new SDSS will measure light from all over. These better maps are made possible through a new technique of bundling sets of fiber optic cables into tightly-packed arrays. Those collect light from across the entire face of a galaxy, enabling detailed spectral measurements of more than 10,000 nearby galaxies in less than one-twentieth of the time. MPA scientist Guinevere Kauffmann was heavily involved in planning the "Mapping Nearby Galaxies at APO" (MaNGA) survey right from the beginning. MaNGA's goal is to understand the "life cycle" of present day galaxies from imprinted clues of their birth and assembly, through their ongoing growth via star formation and merging, to their death from quenching at late times. 

"MaNGA will be key to disentangling the physical processes important in the lives of galaxies," Guinevere Kauffmann points out. "In particular, we need to understand which aspects of galaxies are set by cosmological initial conditions and which are set by black holes." 

And the new SDSS will continue to improve our understanding of the Universe as a whole. It will precisely measure the expansion history of the universe through 80% of cosmic history, back to when the Universe was less than three billion years old. These new detailed measurements will help to improve constraints on the nature of dark energy, the most mysterious experimental result in modern physics. 

The new cosmology measurements will include a survey of nearly all the quasars, which will allow for precision measurements of the history of the Universe's expansion in ways never before possible. Other programs within the new SDSS will follow up on galaxies seen by prior X-ray surveys, and will conduct the first systematic spectral study of variable objects, yielding a critical resource astronomers can use to identify the nature of many types of time-varying light sources discovered in previous surveys. 

SDSS Press Officer:

Jordan Raddick, SDSS-III Public Information Officer, Johns Hopkins University
Email: raddick@jhu.edu
Phone: 1-410-516-8889

Contact at MPA:

Guinevere Kauffmann
Director
Max-Planck-Institut für Astrophysik
Karl-Schwarzschild-Str. 1
D-85748 Garching
Phone: 089 30000-2013
E-mail: gkauffmann@mpa-garching.mpg.de 

Hannelore Hämmerle
Presse- und Öffentlichkeitsarbeit
Max-Planck-Institut für Astrophysik
Tel: +49 (89) 30 000 3980
E-mail: pr@mpa-garching.mpg.de 

ABOUT THE SLOAN DIGITAL SKY SURVEY

Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is www.sdss.org.

SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofisica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU) / University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut für Astrophysik Potsdam (AIP),Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut für Extraterrestrische Physik (MPE), Max-Planck-Institut für Astronomie (MPIA Heidelberg), National Astronomical Observatory of China, New Mexico State University, New York University, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autonoma de Mexico, University of Arizona, University of Colorado Boulder, University of Portsmouth, University of Utah, University of Washington, University of Wisconsin, Vanderbilt University, and Yale University. 

Source:  Max Planck Institute for Astrophysics

A New Approach to SETI: Targeting Alien Polluters

In this artist's conception, the atmosphere of an Earth-like planet displays a brownish haze - the result of widespread pollution. New research shows that the upcoming James Webb Space Telescope potentially could detect certain pollutants, specifically CFCs, in the atmospheres of Earth-sized planets orbiting white dwarf stars. Credit: Christine Pulliam (CfA). High Resolution (jpg) - Low Resolution (jpg)

Cambridge, MA -Humanity is on the threshold of being able to detect signs of alien life on other worlds. By studying exoplanet atmospheres, we can look for gases like oxygen and methane that only coexist if replenished by life. But those gases come from simple life forms like microbes. What about advanced civilizations? Would they leave any detectable signs?

They might, if they spew industrial pollution into the atmosphere. New research by theorists at the Harvard-Smithsonian Center for Astrophysics (CfA) shows that we could spot the fingerprints of certain pollutants under ideal conditions. This would offer a new approach in the search for extraterrestrial intelligence (SETI).

"We consider industrial pollution as a sign of intelligent life, but perhaps civilizations more advanced than us, with their own SETI programs, will consider pollution as a sign of unintelligent life since it's not smart to contaminate your own air," says Harvard student and lead author Henry Lin.

"People often refer to ETs as 'little green men,' but the ETs detectable by this method should not be labeled 'green' since they are environmentally unfriendly," adds Harvard co-author Avi Loeb.

The team, which also includes Smithsonian scientist Gonzalo Gonzalez Abad, finds that the upcoming James Webb Space Telescope (JWST) should be able to detect two kinds of chlorofluorocarbons (CFCs) -- ozone-destroying chemicals used in solvents and aerosols. They calculated that JWST could tease out the signal of CFCs if atmospheric levels were 10 times those on Earth. A particularly advanced civilization might intentionally pollute the atmosphere to high levels and globally warm a planet that is otherwise too cold for life.

There is one big caveat to this work. JWST can only detect pollutants on an Earth-like planet circling a white dwarf star, which is what remains when a star like our Sun dies. That scenario would maximize the atmospheric signal. Finding pollution on an Earth-like planet orbiting a Sun-like star would require an instrument beyond JWST -- a next-next-generation telescope.

The team notes that a white dwarf might be a better place to look for life than previously thought, since recent observations found planets in similar environments. Those planets could have survived the bloating of a dying star during its red giant phase, or have formed from the material shed during the star's death throes.
While searching for CFCs could ferret out an existing alien civilization, it also could detect the remnants of a civilization that annihilated itself. Some pollutants last for 50,000 years in Earth's atmosphere while others last only 10 years. Detecting molecules from the long-lived category but none in the short-lived category would show that the sources are gone.

"In that case, we could speculate that the aliens wised up and cleaned up their act. Or in a darker scenario, it would serve as a warning sign of the dangers of not being good stewards of our own planet," says Loeb.

This work has been accepted for publication in The Astrophysical Journal and is available online.

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
617-495-7462
daguilar@cfa.harvard.edu

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

Source:  Harvard-Smithsonian Center for Astrophysics

New mass map of a distant galaxy cluster is the most precise yet

PR Image heic1416a

Colour image of galaxy cluster MCS J0416.1–2403

PR Image heic1416b

Colour image of galaxy cluster MCS J0416.1–2403, annotated

PR Image heic1416c

Mass map of galaxy cluster MCS J0416.1–2403 using strong and weak lensing

Stunning new observations from Frontier Fields

Astronomers using the NASA/ESA Hubble Space Telescope have mapped the mass within a galaxy cluster more precisely than ever before. Created using observations from Hubble's Frontier Fields observing programme, the map shows the amount and distribution of mass within MCS J0416.1–2403, a massive galaxy cluster found to be 160 trillion times the mass of the Sun. The detail in this mass map was made possible thanks to the unprecedented depth of data provided by new Hubble observations, and the cosmic phenomenon known as strong gravitational lensing.

Measuring the amount and distribution of mass within distant objects in the Universe can be very difficult. A trick often used by astronomers is to explore the contents of large clusters of galaxies by studying the gravitational effects they have on the light from very distant objects beyond them. This is one of the main goals of Hubble's Frontier Fields, an ambitious observing programme scanning six different galaxy clusters — including MCS J0416.1–2403, the cluster shown in this stunning new image [1].

Large clumps of mass in the Universe warp and distort the space-time around them. Acting like lenses, they appear to magnify and bend light that travels through them from more distant objects [2].

Despite their large masses, the effect of galaxy clusters on their surroundings is usually quite minimal. For the most part they cause what is known as weak lensing, making even more distant sources appear as only slightly more elliptical or smeared across the sky. However, when the cluster is large and dense enough and the alignment of cluster and distant object is just right, the effects can be more dramatic. The images of normal galaxies can be transformed into rings and sweeping arcs of light, even appearing several times within the same image. This effect is known as strong lensing, and it is this phenomenon, seen around the six galaxy clusters targeted by the Frontier Fields programme, that has been used to map the mass distribution of MCS J0416.1–2403, using the new Hubble data.

"The depth of the data lets us see very faint objects and has allowed us to identify more strongly lensed galaxies than ever before," explains Mathilde Jauzac of Durham University, UK, and Astrophysics & Cosmology Research Unit, South Africa, lead author of the new Frontier Fields paper. "Even though strong lensing magnifies the background galaxies they are still very far away and very faint. The depth of these data means that we can identify incredibly distant background galaxies. We now know of more than four times as many strongly lensed galaxies in the cluster than we did before."

Using Hubble's Advanced Camera for Surveys, the astronomers identified 51 new multiply imaged galaxies around the cluster, quadrupling the number found in previous surveys and bringing the grand total of lensed galaxies to 68. Because these galaxies are seen several times this equates to almost 200 individual strongly lensed images which can be seen across the frame. This effect has allowed Jauzac and her colleagues to calculate the distribution of visible and dark matter in the cluster and produce a highly constrained map of its mass [3].

"Although we’ve known how to map the mass of a cluster using strong lensing for more than twenty years, it’s taken a long time to get telescopes that can make sufficiently deep and sharp observations, and for our models to become sophisticated enough for us to map, in such unprecedented detail, a system as complicated as MCS J0416.1–2403," says team member Jean-Paul Kneib.

By studying 57 of the most reliably and clearly lensed galaxies, the astronomers modelled the mass of both normal and dark matter within MCS J0416.1-2403. "Our map is twice as good as any previous models of this cluster!" adds Jauzac.

The total mass within MCS J0416.1-2403 — modelled to be over 650 000 light-years across — was found to be 160 trillion times the mass of the Sun. This measurement is several times more precise than any other cluster map, and is the most precise ever produced [4]. By precisely pinpointing where the mass resides within clusters like this one, the astronomers are also measuring the warping of space-time with high precision.

"Frontier Fields' observations and gravitational lensing techniques have opened up a way to very precisely characterise distant objects — in this case a cluster so far away that its light has taken four and a half billion years to reach us," adds Jean-Paul Kneib. "But, we will not stop here. To get a full picture of the mass we need to include weak lensing measurements too. Whilst it can only give a rough estimate of the inner core mass of a cluster, weak lensing provides valuable information about the mass surrounding the cluster core."

The team will continue to study the cluster using ultra-deep Hubble imaging and detailed strong and weak lensing information to map the outer regions of the cluster as well as its inner core, and will thus be able to detect substructures in the cluster's surroundings. They will also take advantage of X-ray measurements of hot gas and spectroscopic redshifts to map the contents of the cluster, evaluating the respective contribution of dark matter, gas and stars [5].

Combining these sources of data will further enhance the detail of this mass distribution map, showing it in 3D and including the relative velocities of the galaxies within it. This paves the way to understanding the history and evolution of this galaxy cluster.

The results of the study will be published online in Monthly Notices of the Royal Astronomical Society on 24 July 2014.

Notes

[1] The cluster is also known as MACS J0416.1–2403.

[2] The warping of space-time by large objects in the Universe was one of the predictions of Albert Einstein’s theory of general relativity.

[3] Gravitational lensing is one of the few methods astronomers have to find out about dark matter. Dark matter, which makes up around three quarters of all matter in the Universe, cannot be seen directly as it does not emit or reflect any light, and can pass through other matter without friction (it is collisionless). It interacts only by gravity, and its presence must be deduced from its gravitational effects.

[4] The uncertainty on the measurement is only around 0.5%, or 1 trillion times the mass of the sun. This may not seem precise but it is for a measurement such as this.

[5] NASA's Chandra X-ray Observatory was used to obtain X-ray measurements of hot gas in the cluster and ground based observatories provide the data needed to measure spectroscopic redshifts.

Notes for editors

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The international team of astronomers in this study consists of M. Jauzac (Durham University, UK and Astrophysics & Cosmology Research Unit, South Africa); B. Clement (University of Arizona, USA); M. Limousin (Laboratoire d’Astrophysique de Marseille, France and University of Copenhagen, Denmark); J. Richard (Université Lyon, France); E. Jullo (Laboratoire d’Astrophysique de Marseille, France); H. Ebeling (University of Hawaii, USA); H. Atek (Ecole Polytechnique Fédérale de Lausanne, Switzerland); J.-P. Kneib (Ecole Polytechnique Fédérale de Lausanne, Switzerland and Laboratoire d’Astrophysique de Marseille, France); K. Knowles (University of KwaZulu-Natal, South Africa); P. Natarajan (Yale University, USA); D. Eckert (University of Geneva, Switzerland); E. Egami (University of Arizona, USA); R. Massey (Durham University, UK); and M. Rexroth (Ecole Polytechnique Fédérale de Lausanne, Switzerland).

More information

Image credit: ESA/Hubble, NASA, HST Frontier Fields

Acknowledgement: Mathilde Jauzac (Durham University, UK and Astrophysics & Cosmology Research Unit, South Africa) and Jean-Paul Kneib (École Polytechnique Fédérale de Lausanne, Switzerland)

Links

• Images of Hubble
• Paper in Monthly Notices of the Royal Astronomical Society
• Science paper
• University of Hawaii Institute for Astronomy press release

Contacts

Mathilde Jauzac
Durham University, Institute for Computational Cosmology
Durham, United Kingdom
Tel: +33 6 52 67 15 39 (France)
Cell: +44 7445 218614 (UK)
Email: mathilde.jauzac@dur.ac.uk

Jean-Paul Kneib
École Polytechnique Fédérale de Lausanne, Observatoire de Sauverny
Versoix, Switzerland
Tel: +41 22 3792473
Cell: +33 695 795 392
Email: jean-paul.kneib@epfl.ch

Eric Jullo
Laboratoire d'Astrophysique de Marseille
Marseille, France
Tel: +33 4 91 05 5951
Email: eric.jullo@lam.fr

Johan Richard
Centre de Recherche Astronomique de Lyon, Observatoire de Lyon
Lyon, France
Tel: +33 478 868 378
Email: johan.richard@univ-lyon1.fr

Georgia Bladon
ESA/Hubble, Public Information Officer
Garching bei München, Germany
Tel: +44 7816291261
Email: gbladon@partner.eso.org

Source: ESA/Hubble - Space Telescope

A slice of stars

NGC 3501

Credit: ESA/Hubble & NASA
Acknowledgement: Nick Rose

The thin, glowing streak slicing across this image cuts a lonely figure, with only a few foreground stars and galaxies in the distant background for company.

However, this is all a case of perspective; lying out of frame is another nearby spiral. Together, these two galaxies make up a pair, moving through space together and keeping one another company.

The subject of this Hubble image is called NGC 3501, with NGC 3507 as its out-of-frame companion. The two galaxies look very different — another example of the importance of perspective. NGC 3501 appears edge-on, giving it an elongated and very narrow appearance. Its partner, however, looks very different indeed, appearing face-on and giving us a fantastic view of its barred swirling arms.

While similar arms may not be visible in this image of NGC 3501, this galaxy is also a spiral — although it is somewhat different from its companion. While NGC 3507 has bars cutting through its centre, NGC 3501 does not. Instead, its loosely wound spiral arms all originate from its centre. The bright gas and stars that make up these arms can be seen here glowing brightly, mottled by the dark dust lanes that trace across the galaxy.

A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Nick Rose.

Source: ESA/Hubble - Space Telescope

Hubble Finds Three Surprisingly Dry Exoplanets

This is an artistic illustration of the gas giant planet HD 209458b (unofficially named Osiris) located 150 light-years away in the constellation Pegasus. This is a "hot Jupiter" class planet. Estimated to be 220 times the mass of Earth. The planet's atmosphere is a seething 2,150 degrees Fahrenheit. It orbits very closely to its bright sunlike star, and the orbit is tilted edge-on to Earth. This makes the planet an ideal candidate for the Hubble Space Telescope to be used to make precise measurements of the chemical composition of the giant's atmosphere as starlight filters though it. To the surprise of astronomers, they have found much less water vapor in the atmosphere than standard planet-formation models predict.  Credit: NASA, ESA, and G. Bacon (STScI)

This graph compares observations with modeled infrared spectra of three hot-Jupiter-class exoplanets that were spectroscopically observed with the Hubble Space Telescope. The red curve in each case is the best-fit model spectrum for the detection of water vapor absorption in the planetary atmosphere. The blue circles and error bars show the processed and analyzed data from Hubble's spectroscopic observations.  Credit: NASA, ESA, N. Madhusudhan (University of Cambridge), and A. Feild and G. Bacon (STScI)

Astronomers using NASA's Hubble Space Telescope have gone looking for water vapor in the atmospheres of three planets orbiting stars similar to the Sun — and have come up nearly dry.

The three planets, HD 189733b, HD 209458b, and WASP-12b, are between 60 and 900 light-years away. These giant gaseous worlds are so hot, with temperatures between 1,500 and 4,000 degrees Fahrenheit, that they are ideal candidates for detecting water vapor in their atmospheres.

However, to the surprise of the researchers, the planets surveyed have only one-tenth to one one-thousandth the amount of water predicted by standard planet-formation theories.

"Our water measurement in one of the planets, HD 209458b, is the highest-precision measurement of any chemical compound in a planet outside the solar system, and we can now say with much greater certainty than ever before that we've found water in an exoplanet," said Dr. Nikku Madhusudhan of the Institute of Astronomy at the University of Cambridge, United Kingdom, who led the research. "However, the low water abundance we are finding is quite astonishing."

Madhusudhan said that this finding presents a major challenge to exoplanet theory. "It basically opens a whole can of worms in planet formation. We expected all these planets to have lots of water in them. We have to revisit planet formation and migration models of giant planets, especially 'hot Jupiters', and investigate how they're formed."

He emphasizes that these results, though found in these large hot planets close to their parent stars, may have major implications for the search for water in potentially habitable Earth-sized exoplanets. Instruments on future space telescopes may need to be designed with a higher sensitivity if target planets are drier than predicted. "We should be prepared for much lower water abundances than predicted when looking at super-Earths (rocky planets that are several times the mass of Earth)," Madhusudhan said.

Using near-infrared spectra of the planets observed with Hubble, Madhusudhan and his collaborators from the Space Telescope Science Institute, Baltimore, Maryland; the University of Maryland, College Park, Maryland; the Johns Hopkins University, Baltimore, Maryland; and the Dunlap Institute at the University of Toronto, Ontario, Canada, estimated the amount of water vapor in the planetary atmospheres based on sophisticated computer models and statistical techniques to explain the data.

The planets were selected because they orbit relatively bright stars that provide enough radiation for an infrared-light spectrum to be taken. Absorption features from the water vapor in the planet's atmosphere are superimposed on the small amount of starlight that glances through the planet's atmosphere.

Detecting water is almost impossible for transiting planets from the ground because Earth's atmosphere has a lot of water in it that contaminates the observation. "We really need the Hubble Space Telescope to make such observations," said Nicolas Crouzet of the Dunlap Institute at the University of Toronto and co-author of the study.

The currently accepted theory on how giant planets in our solar system formed is known as core accretion, in which a planet is formed around the young star in a protoplanetary disk made primarily of hydrogen, helium, and particles of ices and dust composed of other chemical elements. The dust particles stick to each other, eventually forming larger and larger grains. The gravitational forces of the disk draw in these grains and larger particles until a solid core forms. This core then leads to runaway accretion of both solids and gas to eventually form a giant planet.

This theory predicts that the proportions of the different elements in the planet are enhanced relative to those in their star, especially oxygen that is supposed to be the most enhanced. Once the giant planet forms, its atmospheric oxygen is expected to be largely encompassed within water molecules. The very low levels of water vapor found by this research raises a number of questions about the chemical ingredients that lead to planet formation, say researchers.

"There are so many things we still don't know about exoplanets, so this opens up a new chapter in understanding how planets and solar systems form," said Drake Deming of the University of Maryland, who led one of the precursor studies. "The problem is that we are assuming the water to be as abundant as in our own solar system. What our study has shown is that water features could be a lot weaker than our expectations."

The findings are being published on July 24 in The Astrophysical Journal Letters.

CONTACT

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu

Nikku Madhusudhan
Institute of Astronomy, University of Cambridge, United Kingdom
617-475-5112 (or 011-44-01223-766619)
nmadhu@ast.cam.ac.uk

Source: HubbleSite

The Most Precise Measurement of an Alien World's Size

Using data from NASA's Kepler and Spitzer Space Telescopes, scientists have made the most precise measurement ever of the size of a world outside our solar system, as illustrated in this artist's conception. Image Credit: NASA/JPL-Caltech.  Full image and caption

 

Thanks to NASA's Kepler and Spitzer Space Telescopes, scientists have made the most precise measurement ever of the radius of a planet outside our solar system. The size of the exoplanet, dubbed Kepler-93b, is now known to an uncertainty of just 74 miles (119 kilometers) on either side of the planetary body.

The findings confirm Kepler-93b as a "super-Earth" that is about one-and-a-half times the size of our planet. Although super-Earths are common in the galaxy, none exist in our solar system. Exoplanets like Kepler-93b are therefore our only laboratories to study this major class of planet.

With good limits on the sizes and masses of super-Earths, scientists can finally start to theorize about what makes up these weird worlds. Previous measurements, by the Keck Observatory in Hawaii, had put Kepler-93b's mass at about 3.8 times that of Earth. The density of Kepler-93b, derived from its mass and newly obtained radius, indicates the planet is in fact very likely made of iron and rock, like Earth. 

"With Kepler and Spitzer, we've captured the most precise measurement to date of an alien planet's size, which is critical for understanding these far-off worlds," said Sarah Ballard, a NASA Carl Sagan Fellow at the University of Washington in Seattle and lead author of a paper on the findings published in the Astrophysical Journal.

"The measurement is so precise that it's literally like being able to measure the height of a six-foot tall person to within three quarters of an inch -- if that person were standing on Jupiter," said Ballard.

Kepler-93b orbits a star located about 300 light-years away, with approximately 90 percent of the sun's mass and radius. The exoplanet's orbital distance -- only about one-sixth that of Mercury's from the sun -- implies a scorching surface temperature around 1,400 degrees Fahrenheit (760 degrees Celsius). Despite its newfound similarities in composition to Earth, Kepler-93b is far too hot for life.  

To make the key measurement about this toasty exoplanet's radius, the Kepler and Spitzer telescopes each watched Kepler-93b cross, or transit, the face of its star, eclipsing a tiny portion of starlight. Kepler's unflinching gaze also simultaneously tracked the dimming of the star caused by seismic waves moving within its interior. These readings encode precise information about the star's interior. The team leveraged them to narrowly gauge the star's radius, which is crucial for measuring the planetary radius.

Spitzer, meanwhile, confirmed that the exoplanet's transit looked the same in infrared light as in Kepler's visible-light observations. These corroborating data from Spitzer -- some of which were gathered in a new, precision observing mode -- ruled out the possibility that Kepler's detection of the exoplanet was bogus, or a so-called false positive.

Taken together, the data boast an error bar of just one percent of the radius of Kepler-93b. The measurements mean that the planet, estimated at about 11,700 miles (18,800 kilometers) in diameter, could be bigger or smaller by about 150 miles (240 kilometers), the approximate distance between Washington, D.C., and Philadelphia.

Spitzer racked up a total of seven transits of Kepler-93b between 2010 and 2011. Three of the transits were snapped using a "peak-up" observational technique. In 2011, Spitzer engineers repurposed the spacecraft's peak-up camera, originally used to point the telescope precisely, to control where light lands on individual pixels within Spitzer's infrared camera.

The upshot of this rejiggering: Ballard and her colleagues were able to cut in half the range of uncertainty of the Spitzer measurements of the exoplanet radius, improving the agreement between the Spitzer and Kepler measurements.

"Ballard and her team have made a major scientific advance while demonstrating the power of Spitzer's new approach to exoplanet observations," said Michael Werner, project scientist for the Spitzer Space Telescope at NASA's Jet Propulsion Laboratory, Pasadena, California.

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

NASA's Ames Research Center in Moffett Field, California, is responsible for Kepler's ground system development, mission operations and science data analysis. JPL managed Kepler mission development. Ball Aerospace & Technologies Corp. in Boulder, Colorado, developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and was funded by the agency's Science Mission Directorate.

For more information about the Kepler mission, visit:

• http://www.nasa.gov/kepler

For more information about Spitzer, visit:

• http://spitzer.caltech.edu

• http://www.nasa.gov/spitzer

Whitney Clavin
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-4673
whitney.clavin@jpl.nasa.gov