Hearts of Galaxies Close in for Cosmic Train Wreck

A new image from NASA's Spitzer Space Telescope offers a rare view of an imminent collision between the cores of two merging galaxies, each powered by a black hole with millions of times the mass of the sun.

The galactic cores are in a single, tangled galaxy called NGC 6240, located 400-million light years away in the constellation Ophiuchus. Millions of years ago, each core was the dense center of its own galaxy before the two galaxies collided and ripped each other apart. Now, these cores are approaching each other at tremendous speeds and preparing for the final cataclysmic collision. They will crash into each other in a few million years, a relatively short period on a galactic timescale.

The spectacular image combines visible light from NASA's Hubble Space Telescope and infrared light from Spitzer. It catches the two galaxies during a rare, short-lived phase of their evolution, when both cores of the interacting galaxies are still visible but closing in on each other fast.

"One of the most exciting things about the image is that this object is unique," said Stephanie Bush of the Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass., lead author of a new paper describing the observation in an upcoming issue of the Astrophysical Journal. "Merging is a quick process, especially when you get to the train wreck that is happening. There just aren't many galactic mergers at this stage in the nearby universe."

NGC 6240 is already putting out huge amounts of infrared light, an indication that a burst of star formation is underway. The extra infrared radiation is common in interacting galaxies; as the two galaxies interact, dust and gas swept up by the collision form a burst of new stars that give off infrared light. Such galaxies are called luminous infrared galaxies. Spitzer's infrared array camera can image the extra heat from newly formed stars, even though their visible light is obscured by thick dust clouds around them.

The blob-like shape of the galaxy is due to the sustained violence of the collision. Streams of millions of stars are being ripped off the galaxy, forming wispy "tidal tails" that lead off NGC 6240 in several directions. But things are about to get even more violent as the main event approaches and the two galactic cores meld into one.

In the center of NGC 6240, the two black holes in the cores will whip up a frenzy of radiation as they careen towards one another head-on, likely transforming the galaxy into a monster known as an ultra-luminous infrared galaxy, thousands of times as bright in infrared as our Milky Way.

Another fascinating aspect of this rare object is that no two galactic mergers are the same. "Not only are there few objects at this stage, but each object is unique because it came from different progenitor galaxies," said Bush. "These observations give us another layer of information about this galaxy, and galactic mergers in general."

Infrared light taken by Spitzer's infrared array camera at 3.6 and 8.8 microns (red) shows cold dust and radiation from star formation; visible light from Hubble (green and blue) shows hot gas and stars.

Other authors of this paper include Zhong Wang, Margarita Karovska and Giovanni Fazio, all of the Harvard-Smithsonian Center for Astrophysics. NASA's Jet Propulsion Laboratory, Pasadena, Calif., 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, also in Pasadena. Caltech manages JPL for NASA.

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov
ssc2009-06
jpl2009-050

About the Object

• Object name: NGC 6240

• Object type: Galaxy

• Position (J2000): RA: 16h 52m 58.97s Dec: 2° 24' 1.70"

• Distance: 400,000,000 Light Years

• Constellation: Ophiuchus

About the Data - Spitzer Data

• Image Credit: NASA/JPL-Caltech/STScI-ESA

• Instrument: IRAC

• Wavelength: 3.6 and 8.0 microns (red), visible light (green and blue)

Printable version (PDF) of this release

New Horizons Detects Neptune’s Moon Triton

The top frame is a composite, full-frame (0.29° by 0.29°) LORRI image of Neptune taken Oct. 16, 2008, using an exposure time of 10 seconds and 4-by-4 pixel re-binning to achieve its highest possible sensitivity. The bottom frame is a twice-magnified view that more clearly shows the detection of Triton, Neptune’s largest moon. Neptune is the brightest object in the field and is saturated (on purpose) in this long exposure. Triton, which is about 16 arcsec east (celestial north is up, east is to the left) of Neptune, is approximately 180 times fainter.

Scientists consider Triton to be one of the best analogs of Pluto in the solar system. All the other objects in the image are background field stars. The dark “tails” on the brightest objects are artifacts of the LORRI charge-coupled device (CCD); the effect is small but easily seen in this logarithmic intensity stretch.
The original image was taken to test New Horizons’ optical navigation capabilities.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

Add another moon to the New Horizons photo gallery: the spacecraft’s Long Range Reconnaissance Imager detected Triton, the largest of Neptune’s 13 known moons, during the annual spacecraft checkout last fall.

New Horizons was 2.33 billion miles (3.75 billion kilometers) from Neptune on Oct. 16, when LORRI, following a programmed sequence of commands, locked onto the planet and snapped away.

“We wanted to test LORRI’s ability to measure a faint object near a much brighter one using a special tracking mode,” says New Horizons Project Scientist Hal Weaver, of the Johns Hopkins University Applied Physics Laboratory, “and the Neptune-Triton pair perfectly fit the bill.” LORRI was operated in 4-by-4 format (the original pixels are binned in groups of 16), and the spacecraft was put into a special tracking mode to allow for longer exposure times. “We needed to achieve the highest possible sensitivity,” Weaver adds.

Mission scientists also wanted to measure Triton itself. “Among the objects visited by spacecraft so far, Triton is by far the best analog of Pluto,” says New Horizons Principal Investigator Alan Stern. The Voyager 2 spacecraft took spectacular images of Triton during its flyby of Neptune in 1989, showing evidence of cryovolcanic activity and cantaloupe-like terrain.

Triton is only slightly larger than Pluto (1,700 miles [2,700 kilometers] in diameter compared to Pluto’s 1,500 miles [2,400 kilometers]). Both objects have atmospheres primarily composed of nitrogen gas with a surface pressure only 1/70,000th of Earth’s, and comparably cold surface temperatures (-390° F on Triton and -370° F on Pluto). Triton is widely believed to have once been a member of the Kuiper Belt (as Pluto still is) that was captured into orbit around Neptune, probably during a collision early in the solar system’s history.

New Horizons can observe Neptune and Triton at solar phase angles (the Sun-object-spacecraft angle) that are not possible to achieve from Earth-based facilities, and this unique perspective can provide insight into the properties of Titan’s surface and Neptune’s atmosphere.

LORRI will continue to observe the Neptune-Triton pair during annual checkouts until the Pluto encounter in 2015.

New Horizons is currently in electronic hibernation, 1.2 billion miles (1.93 billion kilometers) from home, speeding away from the Sun at 38,520 miles (61,991 kilometers) per hour.

Source: New Horizons Web Site

NGC 4194 - A Black Hole in Medusa's Hair

Credit: X-ray: NASA/CXC/Univ of Iowa/P.Kaaret et al.;
Optical: NASA/ESA/STScI/Univ of Iowa/P.Kaaret et al.

This composite image of the Medusa galaxy (also known as NGC 4194) shows X-ray data from NASA's Chandra X-ray Observatory in blue and optical light from the Hubble Space Telescope in orange.

Located above the center of the galaxy and seen in the optical data, the "hair" of the Medusa -- made of snakes in the Greek myth -- is a tidal tail formed by a collision between galaxies. The bright X-ray source found towards the left side of Medusa's hair is a black hole.

Most bright X-ray sources in galaxies are binaries containing either stellar mass black holes or neutron stars that remain after the supernova explosion of a massive star. Because these compact objects can generate X-rays for much longer periods of time than the lifetime of their massive progenitor stars, X-ray binaries may be used as "fossils" to study the star formation history of their host galaxies. In this Medusa image, the X-ray binaries are seen as the bright blue point-like objects.

A recent study of the Medusa galaxy and nine other galaxies measured the correlation between the formation of stars and the production of X- ray binaries. A key feature was to study this correlation for the Medusa galaxy and NGC 7541, two galaxies with particularly high star formation rates. It was found that both the number of bright X-ray sources and their average brightness were related to the rate at which stars formed. This work may be useful for attempts to use X-ray brightness to measure the rate of star formation in galaxies at very large distances.

It was also found that for every one million tons of gas that goes into making stars, one ton gets pulled onto a stellar mass black hole or a neutron star. This result may help create more accurate models of the formation of X-ray binaries.

Fast Facts for NGC 4194 :

Scale: Image is 2.5 arcmin across.
Category: Groups & Clusters of Galaxies
Coordinates: (J2000) RA 12h 14m 09.5s | Dec +54° 31' 37
Constellation: Ursa Major
Observation Date: September 9th, 2006
Observation Time: 10 hours
Obs. ID: 7071
Color Code: X-ray (Blue); Optical (Orange)
Instrument: ACIS
Also Known As: Medusa Galaxy
References: P. Kaaret & A. Alonso-Herrero, 2008, ApJ, 682, 1020
Distance Estimate: About 110 million light years

Source: Chandra X-Ray Observatory

Galactic Dust Bunnies Found to Contain Carbon After All

Cat's Eye Nebula (NGC 6543)
NASA/JPL-Caltech/J. Hora (Harvard-Smithsonian CfA)

The image is a composite of data from Spitzer's infrared array camera. Light with a wavelength of 3.6 microns is rendered as blue, 5.8 microns is displayed as green and 8.0 microns is represented in red. The brightness of the central area has been greatly reduced to make it possible to maintain its visibility while enhancing the brightness of the much fainter outer features. Overall colors have been enhanced to better show slight variations in hue.

Using NASA's Spitzer Space Telescope, researchers have found evidence suggesting that stars rich in carbon complex molecules may form at the center of our Milky Way galaxy.

This discovery is significant because it adds to our knowledge of how stars form heavy elements — like oxygen, carbon, and iron — and then blow them out across the universe, making it possible for life to develop.

Astronomers have long been baffled by a strange phenomenon: Why have their telescopes never detected carbon-rich stars at the center of our galaxy even though they have found these stars in other places? Now, by using Spitzer's powerful infrared detectors, a research team has found the elusive carbon stars in the galactic center.

"The dust surrounding the stars emits very strongly at infrared wavelengths," says Pedro García-Lario, a research team member who is on the faculty of the European Space Astronomy Center, the European Space Agency's center for space science. He co-authored a paper on this subject in the February 2009 issue of the journal Astronomy & Astrophysics.

"With the help of Spitzer spectra, we can easily determine whether the material returned by the stars to the interstellar medium is oxygen-rich or carbon-rich."

The team of scientists analyzed the light emitted from 40 planetary nebulae — blobs of dust and gas surrounding stars — using Spitzer's infrared spectrograph. They analyzed 26 nebulae toward the center of the Milky Way — a region called the "Galactic Bulge" — and 14 nebulae in other parts of the galaxy. The scientists found a large amount of crystalline silicates and polycyclic aromatic hydrocarbons, two substances that indicate the presence of oxygen and carbon.

This combination is unusual. In the Milky Way, dust that combines both oxygen and carbon is rare and is usually only found surrounding a binary system of stars. The research team, however, found that the presence of the carbon-oxygen dust in the Galactic Bulge seems to be suggestive of a recent change of chemistry experienced by the star.

The scientists hypothesize that as the central star of a planetary nebula ages and dies, its heavier elements do not make their way to the star's outer layers, as they do in other stars. Only in the last moments of the central star's life, when it expands and then violently expels almost all of its remaining outer gasses, does the carbon become detectable. That's when astronomers see it in the nebula surrounding the star.

"The carbon produced through these recurrent 'thermal pulses' is very inefficiently dredged up to the surface of the star, contrary to what is observed in low-metallicity, galactic disk stars," said García-Lario. "It only becomes visible when the star is about to die."

This study supports a hypothesis about why the carbon in some stars does not make its way to the stars' surfaces. Scientists believe that small stars — those with masses up to one-and-a-half times the mass of our sun — that contain lots of metal do not bring carbon to their surfaces as they age. Stars in the Galactic Bulge tend to have more metals than other stars, so the Spitzer data support this commonly held hypothesis. Before the Spitzer study, this hypothesis had never been supported by observation.

This aging and expelling process is typical of all stars. As stars age and die, they burn progressively heavier and heavier elements, beginning with hydrogen and ending with iron. Towards the end of their lives, some stars become what are called "red giants." These dying stars swell so large that if one of them were placed in our solar system, where the sun is now, its outermost border would touch Earth's orbit. As these stars pulsate — losing mass in the process — and then contract, they spew out almost all of their heavier elements. These elements are the building blocks of all planets, including our own Earth (as well as of human beings and any other life forms that may exist in the universe).

The paper is co-authored by José Vicente Perea-Calderón of the European Space Astronomy Center in Villanueva de la Cañada, Spain; Domingo Anibal García-Lario-Hernández of the Instituto de Astrofísica de Canarias, on Spain's Tenerife island; Ryszard Szczerba of the Nicolaus Copernicus Astronomical Center in Torun, Poland; and Matt Bobrowsky of the University of Maryland, College Park.

About the Object

• Object name: Cat's Eye, NGC 6543

• Object type: Nebula

• Position (J2000): RA: 17h 58m 33.42s Dec: 66° 37' 59.52"

• Distance: 3300 Light Years

• Constellation: Draco

About the Data - Spitzer Data

• Image Credit: NASA/JPL-Caltech/J. Hora (Harvard-Smithsonian CfA)

• Instrument: IRAC

• Wavelength: 3.6 Micron (Blue), 5.8 Micron (Green), 8.0 Micron (Red)

• Release Date: 2009/03/12

Hubble Provides New Evidence for Dark Matter Around Small Galaxies

Credit: NASA, ESA, and C. Conselice and S. Penny (University of Nottingham)

ABOUT THIS IMAGE: These four dwarf galaxies are part of a census of small galaxies in the tumultuous heart of the nearby Perseus galaxy cluster.
The galaxies appear smooth and symmetrical, suggesting that they have not been tidally disrupted by the pull of gravity in the dense cluster environment. Larger galaxies around them, however, are being ripped apart by the gravitational tug of other galaxies.
The images, taken by NASA's Hubble Space Telescope, are evidence that the undisturbed galaxies are enshrouded by a "cushion" of dark matter, which protects them from their rough-and-tumble neighborhood.

Dark matter is an invisible form of matter that accounts for most of the universe's mass. Astronomers have deduced the existence of dark matter by observing its gravitational influence on normal matter, consisting of stars, gas, and dust.

Observations by Hubble's Advanced Camera for Surveys spotted 29 dwarf elliptical galaxies in the Perseus Cluster, located 250 million light-years away and one of the closest galaxy clusters to Earth. Of those galaxies, 17 are new discoveries.
The images were taken in 2005.

NASA's Hubble Space Telescope has uncovered a strong new line of evidence that galaxies are embedded in halos of dark matter.

Peering into the tumultuous heart of the nearby Perseus galaxy cluster, Hubble discovered a large population of small galaxies that have remained intact while larger galaxies around them are being ripped apart by the gravitational tug of other galaxies.

Dark matter is an invisible form of matter that accounts for most of the universe's mass. Astronomers have deduced the existence of dark matter by observing its gravitational influence on normal matter, consisting of stars, gas, and dust.

The Hubble images provide further evidence that the undisturbed galaxies are enshrouded by a "cushion" of dark matter, which protects them from their rough-and-tumble neighborhood.

"We were surprised to find so many dwarf galaxies in the core of this cluster that were so smooth and round and had no evidence at all of any kind of disturbance," says astronomer Christopher Conselice of the University of Nottingham, U.K., and leader of the Hubble observations. "These dwarfs are very old galaxies that have been in the cluster a long time. So if something was going to disrupt them, it would have happened by now. They must be very, very dark-matter-dominated galaxies."

The dwarf galaxies may have an even higher amount of dark matter than spiral galaxies. "With these results, we cannot say whether the dark-matter content of the dwarfs is higher than in the Milky Way Galaxy," Conselice says. "Although, the fact that spiral galaxies are destroyed in clusters, while the dwarfs are not, suggests that is indeed the case."

First proposed about 80 years ago, dark matter is thought to be the "glue" that holds galaxies together. Astronomers suggest that dark matter provides a vital "scaffolding" for the universe, forming a framework for the formation of galaxies through gravitational attraction. Previous studies with Hubble and NASA's Chandra X-ray Observatory found evidence of dark matter in entire clusters of galaxies such as the Bullet Cluster. The new Hubble observations continue the search for dark matter in individual galaxies.

Observations by Hubble's Advanced Camera for Surveys spotted 29 dwarf elliptical galaxies in the Perseus Cluster, located 250 million light-years away and one of the closest galaxy clusters to Earth. Of those galaxies, 17 are new discoveries.

Because dark matter cannot be seen, astronomers detected its presence through indirect evidence. The most common method is by measuring the velocities of individual stars or groups of stars as they move randomly in the galaxy or as they rotate around the galaxy. The Perseus Cluster is too far away for telescopes to resolve individual stars and measure their motions. So Conselice and his team derived a new technique for uncovering dark matter in these dwarf galaxies by determining the minimum mass the dwarfs must have to protect them from being disrupted by the strong, tidal pull of gravity from larger galaxies.

Studying these small galaxies in detail was possible only because of the sharpness of Hubble's Advanced Camera for Surveys. Conselice and his team first spied the galaxies with the WIYN Telescope at Kitt Peak National Observatory outside Tucson, Ariz. Those observations, Conselice says, only hinted that many of the galaxies were smooth and therefore dark-matter dominated. "Those ground-based observations could not resolve the galaxies, so we needed Hubble imaging to nail it," he says.

The Hubble results appeared in the March 1 issue of the Monthly Notices of the Royal Astronomical Society.

Other team members are Samantha J. Penny of the University of Nottingham; Sven De Rijcke of the University of Ghent in Belgium; and Enrico Held of the University of Padua in Italy.

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

Christopher Conselice
University of Nottingham, Nottingham, UK
011-44-115-951-5137
011-44-750-347-6126 (cell)
conselice@nottingham.ac.uk

Fermi's Best-Ever Look at the Gamma-Ray Sky

A new map combining nearly three months of data from NASA's Fermi Gamma-ray Space Telescope is giving astronomers an unprecedented look at the high-energy cosmos. To Fermi's eyes, the universe is ablaze with gamma rays from sources within the solar system to galaxies billions of light-years away.

This view from NASA's Fermi Gamma-ray Space Telescope is the deepest and best-resolved portrait of the gamma-ray sky to date. The image shows how the sky appears at energies more than 150 million times greater than that of visible light. Among the signatures of bright pulsars and active galaxies is something familiar -- a faint path traced by the sun.
Credit: NASA/DOE/Fermi LAT Collaboration

High resolution labeled view
High resolution unlabeled view

"Fermi has given us a deeper and better-resolved view of the gamma-ray sky than any previous space mission," said Peter Michelson, the lead scientist for the spacecraft's Large Area Telescope (LAT) at Stanford University, Calif. "We're watching flares from supermassive black holes in distant galaxies and seeing pulsars, high-mass binary systems, and even a globular cluster in our own."

A paper describing the 205 brightest sources the LAT sees has been submitted to The Astrophysical Journal Supplement. "This is the first science product from the mission, and it's a major step toward producing our first catalog later this year," said David Thompson, a Fermi deputy project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md.

The LAT scans the entire sky every three hours when operating in survey mode, which is occupying most of the telescope’s observing time during Fermi's first year of operations. These snapshots let scientists monitor rapidly changing sources.

The all-sky image released today shows us how the cosmos would look if our eyes could detect radiation 150 million times more energetic than visible light. The view merges LAT observations spanning 87 days, from August 4 to October 30, 2008.

To better show individual sources, the new map was processed to suppress emissions from gas in the plane of our galaxy, the Milky Way. As a way of underscoring the variety of the objects the LAT is seeing, the Fermi team created a "top ten" list comprising five sources within the Milky Way and five beyond our galaxy.

The Large Area Telescope (LAT) on Fermi detects gamma-rays through matter (electrons) and antimatter (positrons) they produce after striking layers of tungsten. Credit: NASA/Goddard Space Flight Center Conceptual Image Lab

Click to view animation
Click to view hi resolution image

The top five sources within our galaxy are:

The sun. Now near the minimum of its activity cycle, the sun would not be a particularly notable source except for one thing: It's the only one that moves across the sky. The sun's annual motion against the background sky is a reflection of Earth's orbit around the sun.

"The gamma rays Fermi now sees from the sun actually come from high-speed particles colliding with the sun's gas and light," Thompson notes. "The sun is only a gamma-ray source when there's a solar flare." During the next few years, as solar activity increases, scientists expect the sun to produce growing numbers of high-energy flares, and no other instrument will be able to observe them in the LAT's energy range.

LSI +61 303. This is a high-mass X-ray binary located 6,500 light-years away in Cassiopeia. This unusual system contains a hot B-type star and a neutron star and produces radio outbursts that recur every 26.5 days. Astronomers cannot yet account for the energy that powers these emissions.

PSR J1836+5925. This is a pulsar -- a type of spinning neutron star that emits beams of radiation -- located in the constellation Draco. It's one of the new breed of pulsars discovered by Fermi that pulse only in gamma rays.

47 Tucanae. Also known as NGC 104, this is a sphere of ancient stars called a globular cluster. It lies 15,000 light-years away in the southern constellation Tucana.

Unidentified. More than 30 of the brightest gamma-ray sources Fermi sees have no obvious counterparts at other wavelengths. This one, designated 0FGL J1813.5-1248, was not seen by previous missions, and Fermi's LAT sees it as variable. The source lies near the plane of the Milky Way in the constellation Serpens Cauda. As a result, it's likely within our galaxy -- but right now, astronomers don't know much more than that.

The top five sources beyond our galaxy are:

NGC 1275. Also known as Perseus A, this galaxy at the heart of the Perseus Galaxy Cluster is known for its intense radio emissions. It lies 233 million light-years away.

3C 454.3. This is a type of active galaxy called a "blazar." Like many active galaxies, a blazar emits oppositely directed jets of particles traveling near the speed of light as matter falls into a central supermassive black hole. For blazars, the galaxy happens to be oriented so that one jet is aimed right at us. Over the time period represented in this image, 3C 454.3 was the brightest blazar in the gamma-ray sky. It flares and fades, but for Fermi it's never out of sight. The galaxy lies 7.2 billion light-years away in the constellation Pegasus.

PKS 1502+106. This blazar is located 10.1 billion light-years away in the constellation Boötes. It appeared suddenly, briefly outshone 3C 454.3, and then faded away.

PKS 0727-115. This object's location in the plane of the Milky Way would lead one to expect that it's a member of our galaxy, but it isn't. Astronomers believe this source is a type of active galaxy called a quasar. It's located 9.6 billion light-years away in the constellation Puppis.

Unidentified. This source, located in the southern constellation Columba, is designated 0FGL J0614.3-3330 and probably lies outside the Milky Way. "It was seen by the EGRET instrument on NASA's earlier Compton Gamma Ray Observatory, which operated throughout the 1990s, but the nature of this source remains a mystery," Thompson says.

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership mission, developed in collaboration with the U.S. Department of Energy and important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.

Francis Reddy

NASA's Goddard Space Flight Center

Hubble and ESO’s VLT provide unique 3D views of remote galaxies

ESO PR Photo 10a/09

A 3D view of remote galaxies

About this image: Combining the twin strengths of the NASA/ESA Hubble Space Telescope’s acute eye, and the capacity of ESO’s Very Large Telescope (VLT) to probe the motions of gas in tiny objects. Astronomers have obtained exceptional 3D views of distant galaxies, seen when the Universe was half its current age. The VLT’s FLAMES/GIRAFFE spectrograph resolve the motions of the gas in these distant galaxies by measuring the velocity of the gas at various locations in these objects. This diagramme illustrates this by showing a sketch of a remote galaxy (in the box), how Hubble sees it (middle panel) and the gas motion measured with the VLT (left panel). In the latter, parts which are red are moving away from us, while those that are blue are moving towards us.

ESO PR Photo 10b/09
Measuring motions in 3 distant galaxies

About this image: NASA/ESA Hubble Space Telescope images of the three galaxies studied by a team of astronomers who try to understand how galaxies formed when the Universe was half its current age (upper panels). The same galaxies were then studied with the FLAMES/GIRAFFE instrument on ESO’s Very Large Telescope (VLT) to probe the motions of gas in these objects (lower panels). Parts which are red are moving away from us, while those that are blue are moving towards us. By studying at these motions in detail, the astronomers try to read the history book of the Universe.

ESO PR Video 10a/09
Galaxies in collision

Comparisons with computer simulations suggest that the observations of a remote galaxy which presents very peculiar motions, as revealed by Hubble and ESO’s Very Large Telescope, can be explained by the collision of two spiral galaxies. The simulations shows how the two galaxies merge to produce a galaxy looking similar to what the NASA/ESA Hubble Space Telescope observed, and with internal motions similar to what the FLAMES/GIRAFFE spectrograph revealed.

Astronomers have obtained exceptional 3D views of distant galaxies, seen when the Universe was half its current age, by combining the twin strengths of the NASA/ESA Hubble Space Telescope’s acute eye, and the capacity of ESO’s Very Large Telescope to probe the motions of gas in tiny objects. By looking at this unique “history book” of our Universe, at an epoch when the Sun and the Earth did not yet exist, scientists hope to solve the puzzle of how galaxies formed in the remote past.

For decades, distant galaxies that emitted their light six billion years ago were no more than small specks of light on the sky. With the launch of the Hubble Space Telescope in the early 1990s, astronomers were able to scrutinise the structure of distant galaxies in some detail for the first time. Under the superb skies of Paranal, the VLT’s FLAMES/GIRAFFE spectrograph (ESO 13/02) — which obtains simultaneous spectra from small areas of extended objects — can now also resolve the motions of the gas in these distant galaxies (ESO 10/06).

“This unique combination of Hubble and the VLT allows us to model distant galaxies almost as nicely as we can close ones,” says François Hammer, who led the team. “In effect, FLAMES/GIRAFFE now allows us to measure the velocity of the gas at various locations in these objects. This means that we can see how the gas is moving, which provides us with a three-dimensional view of galaxies halfway across the Universe.”

The team has undertaken the Herculean task of reconstituting the history of about one hundred remote galaxies that have been observed with both Hubble and GIRAFFE on the VLT. The first results are coming in and have already provided useful insights for three galaxies.

In one galaxy, GIRAFFE revealed a region full of ionised gas, that is, hot gas composed of atoms that have been stripped of one or several electrons. This is normally due to the presence of very hot, young stars. However, even after staring at the region for more than 11 days, Hubble did not detect any stars! “Clearly this unusual galaxy has some hidden secrets,” says Mathieu Puech, lead author of one of the papers reporting this study. Comparisons with computer simulations suggest that the explanation lies in the collision of two very gas-rich spiral galaxies. The heat produced by the collision would ionise the gas, making it too hot for stars to form.

Another galaxy that the astronomers studied showed the opposite effect. There they discovered a bluish central region enshrouded in a reddish disc, almost completely hidden by dust. “The models indicate that gas and stars could be spiralling inwards rapidly,” says Hammer. This might be the first example of a disc rebuilt after a major merger (ESO 01/05).

Finally, in a third galaxy, the astronomers identified a very unusual, extremely blue, elongated structure — a bar — composed of young, massive stars, rarely observed in nearby galaxies. Comparisons with computer simulations showed the astronomers that the properties of this object are well reproduced by a collision between two galaxies of unequal mass.

“The unique combination of Hubble and FLAMES/GIRAFFE at the VLT makes it possible to model distant galaxies in great detail, and reach a consensus on the crucial role of galaxy collisions for the formation of stars in a remote past,” says Puech. “It is because we can now see how the gas is moving that we can trace back the mass and the orbits of the ancestral galaxies relatively accurately. Hubble and the VLT are real ‘time machines’ for probing the Universe’s history”, adds Sébastien Peirani, lead author of another paper reporting on this study.

The astronomers are now extending their analysis to the whole sample of galaxies observed. “The next step will then be to compare this with closer galaxies, and so, piece together a picture of the evolution of galaxies over the past six to eight billion years, that is, over half the age of the Universe,” concludes Hammer.

More information
The results reported here are either in print or to be printed in Astronomy and Astrophysics:

• Puech et al. 2009, A&A, 493, 899, A forming disk at z~0.6: Collapse of a gaseous disk or major merger remnant?

• Peirani et al. 2009, A giant bar induced by a merger event at z=0.4?

• Hammer et al. 2009, A forming, dust enshrouded disk at z=0.43: the first example of a late type disk rebuilt after a major merger?

The team is composed of F. Hammer, H. Flores, M. Puech, Y. Yang, and M. Rodrigues (Observatoire de Paris, France), L. Athanassoula (LAM, France), B. Neichel (Observatoire de Paris and ONERA, France), and S. Peirani (Institut d'Astrophysique de Paris, France).

The observations were obtained in the framework of the IMAGES ESO Large Programme.

This is a joint ESO/ST-EcF release. The Hubble update is available on:

http://www.spacetelescope.org/updates/html/update0903.html

Contacts
François Hammer, Mathieu Puech
Observatoire de Paris, GEPI, France
Phone: +33 (1) 45 07 74 08, +33 (1) 45 07 71 58

E-mail:Francois.Hammer@obspm.fr , mathieu.puech@obspm.fr

Sébastien Peirani
Institut d'Astrophysique de Paris, France
Phone: +33 (1) 44 32 81 34
E-mail: peirani@iap.fr

ESO La Silla - Paranal - ELT Press Officer: Dr. Henri Boffin - +49 89 3200 6222 - hboffin@eso.org
ESO Press Officer in Chile: Valentina Rodriguez - +56 2 463 3123 - vrodrigu@eso.org

NASA's Kepler Mission Rockets to Space in Search of Other Earths

Liftoff of the Delta II rocket carrying NASA's Kepler spacecraft.
Image credit: NASA/Jack Pfaller

CAPE CANAVERAL, Fla. -- NASA's Kepler mission successfully launched into space from Cape Canaveral Air Force Station, Fla., aboard a United Launch Alliance Delta II at 10:49 p.m. EST, Friday. Kepler is designed to find the first Earth-size planets orbiting stars at distances where water could pool on the planet's surface. Liquid water is believed to be essential for the formation of life.

"It was a stunning launch," said Kepler Project Manager James Fanson of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "Our team is thrilled to be a part of something so meaningful to the human race -- Kepler will help us understand if our Earth is unique or if others like it are out there."

Engineers acquired a signal from Kepler at 12:11 a.m. Saturday, after it separated from its spent third-stage rocket and entered its final sun-centered orbit, trailing 950 miles behind Earth. The spacecraft is generating its own power from its solar panels.

"Kepler now has the perfect place to watch more than 100,000 stars for signs of planets," said William Borucki, the mission's science principal investigator at NASA's Ames Research Center at Moffett Field, Calif. Borucki has worked on the mission for 17 years. "Everyone is very excited as our dream becomes a reality. We are on the verge of learning if other Earths are ubiquitous in the galaxy."

Engineers have begun to check Kepler to ensure it is working properly, a process called "commissioning" that will take about 60 days. In about a month or less, NASA will send up commands for Kepler to eject its dust cover and make its first measurements. After another month of calibrating Kepler's single instrument, a wide-field charge-couple device camera, the telescope will begin to search for planets.

The first planets to roll out on the Kepler "assembly line" are expected to be the portly "hot Jupiters" -- gas giants that circle close and fast around their stars. NASA's Hubble and Spitzer space telescopes will be able to follow up with these planets and learn more about their atmospheres. Neptune-size planets will most likely be found next, followed by rocky ones as small as Earth. The true Earth analogs -- Earth-sized planets orbiting stars like our sun at distances where surface water, and possibly life, could exist -- would take at least three years to discover and confirm. Ground-based telescopes also will contribute to the mission by verifying some of the finds.

In the end, Kepler will give us our first look at the frequency of Earth-size planets in our Milky Way galaxy, as well as the frequency of Earth-size planets that could theoretically be habitable.

"Even if we find no planets like Earth, that by itself would be profound. It would indicate that we are probably alone in the galaxy," said Borucki.

As the mission progresses, Kepler will drift farther and farther behind Earth in its orbit around the sun. NASA's Spitzer Space Telescope, which was launched into the same orbit more than five years ago, is now more than 62 million miles behind Earth.

Kepler is a NASA Discovery mission. Ames is the home organization of the science principal investigator and is responsible for the ground system development, mission operations and science data analysis. JPL manages the Kepler mission development. Ball Aerospace & Technologies Corp. of Boulder, Colo., is responsible for developing the Kepler flight system and supporting mission operations. NASA's Launch Services Program at NASA's Kennedy Space Center, Fla., managed the launch service including payload integration and certifying the Delta II launch vehicle for NASA's use.

Credit: NASA/Ames Research Center - W.Stenzel (OSC)
Kepler Mission Site

Elusive Binary Black Hole System Identified

Artist's conception of the binary supermassive black hole system. Each black hole is surrounded by a disk of material gradually spiraling into its grasp, releasing radiation from x-rays to radio waves. The two black holes complete an orbit around their center of mass every 100 years, traveling with a relative velocity of 6000 kilometers per second.

Credit: p. Marenfeld and NOAO/AURA/NSF

RELEASE NO: NOAO 09-01

Finding a needle in a haystack might be easy compared to finding two very similar black holes closely orbiting each other in a distant galaxy.

Astronomers from the National Optical Astronomy Observatory (NOAO) in Tucson have found what looks like two massive black holes orbiting each other in the center of one galaxy. It has been postulated that twin black holes might exist, but it took an innovative, systematic search to find such a rare pair.

The newly identified black holes appear to be separated by only 1/10 of a parsec—a tenth of the distance from Earth to the nearest star. This discovery of the most plausible binary black hole candidate ever found may lead to a greater understanding of how massive black holes form and evolve at the center of galaxies. Their results are published in this week’s edition of the journal Nature.

After a galaxy forms it is likely that a massive black hole can also form at its center. Since many galaxies are found in cluster of galaxies, individual galaxies can collide with each other as they orbit in the cluster. The mystery is what happens to these central black holes when galaxies collide and ultimately merge together. Theory predicts that they will orbit each other and eventually merge into an even larger black hole.

The signature of a black hole in a galaxy has been known for many years. The material falling into a black hole emits light in narrow wavelength regions forming emission lines that can be seen when the light is dispersed into a spectrum. These emission lines carry the information about the speed and direction of the black hole and the material falling into it. If two black holes are present, they would orbit each other before merging and would have a characteristic dual signature in their emission lines. This signature has now been found.

Former NOAO Director Todd Boroson and NOAO Astronomer Tod Lauer used data from the Sloan Digital Sky Survey, a 2.5-meter diameter telescope at Apache Point in southern New Mexico to look for this characteristic dual black hole signature among 17,500 quasars discovered by the survey. More than 100,000 quasars are known, with most being found in the Sloan Digital Sky Survey and at distances that are billions of light-years away.

Quasars are the most luminous versions of the general class of objects known as active galaxies, which can be a hundred times brighter than our Milky Way galaxy, and powered by the accretion of material into supermassive black holes in their nuclei. The matter falling into the black hole doesn’t go directly in, but orbits around the black hole forming a flat accretion disc, much like the soap scum on water orbiting around an open drain.

It has long been thought that all large galaxies must have a massive black hole in their center and that some galaxies must have two or more black holes, at least until the black holes merge. The black holes would be so close together that it would be nearly impossible to see them or their accretion disks separately. However, the light emitted from the accretion disks, and the galaxy containing the black hole, ought to be identifiable.

Boroson and Lauer had to be especially careful to eliminate the possibility that they were seeing two galaxies, each with its own black hole, superimposed on each other. To try to eliminate this superposition possibility, they determined that the quasars were at the same red-shift determined distance and that there was a signature of only one host galaxy.

If the two quasars were independent objects at different distances, the spectral signature of both host galaxies should have been seen and each would have different red shift and thus different distance, even though they would be in the same line of sight. Determining the spectral signature was critical as it would be impossible to see the host galaxies directly against the glare of the quasar.

“The double set of broad emission lines is pretty conclusive evidence of two black holes,” Boroson argues. “If in fact this were a chance superposition, one of the objects must be quite peculiar. One nice thing about this binary black hole system is that we predict that we will see observable velocity changes within a few years at most. We can test our explanation that the binary black hole system is embedded in a galaxy that is itself the result of a merger of two smaller galaxies, each of which contained one of the two black holes.” The smaller black hole has a mass 20 million times that of the sun; the larger one is 50 times bigger, as determined by the their orbital velocities.

Nature Paper Authors:
Dr. Todd Boroson
National Optical Astronomy Observatory
Phone: (520) 318-8352
E-mail: tboroson@noao.edu

Dr. Tod Lauer
National Optical Astronomy Observatory
Phone: (520) 318-8290
E-mail: tlauer@noao.edu

NOAO is operated by the Association of Universities for Research in Astronomy (AURA) Inc., under a cooperative agreement with the National Science Foundation. Funding for the Sloan Digital Sky Survey has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England.

Mission Status Report Spitzer Space Telescope

NASA's Spitzer Space Telescope has resumed normal operations after entering standby mode on Friday, Feb. 27, 2009, at 8:41a.m. Pacific Standard Time. Standby mode is a state in which the spacecraft awaits further instructions from ground controllers, due to a spacecraft fault. Engineers and scientists ran diagnostic tests over the weekend and found that an anomaly in a portion of the combined electronics system had occurred. They have now restored the spacecraft to a normal state, and observations resumed at 9:04 p.m. Pacific Time the evening of March 2.

Spitzer has been in an Earth-trailing orbit for five-and-a-half years, beaming back colorful images and valuable information about stars, galaxies, exoplanets and other celestial objects.

Jane Platt 818-354-0880
Jet Propulsion Laboratory
jane.platt@jpl.nasa.gov

The lower atmosphere of Pluto revealed

ESO PR Photo 08a/09
Pluto (Artist's Impression)

Using ESO's Very Large Telescope, astronomers have gained valuable new insights about the atmosphere of the dwarf planet Pluto. The scientists found unexpectedly large amounts of methane in the atmosphere, and also discovered that the atmosphere is hotter than the surface by about 40 degrees, although it still only reaches a frigid minus 180 degrees Celsius. These properties of Pluto's atmosphere may be due to the presence of pure methane patches or of a methane-rich layer covering the dwarf planet's surface.

"With lots of methane in the atmosphere, it becomes clear why Pluto's atmosphere is so warm," says Emmanuel Lellouch, lead author of the paper reporting the results.

Pluto, which is about a fifth the size of Earth, is composed primarily of rock and ice. As it is about 40 times further from the Sun than the Earth on average, it is a very cold world with a surface temperature of about minus 220 degrees Celsius!

It has been known since the 1980s that Pluto also has a tenuous atmosphere [1], which consists of a thin envelope of mostly nitrogen, with traces of methane and probably carbon monoxide. As Pluto moves away from the Sun, during its 248 year-long orbit, its atmosphere gradually freezes and falls to the ground. In periods when it is closer to the Sun — as it is now — the temperature of Pluto's solid surface increases, causing the ice to sublimate into gas.

Until recently, only the upper parts of the atmosphere of Pluto could be studied. By observing stellar occultations (ESO 21/02), a phenomenon that occurs when a Solar System body blocks the light from a background star, astronomers were able to demonstrate that Pluto's upper atmosphere was some 50 degrees warmer than the surface, or minus 170 degrees Celsius. These observations couldn't shed any light on the atmospheric temperature and pressure near Pluto's surface. But unique, new observations made with the CRyogenic InfraRed Echelle Spectrograph (CRIRES), attached to ESO's Very Large Telescope, have now revealed that the atmosphere as a whole, not just the upper atmosphere, has a mean temperature of minus 180 degrees Celsius, and so it is indeed "much hotter" than the surface.

In contrast to the Earth's atmosphere [2], most, if not all, of Pluto's atmosphere is thus undergoing a temperature inversion: the temperature is higher, the higher in the atmosphere you look. The change is about 3 to 15 degrees per kilometre. On Earth, under normal circumstances, the temperature decreases through the atmosphere by about 6 degrees per kilometre.

"It is fascinating to think that with CRIRES we are able to precisely measure traces of a gas in an atmosphere 100 000 times more tenuous than the Earth's, on an object five times smaller than our planet and located at the edge of the Solar System," says co-author Hans-Ulrich Käufl. "The combination of CRIRES and the VLT is almost like having an advanced atmospheric research satellite orbiting Pluto."

The reason why Pluto's surface is so cold is linked to the existence of Pluto's atmosphere, and is due to the sublimation of the surface ice; much like sweat cools the body as it evaporates from the surface of the skin, this sublimation has a cooling effect on the surface of Pluto. In this respect, Pluto shares some properties with comets, whose coma and tails arise from sublimating ice as they approach the Sun.

The CRIRES observations also indicate that methane is the second most common gas in Pluto's atmosphere, representing half a percent of the molecules. "We were able to show that these quantities of methane play a crucial role in the heating processes in the atmosphere and can explain the elevated atmospheric temperature," says Lellouch.

Two different models can explain the properties of Pluto's atmosphere. In the first, the astronomers assume that Pluto's surface is covered with a thin layer of methane, which will inhibit the sublimation of the nitrogen frost. The second scenario invokes the existence of pure methane patches on the surface.

"Discriminating between the two will require further study of Pluto as it moves away from the Sun," says Lellouch. "And of course, NASA's New Horizons space probe will also provide us with more clues when it reaches the dwarf planet in 2015."

Notes
[1] The atmospheric pressure on Pluto is only about one hundred thousandth of that on Earth, or about 0.015 millibars.

[2] Usually, air near the surface of the Earth is warmer than the air above it, largely because the atmosphere is heated from below as solar radiation warms the Earth's surface, which, in turn, warms the layer of the atmosphere directly above it. Under certain conditions, this situation is inverted so that the air is colder near the surface of the Earth. Meteorologists call this an inversion layer, and it can cause smog build-up.

More information
E. Lellouch et al. 2009, A&A, in press, Pluto's lower atmosphere structure and methane abundance from high-resolution spectroscopy and stellar occultations.
The team is composed of E. Lellouch, B. Sicardy, and C. de Bergh (Observatoire de Paris, France), H.-U. Käufl (ESO), S. Kassi and A. Campargue (Université Joseph Fourier, France).

Contacts
Emmanuel Lellouch
Observatoire de Paris, France
E-mail: emmanuel.lellouch@obspm.fr
Phone: +33 1 450 77 672

Hans-Ulrich Käufl
ESO, Garching, Germany
E-mail: hukaufl@eso.org
Phone: +49 89 3200 6414
Cell: +49 160 6365135

ESO La Silla - Paranal - ELT Press Officer: Dr. Henri Boffin - +49 89 3200 6222 - hboffin@eso.org
ESO Press Officer in Chile: Valentina Rodriguez - +56 2 463 3123 - vrodrigu@eso.org

Trio of Galaxies Mix It Up

Compass and Scale Illustration of HCG 90

Illustration Credit: NASA, ESA, and Z. Levay (STScI)

Credit: NASA, ESA, and R. Sharples (University of Durham)
Zoomable Image

Introduction:

Though they are the largest and most widely scattered objects in the universe, galaxies do go bump in the night. The Hubble Space Telescope has photographed many pairs of galaxies colliding. Like snowflakes, no two examples look exactly alike. This is one of the most arresting galaxy smash-up images to date.

At first glance, it looks as if a smaller galaxy has been caught in a tug-of-war between a Sumo-wrestler pair of elliptical galaxies. The hapless, mangled galaxy may have once looked more like our Milky Way, a pinwheel-shaped galaxy. But now that it's caught in a cosmic Cuisinart, its dust lanes are being stretched and warped by the tug of gravity.

Unlike the elliptical galaxies, the spiral is rich in dust and gas for the formation of new stars. It is the fate of the spiral galaxy to be pulled like taffy and then swallowed by the pair of elliptical galaxies. This will trigger a firestorm of new stellar creation. If there are astronomers on any planets in this galaxy group, they will have a ringside seat to seeing a flurry of starbirth unfolding over many millions of years to come.

Eventually the ellipticals should merge too, creating one single super-galaxy many times larger than our Milky Way. This trio is part of a tight cluster of 16 galaxies, many of them being dwarf galaxies. The galaxy cluster is called the Hickson Compact Group 90 and lies about 100 million light-years away in the direction of the constellation Piscis Austrinus, the Southern Fish.

About this image:

This NASA Hubble Space Telescope image shows three galaxies playing a game of gravitational tug-of-war that may result in the eventual demise of one of them.

Located about 100 million light-years away in the constellation Piscis Austrinus (the Southern Fish), the galaxy interaction may ultimately lead to the three reforming into two larger star cities.

The three galaxies—NGC 7173 (middle left), NGC 7174 (middle right), and NGC 7176 (lower right)—are part of Hickson Compact Group 90, named after astronomer Paul Hickson, who first cataloged these small clusters of galaxies in the 1980s. NGC 7173 and NGC 7176 appear to be smooth, normal elliptical galaxies without much gas and dust.

In stark contrast, NGC 7174 is a mangled spiral galaxy that appears as though it is being ripped apart by its close neighbors. The galaxies are experiencing a strong gravitational interaction, and as a result, a significant number of stars have been ripped away from their home galaxies. These stars are now spread out, forming a tenuous luminous component in the galaxy group.

Ultimately, astronomers believe that NGC 7174 will be shredded and only the two "normal" elliptical galaxies (NGC 7173 and NGC 7176) will remain.

Hubble imaged these galaxies with the Advanced Camera for Surveys in May 2006.

For additional information, contact:

Colleen Sharkey
Hubble/ESA, Garching, Germany
011-49-89-3200-6306
011-49-015115373591 (cell)
csharkey@eso.org

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

Object Names: Hickson Compact Group 90, HCG 90, M59

Swift Satellite records early phase of gamma ray burst

Illustration of GRB
Credit:NASA

UK astronomers, using a telescope aboard the NASA Swift Satellite, have captured information from the early stages of a gamma ray burst - the most violent and luminous explosions occurring in the Universe since the Big Bang. The work was published on Friday 27th February in the Monthly Notices of the Royal Astronomical society.

Swift is able to both locate and point at gamma ray bursts (GRBs) far quicker than any other telescope, so by using its Ultraviolet/Optical Telescope (UVOT) the astronomers were able to obtain an ultraviolet spectrum of a GRB just 251 seconds after its onset - the earliest ever captured. Further use of the instrument in this way will allow them to calculate the distance and brightness of GRBs within a few hundred seconds of their initial outburst, and gather new information about the causes of bursts and the galaxies they originate from.

“The UVOT’s wavelength range, coupled with the fact that Swift is a space observatory with a speedy response rate, unconstrained by time of day or weather, has allowed us to collect this early ultraviolet spectrum,” said Martin Still from the Mullard Space Science Laboratory (MSSL) at UCL.

Paul Kuin, also from MSSL, who works on the calibration of the UVOT instrument explained: “By looking at these earlier moments of gamma ray bursts, we will not only be able to better calculate things such as the luminosity and distance of a burst, but to find out more about the galaxies that play host to them and the impact these explosions have on their environments. Once this new technique is applied to much brighter bursts, we’ll have a wealth of new data.”

Massimiliano De Pasquale, a GRB scientist of the UVOT team from MSSL, added, “The UVOT instrument is particularly suited to study bursts with an average to high redshift (1) – a part of the ultraviolet spectrum that is difficult for even the very big ground-based telescopes to study. Using UVOT with Swift, we can now find redshifts for bursts that were difficult to capture in the past and find out more about their distant host galaxies, about ten billion light years away.

Professor Keith Mason, Chief Executive of the Science and Technology Facilities Council, said, “This is an amazing first for the UVOT instrument and an exciting new development in the study of these most violent and energetic explosions. Thanks to the hard work of our UK scientists at MSSL, and their partners, we can now gather far more information about gamma ray bursts and the early Universe.

Since its launch in 2004, the Swift satellite has provided the most comprehensive study so far of GRBs and their afterglows. Using the UVOT to obtain ultraviolet spectrums, the Swift team will be able to build on this study and even determine more about the host galaxies’ chemistry.

Paul Kuin said, “The new spectrum has not only allowed us to determine the distance of the gamma ray burst’s host galaxy but has revealed the density of its hydrogen clouds. Learning more about these far-away galaxies helps us to understand how they formed during the early universe. The gamma ray burst observed on this occasion originated in a galaxy 8 billion light years from Earth.

Swift is a NASA mission in collaboration with the STFC in the UK and the Italian Space Agency (ASI).

Notes for editors

A copy of the paper - GRB 081203A: Swift – UVOT captures the earliest ultraviolet spectrum of a gamma ray burst – is available on request from the STFC Press Office.

Images: Illustration of a gamma ray burst

Links:

Royal Astronomical Society

Julia Short
STFC Press Office
Tel: + 44 (0)1793 442012

Dr Paul Kuin
Mullard Space Science Laboratory
Tel: +44(0)1483 204256

Further information:

Swift

Launched in November 2004, Swift detects gamma-ray burst and X-ray flashes, and relays their coordinates to the scientific community within seconds. While Swift rapidly re-points to continue observations with its high resolution telescopes of the decaying X-ray, UV and optical afterglows that accompany these events, rapid follow-up observations may also be undertaken by other more powerful satellites such as Chandra, the Hubble Space Telescope or XMM satellites and by the European Southern Observatory’s Very Large Telescope (VLT) and other major observatories. These powerful co-ordinated observation programmes, instigated by Swift, are slowly unravelling the mystery of star explosions.

Goddard Space Flight Centre in the US manages Swift, a NASA mission with participation of the Italian Space Agency (ASI) and the Science and Technology Facilities Council (STFC) in the United Kingdom. Swift, a medium-class Explorer mission was built in collaboration with national laboratories and universities including the Los Alamos National Laboratory, Penn State University, Sonoma State University, the University of Leicester and University College London Mullard Space Science Laboratory.

(1) Redshift is the systematic displacement of individual lines in the spectrum of a celestial object toward the red or longer wavelength, end of the visible spectrum. All distant galaxies show a redshift proportional to their distance from the earth as a result of the general expansion of space. Known as the cosmological red shift, this results when the wavelength of light is stretched as it moves through the expanding universe.

About STFC

Mega-laser to Probe Secrets of Exoplanets

Artist's impression of a gas giant planet circling the star Gliese 436. The new laser will investigate the internal chemistry of these vast planets (Image: NASA)

AN AWESOME laser facility, built to provide fusion data for nuclear weapons simulations, will soon be used to probe the secrets of extrasolar planets.

The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California was declared ready for action earlier this month. Its vital statistics reveal it to be a powerful beast: its ultraviolet lasers can deliver 500 trillion watts in a 20-nanosecond burst. That power opens up new scientific possibilities.

It can deliver 500 trillion watts in a 20-nanosecond burst - opening up new scientific possibilities
For instance, Raymond Jeanloz, an astronomer at the University of California, Berkeley, will use the device to recreate the conditions inside Jupiter and other larger planets, where pressures can be 1000 times as great as those at the centre of the Earth.

Jeanloz will fire the lasers at an iron sample 800 micrometres in diameter. The intense heat will vaporise the metal, generating a gas jet so powerful it will send a shock wave through the iron, compressing it to over a billion times atmospheric pressure. By measuring how the metal's crystalline structure and melting point change at these pressures, Jeanloz hopes to shed light on the formation of the hundreds of giant exoplanets that we have discovered in the last two decades. "The chemistry of these planets is completely unexplored," says Jeanloz. "It's never been accessible in the laboratory before."

Next year, Livermore teams will start work on experiments that could ultimately have an even bigger impact. They will use the lasers to ignite a fusion reaction in a ball of hydrogen isotopes. Other labs have triggered fusion, but not a self-sustaining reaction. The Livermore facility should deliver a big enough jolt of energy to trigger a reaction that burns until the fuel is used up. The data produced will feed into attempts to design a commercial fusion power plant.

The same reaction will also aid the management of the US nuclear weapons stockpile. It is more than 15 years since the US tested a nuclear weapon. Engineers use computer simulations to determine if warheads are in working order, but the models need to be calibrated using data from experiments like NIF's fusion reactions.

Source: NewScientist

Black Hole Constant Makes Unexpected Appearance

WEIRD CONSTANT

A constant akin to one that emerges when an object, such as a small black hole, orbits a massive rotating black hole (shown in an artist's rendition) shows up in a simple Newtonian system.

Illustration by Don Davis

If you were orbiting a rotating black hole, you might be in for a wild ride of dizzying and seemingly unpredictable gyrations. Yet more than 40 years ago, a physicist found a mathematical constant that revealed regularity in that ride. Now a similar constant has been discovered in a mild-mannered Newtonian system, reports a paper in the Feb. 13 Physical Review Letters.

The findings could be mere coincidence, nothing more than a mathematical curiosity, comments astrophysicist Saul Teukolsky of Cornell University. But, he says, they could shed light on the mysterious conditions of rotating black holes, which are predicted to exist by Einstein’s general relativity equations.

Rotating black holes are thought to be the end point in the evolution of massive stars that collapse under their own gravity when their nuclear fuel is exhausted. For black holes with no electrical charge, the gravitational field depends on only mass and spin (hence the saying that “black holes have no hair”). Strangely, this simplicity holds true even though a rotating black hole doesn’t have perfect symmetry. Like any rotating object, a black hole becomes slightly flattened because of centrifugal forces (like Earth, which bulges at the equator).

That loss of symmetry in a massive rotating black hole should suggest that anything orbiting it, such as a neutron star, would behave erratically. Such orbits do appear chaotic, says physicist Clifford Will of Washington University in St. Louis, author of the new paper.

“The orbits go wild — they gyrate and spin, they’re incredibly complex. It’s fantastic,” Will says.

But in 1968, physicist Brandon Carter discovered a mathematical constant that showed the orbits are predictable.

“Black holes have this extra constant that restores the regularity of the orbits,” Teukolsky says. “It’s a mystery. Every other situation where we have these extra constants, we have symmetry. But there’s no symmetry for an orbiting black hole — that’s why it is regarded as a miracle.”

There’s no obvious reason why the Carter constant should emerge in the general-relativity description of spinning black holes, says Teukolsky. By looking for it in other places, scientists might learn more of the specialness of the conditions surrounding such black holes.

Now Will has found a Carter-like constant in a Newtonian system. The equations describing a third body orbiting two masses that are arranged just right yield a similar constant.

“I still don’t completely understand what it is telling us,” says Will, who says he was amazed at the appearance of the constant.

Other physicists also aren’t sure what specialness leads to the constant in both systems.

“I have no idea — to me this is a mystery,” says Teukolsky, who worked on similar questions as part of his Ph.D. thesis in the 1970s. “I’m still baffled.”

Will is still pushing the pencil, adding higher-order terms to the equations. He says that the constant disappears when he adds the mathematical terms for frame-dragging, the ability of a rotating body to drag spacetime around it, akin to the swirling exhibited around a spoon stirring a bowl of molasses. However, adding the next order of terms brings the constant back, Will says.

“It’s mathematically intriguing,” says E. Sterl Phinney of the California Institute of Technology in Pasadena. Similar work was published in 2003 by English astrophysicist Donald Lynden-Bell, Phinney says. “I don’t know what it means, or that it has deep meaning.”

Source: Science News

Geriatric Pulsar Still Kicking

Artist concept of ancient pulsar J0108

Image credit: X-ray: NASA/CXC/Penn State/G.Pavlov et al.
Optical: ESO/VLT/UCL/R.Mignani et al. Illustration: CXC/M. Weiss

The oldest isolated pulsar ever detected in X-rays has been found with NASA's Chandra X-ray Observatory. This very old and exotic object turns out to be surprisingly active.

The pulsar, PSR J0108-1431 (J0108 for short) is about 200 million years old. Among isolated pulsars -- ones that have not been spun-up in a binary system -- it is over 10 times older than the previous record holder with an X-ray detection. At a distance of 770 light years, it is one of the nearest pulsars known.

Pulsars are born when stars that are much more massive than the Sun collapse in supernova explosions, leaving behind a small, incredibly weighty core, known as a neutron star. At birth, these neutron stars, which contain the densest material known in the Universe, are spinning rapidly, up to a hundred revolutions per second. As the rotating beams of their radiation are seen as pulses by distant observers, similar to a lighthouse beam, astronomers call them "pulsars".

Astronomers observe a gradual slowing of the rotation of the pulsars as they radiate energy away. Radio observations of J0108 show it to be one of the oldest and faintest pulsars known, spinning only slightly faster than one revolution per second.

The surprise came when a team of astronomers led by George Pavlov of Penn State University observed J0108 in X-rays with Chandra. They found that it glows much brighter in X-rays than was expected for a pulsar of such advanced years.

Some of the energy that J0108 is losing as it spins more slowly is converted into X-ray radiation. The efficiency of this process for J0108 is found to be higher than for any other known pulsar.

"This pulsar is pumping out high-energy radiation much more efficiently than its younger cousins," said Pavlov. "So, although it's clearly fading as it ages, it is still more than holding its own with the younger generations."

It's likely that two forms of X-ray emission are produced in J0108: emission from particles spiraling around magnetic fields, and emission from heated areas around the neutron star's magnetic poles. Measuring the temperature and size of these heated regions can provide valuable insight into the extraordinary properties of the neutron star surface and the process by which charged particles are accelerated by the pulsar.

The younger, bright pulsars commonly detected by radio and X-ray telescopes are not representative of the full population of objects, so observing objects like J0108 helps astronomers see a more complete range of behavior. At its advanced age, J0108 is close to the so- called “pulsar death line,” where its pulsed radiation is expected to switch off and it will become much harder, if not impossible, to observe.

"We can now explore the properties of this pulsar in a regime where no other pulsar has been detected outside the radio range," said co- author Oleg Kargaltsev of the University of Florida. "To understand the properties of ‘dying pulsars,’ it is important to study their radiation in X-rays. Our finding that a very old pulsar can be such an efficient X-ray emitter gives us hope to discover new nearby pulsars of this class via their X-ray emission."

The Chandra observations were reported by Pavlov and colleagues in the January 20, 2009, issue of The Astrophysical Journal. However, the extreme nature of J0108 was not fully apparent until a new distance to it was reported on February 6 in the PhD thesis of Adam Deller from Swinburne University in Australia. The new distance is both larger and more accurate than the distance used in the Chandra paper, showing that J0108 was brighter in X-rays than previously thought.

"Suddenly this pulsar became the record holder for its ability to make X-rays," said Pavlov, "and our result became even more interesting without us doing much extra work." The position of the pulsar seen by Chandra in X-rays in early 2007 is slightly different from the radio position observed in early 2001. This implies that the pulsar is moving at a velocity of about 440,000 miles per hour, close to a typical value for pulsars.

Currently the pulsar is moving south from the plane of the Milky Way galaxy, but because it is moving more slowly than the escape velocity of the Galaxy, it will eventually curve back towards the plane of the Galaxy in the opposite direction.

The detection of this motion has allowed Roberto Mignani of University College London, in collaboration with Pavlov and Kargaltsev, to possibly detect J0108 in optical light, using estimates of where it should be found in an image taken in 2000. Such a multi-wavelength study of old pulsars is critical for understanding the long-term evolution of neutron stars, such as how they cool with time, and how their powerful magnetic fields evolve.

The team of astronomers that worked with Pavlov also included Gordon Garmire and Jared Wong at Penn State. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Additional information and images about this discovery is available on the Web at:

• http://chandra.harvard.edu

• http://chandra.nasa.gov
  

Kimberly D. Newton, 256-544-0034
Marshall Space Flight Center, Huntsville, Ala.
Kimberly.D.Newton@nasa.gov

Megan Watzke 617-496-7998
Chandra X-ray Center, Cambridge, Mass.
m.watzke@cfa.harvard.edu