Saturday, October 25, 2014

Galactic Wheel of Life Shines in Infrared

A new image from NASA's Spitzer Space Telescope, taken in infrared light, shows where the action is taking place in galaxy NGC 1291. 
Image credit: NASA/JPL-Caltech.  › Full image and caption

It might look like a spoked wheel or even a "Chakram" weapon wielded by warriors like "Xena," from the fictional TV show, but this ringed galaxy is actually a vast place of stellar life. A newly released image from NASA's Spitzer Space Telescope shows the galaxy NGC 1291. Though the galaxy is quite old, roughly 12 billion years, it is marked by an unusual ring where newborn stars are igniting. 

"The rest of the galaxy is done maturing," said Kartik Sheth of the National Radio Astronomy Observatory of Charlottesville, Virginia. "But the outer ring is just now starting to light up with stars."

NGC 1291 is located about 33 million light-years away in the constellation Eridanus. It is what's known as a barred galaxy, because its central region is dominated by a long bar of stars (in the new image, the bar is within the blue circle and looks like the letter "S"). 

The bar formed early in the history of the galaxy. It churns material around, forcing stars and gas from their original circular orbits into large, non-circular, radial orbits. This creates resonances -- areas where gas is compressed and triggered to form new stars. Our own Milky Way galaxy has a bar, though not as prominent as the one in NGC 1291.

Sheth and his colleagues are busy trying to better understand how bars of stars like these shape the destinies of galaxies. In a program called Spitzer Survey of Stellar Structure in Galaxies, or S4G, Sheth and his team of scientists are analyzing the structures of more than 3,000 galaxies in our local neighborhood. The farthest galaxy of the bunch lies about 120 million light-years away -- practically a stone's throw in comparison to the vastness of space. 

The astronomers are documenting structural features, including bars. They want to know how many of the local galaxies have bars, as well as the environmental conditions in a galaxy that might influence the formation and structure of bars.

"Now, with Spitzer we can measure the precise shape and distribution of matter within the bar structures," said Sheth. "The bars are a natural product of cosmic evolution, and they are part of the galaxies' endoskeleton. Examining this endoskeleton for the fossilized clues to their past gives us a unique view of their evolution."

In the Spitzer image, shorter-wavelength infrared light has been assigned the color blue, and longer-wavelength light, red. The stars that appear blue in the central, bulge region of the galaxy are older; most of the gas, or star-making fuel, there was previously used up by earlier generations of stars. When galaxies are young and gas-rich, stellar bars drive gas toward the center, feeding star formation. 

Over time, as the fuel runs out, the central regions become quiescent and star-formation activity shifts to the outskirts of a galaxy. There, spiral density waves and resonances induced by the central bar help convert gas to stars. The outer ring, seen here in red, is one such resonance area, where gas has been trapped and ignited into star-forming frenzy.

NASA's Jet Propulsion Laboratory, Pasadena, California, 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. 

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


Media Contact
 
Whitney Clavin
818-354-4673
Jet Propulsion Laboratory, Pasadena, California

whitney.clavin@jpl.nasa.gov

Source:  JPL - Caltech


Friday, October 24, 2014

The whirling disc of NGC 4526

Credit: ESA/Hubble & NASA
Acknowledgement: Judy Schmidt

This neat little galaxy is known as NGC 4526. Its dark lanes of dust and bright diffuse glow make the galaxy appear to hang like a halo in the emptiness of space in this new image from the NASA/ESA Hubble Space Telescope.

Although this image paints a picture of serenity, the galaxy is anything but. It is one of the brightest lenticular galaxies known, a category that lies somewhere between spirals and ellipticals. It has hosted two known supernova explosions, one in 1969 and another in 1994, and is known to have a colossal supermassive black hole at its centre that has the mass of 450 million Suns.

NGC 4526 is part of the Virgo cluster of galaxies. Ground-based observations of galaxies in this cluster have revealed that a quarter of these galaxies seem to have rapidly rotating discs of gas at their centres. The most spectacular of these is this galaxy, NGC 4526, whose spinning disc of gas, dust, and stars reaches out uniquely far from its heart, spanning some 7% of the galaxy's entire radius.

This disc is moving incredibly fast, spinning at more than 250 kilometres per second. The dynamics of this quickly whirling region were actually used to infer the mass of NGC 4526’s central black hole — a technique that had not been used before to constrain a galaxy’s central black hole.

This image was taken using Hubble’s Wide Field Planetary Camera 2. 

A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt. Hidden Treasures was an initiative to invite astronomy enthusiasts to search the Hubble archive for stunning images that have never been seen by the general public.


Source:  ESA/Hubble  - Space Telescope

Thursday, October 23, 2014

NASA-led Study Sees Titan Glowing at Dusk and Dawn

High in the atmosphere of Titan, large patches of two trace gases glow near the north pole, on the dusk side of the moon, and near the south pole, on the dawn side. Brighter colors indicate stronger signals from the two gases, HNC (left) and HC3N (right); red hues indicate less pronounced signals.Image Credit:  NRAO/AUI/NSF

New maps of Saturn’s moon Titan reveal large patches of trace gases shining brightly near the north and south poles. These regions are curiously shifted off the poles, to the east or west, so that dawn is breaking over the southern region while dusk is falling over the northern one.
The pair of patches was spotted by a NASA-led international team of researchers investigating the chemical make-up of Titan’s atmosphere.

“This is an unexpected and potentially groundbreaking discovery,” said Martin Cordiner, an astrochemist working at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the lead author of the study. “These kinds of east-to-west variations have never been seen before in Titan’s atmospheric gases. Explaining their origin presents us with a fascinating new problem.”

The mapping comes from observations made by the Atacama Large Millimeter/submillimeter Array (ALMA), a network of high-precision antennas in Chile. At the wavelengths used by these antennas, the gas-rich areas in Titan’s atmosphere glowed brightly. And because of ALMA’s sensitivity, the researchers were able to obtain spatial maps of chemicals in Titan’s atmosphere from a “snapshot” observation that lasted less than three minutes.

Titan’s atmosphere has long been of interest because it acts as a chemical factory, using energy from the sun and Saturn’s magnetic field to produce a wide range of organic, or carbon-based, molecules. Studying this complex chemistry may provide insights into the properties of Earth’s very early atmosphere, which may have shared many chemical characteristics with present-day Titan.

In this study, the researchers focused on two organic molecules, hydrogen isocyanide (HNC) and cyanoacetylene (HC3N), that are formed in Titan’s atmosphere. At lower altitudes, the two molecules appear concentrated above Titan’s north and south poles. These findings are consistent with observations made by NASA’s Cassini spacecraft, which has found a cloud cap and high concentrations of some gases over whichever pole is experiencing winter on Titan.

The surprise came when the researchers compared the gas concentrations at different levels in the atmosphere. At the highest altitudes, the gas pockets appeared to be shifted away from the poles. These off-pole locations are unexpected because the fast-moving winds in Titan’s middle atmosphere move in an east–west direction, forming zones similar to Jupiter’s bands, though much less pronounced. Within each zone, the atmospheric gases should, for the most part, be thoroughly mixed.

The researchers do not have an obvious explanation for these findings yet.

“It seems incredible that chemical mechanisms could be operating on rapid enough timescales to cause enhanced ‘pocket’' in the observed molecules,” said Conor Nixon, a planetary scientist at Goddard and a coauthor of the paper, published online today in the Astrophysical Journal Letters. “We would expect the molecules to be quickly mixed around the globe by Titan’s winds.”

At the moment, the scientists are considering a number of potential explanations, including thermal effects, previously unknown patterns of atmospheric circulation, or the influence of Saturn’s powerful magnetic field, which extends far enough to engulf Titan.

Further observations are expected to improve the understanding of the atmosphere and ongoing processes on Titan and other objects throughout the solar system.

NASA’s Astrobiology Program supported this work through a grant to the Goddard Center for Astrobiology, a part of the NASA Astrobiology Institute. Additional funding came from NASA’s Planetary Atmospheres and Planetary Astronomy programs. ALMA, an international astronomy facility, is funded in Europe by the European Southern Observatory, in North America by the U.S. National Science Foundation in cooperation with the National Research Council of Canada and the National Science Council of Taiwan, and in East Asia by the National Institutes of Natural Sciences of Japan in cooperation with the Academia Sinica in Taiwan.



Nancy Neal-Jones/Elizabeth Zubritsky
Goddard Space Flight Center, Greenbelt, Md.
301-286-0039/301-614-5438
nancy.n.jones@nasa.gov/elizabeth.a.zubritsky@nasa.gov


Two Families of Comets Found Around Nearby Star

Artist’s impression of exocomets around Beta Pictoris

Beta Pictoris as Seen in Infrared Light

Exoplanet caught on the move

Around Beta Pictoris 

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 Videos


Artist’s impression of exocomets around Beta Pictoris
Artist’s impression of exocomets around Beta Pictoris 


Biggest census ever of exocomets around Beta Pictoris

The HARPS instrument at ESO’s La Silla Observatory in Chile has been used to make the most complete census of comets around another star ever created. A French team of astronomers has studied nearly 500 individual comets orbiting the star Beta Pictoris and has discovered that they belong to two distinct families of exocomets: old exocomets that have made multiple passages near the star, and younger exocomets that probably came from the recent breakup of one or more larger objects. The new results will appear in the journal Nature on 23 October 2014.

Beta Pictoris is a young star located about 63 light-years from the Sun. It is only about 20 million years old and is surrounded by a huge disc of material — a very active young planetary system where gas and dust are produced by the evaporation of comets and the collisions of asteroids.

Flavien Kiefer (IAP/CNRS/UPMC), lead author of the new study sets the scene: “Beta Pictoris is a very exciting target! The detailed observations of its exocomets give us clues to help understand what processes occur in this kind of young planetary system.”

For almost 30 years astronomers have seen subtle changes in the light from Beta Pictoris that were thought to be caused by the passage of comets in front of the star itself. Comets are small bodies of a few kilometres in size, but they are rich in ices, which evaporate when they approach their star, producing gigantic tails of gas and dust that can absorb some of the light passing through them. The dim light from the exocomets is swamped by the light of the brilliant star so they cannot be imaged directly from Earth.

To study the Beta Pictoris exocomets, the team analysed more than 1000 observations obtained between 2003 and 2011 with the HARPS instrument on the ESO 3.6-metre telescope at the La Silla Observatory in Chile.

The researchers selected a sample of 493 different exocomets. Some exocomets were observed several times and for a few hours. Careful analysis provided measurements of the speed and the size of the gas clouds. Some of the orbital properties of each of these exocomets, such as the shape and the orientation of the orbit and the distance to the star, could also be deduced.

This analysis of several hundreds of exocomets in a single exo-planetary system is unique. It revealed the presence of two distinct families of exocomets: one family of old exocomets whose orbits are controlled by a massive planet [1], and another family, probably arising from the recent breakdown of one or a few bigger objects. Different families of comets also exist in the Solar System.

The exocomets of the first family have a variety of orbits and show a rather weak activity with low production rates of gas and dust. This suggests that these comets have exhausted their supplies of ices during their multiple passages close to Beta Pictoris [2].

The exocomets of the second family are much more active and are also on nearly identical orbits [3]. This suggests that the members of the second family all arise from the same origin: probably the breakdown of a larger object whose fragments are on an orbit grazing the star Beta Pictoris.

Flavien Kiefer concludes: “For the first time a statistical study has determined the physics and orbits for a large number of exocomets. This work provides a remarkable look at the mechanisms that were at work in the Solar System just after its formation 4.5 billion years ago.”

 

Notes


[1] A giant planet, Beta Pictoris b, has also been discovered in orbit at about a billion kilometres from the star and studied using high resolution images obtained with adaptive optics.

[2] Moreover, the orbits of these comets (eccentricity and orientation) are exactly as predicted for comets trapped in orbital resonance with a massive planet. The properties of the comets of the first family show that this planet in resonance must be at about 700 million kilometres from the star  — close to where the planet Beta Pictoris b was discovered.

[3] This makes them similar to the comets of the Kreutz family in the Solar System, or the fragments of Comet Shoemaker-Levy 9, which impacted Jupiter in July 1994.

 

More information


This research was presented in a paper entitled "Two families of exocomets in the Beta Pictoris system" which will be published in the journal Nature on 23 October 2014.


The team is composed of F. Kiefer (Institut d’astrophysique de Paris [IAP], CNRS, Université Pierre & Marie Curie-Paris 6, Paris, France), A. Lecavelier des Etangs (IAP), J. Boissier (Institut de radioastronomie millimétrique, Saint Martin d’Hères, France), A. Vidal-Madjar (IAP), H. Beust (Institut de planétologie et d'astrophysique de Grenoble [IPAG], CNRS, Université Joseph Fourier-Grenoble 1, Grenoble, France), A.-M. Lagrange (IPAG), G. Hébrard (IAP) and R. Ferlet (IAP).

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

 

Contacts

 
Alain Lecavelier des Etangs
Institut d'astrophysique de Paris (IAP)/CNRS/UPMC
France
Tel: +33-1-44-32-80-77
Cell: +33 6 21 75 12 03
Email:
lecaveli@iap.fr

Flavien Kiefer
Institut d'astrophysique de Paris (IAP)/CNRS/UPMC and School of Physics and Astronomy, Tel Aviv University
France / Israel
Tel: +972-502-838-163
Email:
kiefer@iap.fr

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

Source: ESO

Wednesday, October 22, 2014

NASA's Fermi Satellite Finds Hints of Starquakes in Magnetar 'Storm'

NASA's Fermi Gamma-ray Space Telescope detected a rapid-fire "storm" of high-energy blasts from a highly magnetized neutron star, also called a magnetar, on Jan. 22, 2009. Now astronomers analyzing this data have discovered underlying signals related to seismic waves rippling throughout the magnetar.

A rupture in the crust of a highly magnetized neutron star, shown here in an artist's rendering, can trigger high-energy eruptions. Fermi observations of these blasts include information on how the star's surface twists and vibrates, providing new insights into what lies beneath. Image Credit: NASA's Goddard Space Flight Center/S. Wiessinger. Related multimedia from NASA Goddard's Scientific Visualization Studio

Such signals were first identified during the fadeout of rare giant flares produced by magnetars. Over the past 40 years, giant flares have been observed just three times -- in 1979, 1998 and 2004 -- and signals related to starquakes, which set the neutron stars ringing like a bell, were identified only in the two most recent events.

"Fermi's Gamma-ray Burst Monitor (GBM) has captured the same evidence from smaller and much more frequent eruptions called bursts, opening up the potential for a wealth of new data to help us understand how neutron stars are put together," said Anna Watts, an astrophysicist at the University of Amsterdam in the Netherlands and co-author of a new study about the burst storm. "It turns out that Fermi's GBM is the perfect tool for this work."

In the midst of SGR J1550-5418's 2009 burst storm, Swift's X-Ray Telescope captured an expanding halo produced by the magnetar's brightest bursts. The rings formed as X-rays from the brightest bursts scattered off of intervening dust clouds. Clouds closer to Earth produced larger rings. Image Credit: NASA/Swift/Jules Halpern, Columbia University. Download this video in additional formats from NASA Goddard's Scientific Visualization Studio

This image of NASA's Fermi Gamma-ray Space Telescope, shown here in May 2008 being readied for launch, highlights the spacecraft's instruments. The Gamma-ray Burst Monitor (GBM) is an array of 14 crystal detectors sensitive to short-lived gamma-ray blasts. Image Credit: NASA/Jim Grossmann. Unlabeled image

Neutron stars are the densest, most magnetic and fastest-spinning objects in the universe that scientists can observe directly. Each one is the crushed core of a massive star that ran out of fuel, collapsed under its own weight, and exploded as a supernova. A neutron star packs the equivalent mass of half-a-million Earths into a sphere about 12 miles across, roughly the length of Manhattan Island in New York City.

While typical neutron stars possess magnetic fields trillions of times stronger than Earth's, the eruptive activity observed from magnetars requires fields 1,000 times stronger still. To date, astronomers have confirmed only 23 magnetars.

Because a neutron star's solid crust is locked to its intense magnetic field, a disruption of one immediately affects the other. A fracture in the crust will lead to a reshuffling of the magnetic field, or a sudden reorganization of the magnetic field may instead crack the surface. Either way, the changes trigger a sudden release of stored energy via powerful bursts that vibrate the crust, a motion that becomes imprinted on the burst’s gamma-ray and X-ray signals.

It takes an incredible amount of energy to convulse a neutron star. The closest comparison on Earth is the 9.5-magnitude Chilean earthquake of 1960, which ranks as the most powerful ever recorded on the standard scale used by seismologists. On that scale, said Watts, a starquake associated with a magnetar giant flare would reach magnitude 23.

The 2009 burst storm came from SGR J1550−5418, an object discovered by NASA's Einstein Observatory, which operated from 1978 to 1981. Located about 15,000 light-years away in the constellation Norma, the magnetar was quiet until October 2008, when it entered a period of eruptive activity that ended in April 2009. At times, the object produced hundreds of bursts in as little as 20 minutes, and the most intense explosions emitted more total energy than the sun does in 20 years. High-energy instruments on many spacecraft, including NASA's Swift and Rossi X-ray Timing Explorer, detected hundreds of gamma-ray and X-ray blasts.

Speaking at the Fifth Fermi International Symposium in Nagoya, Japan, on Oct. 21, Watts said the new study examined 263 individual bursts detected by Fermi's GBM and confirms vibrations in the frequency ranges previously seen in giant flares. "We think these are likely twisting oscillations of the star where the crust and the core, bound by the super-strong magnetic field, are vibrating together," she explained. "We also found, in a single burst, an oscillation at a frequency never seen before and which we still do not understand."

A key element of the research is a new analysis technique developed by University of Amsterdam researcher Daniela Huppenkothen. Normally scientists search for oscillations in high-energy data by looking for variations aligned to a particular frequency. Such methods are best suited for finding a strong signal with little competition rather than a faint signal immersed in a bright and rapidly changing environment, such as a burst.

Huppenkothen likens the problem to detecting ripples from a stone tossed into a quiet pond. "Now imagine you're in the middle of the North Atlantic during a storm, searching for those ripples amidst huge waves in a churning sea," she explained. "Our old methods really weren't appropriate for this, but I have in effect developed a way of accounting for the rough sea so we can find ripples even in stormy conditions." 

A paper describing the research, which was led by Huppenkothen, appeared in the June 1 edition of The Astrophysical Journal.

While there are many efforts to describe the interiors of neutron stars, scientists lack enough observational detail to choose between differing models. Neutron stars reach densities far beyond the reach of laboratories and their interiors may exceed the density of an atomic nucleus by as much as 10 times. Knowing more about how bursts shake up these stars will give theorists an important new window into understanding their internal structure.

"Right now," added Watts, "we are waiting for more bursts -- and if we're lucky, a giant flare -- to take advantage of GBM's excellent capabilities."


Related Links

Chandra Archive Collection: Chandra's Archives Come to Life

Chandra Archive Collection
Credit NASA/CXC/SAO 
Instrument: ACIS 


JPEG (293.8 kb) - Large JPEG (2.2 MB) - More Images
(23 Out 13)


Every year, NASA's Chandra X-ray Observatory looks at hundreds of objects throughout space to help expand our understanding of the Universe. Ultimately, these data are stored in the Chandra Data Archive, an electronic repository that provides access to these unique X-ray findings for anyone who would like to explore them. With the passing of Chandra's 15th anniversary in operation on August 26, 1999, the archive continues to grow as each successive year adds to the enormous and invaluable dataset.

To celebrate Chandra's decade and a half in space, and to honor October as American Archives Month, a variety of objects have been selected from Chandra's archive. Each of the new images we have produced combines Chandra data with those from other telescopes. This technique of creating "multiwavelength" images allows scientists and the public to see how X-rays fit with data of other types of light, such as optical, radio, and infrared. As scientists continue to make new discoveries with the telescope, the burgeoning archive will allow us to see the high-energy Universe as only Chandra can. 

PSR B1509-58
PSR B1509-58 (upper left)
Pareidolia is the psychological phenomenon where people see recognizable shapes in clouds, rock formations, or otherwise unrelated objects or data. When Chandra's image of PSR B1509-58, a spinning neutron star surrounded by a cloud of energetic particles, was released in 2009, it quickly gained attention because many saw a hand-like structure in the X-ray emission. In this new image of the system, X-rays from Chandra in gold are seen along with infrared data from NASA's Wide-field Infrared Survey Explorer (WISE) telescope in red, green, and blue. Pareidolia may strike again in this image as some people report seeing a shape of a face in WISE's infrared data.

RCW 38
RCW 38 (upper right)
A young star cluster about 5,500 light years from Earth, RCW 38 provides astronomers a chance to closely examine many young, rapidly evolving stars at once. In this composite image, X-rays from Chandra are blue, while infrared data from NASA's Spitzer Space Telescope are orange and additional infrared data from the 2MASS survey appears white. There are many massive stars in RCW 38 that will likely explode as supernovas. Astronomers studying RCW 38 are hoping to better understand this environment as our Sun was likely born into a similar stellar nursery.

Hercules A
Hercules A (middle left):
Some galaxies have extremely bright cores, suggesting that they contain a supermassive black hole that is pulling in matter at a prodigious rate. Astronomers call these "active galaxies," and Hercules A is one of them. In visible light (colored red, green and blue, with most objects appearing white), Hercules A looks like a typical elliptical galaxy. In X-ray light, however, Chandra detects a giant cloud of multimillion-degree gas (purple). This gas has been heated by energy generated by the infall of matter into a black hole at the center of Hercules A that is over 1,000 times as massive as the one in the middle of the Milky Way. Radio data (blue) show jets of particles streaming away from the black hole. The jets span a length of almost one million light years.

Kes 73
Kes 73 (middle right):
The supernova remnant Kes 73, located about 28,000 light years away, contains a so-called anomalous X-ray pulsar, or AXP, at its center. Astronomers think that most AXPs are magnetars, which are neutron stars with ultra-high magnetic fields. Surrounding the point-like AXP in the middle, Kes 73 has an expanding shell of debris from the supernova explosion that occurred between about 750 and 2100 years ago, as seen from Earth. The Chandra data (blue) reveal clumpy structures along one side of the remnant, and appear to overlap with infrared data (orange). The X-rays partially fill the shell seen in radio emission (red) by the Very Large Array. Data from the Digitized Sky Survey optical telescope (white) show stars in the field-of-view.

Mrk 573
Mrk 573 (lower left):
Markarian 573 is an active galaxy that has two cones of emission streaming away from the supermassive black hole at its center. Several lines of evidence suggest that a torus, or doughnut of cool gas and dust may block some of the radiation produced by matter falling into supermassive black holes, depending on how the torus is oriented toward Earth. Chandra data of Markarian 573 suggest that its torus may not be completely solid, but rather may be clumpy. This composite image shows overlap between X-rays from Chandra (blue), radio emission from the VLA (purple), and optical data from Hubble (gold).

NGC 4736
NGC 4736 (lower right):
NGC 4736 (also known as Messier 94) is a spiral galaxy that is unusual because it has two ring structures. This galaxy is classified as containing a "low ionization nuclear emission region," or LINER, in its center, which produces radiation from specific elements such as oxygen and nitrogen. Chandra observations (gold) of NGC 4736, seen in this composite image with infrared data from Spitzer (red) and optical data from Hubble and the Sloan Digital Sky Survey (blue), suggest that the X-ray emission comes from a recent burst of star formation. Part of the evidence comes from the large number of point sources near the center of the galaxy, showing that strong star formation has occurred. In other galaxies, evidence points to supermassive black holes being responsible for LINER properties. Chandra's result on NGC 4736 shows LINERs may represent more than one physical phenomenon.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington, DC. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.




Tuesday, October 21, 2014

Tiny "Nanoflares" Might Heat the Sun's Corona

A solar flare occurs when a patch of the Sun brightens dramatically at all wavelengths of light. During flares, solar plasma is heated to tens of millions of degrees in a matter of seconds or minutes. Flares also can accelerate electrons (and protons) from the solar plasma to a large fraction of the speed of light. These high-energy electrons can have a significant impact when they reach Earth, causing spectacular aurorae but also disrupting communications, affecting GPS signals, and damaging power grids.

Those speedy electrons also can be generated by scaled-down versions of flares called nanoflares, which are about a billion times less energetic than regular solar flares. "These nanoflares, as well as the energetic particles possibly associated with them, are difficult to study because we can't observe them directly," says Testa.

Testa and her colleagues have found that IRIS provides a new way to observe the telltale signs of nanoflares by looking at the footpoints of coronal loops. As the name suggests, coronal loops are loops of hot plasma that extend from the Sun's surface out into the corona and glow brightly in ultraviolet and X-rays.

IRIS does not observe the hottest coronal plasma in these loops, which can reach temperatures of several million degrees. Instead, it detects the ultraviolet emission from the cooler plasma (~18,000 to 180,000 degrees Fahrenheit) at their footpoints. Even if IRIS can't observe the coronal heating events directly, it reveals the traces of those events when they show up as short-lived, small-scale brightenings at the footpoints of the loops.

The team inferred the presence of high-energy electrons using IRIS high-resolution ultraviolet imaging and spectroscopic observations of those footpoint brightenings. Using computer simulations, they modeled the response of the plasma confined in loops to the energy transported by energetic electrons. The simulations revealed that energy likely was deposited by electrons traveling at about 20 percent of the speed of light.

The high spatial, temporal, and spectral resolution of IRIS was crucial to the discovery. IRIS can resolve solar features only 150 miles in size, has a temporal resolution of a few seconds, and has a spectral resolution capable of measuring plasma flows of a few miles per second.

Finding high-energy electrons that aren't associated with large flares suggests that the solar corona is, at least partly, heated by nanoflares. The new observations, combined with computer modeling, also help astronomers to understand how electrons are accelerated to such high speeds and energies - a process that plays a major role in a wide range of astrophysical phenomena from cosmic rays to supernova remnants. 

These findings also indicate that nanoflares are powerful, natural particle accelerators despite having energies about a billion times lower than large solar flares.

"As usual for science, this work opens up an entirely new set of questions. For example, how frequent are nanoflares? How common are energetic particles in the non-flaring corona? How different are the physical processes at work in these nanoflares compared to larger flares?" says Testa.

The paper reporting this research is part of a special issue of the journal Science focusing on IRIS discoveries.

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




Monday, October 20, 2014

'CT Scan' of Distant Universe Reveals Cosmic Web in 3D

Figure 1: 3D map of the cosmic web at a distance of 10.8 billion light years from Earth. The map was generated from imprints of hydrogen gas observed in the spectrum of 24 background galaxies, which are located behind the volume being mapped. This is the first time that large-scale structures in such a distant part of the Universe have been mapped directly. The coloring represents the density of hydrogen gas tracing the cosmic web, with brighter colors representing higher density. Credit: Casey Stark (UC Berkeley) and Khee-Gan Lee (MPIA).  Larger version for download

Figure 2: Close-up of 3D map of the distant Universe created by MPIA and UC astronomers. The filamentary structures seen in this map span distances of millions of light years, and represent the cosmic web at an earlier stage of cosmic evolution when the Universe was less than a quarter of its current age. The region of space seen here is at a distance of 10.8 billion years from Earth. The coloring represents the density of hydrogen gas tracing the cosmic web, with brighter colors representing higher density. The coloring represents the density of hydrogen gas tracing the cosmic web, with brighter colors representing higher density. Credit: Casey Stark (UC Berkeley) and Khee-Gan Lee (MPIA).  Larger version for download

Figure 3: Artist's impression illustrating the technique of Lyman-alpha tomography: as light from distant background galaxies (yellow arrows) travels through the Universe towards Earth, hydrogen gas in the foreground leaves a characteristic imprint ("absorption signature"). From this imprint, astronomers can reconstruct which clouds the light has encountered as it traverses the "cosmic web" of dark matter and gas that accounts for the biggest structures in our universe. By observing a number of background galaxies in a small patch of the sky, astronomers were able to create a 3D map of the cosmic web using a technique similar to medical computer tomography (CT) scans. The coloring represents the density of hydrogen gas tracing the cosmic web, with brighter colors representing higher density. The rendition of the cosmic web in this image is based on a supercomputer simulation of cosmic structure formation.  Credit: Khee-Gan Lee (MPIA) and Casey Stark (UC Berkeley).  Larger version for download

Figure 4: 3D map of the cosmic web at a distance of 10.8 billion years from Earth. The map was generated from imprints of hydrogen gas observed in the spectrum of 24 background galaxies, which are located behind the volume being mapped. This is the first time that large-scale structures in such a distant part of the Universe have been mapped directly. The coloring represents the density of hydrogen gas tracing the cosmic web, with brighter colors representing higher density.   Credit: Casey Stark (UC Berkeley) and Khee-Gan Lee (MPIA)

On the largest scales, matter in the Universe is arranged in a vast network of filamentary structures known as the 'cosmic web', its tangled strands spanning hundreds of millions of light years. Dark matter, which emits no light, forms the backbone of this web, which is also suffused with primordial hydrogen gas left over from the Big Bang. Galaxies like our own Milky Way are embedded inside this web, but fill only a tiny fraction of its volume.

Now a team of astronomers led by Khee-Gan Lee, a post-doc at the Max Planck Institute for Astronomy, has managed to create a three-dimensional map of a large region of the far-flung cosmic web nearly 11 billion light years away, when the Universe was just a quarter of its current age. Similar to a medical CT scan, which reconstructs a three-dimensional image of the human body from the X-rays passing through a patient, Lee and his colleagues reconstructed their map from the light of distant background galaxies passing through the cosmic web's hydrogen gas.

The use of the combined starlight of background galaxies for this purpose had been thought to be impossible with current telescopes – until Lee carried out calculations that suggested otherwise. Lee says: "I was surprised to find that existing large telescopes should already be able to collect sufficient light from these faint galaxies to map the foreground absorption, albeit at a lower resolution than would be feasible with future telescopes. Still, this would provide an unprecedented view of the cosmic web which has never been mapped at such vast distances."

Lee and his colleagues obtained observing time on one of the largest telescopes in the world: the 10m-diameter Keck I telescope at the W. M. Keck Observatory on Mauna Kea, Hawaii – but were plagued by a problem more terrestrial than cosmic. "We were pretty disappointed as the weather was terrible and we only managed to collect a few hours of good data. But judging by the data quality as it came off the telescope, it was already clear to me that the experiment was going to work," says Joseph Hennawi (MPIA), who was part of the observing team.

Although the astronomers only observed for 4 hours, the data they collected was completely unprecedented. Their absorption measurements using 24 faint background galaxies provided sufficient coverage of a small patch of the sky to be combined into a 3D map of the foreground cosmic web. A crucial element was the computer algorithm used to create the 3D map: due to the large amount of data, a naïve implementation of the map-making procedure would have required an inordinate amount of computing time. Fortunately, team members Casey Stark and Martin White (UC Berkeley and Lawrence Berkeley National Lab) devised a new fast algorithm that could create the map within minutes. "We realized we could simplify the computations by tailoring them to this particular problem, and thus use much less memory. A calculation that previously required a supercomputer now runs on a laptop", says Stark.

The resulting map of hydrogen absorption reveals a three-dimensional section of the universe 11 billions light years away – the first time the cosmic web has been mapped at such a vast distance. Since observing to such immense distances is also looking back in time, the map reveals the early stages of cosmic structure formation when the Universe was only a quarter of its current age, during an era when the galaxies were undergoing a major 'growth spurt'. The map provides a tantalizing glimpse of giant filamentary structures extending across millions of light years, and paves the way for more extensive studies that should reveal not only the structure of the cosmic web, but also details of its function – the ways that pristine gas is funneled along the web into galaxies, providing the raw material for the growth of galaxies through the formation of stars and planets.


Background information

The work described here will be published as K.G. Lee et al., "Lyα Forest Tomography from Background Galaxies: The first Megaparsec-Resolution Large-Scale Structure Map at z > 2" in the Astrophysical Journal Letters.

ADS entry of the article

The team members are Khee-Gan Lee, Joseph F. Hennawi, and Anna-Christina Eilers (Max Planck Institute for Astronomy), Casey Stark and Martin White, (UC Berkeley and Lawrence Berkeley National Laboratory), J. Xavier Prochaska (University of California at Santa Cruz, Lick Observatory), David Schlegel (Lawrence Berkeley National Laboratory), and Andreu Arinyo-i-Prats (Universitat de Barcelona).

This research received financial support from the National Geographic Society/Waitt Grants Program.


Contact

Khee-Gan Lee (first author)
Max Planck Institute for Astronomy
Heidelberg, Germany
Phone: (+49|0) 6221 –528 467
email:
lee@mpia.de

Joe Hennawi (co-author)
Max Planck Institute for Astronomy
Heidelberg, Germany
Phone: (+49|0) 6221 –528 263
email:
joe@mpia.de

Dr. Markus Pössel (public information officer)
Max Planck Institute for Astronomy
Heidelberg, Germany
Phone: (+49|0) 6221 –528 261
email:
pr@mpia.de




Sunday, October 19, 2014

The Debris Disk of a Solar-Type Star

An artist's conception of the planetary system around the nearby solar analog star, Tau Ceti, showing its five putative planets. Astonomers using far infrared observations find a debris disk around the star, and find a model that is consistent with five planets lying within the disk's inner edge at five astronomical units. Credit: NASA

Although thousands of exoplanets and hundreds of planetary systems (stars with multiple exoplanets) are now known, astronomers still don’t know whether our solar system is typical. The distributions of known planetary system parameters are strongly affected by observational biases that are not easy to disentangle from the true distributions. Moreover, our Solar system’s architecture (small rocky inner planets, large gaseous outer planets, and an outer debris disc made of many small objects) has not yet been seen in other systems, most likely due to these same biases. Long time baselines, for example, are required to discover planets at greater than a few astronomical units (one AU is the average distance of the Earth from the Sun) with all techniques except direct imaging, but direct imaging of planets around mature stars is difficult due to the low light from planets compared to their host stars.

Debris disks, because they are spread out over large areas, are easier to see, and structures in debris discs like rings or gaps can indicate the presence of additional planets. CfA astronomer David Wilner joined with his colleagues to search for clues of planets in the debris disc around τ Ceti, a nearby solar-type star located only ten light-years from the Sun. The infrared excess towards τ Ceti has been known for nearly three decades and has been attributed to warm dust particles in a debris disk.

The astronomers used the Herschel Space Telescope to study τ Ceti in far infrared wavelengths where the dust emission should be strongest. The carefully processed images reveal evidence for a uniform and symmetric debris disk with an inner edge about two to three AU from the star and an outer edge fifty-five AU from the star. For comparison, in our Solar system the Kuiper Belt of small objects begins at the orbit of Neptune (about thirty AU from the Sun) and extends out to about fifty AU (the colder Oort Belt of icy objects and comets extends much farther, to about fifty thousand AU).

In previous studies of τ Ceti, other astronomers had found preliminary evidence suggesting the possibility it hosted five planets. Wilner and his colleagues modeled the stellar system with their observed debris disk and including these possible planets and a range of other published observational data, and found that the system was consistent with the observations and could be stable. The putative planets would orbit between the debris disk's inner edge and the star. The scientists conclude by noting that a Jupiter-mass planet could not be present in this system, making it less than ideal as a Solar system analog. Future observations should be able to refine the picture further.

 
Reference(s): 
 
"The Debris Disc of Solar Analogue τ Ceti: Herschel Observations and Dynamical Simulations of the Proposed Multiplanet System," S. M. Lawler, J. Di Francesco, G. M. Kennedy, B. Sibthorpe, M. Booth, B. Vandenbussche, B. C. Matthews, W. S. Holland, J. Greaves, D. J. Wilner, M. Tuomi, J. A. D. L. Blommaert, B. L. de Vries, C. Dominik, M. Fridlund, W. Gear, A. M. Heras, R. Ivison and G. Olofsson, MNRAS 444, 2665, 2014.
  



Saturday, October 18, 2014

Revealing the secrets of galaxies – second CALIFA Data Release

Figure 1: CALIFA data example: Top row: Poststamp images of five galaxies.  Bottom row: Colour coded gas velocity maps of the same galaxies based on CALIFA IFS data.  Credit: Top row: SDSS | Bottom row: CALIFA team

Today, the second large data release of the CALIFA-Survey has been published to the astronomical community and the public. It contains an unprecedented amount of data on 200 galaxies in the local universe allowing astronomers to study in detail numerous galaxy properties regarding their composition, kinematics, formation history and evolution.

The Calar Alto Legacy Integral Field Area survey (CALIFA) is one of the largest surveys of galaxies which is based on an observing technique called "Integral Field Spectroscopy" (IFS). Already a single spectrum of an astronomical object provides important data beyond pure imaging because the light from the source is split into its wavelength-dependent components and shows characteristic signatures related to physical, chemical and dynamical properties. However, using the PMAS Spectrograph at Calar Alto Observatory, the team of the CALIFA Survey is even able to collect 2000 individual spectra for each galaxy which are covering the whole surface of each object.

The 2nd CALIFA data release now provides unique data on a representative sample of 200 galaxies in the local Universe. These spectra allow studies of the stellar content, ages, star formation history, as well as gas and dust properties. However, beyond spectral diagnostics the CALIFA data-cubes allow to study the spatial distribution of all these properties. Moreover, as a unique feature of imaging spectroscopy, the kinematic properties, i.e. motions of the stars and gas over the whole face of a galaxy, enable the inference of the structure of the galaxy, the formation history, and even the presence of dark matter.

Compared to the 1st data release in 2012 this 2nd release presents a much improved preparation of the material. Data is provided with two spectral setups (in low and high resolution) and for each galaxy the data cube contains about 2000 individual spectra. In total this adds up to about 800,000 spectra released in DR2. The data is freely available for anyone interested.


Important Links:
 


Contact

Dr. Glenn van de Ven (Member CALIFA managing board)
Max Planck Institute for Astronomy
Heidelberg, Germany
Phone: (+49|0) 6221 – 528 275
email:
glenn@mpia.de

Dr. Knud Jahnke (co-founding member, CALIFA)
Max Planck Institute for Astronomy
Heidelberg, Germany
Phone: (+49|0) 6221 – 528 398
email:
jahnke@mpia.de

Dr. Klaus Jäger (MPIA Scientific Coordinator, press officer)
Max Planck Institute for Astronomy
Heidelberg, Germany
Phone: (+49|0) 6221 – 528 379
email:
pr@mpia.de 



Friday, October 17, 2014

Milky Way Ransacks Nearby Dwarf Galaxies, Stripping All Traces of Star-Forming Gas

Artist's impression of the Milky Way. Its hot halo appears to be stripping away the star-forming atomic hydrogen from its companion dwarf spheroidal galaxies. Credit: NRAO/AUI/NSF 

Astronomers using the National Science Foundation’s Green Bank Telescope (GBT) in West Virginia, along with data from other large radio telescopes, have discovered that our nearest galactic neighbors, the dwarf spheroidal galaxies, are devoid of star-forming gas, and that our Milky Way Galaxy is to blame.

These new radio observations, which are the highest sensitivity of their kind ever undertaken, reveal that within a well-defined boundary around our Galaxy, dwarf galaxies are completely devoid of hydrogen gas; beyond this point, dwarf galaxies are teeming with star-forming material.

The Milky Way Galaxy is actually the largest member of a compact clutch of galaxies that are bound together by gravity. Swarming around our home Galaxy is a menagerie of smaller dwarf galaxies, the smallest of which are the relatively nearby dwarf spheroidals, which may be the leftover building blocks of galaxy formation. Further out are a number of similarly sized and slightly misshaped dwarf irregular galaxies, which are not gravitationally bound to the Milky Way and may be relative newcomers to our galactic neighborhood.

“Astronomers wondered if, after billions of years of interaction, the nearby dwarf spheroidal galaxies have all the same star-forming ‘stuff’ that we find in more distant dwarf galaxies,” said astronomer Kristine Spekkens, assistant professor at the Royal Military College of Canada and lead author on a paper published in the Astrophysical Journal Letters.

Previous studies have shown that the more distant dwarf irregular galaxies have large reservoirs of neutral hydrogen gas, the fuel for star formation. These past observations, however, were not sensitive enough to rule out the presence of this gas in the smallest dwarf spheroidal galaxies.

By bringing to bear the combined power of the GBT (the world’s largest fully steerable radio telescope) and other giant telescopes from around the world, Spekkens and her team were able to probe the dwarf galaxies that have been swarming around the Milky Way for billions of years for tiny amounts of atomic hydrogen.

“What we found is that there is a clear break, a point near our home Galaxy where dwarf galaxies are completely devoid of any traces of neutral atomic hydrogen,” noted Spekkens. Beyond this point, which extends approximately 1,000 light-years from the edge of the Milky Way’s star-filled disk to a point that is thought to coincide with the edge of its dark matter distribution, dwarf spheroidals become vanishingly rare while their gas-rich, dwarf irregular counterparts flourish.

There are many ways that larger, mature galaxies can lose their star-forming material, but this is mostly tied to furious star formation or powerful jets of material driven by supermassive black holes. The dwarf galaxies that orbit the Milky Way contain neither of these energetic processes. They are, however, susceptible to the broader influences of the Milky Way, which itself resides within an extended, diffuse halo of hot hydrogen plasma.

The researchers believe that, up to a certain distance from the galactic disk, this halo is dense enough to affect the composition of dwarf galaxies. Within this “danger zone,” the pressure created by the million-mile-per-hour orbital velocities of the dwarf spheroidals can actually strip away any detectable traces of neutral hydrogen. The Milky Way thus shuts down star formation in its smallest neighbors.

"These observations therefore reveal a great deal about size of the hot halo and about how companions orbit the Milky Way," concludes Spekkens.

#  #  #

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.


Contact: 

Charles E. Blue, Public Information Officer
(434) 296-0314
Email: cblue@nrao.edu



Turquoise-tinted plumes in the Large Magellanic Cloud

Credit: ESA/Hubble & NASA
Acknowledgement: Josh Barrington

The brightly glowing plumes seen in this image are reminiscent of an underwater scene, with turquoise-tinted currents and nebulous strands reaching out into the surroundings.

However, this is no ocean. This image actually shows part of the Large Magellanic Cloud (LMC), a small nearby galaxy that orbits our galaxy, the Milky Way, and appears as a blurred blob in our skies. The NASA/ESA Hubble Space Telescope has peeked many times into this galaxy, releasing stunning images of the whirling clouds of gas and sparkling stars (opo9944a, heic1301, potw1408a).

This image shows part of the Tarantula Nebula's outskirts. This famously beautiful nebula, located within the LMC, is a frequent target for Hubble (heic1206, heic1402). 

In most images of the LMC the colour is completely different to that seen here. This is because, in this new image, a different set of filters was used. The customary R filter, which selects the red light, was replaced by a filter letting through the near-infrared light. In traditional images, the hydrogen gas appears pink because it shines most brightly in the red. Here however, other less prominent emission lines dominate in the blue and green filters.

This data is part of the Archival Pure Parallel Project (APPP), a project that gathered together and processed over 1000 images taken using Hubble’s Wide Field Planetary Camera 2, obtained in parallel with other Hubble instruments. Much of the data in the project could be used to study a wide range of astronomical topics, including gravitational lensing and cosmic shear, exploring distant star-forming galaxies, supplementing observations in other wavelength ranges with optical data, and examining star populations from stellar heavyweights all the way down to solar-mass stars.

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


Source:  ESA/Hubble - Space Telescope

Thursday, October 16, 2014

Hubble Finds Extremely Distant Galaxy through Cosmic Magnifying Glass

Hubble Uncovers One of the Smallest and Farthest Galaxies in the Universe
Credit: NASA, ESA, A. Zitrin (California Institute of Technology), and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

Artist's Illustration of a Giant Cosmic Magnifying Glass
Illustration Credit: NASA, ESA, and Z. Levay (STScI). Science Credit: NASA, ESA, A. Zitrin (Caltech), and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)


Peering through a giant cosmic magnifying glass, NASA's Hubble Space Telescope has spotted one of the farthest, faintest, and smallest galaxies ever seen. The diminutive object is estimated to be over 13 billion light-years away.

This new detection is considered one of the most reliable distance measurements of a galaxy that existed in the early universe, said the Hubble researchers. They used two independent methods to estimate its distance.
The galaxy appears as a tiny blob that is only a small fraction of the size of our Milky Way galaxy. But it offers a peek back into a time when the universe was only about 500 million years old, roughly 3 percent of its current age of 13.7 billion years. Astronomers have uncovered about 10 other galaxy candidates at this early era. But this newly found galaxy is significantly smaller and fainter than most of those other remote objects detected to date.

"This object is a unique example of what is suspected to be an abundant, underlying population of extremely small and faint galaxies at about 500 million years after the big bang," explained study leader Adi Zitrin of the California Institute of Technology in Pasadena. "The discovery is telling us that galaxies as faint as this one exist, and we should continue looking for them and even fainter objects so that we can understand how galaxies and the universe have evolved over time."

The galaxy was detected as part of the Frontier Fields program, an ambitious three-year effort, begun in 2013, that teams Hubble with NASA's other Great Observatories — the Spitzer Space Telescope and the Chandra X-ray Observatory — to probe the early universe by studying large galaxy clusters. These clusters are so massive that their gravity deflects light passing through them, magnifying, brightening, and distorting background objects in a phenomenon called gravitational lensing. These powerful lenses allow astronomers to find many dim, distant structures that otherwise might be too faint to see.

In this new discovery, the lensing power of the mammoth galaxy cluster Abell 2744, nicknamed Pandora's Cluster, produced three magnified images of the same galaxy. Each magnified image makes the galaxy appear as much as 10 times larger and brighter than it would look without the intervening lens.

An analysis of the distant galaxy shows that it measures merely 850 light-years across, 500 times smaller than the Milky Way, and is estimated to have a mass of only 40 million suns. The galaxy's star formation rate is about one star every three years (one-third the star formation rate in the Milky Way). Although this may seem low, Zitrin said that given its small size and low mass, the tiny galaxy is in fact rapidly evolving and efficiently forming stars.

"Galaxies such as this one are probably small clumps of matter that are starting to form stars and shine light, but they don't have a defined structure yet," Zitrin said. "Therefore, it's possible that we only see one bright clump magnified due to the lensing, and this is one possibility as to why it is smaller than typical field galaxies of that time."

Zitrin's team spotted the galaxy's gravitationally multiplied images using near-infrared and visible-light photos of the galaxy cluster taken by Hubble's Wide Field Camera 3 and Advanced Camera for Surveys. But at first they didn't know how far away it was from Earth.

Normally, astronomers use spectroscopy to determine an object's distance. The farther away a galaxy, the more its light has been stretched by the universe's expansion. Astronomers can precisely measure this effect through spectroscopy, which characterizes an object's light.

But the gravitationally lensed galaxy and other objects found at this early epoch are too far away and too dim for astronomers to use spectroscopy. Astronomers instead analyze an object's color to estimate its distance. The universe's expansion reddens an object's color in predictable ways, which scientists can measure.

Members of Zitrin's team not only performed the color-analysis technique, but they also took advantage of the multiple images produced by the gravitational lens to independently confirm their distance estimate. The astronomers measured the angular separation between the three magnified images of the galaxy in the Hubble photos. The greater the angular separation due to lensing, the farther away the object is from Earth. To test this concept, the astronomers compared the three magnified images with the locations of several other multiply imaged objects lensed by Abell 2744 that are not as far behind the cluster. The angular distance between the magnified images of the closer galaxies was smaller.

"These measurements imply that, given the large angular separation between the three images of our background galaxy, the object must lie very far away," Zitrin explained. "It also matches the distance estimate we calculated, based on the color-analysis technique. So we are about 95 percent confident that this object is at a remote distance, at redshift 10 (a measure of the stretching of space since the big bang). The lensing takes away any doubt that this might be a heavily reddened, nearby object masquerading as a far more distant object."

Astronomers have long debated whether such early galaxies could have provided enough radiation to warm the hydrogen that cooled soon after the big bang. This process, called "reionization," is thought to have occurred 200 million to 1 billion years after the birth of the universe. Reionization made the universe transparent to light, allowing astronomers to look far back into time without running into a "fog" of cold hydrogen.

"We tend to assume that galaxies ionized the universe with their ultraviolet light," Zitrin said. "But we do not see enough galaxies or light that could do that. So we need to look at fainter and fainter galaxies, and the Frontier Fields and galaxy cluster lensing can help us achieve this goal."

The team's results appeared in the Sept. 5 online edition of The Astrophysical Journal Letters.

CONTACT

Felicia Chou
NASA Headquarters, Washington, D.C.
202-358-0257
felicia.chou@nasa.gov

Donna Weaver
Space Telescope Science Institute, Baltimore, Md.
410-338-4493

dweaver@stsci.edu