Friday, April 29, 2011

Student's Prediction Points the Way to Hot, Dense Super-Earth


This illustration shows the current night sky at 9:00 p.m. Local time. The constellation Cancer the Crab is well placed for viewing. Credit: Created with Voyager 4, copyright Carina Software

This close-up of the constellation Cancer shows the location of 55 Cancri (circled in red). Its larger component, 55 Cancri A, hosts a planetary system that includes the hottest, densest super-Earth currently known: 55 Cancri e. Credit: Created with Voyager 4, copyright Carina Software

Cambridge, MA - A planet that we thought we knew turns out to be rather different than first suspected. Our revised view comes from new data released today by an international team of astronomers. They made their observations of the planet "55 Cancri e" based on calculations by Harvard graduate student Rebekah Dawson (Harvard-Smithsonian Center for Astrophysics), who worked with Daniel Fabrycky (now at the University of California, Santa Cruz) to predict when the planet crosses in front of its star as seen from Earth. Such transits give crucial information about a planet's size and orbit.

The team found that 55 Cancri e is 60 percent larger in diameter than Earth but eight times as massive. (A super-Earth has one to 10 times the mass of Earth.) It's the densest solid planet known, almost as dense as lead. Even better, the star it orbits is so close and bright that it's visible to the naked eye in the constellation Cancer the Crab. This makes it an excellent target for follow-up studies.

Dawson and Fabrycky's prediction played a crucial role in this new work by motivating the search for transits. When the planet was discovered by a Texas team in 2004, it was calculated to orbit its star every 2.8 days. Dawson and Fabrycky reanalyzed the data and found that 55 Cancri e was much closer to its star, orbiting it in less than 18 hours. As a result, the chances of seeing a transit were much higher.

Josh Winn of MIT and Smithsonian astronomer Matthew Holman brought the new calculation to Jaymie Matthews (University of British Columbia), who scheduled observations with Canada's MOST (Microvariability & Oscillations of STars) satellite. The research team found that 55 Cancri e transits its star every 17 hours and 41 minutes, just as Dawson and Fabrycky predicted.

"I'm excited that by calculating the planet's true orbital period, we were able to detect transits, which tell us so much more about it," said Dawson.

The new technique applies to planets discovered by the radial velocity method, in which astronomers hunt for a star that "wobbles" from the gravitational tug of an orbiting world.

The initial confusion about the orbit of 55 Cancri e arose because of natural gaps in the radial velocity data (because astronomers can only observe a star at night and when it's above the horizon). Sometimes these gaps introduce "ghost" signals that can masquerade as the planet's true signal.

Dawson and Fabrycky chose to analyze six planetary systems where the data seemed particularly ambiguous. In two cases they confirmed previous results, while some remained unclear. For 55 Cancri e, a period revision was certainly needed.

"It became very clear that the planet's actual orbital period was closer to 18 hours," stated Dawson.

This places the planet so close to its star that it's blasted with heat, baked to a temperature of 4,900 degrees F.

The star itself, 55 Cancri A, is a yellow star very similar to the Sun and located 40 light-years away. It's the brightest, closest star known to have a transiting planet.

Dawson recommends that the analysis method she developed with Fabrycky be used on future planet discoveries. "We've cleared up some confusion in the systems we studied, and we believe we've provided a way to avoid future confusion," she said. 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

HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS

Thursday, April 28, 2011

NASA's SWIFT and Hubble Probe Asteroid Collision Debris

Annotated Illustration and Compass Image
of Hubble Image of Asteroid (596) Scheila

Credit:
NASA, ESA, D. Jewitt (UCLA), and M. Mutchler (STScI)

Asteroid (596) Scheila
Faint dust plumes bookend asteroid (596) Scheila, which is overexposed in this composite image. Visible and ultraviolet images from Swift's UVOT (circled) are merged with a Digital Sky Survey image of the same region. The UVOT images were acquired on Dec. 15, 2010, when the asteroid was about 232 million miles from Earth. Credit: NASA/Swift/DSS/D. Bodewits (University of Maryland, College Park)

Late last year, astronomers noticed an asteroid named Scheila had unexpectedly brightened, and it was sporting short-lived plumes. Data from NASA's Swift satellite and Hubble Space Telescope showed these changes likely occurred after Scheila was struck by a much smaller asteroid.

"Collisions between asteroids create rock fragments, from fine dust to huge boulders, that impact planets and their moons," said Dennis Bodewits, an astronomer at the University of Maryland in College Park and lead author of the Swift study. "Yet this is the first time we've been able to catch one just weeks after the smash-up, long before the evidence fades away."

Asteroids are rocky fragments thought to be debris from the formation and evolution of the solar system approximately 4.6 billion years ago. Millions of them orbit the Sun between Mars and Jupiter in the main asteroid belt. Scheila is approximately 70 miles across and orbits the Sun every five years.

"The Hubble data are most simply explained by the impact, at 11,000 mph, of a previously unknown asteroid about 100 feet in diameter," said Hubble team leader David Jewitt at the University of California in Los Angeles. Hubble did not see any discrete collision fragments, unlike its 2009 observations of P/2010 A2, the first identified asteroid collision.

The studies will appear in the May 20 edition of The Astrophysical Journal Letters and are available online.

Astronomers have known for decades that comets contain icy material that erupts when warmed by the Sun. They regarded asteroids as inactive rocks whose densities, surfaces, shapes, and sizes were determined by mutual impacts. However, this simple picture has grown more complex over the past few years.

During certain parts of their orbits, some objects, once categorized as asteroids, clearly develop comet-like features that can last for many months. Others display much shorter outbursts. Icy materials may be occasionally exposed, either by internal geological processes or by an external one, such as an impact.

On Dec. 11, 2010, images from the University of Arizona's Catalina Sky Survey, a project of NASA's Near Earth Object Observations Program, revealed Scheila to be twice as bright as expected and immersed in a faint comet-like glow. Looking through the survey's archived images, astronomers inferred the outburst began between Nov. 11 and Dec. 3.

Three days after the outburst was announced, Swift's Ultraviolet/Optical Telescope (UVOT) captured multiple images and a spectrum of the asteroid. Ultraviolet sunlight breaks up the gas molecules surrounding comets; water, for example, is transformed into hydroxyl and hydrogen. But none of the emissions most commonly identified in comets, such as hydroxyl or cyanogen, show up in the UVOT spectrum. The absence of gas around Scheila led the Swift team to reject scenarios where exposed ice accounted for the activity.

Images show the asteroid was flanked in the north by a bright dust plume and in the south by a fainter one. The dual plumes formed as small dust particles excavated by the impact were pushed away from the asteroid by sunlight. Hubble observed the asteroid's fading dust cloud on Dec. 27, 2010, and Jan. 4, 2011.

The two teams found the observations were best explained by a collision with a small asteroid impacting Scheila's surface at an angle of less than 30 degrees, leaving a crater 1,000 feet across. Laboratory experiments show a more direct strike probably wouldn't have produced two distinct dust plumes. The researchers estimated the crash ejected more than 660,000 tons of dust — equivalent to nearly twice the mass of the Empire State Building.

The Swift team also includes Michael F. A'Hearn, Jian-Yang Li, and Sebastien Besse at the University of Maryland, College Park, and Wayne Landsman at NASA's Goddard Space Flight Center in Greenbelt, Md. Additional members of the Hubble team include Harold Weaver at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.; Max Mutchler at the Space Telescope Science Institute in Baltimore; Stephen Larson at the University of Arizona, Tucson; and Jessica Agarwal at the University of Potsdam in Germany.

"The dust cloud around Scheila could be 10,000 times as massive as the one ejected from comet 9P/Tempel 1 during NASA's University of Maryland-led Deep Impact mission," said co-author Michael Kelley, also at the University of Maryland. "Collisions allow us to peek inside comets and asteroids. Ejecta kicked up by Deep Impact contained lots of ice, and the absence of ice in Scheila's interior shows that it's entirely unlike comets."

Contact:

Trent J. Perrotto
Headquarters, Washington
202-358-0321
trent.j.perrotto@nasa.gov

Lynn Chandler
Goddard Space Flight Center, Greenbelt, Md.
301-286-2806
lynn.chandler-1@nasa.gov

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

SPINSTARS: the first polluters of the Universe?

Simulation of the formation of the first stars showing fast rotation
Credits: A. Stacy, University of Texas
Full Screen Image

Astrophysicists find imprints of fast rotating massive stars
in the bulge of our galaxy


From the analysis of the chemical composition of some of the oldest stars in our Galaxy, an international team of astronomers led by Cristina Chiappini from the Leibniz-Institut für Astrophysik Potsdam (AIP) and the Instituto Nazionale di Astrofisica (INAF) presents new clues on the nature of the first stellar generations in our Universe. “We think that the first generations of massive stars were very fast rotators – that’s why we called them spinstars”, explains Chiappini. Their findings will be published in a Nature article on April 28, 2011.

Massive stars live fast and furious, and hence the first generations of massive stars in the Universe are already dead. However, their chemical imprints, like fingerprints, can still be found today in the oldest stars in our Galaxy. These fossil records are thus the witnesses of the nature of the first stellar generations to pollute our Universe. “It is like if we tried to reveal the character of a cook from the taste of his dishes”, says Prof. Georges Meynet, from the Geneva University.

How were these first stars? Were they different from the stars we observe today?

Soon after the Big Bang, the composition of the Universe was much simpler than at present as it was made of essentially only hydrogen and helium. The chemical enrichment of the Universe with other elements had to wait around 300 million years until the fireworks started with the death of the first generations of massive stars, polluting the primordial gas with new chemical elements, which were later incorporated in the next generations of stars.

Using data from ESO’s Very Large Telescope (VLT), the astronomers reanalyzed spectra of a group of very old stars in the Galactic Bulge. These stars are so old that only very massive, short-living stars with masses larger than around ten times the mass of our Sun should have had time to die and to pollute the gas from which these fossil records then formed. As expected, the chemical composition of the observed stars showed elements typical for enrichment by massive stars. However, the new analysis unexpectedly also revealed elements usually thought to be produced only by stars of smaller masses. Fast-rotating massive stars on the other hand would succeed in manufacturing these elements themselves.

“Alternative scenarios cannot yet be discarded - but - we show that if the first generations of massive stars were spinstars, this would offer a very elegant explanation to this puzzle!”, says Cristina Chiappini. Team member Urs Frischknecht, a PhD student at the Basel University, is already working on extending the stellar simulations in order to further test the proposed scenario.

The impact of having had an early generation of spinstars in the Universe is manifold. Fast rotation also affects other properties of a star, such as its colour, its lifetime and its luminosity. Spinstars would therefore also have strongly influenced the properties and appearance of the first galaxies which were formed in the Universe. The existence of spinstars is now also supported by recent hydrodynamic simulations of the formation of the first stars of the universe by an independent research group.


Further information:

Original publication: Chiappini et al., Imprints of fast-rotating massive stars in the Galactic Bulge, to be published in Nature, 2011. (DOI: 10.1038/nature10000, publication date: April 28, 2011)
Leibniz-Institut für Astrophysik Potsdam (AIP) - www.aip.de


Image:


Simulation of the formation of the first stars showing fast rotation (Credits: A. Stacy, University of Texas).


Scientific Contact:

Dr. Cristina Chiappini, Leibniz-Institut für Astrophysik Potsdam (AIP), Email: cristina.chiappini@aip.de, Tel.: +49 331 7499 454


Press Contact:


Dr. Gabriele Schönherr, Leibniz-Institut für Astrophysik Potsdam (AIP), Email: presse@aip.de, Tel.: +49 331 7499 383

Madleen Köppen, AIP, Email: presse@aip.de, Tel.: +49 331 7499 469

The key topics of the Leibniz Institute for Astrophysics (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. The AIP is a foundation according to civil law and is a member of the Leibniz Association. The Leibniz Association is a network of 87 independent research institutes and scientific service facilities, which strive for scientific solutions for major social challenges.

Wednesday, April 27, 2011

Andromeda’s coat of many colours


Andromeda in multiple wavelengths

Link YouTube

ESA’s fleet of space telescopes has captured the nearby Andromeda Galaxy, also known as M31, in different wavelengths. Most of these wavelengths are invisible to the eye and each shows a different aspect of the galaxy’s nature.

Visible light, as seen by optical ground-based telescopes and our eyes, reveals the various stars that shine in the Andromeda Galaxy, yet it is just one small part of the full spectrum of electromagnetic radiation. There are many different wavelengths that are invisible to us but which are revealed by ESA’s orbiting telescopes.

Starting at the long wavelength end, the Planck spacecraft collects microwaves. These show up particles of incredibly cold dust, at just a few tens of degrees above absolute zero. Slightly higher temperature dust is revealed by the shorter, infrared wavelengths observed by the Herschel space telescope. This dust traces locations in the spiral arms of the Andromeda Galaxy where new stars are being born today.

The XMM-Newton telescope detects wavelengths shorter than visible light, collecting ultraviolet and X-rays. These show older stars, many nearing the end of their lives and others that have already exploded, sending shockwaves rolling through space. By monitoring the core of Andromeda since 2002, XMM-Newton has revealed many variable stars, some of which have undergone large stellar detonations known as novae.

Ultraviolet wavelengths also display the light from extremely massive stars. These are young stars that will not live long. They exhaust their nuclear fuel and explode as supernovae typically within a few tens of millions of years after they are born. The ultraviolet light is usually absorbed by dust and re-emitted as infrared, so the areas where ultraviolet light is seen directly correspond to relatively clear, dust-free parts of Andromeda.

By putting all of these observations together, and seeing Andromeda in its many different colours, astronomers are able to follow the life cycle of the stars.

Source: ESA

Tuesday, April 26, 2011

NASA Invites Public to Journey Toward Interstellar Space

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

NASA will hold a special NASA Science Update at 10 a.m. PDT (1 p.m. EDT) on Thursday, April 28, to discuss the unprecedented journey of NASA's twin Voyager spacecraft to the edge of our solar system.

The event will be held at NASA Headquarters in Washington and will be broadcast live on NASA Television and streamed at http://www.nasa.gov . In addition, the event will be carried live on Ustream, with a live chat box available, at http://www.ustream.tv/nasajpl2 .

After 33 years in space, the spacecraft are still operating and returning data from about 16 billion kilometers (10 billion miles) away from our sun. The Voyagers also carry a collection of images and sounds from Earth as a message to possible life elsewhere in the galaxy.

The participants are:
-- Ed Stone, Voyager project scientist and professor of physics, California Institute of Technology, Pasadena, Calif.
-- Ann Druyan, creative director, Voyager Interstellar Message Project; Carl Sagan's co-author and widow
-- Suzanne Dodd, Voyager project manager, NASA's Jet Propulsion Laboratory, Pasadena, Calif.
-- Merav Opher, Voyager guest investigator and assistant professor of astronomy, Boston University

For more information about the Voyager mission, visit: http://www.nasa.gov/voyager .

For NASA TV streaming video and downlink information, visit: http://www.nasa.gov/ntv .

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.cbrown@nasa.gov

Tycho's Supernova Remnant: NASA'S Chandra Finds New Evidence on Origin of Supernovas

Tycho's Supernova Remnant
Credit NASA/CXC/Chinese Academy of Sciences/F. Lu et al

Image Showing the "Shadow" of the Arc
This image shows iron debris in Tycho's supernova remnant. The site of the supernova explosion is shown, as inferred from the motion of the possible companion to the exploded white dwarf. The position of material stripped off the companion star by the explosion, and forming an X-ray arc, is shown by the white dotted line. This structure is most easily seen in an image showing X-rays from the arc's shock wave. Finally, the arc has blocked debris from the explosion creating a "shadow" in the debris between the red dotted lines, extending from the arc to the edge of the remnant. Credit: NASA/CXC/Chinese Academy of Sciences/F. Lu et al

This new image of Tycho's supernova remnant, dubbed Tycho for short, contains striking new evidence for what triggered the original supernova explosion, as seen from Earth in 1572. Tycho was formed by a Type Ia supernova, a category of stellar explosion used in measuring astronomical distances because of their reliable brightness.

Low and medium energy X-rays in red and green show expanding debris from the supernova explosion. High energy X-rays in blue reveal the blast wave, a shell of extremely energetic electrons. Also shown in the lower left region of Tycho is a blue arc of X-ray emission. Several lines of evidence support the conclusion that this arc is due to a shock wave created when a white dwarf exploded and blew material off the surface of a nearby companion star (see accompanying illustration below). Previously, studies with optical telescopes have revealed a star within the remnant that is moving much more quickly than its neighbors, hinting that it could be the companion to the supernova that was given a kick by the explosion.

Illustration Explaining the Arc in Tycho
This is an artist's impression showing an explanation from scientists for the origin of an X-ray arc in Tycho's supernova remnant. It is believed that material was stripped off the companion star by the explosion of the white dwarf in the Type Ia supernova explosion, forming the shock wave seen in the arc. The arc has blocked debris from the explosion, creating a "shadow" behind the arc. The force of the explosion imparted a kick to the companion star, and this combined with the orbital velocity of the companion before the explosion to give the "observed" motion of the companion. Previously, studies with optical telescopes have revealed a star within the remnant that is moving much more quickly than its neighbors, showing that it could be the companion to the supernova. The size of the companion's orbit is not shown to scale here: the separation between it and the white dwarf before the explosion is estimated to have only been about a millionth of a light year, while the full scale of the illustration is over 10 light years. Credit: NASA/CXC/M.Weiss

Other details of the arc support the idea that it was blasted away from the companion star. For example, the X-ray emission of the remnant shows an apparent "shadow" next to the arc, consistent with the blocking of debris from the explosion by the expanding cone of material stripped from the companion. This shadow is most obvious in very high energy X-rays showing iron debris.

These pieces of evidence support a popular scenario for triggering a Type Ia supernova, where a white dwarf pulls material from a "normal," or Sun-like, companion star until a thermonuclear explosion occurs. In the other main competing theory, a merger of two white dwarfs occurs, and in this case, no companion star or evidence for material blasted off a companion, should exist. Both scenarios may actually occur under different conditions, but the latest Chandra result from Tycho supports the former one.

The shape of the arc is different from any other feature seen in the remnant. Other features in the interior of the remnant include recently announced stripes, which have a different shape and are thought to be features in the outer blast wave caused by cosmic ray acceleration.

Fast Facts for Tycho's Supernova Remnant:

Scale: Image is 10 arcmin across
Category: Supernovas & Supernova Remnants
Coordinates: (J2000) RA 00h 25m 17s | Dec +64° 08' 37"
Constellation: Cassiopeia
Observation Date: 2 pointings between April 29, 2003 and May 3, 2009
Observation Time: 283
Obs. ID: 3837, 7639, 8551, 10093-10097; 10902-10904; 10906
Color Code: Energy: Red 1.6-2.0 keV, Green 2.2-2.6 keV, Blue 4-6 keV
Instrument: ACIS
Also Known As: G120.1+01.4, SN 1572
References Lu, F.J. et al, 2011, ApJ, 732:11
Distance Estimate About 13,000 light years

Giant Black Holes Revealed in the Nuclei of Merging Galaxies

Figure 1: Schematic diagrams of obscured AGNs. left: A doughnut-shaped dusty medium hides an active mass-accreting SMBH. Photons from the central AGN (= a mass accreting SMBH) can escape along the doughnut axis and ionize the gas there. Since the emission pattern of such AGN-ionized gas clouds differs from those in star-forming regions, we can use optical spectroscopy to easily infer the presence of an AGN hidden behind the dusty medium. right: Dust in all lines-of-sight obscures and buries the active mass-accreting SMBH, which is very difficult to detect with conventional optical spectroscopy. Image credits: NASA for the images of mass accreting SMBH (lower), and mass accreting SMBH surrounded by doughnut-shaped dusty medium (upper left). NAOJ, Naomi Ishikawa, for the upper-right image.


Figure 2: High-spatial-resolution infrared 18-micrometer images, obtained with the Subaru telescope (top) and the Gemini South telescope (bottom). The field of view (FOV) is 8 x 8 arcsec2. N and E indicate north and east directions, respectively. left: Image of a standard star. Three dots (top) or three dots with a ring pattern (bottom) demonstrate that the image has reached or is close to the limit for its highest possible resolution. middle: Image of an infrared luminous merging galaxy, with indication of a luminous AGN. The infrared emission is very compact, indistinguishable from the stellar image. The emission surface brightness is estimated to be significantly higher than the upper limit achieved by star-formation activity. right: Image of an infrared luminous merging galaxy, typical of a star-formation dominated source. The emission is spatially extended, and the emission surface brightness is within a range explained by star-formation activity.

A research team led by Dr. Masatoshi Imanishi (Subaru Telescope, National Astronomical Observatory of Japan) sampled many infrared bright, merging galaxies and determined the presence of active supermassive black holes (SMBH) deeply buried in their centers. (Notes 1 and Notes 2). The scientists used the 8.2 m Subaru Telescope atop Mauna Kea (4200 m in elevation) as well as the Gemini South telescope at Cerro Pachon, Chile (2700 m in elevation) to perform high-spatial-resolution infrared imaging observations of nearby infrared luminous merging galaxies. Observations with both telescopes revealed that some samples show characteristics of rapid star-formation, while others display the signature of active galactic nuclei (AGN) that draw their energy from SMBH.

According to prevailing galaxy formation theories, small gas-rich galaxies with central SMBHs collide and merge, and then grow into the matured galaxies of the current universe. This is why the investigation of nearby infrared luminous merging galaxies helps to clarify the process of galaxy formation. The collision and compression of gas clouds from the galaxy merger causes the rapid formation of new stars, a heating-up of the surrounding dust, and the consequent production of strong infrared radiation. Also the supply of material increases the accretion to the SMBHs.

Although the merging galaxies enhance star formation as well as accretion to SMBHs, they also hinder these processes. A large amount of gas and dust are supplied to their nuclear regions, a process that can easily bury the compact SMBHs and make them difficult to find. By chance some objects have a ring-shaped distribution of the dust and gas, allowing observers to peek into the effect of the active SMBHs (Figure 1).

To detect emission behind dust and gas, the current research team made observations at 18 micrometers, using Subaru Telescope's COMICS (Cooled Mid-Infrared Camera and Spectrometer) as well as Gemini South's T-ReCS (Thermal-Region Camera Spectrograph). By utilizing the time exchange program, the team could use both telescopes to survey objects all over the sky. Subaru's observations captured images in the northern hemisphere and Gemini South, in the southern hemisphere.

How, then, could they confirm the presence of active SMBHs? It was neither an easy nor a trivial task to discover active SMBHs in merging galaxies. The researchers had used their methodology and choice of instruments to overcome a number of challenges. First they needed to identify an object had a bright infrared emission but was compact in size. Both AGN activity (a mass accreting SMBH) and compact star formation region are spatially confined. Measuring the luminosity in the infrared was the key for the finally categorizing their source. If the emission surface brightness at the nucleus of a merging galaxy is substantially higher than the maximum brightness expected from star-formation, then one can infer that the emission comes from a luminous buried AGN, because an accreting SMBH can emit radiation much more efficiently than a star. Observations at infrared 18 micrometers with both the Subaru and Gemini South telescopes demonstrated that some infrared luminous merging galaxies show a star formation type of emission (spatially extended with modest surface brightness) while others had an emission typical of AGNs (spatially compact with high surface brightness) (Figure 2). Ten of the current sample of eighteen objects showed the characteristics of the AGNs.

The team's coherent, logical steps used to investigate the presence of supermassive black holes in merging galaxies yielded clear and important results, which were published in the Astronomical Journal: Imanishi et al. 2011 Astronomical Journal, 141, 156). Comparison of the results from high spatial resolution infrared observations with those from research using infrared spectroscopy to investigate deeply buried AGNs (Press Release from Subaru Telescope on Feb. 15, 2006) shows that both are reliable energy diagnostic tools and provide a consistent picture of the nature of hidden energy sources in merging galaxies.

Note 1: SMBH refers to masses with a weight more than one million times that of the Sun. Recent observations have revealed that supermassive black holes are found everywhere in the spheroidal components of galaxies, and that the masses of SMBHs and spheroidal stars are correlated.

Note 2: An active black hole occurs when material is pulled into a black hole and loses its gravitational energy, which is then converted into radiation energy. This process is called "accretion", and a black hole with accretion is called "active".

Monday, April 25, 2011

ING Joins Efforts with GTC to Discover a Galactic Black Hole

XTE J1859+226 is a transient X-ray binary discovered in 1999 by the X-ray satellite RXTE. X-ray binaries are formed from the pairing of a compact object, either a neutron star or a black hole, and a 'normal' star. The compact object pulls out material from the star which eventually falls onto an accretion disc surrounding the compact object. This type of binary system stays in quiescence for most of its life; however, from time-to-time the system can show an outburst at all wavelengths which can subsequently be detected by X-ray satellites.

Artist impression of XTE J1859+226 system [ JPEG ]

Observations of XTE J1859+226 taken in 2000 with the William Herschel Telescope (WHT) and the Isaac Newton Telescope (INT) exhibited the sinusoidal modulation of a secondary star. Unfortunately the periodogram showed a range of possible orbital periods at a 68% confidence level (Zurita et al., 2002, MNRAS, 334, 999) and more data were necessary to come to a conclusion about the nature of the object.

New photometry was acquired in 2008 from the Nordic Optical Telescope (NOT) and again in 2010 using both the NOT and WHT, and spectra were acquired from the Gran Telescopio Canarias (GTC). Due to the short integration time of the WHT images the astronomers were able to resolve an intense flickering which strongly dilutes the secondary star's ellipsoidal modulation. The object was about one magnitude brighter than in its quiescence state and showed flares with a time-scale of order 10 minutes and amplitudes of up to magnitude 0.5.

By combining the data taken using the INT and the WHT in 2000 with the photometry taken in 2008, an orbital period of 6.6 hours was derived. The spectra taken with the GTC gave a radial velocity of semi-amplitude 541 km/s. These values give a mass function of 4.5 solar masses which sets a lower limit to the mass of the compact object, therefore implying the presence of a black hole. The lack of eclipses and the depth of the minima in the light curve constrains the inclination of the system to be between 40° and 70°, giving a lower limit to the mass of the black hole of 5.42 solar masses.

There are ~20 dynamically confirmed binaries with black holes out of an estimated population of a few thousand in our Galaxy.

More information:
J. M. Corral-Santana, J. Casares, T. Shahbaz, C. Zurita, I. G. Martínez-Pais, P. Rodríguez-Gil, 2011, MNRAS, article first published online: 25 Feb 2011.
"Descubren un agujero negro de más de cinco veces la masa del Sol", IAC Press Release, 23/03/2011..

Javier Méndez
Public Relations Officer

NAM 10: The shocking environment of hot Jupiters

Artists impression of the WASP-12 system.
© ESA/C Carreau

Jupiter-like worlds around other stars push shock waves ahead of them, according to a team of UK astronomers. Just as the Earth's magnetic "bow-shock" protects us from the high-energy solar wind, these planetary shocks protect their atmospheres from their star's damaging emissions. Team member Dr Aline Vidotto of the University of St Andrews will present a new model based on observations made with the SuperWASP (Wide Angle Search for Planets) project on Monday 18 April at the National Astronomy Meeting in Llandudno, Wales.


In 2008, observations of WASP-12 detected a periodic dip in light as a large planet (catalogued as WASP-12b) passed in front of its host star. Planet hunting with transit instruments like SuperWASP allows astronomers to obtain a wealth of information about exoplanetary systems including their composition and size.

WASP-12b turns out to be one of the largest exoplanets found to date and completes each orbit around its parent star in just 26 hours. The planet is more than 250,000 km across, with its atmosphere swollen by the intense heat it receives from the star, making it a so-called ‘hot Jupiter’.

Hot Jupiters are similar to the planet Jupiter in our own Solar System but located far closer to their host star (WASP-12b is 3.4 million km away from WASP-12 which compares with the Earth-Sun distance of 150 million km). With such a small distance between them violent interactions between the star and the planet can take place.

As one of the largest hot Jupiters discovered to date, WASP-12b also gives a unique opportunity to observe the interactions between the planetary magnetic field and the host star’s magnetic field. The very presence of a magnetic field reveals that the planet must have a conducting, rotating interior.

There is now tantalizing new evidence from Hubble Space Telescope data that a magnetosphere exists around WASP-12b. Observations of the planet taken in ultraviolet wavelengths by a team including scientists from the Open University reveal that the start of the dip in the light from the star during the transit of the planet is earlier in ultraviolet than visible light. Originally, this was thought to be caused by material flowing from the planet onto the star. The St Andrews group have however determined that the planet ploughs into a supersonic headwind and pushes a shock ahead it – just like the one around a supersonic jet aircraft.

The St Andrews astronomers carried out simulations of a planet and its bow shock transiting a star and by investigating various shock geometries, orientations and densities have reproduced the dip in ultraviolet light observed in WASP-12b.

Team leader Dr Aline Vidotto commented on the new result. "The location of this bow shock provides us with an exciting new tool to measure the strength of planetary magnetic fields. This is something that presently cannot be done in any other way."

Joe Llama, a PhD student who carried out the simulations of the bow shock, said "Our models are able to reproduce the data from the Hubble Space telescope for a range of wind speeds implying that bow shocks could be far more commonplace than had been thought.”

Bow shocks may also protect the atmospheres of hot Jupiters from their harsh environment. These planets are constantly bombarded with highly charged, energized particles from the wind from their parent stars, meaning that their atmosphere can be eroded. The presence of a magnetic field could greatly reduce the amount of stellar wind the planet is exposed to, effectively acting as a shield and helping the atmosphere survive.

Joe Llama concludes, “Although our model predicts a bow shock similar to that of the Earth, we are not expecting any messages from WASP-12b as it is too hot to support life. But the first hints that extrasolar planets have magnetosphere is a big step forward in understanding and identifying the habitable zones where we ultimately hope to find signs of life”.

Science contacts

Dr Aline Vidotto (at NAM Monday and Tuesday morning)
University of St Andrews
Tel: +44(0)1334 462823
Email: Aline.Vidotto@st-andrews.ac.uk

Joe Llama (at NAM all week)
University of St Andrews
Email: jl386@st-andrews.ac.uk

Dr Kenny Wood
University of St Andrews
Tel: +44 (0)1334 463116
Email: kw25@st-andrews.ac.uk

Prof. Moira Jardine
University of St Andrews
Tel: +44 (0)1334 463146
Email: mmj@st-andrews.ac.uk

Dr Christiane Helling
University of St Andrews
Tel: +43 1 4277 53834
Email: ch80@st-andrews.ac.uk

Press contacts

NAM 2011 Press Office (0900 – 1730 BST, 18-21 April only)
Conwy Room
Venue Cymru conference centre
Llandudno
Tel: +44 (0)1492 873 637, +44 (0)1492 873 638

Dr Robert Massey
Royal Astronomical Society
Mob: +44 (0)794 124 8035
Email: rm@ras.org.uk

Anita Heward
Royal Astronomical Society
Mob: +44 (0)7756 034 243
Email: anitaheward@btinternet.com

Image and animation

An artist’s impression of WASP-12b is available from the European Space Agency. See http://www-star.st-and.ac.uk/~jl386/shocks/

An animation of WASP-12b and its bow shock moving in front of the star WASP-12 can be downloaded from http://star-www.st-andrews.ac.uk/~jl386/shocks/
Credit: Joe Llama

Further information

The results also appear in two papers in ApJ Letters (2010) 722, 168 and MNRAS Letters (2011), 411, 46.

Notes for editors

NAM 2011

Bringing together around 500 astronomers and space scientists, the RAS National Astronomy Meeting 2011 (NAM 2011: http://www.ras.org.uk/nam-2011) will take place from 17-21 April in Venue Cymru (http://www.venuecymru.co.uk), Llandudno, Wales. The conference is held in conjunction with the UK Solar Physics (UKSP: http://www.uksolphys.org) and Magnetosphere Ionosphere and Solar-Terrestrial Physics (http://www.mist.ac.uk) meetings. NAM 2011 is principally sponsored by the RAS and the Science and Technology Facilities Council (STFC: http://www.stfc.ac.uk).

The Royal Astronomical Society

The Royal Astronomical Society (RAS: http://www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3500 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

The Science and Technology Facilities Council

The Science and Technology Facilities Council (http://www.stfc.ac.uk) ensures the UK retains its leading place on the world stage by delivering world-class science; accessing and hosting international facilities; developing innovative technologies; and increasing the socio-economic impact of its research through effective knowledge exchange. The Council has a broad science portfolio including Astronomy, Particle Astrophysics and Space Science. In the area of astronomy it funds the UK membership of international bodies such as the European Southern Observatory.

Venue Cymru

Venue Cymru (http://www.venuecymru.co.uk) is a purpose built conference centre and theatre with modern facilities for up to 2000 delegates. Located on the Llandudno promenade with stunning sea and mountain views; Venue Cymru comprises a stunning location, outstanding quality and exceptional value: the perfect conference package.

Thursday, April 21, 2011

Ultraviolet Spotlight on Plump Stars in Tiny Galaxies

Little Galaxies Pack a Big Punch
Credit: NASA/JPL-Caltech

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Astronomers using NASA's Galaxy Evolution Explorer may be closer to knowing why some of the most massive stellar explosions ever observed occur in the tiniest of galaxies.

"It's like finding a sumo wrestler in a little 'Smart Car,'" said Don Neill, a member of NASA's Galaxy Evolution Explorer team at the California Institute of Technology in Pasadena, and lead author of a new study published in the Astrophysical Journal.

"The most powerful explosions of massive stars are happening in extremely low-mass galaxies. New data are revealing that the stars that start out massive in these little galaxies stay massive until they explode, while in larger galaxies they are whittled away as they age, and are less massive when they explode," said Neill.

Over the past few years, astronomers using data from the Palomar Transient Factory, a sky survey based at the ground-based Palomar Observatory near San Diego, have discovered a surprising number of exceptionally bright stellar explosions in so-called dwarf galaxies up to 1,000 times smaller than our Milky Way galaxy. Stellar explosions, called supernovae, occur when massive stars -- some up to 100 times the mass of our sun -- end their lives.

The Palomar observations may explain a mystery first pointed out by Neil deGrasse Tyson and John Scalo when they were at the University of Austin Texas (Tyson is now the director of the Hayden Planetarium in New York, N.Y.). They noted that supernovae were occurring where there seemed to be no galaxies at all, and they even proposed that dwarf galaxies were the culprits, as the Palomar data now indicate.

Now, astronomers are using ultraviolet data from the Galaxy Evolution Explorer to further examine the dwarf galaxies. Newly formed stars tend to radiate copious amounts of ultraviolet light, so the Galaxy Evolution Explorer, which has scanned much of the sky in ultraviolet light, is the ideal tool for measuring the rate of star birth in galaxies.

The results show that the little galaxies are low in mass, as suspected, and have low rates of star formation. In other words, the petite galaxies are not producing that many huge stars.

"Even in these little galaxies where the explosions are happening, the big guys are rare," said co-author Michael Rich of UCLA, who is a member of the mission team.

In addition, the new study helps explain why massive stars in little galaxies undergo even more powerful explosions than stars of a similar heft in larger galaxies like our Milky Way. The reason is that low-mass galaxies tend to have fewer heavy atoms, such as carbon and oxygen, than their larger counterparts. These small galaxies are younger, and thus their stars have had less time to enrich the environment with heavy atoms.

According to Neill and his collaborators, the lack of heavy atoms in the atmosphere around a massive star causes it to shed less material as it ages. In essence, the massive stars in little galaxies are fatter in their old age than the massive stars in larger galaxies. And the fatter the star, the bigger the blast that will occur when it finally goes supernova. This, according to the astronomers, may explain why super supernovae are occurring in the not-so-super galaxies.

"These stars are like heavyweight champions, breaking all the records," said Neill.

Added Rich, "These dwarf galaxies are especially interesting to astronomers, because they are quite similar to the kinds of galaxies that may have been present in our young universe, shortly after the Big Bang. The Galaxy Evolution Explorer has given us a powerful tool for learning what galaxies were like when the universe was just a child."

Caltech leads the Galaxy Evolution Explorer mission and is responsible for science operations and data analysis. NASA's Jet Propulsion Laboratory in Pasadena manages the mission and built the science instrument. Caltech manages JPL for NASA. The mission was developed under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. Researchers sponsored by Yonsei University in South Korea and the Centre National d'Etudes Spatiales (CNES) in France collaborated on this mission.

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

Wednesday, April 20, 2011

Cassini Sees Saturn Electric Link With Enceladus

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Electrical Circuit Between Saturn and Enceladus
NASA's Cassini spacecraft has spotted a glowing patch of ultraviolet light near Saturn's north pole that marks the presence of an electrical circuit that connects Saturn with its moon Enceladus. Image credit: NASA/JPL/University of Colorado/Central Arizona College. Full image and caption

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Enceladus 'Footprint' on Saturn
This artist's concept shows a glowing patch of ultraviolet light near Saturn's north pole that occurs at the "footprint" of the magnetic connection between Saturn and its moon Enceladus. Credit: NASA/JPL/JHUAPL/University of Colorado/Central Arizona College/SSI. Full image and caption

Photo 3 of 5
Hiss from Aurora Caused by Enceladus
This video demonstrates the hiss-like radio noise generated by electrons moving along magnetic field lines from the Saturnian moon Enceladus to a glowing patch of ultraviolet light on Saturn. Image credit: NASA/JPL/University of Iowa. Radio noise video

Photo 4 of 5
Saturn and Enceladus Electrical Link
This animated graphic shows how Saturn and its moon Enceladus are electrically linked. Magnetic field lines, invisible to the human eye but detectable by the fields and particles instruments on NASA’s Cassini spacecraft, arc from Saturn’s north polar region to south polar region. Image credit: NASA/JPL/University of Iowa. Enceladus animation

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Movie of Enceladus 'Footprint' on Saturn
NASA's Cassini spacecraft has spotted a glowing patch of ultraviolet light near Saturn's north pole that marks the presence of an electrical circuit that connects Saturn with its moon Enceladus. Image Credit: NASA/JPL/University of Colorado/Central Arizona College. Play video


PASADENA, Calif. -- NASA is releasing the first images and sounds of an electrical connection between Saturn and one of its moons, Enceladus. The data collected by the agency's Cassini spacecraft enable scientists to improve their understanding of the complex web of interaction between the planet and its numerous moons. The results of the data analysis are published in the journals Nature

Scientists previously theorized an electrical circuit should exist at Saturn. After analyzing data that Cassini collected in 2008, scientists saw a glowing patch of ultraviolet light emissions near Saturn's north pole that marked the presence of a circuit, even though the moon is 240,000 kilometers (150,000 miles) away from the planet.

The patch occurs at the end of a magnetic field line connecting Saturn and its moon Enceladus. The area, known as an auroral footprint, is the spot where energetic electrons dive into the planet's atmosphere, following magnetic field lines that arc between the planet's north and south polar regions.

"The footprint discovery at Saturn is one of the most important fields and particle revelations from Cassini and ultimately may help us understand Saturn's strange magnetic field," said Marcia Burton, a Cassini fields and particles scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It gives us the first visual connection between Saturn and one of its moons."

The auroral footprint measures approximately 1,200 kilometers (750 miles) by less than 400 kilometers (250 miles), covering an area comparable to California or Sweden. At its brightest, the footprint shone with an ultraviolet light intensity far less than Saturn's polar auroral rings, but comparable to the faintest aurora visible at Earth without a telescope in the visible light spectrum. Scientists have not found a matching footprint at the southern end of the magnetic field line.
Jupiter's active moon Io creates glowing footprints near Jupiter's north and south poles, so scientists suspected there was an analogous electrical connection between Saturn and Enceladus. It is the only known active moon in the Saturn system with jets spraying water vapor and organic particles into space. For years, scientists used space telescopes to search Saturn's poles for footprints, but they found none.

"Cassini fields and particles instruments found particle beams aligned with Saturn's magnetic field near Enceladus, and scientists started asking if we could see an expected ultraviolet spot at the end of the magnetic field line on Saturn," said Wayne Pryor, a lead author of the Nature study released today, and Cassini co-investigator at Central Arizona College in Coolidge, Ariz. "We were delighted to find the glow close to the 'bulls-eye' at the center of our target."

In 2008, Cassini detected a beam of energetic protons near Enceladus aligned with the magnetic field and field-aligned electron beams. A team of scientists analyzed the data and concluded the electron beams had sufficient energy flux to generate a detectable level of auroral emission at Saturn. A few weeks later, Cassini captured images of an auroral footprint in Saturn's northern hemisphere. In 2009, a group of Cassini scientists led by Donald Gurnett at the University of Iowa in Iowa City, detected more complementary signals near Enceladus consistent with currents that travel from the moon to the top of Saturn's atmosphere, including a hiss-like sound from the magnetic connection. That paper was published in March in Geophysical Research Letters.

The water cloud above the Enceladus jets produces a massive, ionized "plasma" cloud through its interactions with the magnetic bubble around Saturn. This cloud disturbs the magnetic field lines. The footprint appears to flicker in these new data, so the rate at which Enceladus is spewing particles may vary.

"The new data are adding fuel to the fire of some long-standing debates about this active little moon," said Abigail Rymer, the other lead author of the Nature study and a Cassini team scientist based at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "Scientists have been wondering whether the venting rate is variable, and these new data suggest that it is."

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

To see a video and hear the sounds of the electrical connection, and to get more information about the Cassini mission, visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Jia-Rui Cook 818-354-0850
Jet Propulsion Laboratory, Pasadena, Calif.
jccook@jpl.nasa.gov

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

NASA's Hubble Celebrates 21st Anniversary with "Rose" of Galaxies

Arp 273
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

To celebrate the 21st anniversary of the Hubble Space Telescope's deployment into space, astronomers at the Space Telescope Science Institute in Baltimore, Md., pointed Hubble's eye at an especially photogenic pair of interacting galaxies called Arp 273.

"For 21 years, Hubble has profoundly changed our view of the universe, allowing us to see deep into the past while opening our eyes to the majesty and wonders around us," NASA Administrator Charles Bolden said. "I was privileged to pilot space shuttle Discovery as it deployed Hubble. After all this time, new Hubble images still inspire awe and are a testament to the extraordinary work of the many people behind the world's most famous observatory."

Hubble was launched April 24, 1990, aboard Discovery's STS-31 mission. Hubble discoveries revolutionized nearly all areas of current astronomical research from planetary science to cosmology.

"Hubble is America's gift to the world," Sen. Barbara Mikulski of Maryland said. "Its jaw-dropping images have rewritten the textbooks and inspired generations of schoolchildren to study math and science. It has been documenting the history of our universe for 21 years. Thanks to the daring of our brave astronauts, a successful servicing mission in 2009 gave Hubble new life. I look forward to Hubble's amazing images and inspiring discoveries for years to come."

The newly released Hubble image shows a large spiral galaxy, known as UGC 1810, with a disk that is distorted into a rose-like shape by the gravitational tidal pull of the companion galaxy below it, known as UGC 1813. A swath of blue jewel-like points across the top is the combined light from clusters of intensely bright and hot young blue stars. These massive stars glow fiercely in ultraviolet light.

The smaller, nearly edge-on companion shows distinct signs of intense star formation at its nucleus, perhaps triggered by the encounter with the companion galaxy.

Arp 273 lies in the constellation Andromeda and is roughly 300 million light-years away from Earth. The image shows a tenuous tidal bridge of material between the two galaxies that are separated from each other by tens of thousands of light-years.

A series of uncommon spiral patterns in the large galaxy is a tell-tale sign of interaction. The large, outer arm appears partially as a ring, a feature seen when interacting galaxies actually pass through one another. This suggests that the smaller companion actually dived deep, but off-center, through UGC 1810. The inner set of spiral arms is highly warped out of the plane, with one of the arms going behind the bulge and coming back out the other side. How these two spiral patterns connect is still not precisely known.

A possible mini-spiral may be visible in the spiral arms of UGC 1810 to the upper right. It is noticeable how the outermost spiral arm changes character as it passes this third galaxy, from smooth with lots of old stars (reddish in color) on one side to clumpy and extremely blue on the other. The fairly regular spacing of the blue star-forming knots fits with what is seen in the spiral arms of other galaxies and is predictable based on instabilities in the gas contained within the arm.

The larger galaxy in the UGC 1810 - UGC 1813 pair has a mass that is about five times that of the smaller galaxy. In unequal pairs such as this, the relatively rapid passage of a companion galaxy produces the lopsided or asymmetric structure in the main spiral. Also in such encounters, the starburst activity typically begins in the minor galaxies earlier than in the major galaxies. These effects could be because the smaller galaxies have consumed less of the gas present in their nuclei, from which new stars are born.

The interaction was imaged on December 17, 2010, with Hubble's Wide Field Camera 3 (WFC3). The picture is a composite of data taken with three separate filters on WFC3 that allow a broad range of wavelengths covering the ultraviolet, blue, and red portions of the spectrum.

CONTACT

Trent J. Perrotto
NASA Headquarters, Washington
202-358-0321
trent.j.perrotto@nasa.gov

Ray Villard / Mario Livio / Keith Noll
Space Telescope Science Institute, Baltimore, Md.
410-338-4514 / 410-338-4439 / 410-338-1828
villard@stsci.edu / mlivio@stsci.edu / noll@stsci.edu

A Disturbed Galactic Duo

PR Image eso1114a
The disturbed galactic duo NGC 3169 and NGC 3166

PR Image eso1114b
NGC 3169 and NGC 3166 in the constellation of Sextans

PR Image eso1114c
Wide-field view of the sky around NGC 3169 and NGC 3166

PR Image eso1114d
Supernova 2003cg in the galaxy NGC 3169

PR Video eso1114a
Zooming in on the disturbed galactic duo NGC 3169 and NGC 3166

The galaxies in this cosmic pairing, captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, display some curious features, demonstrating that each member of the duo is close enough to feel the distorting gravitational influence of the other. The gravitational tug of war has warped the spiral shape of one galaxy, NGC 3169, and fragmented the dust lanes in its companion NGC 3166. Meanwhile, a third, smaller galaxy to the lower right, NGC 3165, has a front-row seat to the gravitational twisting and pulling of its bigger neighbours.

This galactic grouping, found about 70 million light-years away in the constellation Sextans (The Sextant), was discovered by the English astronomer William Herschel in 1783. Modern astronomers have gauged the distance between NGC 3169 (left) and NGC 3166 (right) as a mere 50 000 light-years, a separation that is only about half the diameter of the Milky Way galaxy. In such tight quarters, gravity can start to play havoc with galactic structure.

Spiral galaxies like NGC 3169 and NGC 3166 tend to have orderly swirls of stars and dust pinwheeling about their glowing centres. Close encounters with other massive objects can jumble this classic configuration, often serving as a disfiguring prelude to the merging of galaxies into one larger galaxy. So far, the interactions of NGC 3169 and NGC 3166 have just lent a bit of character. NGC 3169’s arms, shining bright with big, young, blue stars, have been teased apart, and lots of luminous gas has been drawn out from its disc. In NGC 3166’s case, the dust lanes that also usually outline spiral arms are in disarray. Unlike its bluer counterpart, NGC 3166 is not forming many new stars.

NGC 3169 has another distinction: the faint yellow dot beaming through a veil of dark dust just to the left of and close to the galaxy’s centre [1]. This flash is the leftover of a supernova detected in 2003 and known accordingly as SN 2003cg. A supernova of this variety, classified as a Type Ia, is thought to occur when a dense, hot star called a white dwarf — a remnant of medium-sized stars like our Sun — gravitationally sucks gas away from a nearby companion star. This added fuel eventually causes the whole star to explode in a runaway fusion reaction.

The new image presented here of a remarkable galactic dynamic duo is based on data selected by Igor Chekalin for ESO’s Hidden Treasures 2010 astrophotography competition. Chekalin won the first overall prize and this image received the second highest ranking of the nearly 100 contest entries [2].

Notes

[1] Other much more noticeable points of light, such as the one toward the left end of the spiral arm running underneath of NGC 3169’s core, are stars within the Milky Way that happen to fall by chance very close to the line of sight between our telescopes and the galaxies.

[2] ESO’s Hidden Treasures 2010 competition gave amateur astronomers the opportunity to search through ESO’s vast archives of astronomical data, hoping to find a well-hidden gem that needed polishing by the entrants. To find out more about Hidden Treasures, visit http://www.eso.org/public/outreach/hiddentreasures/.

More information

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. 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 VISTA, the world’s largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links
Photos of La Silla Observatory
The MPG/ESO 2.2-metre telescope

Contacts

Richard Hook
ESO, La Silla, Paranal, E-ELT and Survey Telescopes Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org

Monday, April 18, 2011

NASA Kepler Reaching into the Stars

An artist's rendering that compares the approximate size and color of the stars in the triple-eclipsing system HD 181068. Image credit: NASA/KASC. Full-Res image

We are entering a golden era for "stellar physics" – a term coined to describe research about the formation, evolution, interior and the atmospheres of stars. Thanks to a partnership forged among stellar astrophysics, scientists and NASA’s Kepler Mission, a goldmine of data is now available to support the world's efforts to detect planets in the habitable zone around other stars.

The Kepler photometric data is a measurement of light’s “brightness,” and provides an unprecedented opportunity for the emerging field of asteroseismology, the study of the internal structure of stars by observing minuscule pulsations in the star brightness. Asteroseismic research is giving insights into the fundamental properties of stars, including their mass, size, age and internal structure. Kepler enables studies of a large number of stars representing a broad range of types. This asteroseismic research will substantially improve our understanding of stellar evolution. It also will help determine the properties of stars that have planetary systems studied in the Kepler exoplanet program.

The Kepler Asteroseismic Science Consortium (KASC) pushes the envelope in this field of study. Using the unparalleled precision and quality of Kepler data, the KASC research is contributing to stellar astrophysics in profound ways. The consortium is comprised of more than 400 scientists and is led by the Danish Asteroseismology Centre in the Department of Physics and Astronomy at the University of Aarhus, Denmark.

The KASC recently presented new findings published in three papers in the journal Science. In combination, these latest results illustrate the power of the Kepler Space Telescope to probe the internal structure of distant stars.

Kepler Listens to an Orchestra of Sun-like Stars to Tune the Galactic Models

The scientific investigation of sun-like stars has taken a major step forward thanks to the Kepler Mission. In addition to searching for exoplanets, it is providing exquisite data on stellar oscillations.

"The sound inside the stars makes them ring or vibrate like musical instruments," said Bill Chaplin from the University of Birmingham’s School of Physics and Astronomy, the lead author of this paper. "If you measure the pitch of the notes produced by an instrument it can tell you how big the instrument is. The bigger the instrument is, the lower the pitch and deeper the sound. This is how we can tell how big a star is - from its stellar music."

Oscillation measurements are used to accurately determine fundamental stellar properties like mass, size, and age. This is where theory meets observation. Scientists can synthesize a snapshot of our galaxy and all the stars it contains using models based on everything we know about how much raw material there is in our galaxy for building stars, what types of stars are made, how they evolve with time, and how long they live. They can then compare the properties of stars in this synthetic snapshot with the properties of the sun-like stars in the asteroseismic survey. In essence, the team has taken a census and compared it to predictions, and found that the sizes of the stars are consistent with the predictions, but the masses are not. The asteroseismic survey suggests that the number of low mass stars is slightly larger than expected. This work sends theoreticians back to refine their models and will ultimately lead to a better understanding of the structure and evolution of stars in our galaxy.

"Before Kepler we had asteroseismic data on only about 20 such stars - We now have an orchestra of stars to play with," said Hans Kjeldsen from Aarhus from the Danish Asteroseismology Centre in Aarhus, who coordinates KASC. "This opens up huge possibilities for probing stellar evolution and obtaining a clearer picture of the past and future of our own sun and how our galaxy, and others like it, has evolved over time. We can, for example, pick out stars that have the same mass of the sun but have different ages, to, in effect, follow the sun in time."

To read the full paper in Science, visit: Ensemble Asteroseismology of Solar-type Stars with the NASA Kepler Mission, by W. J. Chaplin et al, Science 8 April 2011: 213-216. [DOI:10.1126/science.1201827]

Astronomers Detect Echoes from the Depth of a Red Giant Star

An international team of astronomers reports the unexpected discovery of waves inside a star that travel so deep that they reach the core. Waves traversing stars, similar to sound waves here on Earth, were already known to exist, but until now only waves traveling the outer part of the star, or as deep as hundreds of thousands of kilometers, were detected. At a certain depth, the stellar material is too dense for waves to penetrate so they bounce back to the surface. The detection of waves that reach the star's core reveal conditions that open a window to an inferno that otherwise would remain unreachable and hidden. The discovery was made in a red giant star, an elderly star, similar to what our sun will become in about 5 billion years.

"Having a view into the core of these red giants will teach us exactly what will happen to our sun when it grows older," said Paul Beck, a PhD student at Leuven University in Belgium.

To read the full paper in Science, visit: Kepler-Detected Gravity-Mode Period Spacings in a Red Giant Star, by P.G. Beck et al, Science 8 April 2011: 180-181. [DOI: 10.1126/science.1203887]

Kepler Discovery of a Unique Triply Eclipsing Triple Star

Aliz Derekas of Eotvos University and Konkoly Observatoryin Budapest, Hungary, used Kepler data to learn more about a unique three-star system known as HD 181068, which the authors named 'Trinity.' The triple system is comprised of two red dwarfs orbiting each other and simultaneously orbiting a more distant red giant star that is 12.4 times larger than our sun (figure 1). These systems are important for testing theories of star formation and evolution. While triple systems are not uncommon, this particular triple system is oriented perfectly to make the red dwarfs and the red giant regularly eclipse each other. The surface brightness of the three stars are very similar, so just as a white rabbit is camouflaged in snow, when the red dwarfs are in front of the red giant, their eclipses are nearly undetectable. Careful analyses of red giant stars observed by Kepler have shown that they exhibit oscillations similar to those in the sun. Trinity’s red giant star does not. This would indicate a mysterious mechanism that suppresses the pulsation.

"Surprisingly, we do detect some variability but with periods that are closely linked to the orbital period of the close pair in the system," said Derekas. "This may indicate that tidal forces of the close pair induce vibrations in the red giant. The intriguing nature of this unique system remained unnoticed until now despite the fact that it is nearly bright enough to be visible to the naked eye. We really needed Kepler with its unprecedentedly precise and uninterrupted photometric monitoring to uncover such a rare gem," she added.

To read the full paper in Science, visit: A Red Giant in a Triply-Eclipsing Compact Hierarchical Triple System, by Derekas et al, Science 8 April 2011: 216-218. [DOI:10.1126/science.1201762]

To listen to an interview with Michael Montgomery, University of Texas at Austin, as he discusses Kepler's observations and what they reveal about the internal structure of distant stars, visit: Science Podcast.

Michele Johnson, Public Affairs Officer, Kepler Mission
Ames Research Center, Moffett Field, Calif.

Thursday, April 14, 2011

WISE Delivers Millions of Galaxies, Stars, Asteroids

NASA's Wide-field Infrared Survey Explorer (WISE)
Play Slideshow

First Batch of Data Released
WISE has released 57 percent of its first sky survey to the astronomy community, as depicted here in this two-dimensional projection of the whole sky. The fuzzy line down the middle is our Milky Way galaxy, and bright clouds are star-forming complexes. Image credit: NASA/JPL-Caltech/UCLA .

Orion’s Big Head Revealed
In Greek mythology, Orion was a vain hunter who was banished to the sky. NASA’s Wide-field Infrared Survey Explorer, or WISE, has captured a picture of the hunter's "head" (fuzzy red star in middle). The picture shows a giant nebula around the star -- inflating Orion's head to huge proportions.

The Art of Making Stars
It might look like an abstract painting, but this splash of colors is in fact a busy star-forming complex called Rho Ophiuchi. WISE captured this picturesque image of the region, which is one of the closest star-forming complexes to Earth.

Star Plows Through Space
A massive star flung away from its former companion is plowing through space dust. The result is a brilliant bow shock, seen here as a yellow arc.

Galaxies of a Different Color
WISE captured a striking view of two companion galaxies -- a somewhat tranquil spiral beauty (blue galaxy) and its rambunctious partner blazing with smoky star formation (yellow galaxy).

Jellyfish or Dying Star?
This image composite shows two views of a puffy, dying star, or planetary nebula, known as NGC 1514. The view on the left is from a ground-based, visible-light telescope; the view on the right shows the object in infrared light, as seen by WISE.

Andromeda Galaxy (M31)
The immense Andromeda galaxy, also known as Messier 31 or simply M31, is captured in full. The mosaic covers an area equivalent to more than 100 full moons, or five degrees across the sky.

Cosmic Rosebud
This image shows a cosmic rosebud blossoming with new stars. The stars, called the Berkeley 59 cluster, are the blue dots to the right of the image center. They are ripening out of the dust cloud from which they formed, and at just a few million years old, are young on stellar time scales.

The Hidden Galaxy (IC 342)
The spiral beauty, called IC 342 and sometimes Hidden galaxy, is shrouded behind our Milky Way galaxy's bright band of stars, dust and gas. WISE's infrared vision cuts through this veil, offering a crisp view.
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Soul Nebula
This cosmic cloud, known as the Soul nebula, is one of many sites of star formation within the Milky Way galaxy. It is located 3,800 light-years away from Earth and is nearly 240 light-years across.

Tycho's Supernova Remnant
The red circle visible in the image is SN 1572, also known as Tycho's supernova remnant. When the star exploded, it sent a blast wave into the surrounding material, scooping up interstellar dust and gas as it went. The light captured by WISE in this view is from dust heated by the shock wave.
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Comet Siding Spring
A comet like this one spends most of its long life in the darkest, coldest parts of our solar system. It heats up as it approaches the sun, shedding ices and dust in a long tail. Comet Siding Spring, having experienced this warm awakening, is glowing in infrared light that WISE can see.

WISE's First Near-Earth Asteroid
The red dot near the center of this image is the first near-Earth asteroid discovered by WISE. This particular asteroid, 2010 AB78, is roughly one kilometer (0.6 miles) in diameter, and is about 158 million kilometers (98 million miles) away from Earth. Its path will not intersect with Earth.

Star Clusters
This colorful image is a view of an area of the sky more than 12 times the size of our full moon. Two types of star clusters are visible -- a wispy nebula and a globular star cluster.

Astronomers across the globe can now sift through hundreds of millions of galaxies, stars and asteroids collected in the first bundle of data from NASA's Wide-field Infrared Survey Explorer (WISE) mission.

"Starting today thousands of new eyes will be looking at WISE data, and I expect many surprises," said Edward (Ned) Wright of UCLA, the mission's principal investigator.

WISE launched into space on Dec. 14, 2009 on a mission to map the entire sky in infrared light with greatly improved sensitivity and resolution over its predecessors. From its polar orbit, it scanned the skies about one-and-a-half times while collecting images taken at four infrared wavelengths of light. It took more than 2.7 million images over the course of its mission, capturing objects ranging from faraway galaxies to asteroids relatively close to Earth.

Like other infrared telescopes, WISE required coolant to chill its heat-sensitive detectors. When this frozen hydrogen coolant ran out, as expected, in early October, 2010, two of its four infrared channels were still operational. The survey was then extended for four more months, with the goal of finishing its sweep for asteroids and comets in the main asteroid belt of our solar system.

The mission's nearby discoveries included 20 comets, more than 33,000 asteroids between Mars and Jupiter, and 133 near-Earth objects (NEOs), which are those asteroids and comets with orbits that come within 28 million miles (about 45 million kilometers) of Earth's path around the sun. The satellite went into hibernation in early February of this year.

Today, WISE is taking the first major step in meeting its primary goal of delivering the mission's trove of objects to astronomers. Data from the first 57 percent of the sky surveyed is accessible through an online public archive. The complete survey, with improved data processing, will be made available in the spring of 2012. A predecessor to WISE, the Infrared Astronomical Satellite, served a similar role about 25 years ago, and those data are still valuable to astronomers today. Likewise, the WISE legacy is expected to endure for decades.

"We are excited that the preliminary data contain millions of newfound objects," said Fengchuan Liu, the project manager for WISE at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "But the mission is not yet over -- the real treasure is the final catalog available a year from now, which will have twice as many sources, covering the entire sky and reaching even deeper into the universe than today's release."

Astronomers will use WISE's infrared data to hunt for hidden oddities, and to study trends in large populations of known objects. Survey missions often result in the unexpected discoveries too, because they are looking everywhere in the sky rather than at known targets. Data from the mission are also critical for finding the best candidates for follow-up studies with other telescopes, including the European Space Agency's Herschel observatory, which has important NASA contributions.

"WISE is providing the newest-generation 'address book' of the infrared universe with the precise location and brightness of hundreds of millions of celestial objects," said Roc Cutri, lead scientist for WISE data processing at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, Calif. "WISE continues the long tradition of infrared sky surveys supported by Caltech, stretching back to the 1969 Two Micron Sky Survey."

So far, the WISE mission has released dozens of colorful images of the cosmos, in which infrared light has been assigned colors we see with our eyes. The whole collection can be seen at http://wise.ssl.berkeley.edu/gallery_images.html .

The public archive for astronomers is online at http://wise2.ipac.caltech.edu/docs/release/prelim/index.html. Instructions for astronomy enthusiasts wanting to try their hand at using the archive are at http://wise.ssl.berkeley.edu/wise_image_service.html.

JPL manages and operates the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.


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