An Eagle of Cosmic Proportions

ESO PR Photo 26a/09

The Eagle Nebula

Three-colour composite mosaic image of the Eagle Nebula (Messier 16), based on images obtained with the Wide-Field Imager camera on the MPG/ESO 2.2-metre telescope at the La Silla Observatory. At the centre, the so-called “Pillars of Creation” can be seen. This wide-field infrared image shows not only the central pillars, but also several others in the same star-forming region, as well as a huge number of stars in front of, in, or behind the Eagle Nebula. The cluster of bright stars to the upper right is NGC 6611, home to the massive and hot stars that illuminate the pillars. The “Spire” — another large pillar — is in the middle left of the image.

ESO PR Video 26a/09

Into the Eagle Nebula

ESO PR Video 26b/09

Pan over the Eagle Nebula

ESO PR Video 26c/09

VLT, WFI and Hubble

observations of the Eagle Nebula

Today ESO has released a new and stunning image of the sky around the Eagle Nebula, a stellar nursery where infant star clusters carve out monster columns of dust and gas.

Located 7000 light-years away, towards the constellation of Serpens (the Snake), the Eagle Nebula is a dazzling stellar nursery, a region of gas and dust where young stars are currently being formed and where a cluster of massive, hot stars, NGC 6611, has just been born. The powerful light and strong winds from these massive new arrivals are shaping light-year long pillars, seen in the image partly silhouetted against the bright background of the nebula. The nebula itself has a shape vaguely reminiscent of an eagle, with the central pillars being the “talons”.

The star cluster was discovered by the Swiss astronomer, Jean Philippe Loys de Chéseaux, in 1745–46. It was independently rediscovered about twenty years later by the French comet hunter, Charles Messier, who included it as number 16 in his famous catalogue, and remarked that the stars were surrounded by a faint glow. The Eagle Nebula achieved iconic status in 1995, when its central pillars were depicted in a famous image obtained with the NASA/ESA Hubble Space Telescope. In 2001, ESO’s Very Large Telescope (VLT) captured another breathtaking image of the nebula (ESO Press Photo 37/01), in the near-infrared, giving astronomers a penetrating view through the obscuring dust, and clearly showing stars being formed in the pillars.

The newly released image, obtained with the Wide-Field Imager camera attached to the MPG/ESO 2.2-metre telescope at La Silla, Chile, covers an area on the sky as large as the full Moon, and is about 15 times more extensive than the previous VLT image, and more than 200 times more extensive than the iconic Hubble visible-light image. The whole region around the pillars can now be seen in exquisite detail.

The “Pillars of Creation” are in the middle of the image, with the cluster of young stars, NGC 6611, lying above and to the right. The “Spire” — another pillar captured by Hubble — is at the centre left of the image.

Finger-like features protrude from the vast cloud wall of cold gas and dust, not unlike stalagmites rising from the floor of a cave. Inside the pillars, the gas is dense enough to collapse under its own weight, forming young stars. These light-year long columns of gas and dust are being simultaneously sculpted, illuminated and destroyed by the intense ultraviolet light from massive stars in NGC 6611, the adjacent young stellar cluster. Within a few million years — a mere blink of the universal eye — they will be gone forever.

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 14 countries: Austria, Belgium, 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. 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”.

Contact
Henri Boffin
ESO
Phone: +49 89 3200 6222
cell: +49 174 51 54 324
E-mail: hboffin@eso.org

ESO Press Officer in Chile: Valeria Foncea - +56 2 463 3123 - vfoncea@eso.org

National contacts for the media: http://www.eso.org/public/outreach/eson/

Living Fossils Hold Record of ‘Supermassive’ Kick

Credit: Space Telescope Science Institute

This artist’s conception shows a rogue black hole that has been kicked out from the center of two merging galaxies. The black hole is surrounded by a cluster of stars that were ripped from the galaxies. New calculations by David Merritt, from Rochester Institute of Technology, Jeremy Schnittman, from Johns Hopkins University, and Stefanie Komossa, from the Max-Planck-Institut for Extraterrestrial Physics in Germany suggest that hundreds of massive black holes, left over from the epoch of galaxy formation, are waiting to be detected in the nearby universe.

Star clusters point to black holes ejected from host galaxies
By Susan Gawlowicz

The tight cluster of stars surrounding a supermassive black hole after it has been violently kicked out of a galaxy represents a new kind of astronomical object and a fossil record of the kick.

A paper published in the July 10 issue of The Astrophysical Journal discusses the theoretical properties of “hypercompact stellar systems” and suggests that hundreds of these faint star clusters might be detected at optical wavelengths in our immediate cosmic environment. Some of these objects may already have been picked up in astronomical surveys, reports David Merritt, from Rochester Institute of Technology, Jeremy Schnittman, from Johns Hopkins University, and Stefanie Komossa, from the Max-Planck-Institut for Extraterrestrial Physics in Germany.

Hypercompact stellar systems result when a supermassive black hole is violently ejected from a galaxy, following a merger with another supermassive black hole. The evicted black hole rips stars from the galaxy as it is thrown out. The stars closest to the black hole move in tandem with the massive object and become a permanent record of the velocity at which the kick occurred.

“You can measure how big the kick was by measuring how fast the stars are moving around the black hole,” says Merritt, professor of physics at RIT. “Only stars orbiting faster than the kick velocity remain attached to the black hole after the kick. These stars carry with them a kind of fossil record of the kick, even after the black hole has slowed down. In principle, you can reconstruct the properties of the kick, which is nice because there would be no other way to do it.”

“Finding these objects would be like discovering DNA from a long-extinct species,” adds Komossa.

The best place to find hypercompact stellar systems, the authors argued, is in cluster of galaxies like the nearby Coma and Virgo clusters. These dense regions of space contain thousands of galaxies that have been merging for a long time. Merging galaxies result in merging black holes, which is a prerequisite for the kicks.

“Even if the black hole gets kicked out of one galaxy, it’s still going to be gravitationally bound to the whole cluster of galaxies,” Merritt says. “The total gravity of all the galaxies is acting on that black hole. If it was ever produced, it’s still going to be there somewhere in that cluster.”

Merritt and his co-authors think that scientists may have already seen hypercompact stellar systems and not realized it. These objects would be easy to mistake for common star systems like globular clusters. The key signature making hypercompact stellar systems unique is a high internal velocity. This is detectable only by measuring the velocities of stars moving around the black hole, a difficult measurement that would require a long time exposure on a large telescope.

From time to time, a hypercompact stellar system will make its presence known in a much more dramatic way, when one of the stars is tidally disrupted by the supermassive black hole. In this case, gravity stretches the star and sucks it into the black hole. The star is torn apart, causing a beacon-like flare that signals a black hole. The possibility of detecting one of these “recoil flares” was first discussed in an August 2008 paper by co-authors Merritt and Komossa.

“The only contact of these floating black holes with the rest of the universe is through their armada of stars,” Merritt says, “with an occasional display of stellar fireworks to signal ‘here we are.’”

Contact:

David Merritt
Department of Physics - Rochester Institute of Technology
Phone: 585-475-7973
merritt@astro.rit.edu
http://ccrg.rit.edu/people/merritt/

Turbulence responsible for black holes' balancing act

Image: E. Scannapieco/ M. Brueggen /
ASU Fulton High Performance Computing Initiative

TURBULENCE RESPONSIBLE FOR BLACK HOLES’ BALANCING ACT
(RAS PN 09/48)

New simulations reveal that turbulence created by jets of material ejected from the disks of the Universe’s largest black holes is responsible for halting star formation. Evan Scannapieco, an assistant professor in the School of Earth and Space Exploration in the College of Liberal Arts and Sciences at Arizona State University (ASU) and Professor Marcus Brueggen of Jacobs University in Bremen, Germany, present the new model in a paper in the journal Monthly Notices of the Royal Astronomical Society.

We live in a hierarchical Universe where small structures join into larger ones. Earth is a planet in our Solar System, the Solar System resides in the Milky Way Galaxy, and galaxies combine into groups and clusters. Clusters are the largest structures in the Universe, but sadly our knowledge of them is not proportional to their size. Researchers have long known that the gas in the centres of some galaxy clusters is rapidly cooling and condensing, but were puzzled why this condensed gas did not form into stars. Until recently, no model existed that successfully explained how this was possible.

Professor Scannapieco has spent much of his career studying the evolution of galaxies and clusters. “There are two types of clusters: cool-core clusters and non-cool core clusters,” he explains. “Non-cool core clusters haven’t been around long enough to cool, whereas cool-core clusters are rapidly cooling, although by our standards they are still very hot.”

X-ray telescopes have revolutionized our understanding of the activity occurring within cool-core clusters. Although these clusters can contain hundreds or even thousands of galaxies, they are mostly made up of a diffuse, but very hot gas known as the intracluster medium. This intergalactic gas is only visible to X-ray telescopes, which are able to map out its temperature and structure. These observations show that the diffuse gas is rapidly cooling into the centres of cool-core clusters.

At the core of each of these clusters is a black hole, billions of times more massive than the Sun. Some of the cooling medium makes its way down to a dense disk surrounding this black hole, some of it goes into the black hole itself, and some of it is shot outward. X-ray images clearly show jet-like bursts of ejected material, which occur in regular cycles.

But why were these outbursts so regular, and why did the cooling gas never drop to colder temperatures that lead to the formation of stars? Some unknown mechanism was creating an impressive balancing act.

“It looked like the jets coming from black holes were somehow responsible for stopping the cooling,” says Scannapieco, “but until now no one was able to determine how exactly.”

Scannapieco and Brueggen used the enormous supercomputers at ASU to develop their own three-dimensional simulation of the galaxy cluster surrounding one of the Universe’s biggest black holes. By adapting an approach developed by Guy Dimonte at Los Alamos National Laboratory and Robert Tipton at Lawrence Livermore National Laboratory, Scannapieco and Brueggen added the component of turbulence to the simulations, which was never accounted for in the past.

And that was the key ingredient.

Turbulence works in partnership with the black hole to maintain the balance. Without the turbulence, the jets coming from around the black hole would grow stronger and stronger, and the gas would cool catastrophically into a swarm of new stars. When turbulence is accounted for, the black hole not only balances the cooling, but goes through regular cycles of activity.

“When you have turbulent flow, you have random motions on all scales,” explains Scannapieco. “Each jet of material ejected from the disk creates turbulence that mixes everything together.”

Scannapieco and Brueggen’s results reveal that turbulence acts to effectively mix the heated region with its surroundings so that the cool gas can’t make it down to the black hole, thus preventing star formation.

Every time some cool gas reaches the black hole, it is shot out in a jet. This generates turbulence that mixes the hot gas with the cold gas. This mixture becomes so hot that it doesn’t accrete onto the black hole. The jet stops and there is nothing to drive the turbulence so it fades away. At that point, the hot gas no longer mixes with the cold gas, so the centre of the cluster cools, and more gas makes its way down to the black hole.

Before long, another jet forms and the gas is once again mixed together.

“We improved our simulations so that they could capture those tiny turbulent motions,” explains Scannapieco. “Even though we can’t see them, we can estimate what they would do. The time it takes for the turbulence to decay away is exactly the same amount of time observed between the outbursts.”

IMAGES AND ANIMATIONS The MNRAS paper is available from http://arxiv.org/abs/0905.4726

A high-res image and video is available at: http://scannapieco.asu.edu/cool_core.html

Caption: Snapshot of gas temperatures in a three-dimensional computer simulation of a cool-core cluster. The blue ring shows the cool gas accreting onto the central black hole disk; the red and yellow jets show the hot gas ejected by this disk. Older bubbles from an earlier outburst are visible on the far left and right sides of the image. Turbulence generated by the jets mixes the hot and cool material together, which stabilizes further accretion and allows the cluster to perform its remarkable balancing act. (Credit: E. Scannapieco/ M. Brueggen / ASU Fulton High Performance Computing Initiative.)

CONTACTS:

Evan Scannapieco Tel: +1 480 727 6788 E-mail: Evan.Scannapieco@asu.edu

Marcus Brueggen Tel: +49 421 200 3251
E-mail: m.brueggen@jacobs-university.de

MEDIA CONTACT:

Nikki Staab E-mail: nstaab@asu.edu
Tel: +1 480 965 5081

Arizona State University College of Liberal Arts and Sciences School of Earth and Space Exploration Tempe, Arizona USA
www.sese.asu.edu

Forwarded from Arizona State University by:

Dr Robert Massey
Press and Policy Officer
Royal Astronomical Society
Burlington House
Piccadilly
London W1J 0BQ
Tel: +44 (0)794 124 8035, +44 (0)20 7734 4582
E-mail: rm@ras.org.uk
Web: www.ras.org.uk

The Royal Astronomical Society (RAS), 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 3000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

Adaptive Optics Reveals Strange Dynamics in Ultra-Compact Star-forming Region

Figure 1. Velocity (km s−1) for the principal component of the Br line in each NIFS spaxel derived from the data with a Gaussian fit to the line profile. The mean Br velocity (VLSR = −62.5 km s−1) of the principal component has been removed from the map. The bipolar structure does not line up with any known point source, and the axis does not align with the direction of the large scale ionized flow detected at radio wavelengths. The peak relative velocities are −24 km s−1 and +31 km s−1, but the color map is “stretched” slightly to show smaller velocities.

Figure 2. K−band spectrum extracted from the central 2.5 arcsecond diameter of the NIFS field-of-view.

Using the Altair adaptive optics system with the Gemini Near-Infrared Spectrograph (NIFS) on Gemini North, a US/Australian team have obtained unprecedented high-spatial resolution integral field spectra of the Ultra-Compact H II Region K3-50A. The study reveals never-before-seen morphology and kinematics within this complex region of star formation (see Figure 1).

The team of Robert Blum (NOAO, Gemini Science Center) and Peter McGregor (Australian National University), observed the 3 arcsecond NIFS field at the core of the region, (covering 0.1 parsec at the object’s estimated distance of 7 kiloparsecs), and found sharp density variations that are thought to result from the action of a high mass central source radiation field and stellar wind on its birth cocoon and immediate surroundings. The observations were made at the Fredrick C. Gillett, Gemini North telescope on Mauna Kea, Hawai‘i in July of 2006.

The high angular resolution of the data (~0.2 arcsecond), moderate spectral resolution (approximately R = 5200), and detection of multiple spectral lines (Brγ, He I, [Fe III], [Kr III], [Se IV] and H2) allowed a detailed analysis of K3-50A (see Figure 2), including resolving ionization structure in the HII region as a function of position. Among the findings of this analysis is a bipolar kinematic feature that is not symmetric about any detected point source or ionized outflow seen in earlier radio continuum and recombination line studies. Several possibilities exist to explain the feature. It may be that a lower mass protostar is associated with the central star of K3-50A and its protostellar outflow is being ionized by the hot central source. Alternately, the bipolar flow may be the origin of a large-scale outflow seen in the radio which is re-directed by the material surrounding the compact central source.

K3-50A has a long history of observations that have spanned the spectrum from optical to radio (though the central source itself is highly obscured at optical wavelengths). The Gemini observations consist of near-infrared K-band spectra over NIFS’s ~3x3 arcsecond field which is sliced into 29x69 rectangular spatial pixels (spaxels) for a datacube of 2,001 elements. While this data cube has provided a detailed look at the nebular structure on a fine spatial scale, the central source itself remains a mystery. The putative massive young star is still veiled by the intense nebular continuum arising in its circumstellar environment: even with adaptive optics, no photospheric features of the star were detected.

The paper has been accepted for publication in the Astrophysical Journal and is available as a pre-print on astro-ph at: http://arxiv.org/abs/0906.2793.

Herschel's UK-led SPIRE instrument returns first images

M66 and M74
Credit:ESA

M66 SPIRE 250 microns and M66 Spitzer 160 microns

Credit:SPIRE: ESA, Spitzer: NASA

M74 SPIRE 250 microns and M74 Spitzer 160 microns
Credit:SPIRE: ESA, Spitzer: NASA

SPIRE images of M74 at three different wavelengths

Credit:ESA
More Images

The UK-led SPIRE instrument on board the Herschel Space Observatory has made its first astronomical observations, with spectacular results. The first SPIRE images, together with first light observations from the other two Herschel instruments, are released today (Friday 10th July) by the European Space Agency (ESA)

The SPIRE camera responds to light at wavelengths between 250 and 500 microns (500-1000 times longer than the wavelength of visible light). It is designed to look for emission from clouds of dust in regions where stars are forming in our own and other galaxies.

On June 24, SPIRE was able to observe the sky for the first time. The telescope was trained on two galaxies to get a first impression of what the instrument could see. The results were better than anyone expected from first observations, made before any attempt to set up the instrument or to tune the image-making software. The target galaxies showed up prominently, providing by far the best images yet seen at these wavelengths. Many other, more distant, galaxies were also seen in the field of view.

The images show two galaxies, M66 and M74, at a wavelength of 250 microns. The images trace emission by dust in clouds where star formation is active, and the nucleus and spiral arms show up clearly. Dust is part of the interstellar material that fuels star formation, and these images effectively show the reservoirs of gas and dust that are ready to be turned into stars in the galaxies. Very significantly, the frames are also filled with many other galaxies which are much more distant and only show up as point sources, and there are also some extended structures, possibly due to clouds of dust in our own galaxy.

These images have given astronomers an exciting foretaste of the important scientific studies planned with SPIRE: the instrument will look at star formation close up in our own galaxy and in nearby galaxies, and it will search for star-forming galaxies in the very distant Universe. Because these galaxies are so far away, their light has taken a very long time to reach us, so by detecting them we are looking into the past and learning how and when galaxies like the Milky Way were formed.

Professor Matt Griffin of Cardiff University, who is the SPIRE Principal Investigator, said: “These quick first light observations have produced dramatic results when we consider that they were made on day one. Astronomers planning to use SPIRE are delighted because they can see straight away that the main scientific studies planned with the instrument are going to work extremely well. In fact all three instruments on Herschel have now shown what they can do, and the results are spectacular all round.”

Professor Robert Kennicutt of Cambridge University, who will use Herschel to study nearby galaxies, including the two selected for SPIRE first light, said: “I am thrilled by the quality of these first images from SPIRE. They reveal the cold dust and star formation in these galaxies in stunning detail, and are a sneak preview of future observations that promise to revolutionise our understanding of star formation in the Universe.”

Dr. Laurent Vigroux of CEA/IRFU Saclay and Institut d'Astrophysique de Paris, who is the Co-Principal Investigator for the SPIRE Team, said: “We have dreamed of seeing such images for a very long time, more than ten years. And they are an achievement: the first real images in the far infrared, opening a new window in astronomy. These images are the start of another ten years or more of work to exploit all the scientific results that SPIRE will produce."

Professor Keith Mason, Chief Executive of the Science and Technology Facilities Council (STFC), which provides the UK funding for Herschel, said, “We are delighted to see that the SPIRE instrument is working so effectively and returning such detailed, high quality images. UK researchers have put a great deal of hard work into this complicated camera and these amazing new images are proof of the skill and expertise we have here in the UK and why we continue to be at the forefront of new technology development for Europe’s growing space exploration activities.”

Notes for editors

Image

SPIRE images of two galaxies, M66 and M74, at a wavelength of 250 microns.
The images trace emission by dust in clouds where star formation is active, and the nucleus and spiral arms show up clearly.

M66 SPIRE 250 microns (ESA) and M66 Spitzer 160 microns (Credit: NASA)

M74 SPIRE 250 microns (ESA) and M74 Spitzer 160 microns (Credit: NASA)
To illustrate the advance made by Herschel, the pictures compare the SPIRE images with the best previous images of these galaxies in this part of the spectrum, made by NASA’s Spitzer space observatory at a wavelength of 160 microns. The huge difference in image quality is attributable to the much larger Herschel telescope (3.5 m compared to Spitzer’s 85 cm) and to SPIRE’s highly sensitive detectors.

SPIRE images of M74 at three different wavelengths (equivalent to three different colours).
These images are scaled to show up the extended nature of the galaxies and the rich detail in the background sky. The image quality is best at 250 microns because telescopes produce sharper images at their shortest wavelengths. By combining the three images, astronomers can measure the properties of the emitting dust and identify the nature of the many distant galaxies that also appear in the pictures

Herschel and SPIRE

The European Space Agency’s Herschel satellite carries the largest telescope to be flown in space and will study the Universe at far infrared wavelengths. It will reveal the early stages of star birth and galaxy formation; it will examine the composition and chemistry of comets and planetary atmospheres in the Solar System; and it will examine the star-dust ejected by dying stars into interstellar space which form the raw material for planets like the Earth.

The SPIRE instrument has been built by a consortium of 18 institutes in eight countries (UK, France, Italy, Spain, Sweden, USA, and China), led by Prof. Matt Griffin of Cardiff University. The instrument was assembled at the STFC’s Rutherford Appleton Laboratory in the UK.

Galaxies in SPIRE first light observations

M74 (also known as NGC 628) is a face-on spiral galaxy located about 24 million light years from Earth in the constellation Pisces. In visible light, produced mainly by the stars within the galaxy, we see a bright nucleus and well-defined spiral arms that contain many small, bright regions young massive stars have formed recently. The submillimetre SPIRE images trace the cold dust between the stars, and the spiral arms appear much more enhanced. They also contain many faint dots that are actually distant galaxies in the background. These galaxies also contain dust that radiates at submillimetre wavelengths, but because they are much further away, we cannot actually see the structure in the galaxies.

M66 (also known as NGC 3627) is a barred spiral galaxy located about 36 million light years away in the constellation Leo. The bar is a structure made out of stars, gas, and dust. In visible light, we see the starlight tracing both the bar and the spiral arms attached to the bar, but we also see many dark lanes in the starlight caused by interstellar dust that absorbs the starlight. In the submillimetre SPIRE images, we see the thermal radiation from that dust. SPIRE shows show that most of the dust is located in the center and near the ends of the bar, with additional dust found in the spiral arms. The bar exerts forces on other objects within the disk of the galaxy and causes gas and dust to accumulate in the center and near the ends of the bar, which is why these locations look so bright in the SPIRE image. Again we see many other galaxies within the field of view.

Herschel Mission timeline:

Herschel and Planck were launched on an Ariane 5 from Europe’s Spaceport in Kourou, French Guiana, on 14 May 2009.
Commissioning Phase: In the first few days after launch basic spacecraft checks were done.
One to two weeks after launch, the Herschel scientific instruments were switched on for the first time and detailed commissioning of the instruments began. This will continue until around the end of July. The satellite is already nearing its operational orbit, about 1.5 million km from the Earth.
Performance Verification Phase: This will begin about 60 days after launch, and will involve tests to ensure that the instrument operational modes and scientific data processing software are thoroughly checked and optimised.
Science Demonstration Phase: About 150 days into the mission, spacecraft and instrument testing will be complete and comprehensive trial scientific observations will begin, involving execution of a selection of different kinds of observations and processing the data to produce scientific results.
Routine Operations Phase: About six months after launch, routine operations will begin, and will last for at least three years. The observational programmes for the first 18 months have already been selected.

UK Participation in Herschel

The UK contribution to Herschel includes leadership of the international consortium that designed and built the SPIRE instrument. The UK SPIRE team is also responsible for the development of software for instrument control and processing of the scientific data, and leads the in-flight testing and operation of SPIRE. The Herschel programme in the UK is funded by the Science and Technology Facilities Council.

SPIRE comprises a three band imaging photometer and an imaging Fourier transform spectrometer and has been designed and built by a consortium of institutes including a number from the UK (Cardiff University; Imperial College, London; the Mullard Space Science Laboratory; the University of Sussex; and STFC’s Rutherford Appleton Laboratory and UK Astronomy Technology Centre). The UK is also leading the development of software for controlling the instrument from the ground and processing the data to produce scientific results. The SPIRE Operations Centre, responsible for delivering all instrument software to ESA, and for day-to-day instrument monitoring, operation, and calibration, is located at the Rutherford Appleton Laboratory with contributions from the Imperial College and Cardiff groups. The UK SPIRE institutes, together with astronomers in many other UK universities, are also strongly involved in the Herschel scientific programmes which have already been selected for the first 18 months of Herschel observations, and cover a wide range of science topics from our own solar system to the most distant galaxies.

Contact

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

Prof. Matt Griffin
Herschel-SPIRE Principal Investigator
School of Physics and Astronomy
Cardiff University
Tel: +44 (0)29 2087 4203

Prof. Robert Kennicutt
Cambridge University
Institute of Astronomy
University of Cambridge
Tel: +44 (0)1223-765844

Dr Laurent Vigroux
Institut d'Astrophysique de Paris
Tel: +33 1 44 32 80 00

About STFC

Stephan's Quintet: A Galaxy Collision in Action

Credit X-ray (NASA/CXC/CfA/E.O'Sullivan);

Optical (Canada-France-Hawaii-Telescope/Coelum)

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Images of Stephan's Quintet (Runtime: 00:15)

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This beautiful image gives a new look at Stephan's Quintet, a compact group of galaxies discovered about 130 years ago and located about 280 million light years from Earth. The curved, light blue ridge running down the center of the image shows X-ray data from the Chandra X-ray Observatory. Four of the galaxies in the group are visible in the optical image (yellow, red, white and blue) from the Canada-France-Hawaii Telescope. A labeled version identifies these galaxies (NGC 7317, NGC 7318a, NGC 7318b and NGC 7319) as well as a prominent foreground galaxy (NGC 7320) that is not a member of the group. The galaxy NGC 7318b is passing through the core of galaxies at almost 2 million miles per hour, and is thought to be causing the ridge of X-ray emission by generating a shock wave that heats the gas.

Additional heating by supernova explosions and stellar winds has also probably taken place in Stephan's Quintet. A larger halo of X-ray emission - not shown here - detected by ESA's XMM-Newton could be evidence of shock-heating by previous collisions between galaxies in this group. Some of the X-ray emission is likely also caused by binary systems containing massive stars that are losing material to neutron stars or black holes.

Stephan's Quintet provides a rare opportunity to observe a galaxy group in the process of evolving from an X-ray faint system dominated by spiral galaxies to a more developed system dominated by elliptical galaxies and bright X-ray emission. Being able to witness the dramatic effect of collisions in causing this evolution is important for increasing our understanding of the origins of the hot, X-ray bright halos of gas in groups of galaxies.

Stephan's Quintet shows an additional sign of complex interactions in the past, notably the long tails visible in the optical image. These features were probably caused by one or more passages through the galaxy group by NGC 7317.

Fast Facts for Stephan's Quintet:

Scale: Image is 6.3 arcmin across
Category: Groups & Clusters of Galaxies
Coordinates: (J2000) RA 22h 36m 00.00s | Dec +33° 59’ 00.00"
Constellation: Pegasus
Observation Date: 07/09/2000-08/17/2007
Observation Time: 31 hours
Obs. ID: 789, 7924
Color Code: X-ray (Cyan); Optical (Red, Yellow, Blue, White)
Instrument: ACIS
Also Known As: HCG 92
Distance Estimate: About 280 million light years (redshift z = 0.02)

Outburst of the dwarf nova WX Cet

AAVSO Special Notice #161

Hazel McGee (Guildford, UK) has reported that the infrequently outbursting dwarf nova WX Cet is in outburst. WX Cet was recorded at a magnitude of 12.62 (clear filter, V zeropoint) on 2009 July 8.44375 (JD 2455020.94375). The observation was obtained remotely with GRAS-001 (New Mexico).

Follow-up observations of this outburst are urgently requested, including both visual estimates and instrumental photometry. CCD time-series observations capable of detecting possible superhumps are particularly important. Please obtain the highest signal-to-noise data you can with the shortest exposures possible; filtered observations are not required.

WX Cet is located at the following (J2000) coordinates: RA: 01 17 04.20 , Dec: -17 56 23.0

Charts for WX Cet may be obtained via AAVSO VSP at the following URL:

http://www.aavso.org/observing/charts/vsp/index.html?pickname=WX%20Cet

Please report all observations to the AAVSO with the name "WX CET".

This AAVSO Special Notice was prepared by M. Templeton.

SUBMIT OBSERVATIONS TO THE AAVSO
Information on submitting observations to the AAVSO may be found at:
http://www.aavso.org/observing/submit/

SPECIAL NOTICE ARCHIVE AND SUBSCRIPTION INFORMATION
A Special Notice archive is available at the following URL:
http://www.aavso.org/publications/specialnotice/

Subscribing and Unsubscribing may be done at the following URL:
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New Method Finds Most Distant Supernovae

This image was taken with CFHT as part of the telescope’s Legacy Survey and shows one of the deep fields used to find the most distant supernovae to date. Credit: Jeff Cooke/CFHT

This image shows the host galaxy containing one of the newly discovered supernovae. Comparing the images shows how the galaxy visibly brightens in 2004 and then returns to normal. This suggested that in 2003 the supernova was not detected; it appeared in 2004 and was beginning to fade in 2005. The last frame subtracts the images from the years that the supernova was not detected as well as the galaxy’s light to reveal only the supernova. Credit: Jeff Cooke/CFHT

This artist’s impression of a supernova shows the layers of gas ejected prior to the final deathly explosion of a massive star.
Credit: NASA/Swift/Skyworks Digital/Dana Berry

Astronomers have yet again rewritten the record books for discovering the most distant supernovae. Using Hawaii’s W. M. Keck Observatory and Canada-France-Hawaii Telescope (CFHT), a team has identified remnants of two massive stars that exploded roughly 11 billion years ago.

Studying the deaths of these early stars is essential to understanding the evolution of the Universe and how its elements were formed and distributed to create later stars and even planets, said cosmologist Jeff Cooke of the University of California, Irvine.

He added that while the newly identified explosions may be the farthest of any supernovae type found to date, the innovative method developed to identify the explosions should make it possible to discover even more distant supernovae—possibly even a few of the very first stars to blow themselves apart.

Cooke developed this new method to study the explosive death of stars that are 50 to 100 times the mass of the Sun. The progenitor stars of this kind of supernovae, the type IIn, are distinct because they shed most of their material into the cosmos just before they die. When the stars finally explode, they spew out their remaining material, which ploughs into the previously expelled gas. The collisions make the entire stellar remnant so bright that its glow can still be detected many years after the star’s demise.

To find the most distant of these supernovae, the astronomers examined archival data from the CFHT Legacy Survey to identify four, extremely distant objects that appeared to brighten and then fade over time, resembling distant supernovae. Cooke, who led the team, explained that cosmologists typically identify supernovae by comparing nightly images of the same patch of space taken at regular intervals throughout the year. The images show several hundred to thousands of galaxies, and a slight increase in the amount of light in any one of the galaxies in one image compared to the previous image may indicate a star has blown apart and died.

Using this knowledge, the astronomers stacked and blended a year’s worth of CFHT images taken of the same, dark patch of sky and did this for four separate years. Stacking the images into one composite enable the team to detect fainter objects and thereby probe farther back in the Universe. “It’s like in photography when you open the shutter for a long time. You’ll collect more light with a longer exposure,” Cooke said.

By comparing composite images over the four years, Cooke’s team identified four potential supernovae. The astronomers then used the Low Resolution Imaging Spectrograph (LRIS) on the Keck I telescope and the Deep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck II telescope to analyze the spectrum of light that each object emitted to determine the objects’ composition and distance. The data showed that the light from the supernovae had traveled nearly 11 billion light years to reach Earth. Both the results and the new method appear in the July 9 edition of Nature.

Cooke’s technique is “powerful and reliable,” because “it’s simple, clean and the results are unambiguous. In retrospect, I can’t believe we haven’t capitalized on this method sooner,” said astronomer Alicia Soderberg, who studies supernovae at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. and was not involved in the study. The technique will revitalize research on this kind of supernovae and will provide astronomers with a much-needed process to probe the deaths of some of the earliest stars in the Universe, she added.

Prior to this discovery, astronomers’ records showed that the most distant supernova of this type exploded roughly six billion years ago, and the most distant of any supernovae type exploded roughly nine billion years ago. Cooke said that by studying extremely distant supernovae, astronomers will better understand where stars were exploding just after the Big Bang and how stellar properties change as the Universe evolved. And, because stars form heavier and heavier elements in their core, the technique might also give astronomers a glimpse of how the elements essential to planet formation and to the existence of life were initially created and distributed throughout the cosmos.

“This new method could not have been published at a better time,” Soderberg said, explaining that many large survey telescopes, such as the Large Synoptic Survey Telescope, will soon be online to identify thousands of candidate supernovae. Astronomers can then use large eight to ten meter telescopes, such as Keck, to obtain the necessary deep spectra of the supernovae to determine their distance and the abundance of elements that they spew into space after they explode.

The W. M. Keck Observatory operates two 10-meter optical/infrared telescopes on the summit of Mauna Kea on the island of Hawai’i. The twin telescopes feature a suite of advanced instrumentation including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrographs and a world-leading laser-guide-star adaptive optics system. The Observatory is a scientific partnership of the California Institute of Technology, the University of California and NASA. For more information please call 808.881.3827 or visit http://www.keckobservatory.org.

The research was funded by the National Science Foundation and by generous support from Gary McCue to the Center for Cosmology at UCI.

New portrait of Omega Nebula's glistening watercolours

Three-colour composite image of the Omega Nebula (Messier 17), based on images obtained with the EMMI instrument on the ESO 3.58-metre New Technology Telescope at the La Silla Observatory. North is down and East is to the right in the image. It spans an angle equal to about one third the diameter of the Full Moon, corresponding to about 15 light-years at the distance of the Omega Nebula.

ESO PR Photo 24a/09
The Omega Nebula

ESO PR Video 24a/09

Zoom in on the Omega Nebula

ESO PR Video 24b/09
Pan on the Omega Nebula

The Omega Nebula, a stellar nursery where infant stars illuminate and sculpt a vast pastel fantasy of dust and gas, is revealed in all its glory by a new ESO image.

The Omega Nebula, sometimes called the Swan Nebula, is a dazzling stellar nursery located about 5500 light-years away towards the constellation of Sagittarius (the Archer). An active star-forming region of gas and dust about 15 light-years across, the nebula has recently spawned a cluster of massive, hot stars. The intense light and strong winds from these hulking infants have carved remarkable filigree structures in the gas and dust.

When seen through a small telescope the nebula has a shape that reminds some observers of the final letter of the Greek alphabet, omega, while others see a swan with its distinctive long, curved neck. Yet other nicknames for this evocative cosmic landmark include the Horseshoe and the Lobster Nebula.

Swiss astronomer Jean-Philippe Loys de Chéseaux discovered the nebula around 1745. The French comet hunter Charles Messier independently rediscovered it about twenty years later and included it as number 17 in his famous catalogue. In a small telescope, the Omega Nebula appears as an enigmatic ghostly bar of light set against the star fields of the Milky Way. Early observers were unsure whether this curiosity was really a cloud of gas or a remote cluster of stars too faint to be resolved. In 1866, William Huggins settled the debate when he confirmed the Omega Nebula to be a cloud of glowing gas, through the use of a new instrument, the astronomical spectrograph.

In recent years, astronomers have discovered that the Omega Nebula is one of the youngest and most massive star-forming regions in the Milky Way. Active star-birth started a few million years ago and continues through today. The brightly shining gas shown in this picture is just a blister erupting from the side of a much larger dark cloud of molecular gas. The dust that is so prominent in this picture comes from the remains of massive hot stars that have ended their brief lives and ejected material back into space, as well as the cosmic detritus from which future suns form.

The newly released image, obtained with the EMMI instrument attached to the ESO 3.58-metre New Technology Telescope (NTT) at La Silla, Chile, shows the central region of the Omega Nebula in exquisite detail. In 2000, another instrument on the NTT, called SOFI, captured another striking image of the nebula (ESO Press Photo 24a/00) in the near-infrared, giving astronomers a penetrating view through the obscuring dust, and clearly showing many previously hidden stars. The NASA/ESA Hubble Space Telescope has also imaged small parts of this nebula (heic0305a and heic0206d) in fine detail.

At the left of the image a huge and strangely box-shaped cloud of dust covers the glowing gas. The fascinating palette of subtle colour shades across the image comes from the presence of different gases (mostly hydrogen, but also oxygen, nitrogen and sulphur) that are glowing under the fierce ultraviolet light radiated by the hot young stars.

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 14 countries: Austria, Belgium, 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. 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”.

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A Fireworks Display in the Helix Nebula

Figure1: New near-infrared image of the Helix Nebula, showing comet-shaped knots within. These features look like a fireworks display in space. (enlarge)

Figure2: Enlarged image, showing an enormous number of knots. The size of each knot is about five times as big as Pluto’s orbit in the Solar System. (enlarge)

Figure3: Enlarged image, showing cometary shaped knots. Knots have gradually formed from material ejected from stars in the past, which are now exposed to ultraviolet radiation and wind from the central star. (enlarge)

Sample:Previous optical image of the Helix Nebula, demonstrating diffuse gas surrounding a central star. The white box shows the area observed by the Subaru Telescope. Credit: NASA, NOAO, ESA, the Hubble Helix Nebula Team, M. Meixner [STScI], and T.A. Rector [NRAO] (enlarge)

The Helix Nebula, NGC 7293, is not only one of the most interesting and beautiful planetary nebulae; it is also one of the closest nebulae to Earth, at a distance of only 710 light years away. This new image, taken with an infrared camera on the Subaru Telescope in Hawaii, shows tens of thousands of previously unseen comet-shaped knots inside the nebula. The sheer number of knots--more than have ever been seen before—looks like a massive fireworks display in space.

The Helix Nebula was the first planetary nebula in which knots were seen, and their presence may provide clues to what planetary material may survive at the end of a star’s life. Planetary nebulae are the final stages in the lives of low-mass stars, such as our Sun. As they reach the ends of their lives they throw off large amounts of material into space. Although the nebula looks like a fireworks display, the process of developing a nebula is neither explosive nor instantaneous; it takes place slowly, over a period of about 10,000 to 1,000,000 years. This gradual process creates these nebulae by exposing their inner cores, where nuclear burning once took place and from which bright ultraviolet radiation illuminates the ejected material.

Astronomers from the National Astronomical Observatory of Japan (NAOJ), from London, Manchester and Kent universities in the UK and from a university in Missouri in the USA studied the emissions from hydrogen molecules in the infrared and found that knots are found throughout the entire nebula. Although these molecules are often destroyed by ultraviolet radiation in space, they have survived in these knots, shielded by dust and gas that can be seen in optical images. The comet-like shape of these knots results from the steady evaporation of gas from the knots, produced by the strong winds and ultraviolet radiation from the dying star in the center of the nebula.

Unlike previous optical images of the Helix Nebula knots, the infrared image shows thousands of clearly resolved knots, extending out from the central star at greater distances than previously observed. The extent of the cometary tails varies with the distance from the central star, just as Solar System comets have larger tails when they are closer to the Sun and when wind and radiation are stronger. “This research shows how the central star slowly destroys the knots and highlights the places where molecular and atomic material can be found in space,”says lead astronomer Dr. Mikako Matsuura, previously at NAOJ and now from University College London.

These images enable astronomers to estimate that there may be as many as 40,000 knots in the entire nebula, each of which are billions of kilometers/miles across. Their total mass may be as much as 30,000 Earths, or one-tenth the mass of our Sun. The origin of the knots is currently unknown. Are they remnants of the star's planetary system or are they material ejected from the star at some stage in its life? Either answer will help astronomers answer important questions about the lives of stars and planetary systems.

The innovative technology of the Subaru Telescope with its near-infrared camera, MOIRCS, enabled researchers to produce such impressive images. Mounted on one of the largest infrared optical telescopes in the world, MOIRCS (Multi-object Infrared Camera and Spectrograph) has a large (4 arcmin by 7 arcmin) field of view, allowing it to capture, with a single shot, such detailed features in a large PN.

This paper will be published in the

Astrophysical Journal in August 2009

Source: Subaru Telescope

NASA'S Fermi Telescope Probes Dozens of Pulsars

This all-sky map shows the positions and names of 16 new pulsars (yellow) and eight millisecond pulsars (magenta) studied using Fermi's LAT. The famous Vela, Crab, and Geminga pulsars (right) are the brightest ones Fermi sees. The pulsars Taz, Eel, and Rabbit have taken the nicknames of nebulae they are now known to power. The Gamma Cygni pulsar resides within a supernova remnant of the same name. Credit: NASA/DOE/Fermi LAT Collaboration

Larger image

Larger image (unlabeled)

This movie shows one cycle of pulsed gamma rays from the Vela pulsar as constructed from photons detected by Fermi's Large Area Telescope. The movie includes data from August 4 to Sept. 15, 2008. The bluer color in the latter part of the pulse indicates the presence of gamma rays with energies exceeding a billion electron volts. For comparison, visible light has energies between two and three electron volts. Credit: NASA/DOE/Fermi LAT Collaboration

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With NASA's Fermi Gamma-ray Space Telescope, astronomers now are getting their best look at those whirling stellar cinders known as pulsars. In two studies published in the July 2 edition of Science Express, international teams have analyzed gamma-rays from two dozen pulsars, including 16 discovered by Fermi. Fermi is the first spacecraft able to identify pulsars by their gamma-ray emission alone.

A pulsar is the rapidly spinning and highly magnetized core left behind when a massive star explodes. Most of the 1,800 cataloged pulsars were found through their periodic radio emissions. Astronomers believe these pulses are caused by narrow, lighthouse-like radio beams emanating from the pulsar's magnetic poles.

"Fermi has truly unprecedented power for discovering and studying gamma-ray pulsars," said Paul Ray of the Naval Research Laboratory in Washington. "Since the demise of the Compton Gamma Ray Observatory a decade ago, we've wondered about the nature of unidentified gamma-ray sources it detected in our galaxy. These studies from Fermi lift the veil on many of them."

The Vela pulsar, which spins 11 times a second, is the brightest persistent source of gamma rays in the sky. Yet gamma rays -- the most energetic form of light -- are few and far between. Even Fermi's Large Area Telescope sees only about one gamma-ray photon from Vela every two minutes.

"That's about one photon for every thousand Vela rotations," said Marcus Ziegler, a member of the team reporting on the new pulsars at the University of California, Santa Cruz. "From the faintest pulsar we studied, we see only two gamma-ray photons a day."

Radio telescopes on Earth can detect a pulsar easily only if one of the narrow radio beams happens to swing our way. If not, the pulsar can remain hidden.

A pulsar's radio beams represent only a few parts per million of its total power, whereas its gamma rays account for 10 percent or more. Somehow, pulsars are able to accelerate particles to speeds near that of light. These particles emit a broad beam of gamma rays as they arc along curved magnetic field lines.

The new pulsars were discovered as part of a comprehensive search for periodic gamma-ray fluctuations using five months of Fermi Large Area Telescope data and new computational techniques.

"Before launch, some predicted Fermi might uncover a handful of new pulsars during its mission," Ziegler added. "To discover 16 in its first five months of operation is really beyond our wildest dreams."

Like spinning tops, pulsars slow down as they lose energy. Eventually, they spin too slowly to power their characteristic emissions and become undetectable.

But pair a slowed dormant pulsar with a normal star, and a stream of stellar matter from the companion can spill onto the pulsar and increase its spin. At rotation periods between 100 and 1,000 times a second, ancient pulsars can resume the activity of their youth. In the second study, Fermi scientists examined gamma rays from eight of these "born-again" pulsars, all of which were previously discovered at radio wavelengths.

"Before Fermi launched, it wasn't clear that pulsars with millisecond periods could emit gamma rays at all," said Lucas Guillemot at the Center for Nuclear Studies in Gradignan, near Bordeaux, France. "Now we know they do. It's also clear that, despite their differences, both normal and millisecond pulsars share similar mechanisms for emitting gamma rays."

NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with 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

VLBA Locates Origin of Superenergetic Bursts Near Giant Black Hole

Zooming in on the powerful core

of the galaxy M87

CREDIT: Bill Saxton, NRAO/AUI/NSF

Artists's Conception of M87's inner core:

Black hole, accretion disk, and inner jets.

CREDIT: Bill Saxton, NRAO/AUI/NSF

Large-scale VLA image of M87: White circle indicates the area within which the gamma-ray telescopes could tell the very energetic gamma rays were being emitted. To narrow down the location further required the VLBA. CREDIT: NRAO/AUI/NSF

"Light Curves" of very-high-energy gamma rays and radio waves emitted by M87, showing that radio flare followed gamma-ray flare. CREDIT: VERITAS, VLBA, H.E.S.S., and MAGIC Collaborations, NRAO/AUI/NSF

Full pages of Graphics

Using a worldwide combination of diverse telescopes, astronomers have discovered that a giant galaxy's bursts of very high energy gamma rays are coming from a region very close to the supermassive black hole at its core. The discovery provides important new information about the mysterious workings of the powerful "engines" in the centers of innumerable galaxies throughout the Universe.

The galaxy M87, 50 million light-years from Earth, harbors at its center a black hole more than six billion times more massive than the Sun. Black holes are concentrations of matter so dense that not even light can escape their gravitational pull. The black hole is believed to draw material from its surroundings -- material that, as it falls toward the black hole, forms a tightly-rotating disk.

Processes near this accretion disk, powered by the immense gravitational energy of the black hole, propel energetic material outward for thousands of light-years. This produces the "jets" seen emerging from many galaxies. In 1998, astronomers found that M87 also was emitting flares of gamma rays a trillion times more energetic than visible light.

However, the telescopes that discovered these bursts of very high energy gamma rays could not determine exactly where in the galaxy they originated. In 2007 and 2008, the astronomers using these gamma-ray telescopes combined forces with a team using the National Science Foundation's continent-wide Very Long Baseline Array (VLBA), a radio telescope with extremely high resolving power, or ability to see fine detail.

"Combining the gamma-ray observations with the supersharp radio 'vision' of the VLBA allowed us to see that the gamma rays are coming from a region very near the black hole itself," said Craig Walker, of the National Radio Astronomy Observatory (NRAO).

"Pinning down this location addresses what was an open question and provides important clues for understanding how such highly energetic emissions are produced in the jets of active galaxies," said Matthias Beilicke, of Washington University in St. Louis, MO.

The gamma-ray flares from the galaxy were monitored by systems of large telescopes designed to detect faint flashes of blue light that result when gamma rays enter the Earth's atmosphere. Data from sensitive cameras in these systems can allow astronomers to infer the energy of the gamma rays and the direction from which they came. Their directional information, however, is not precise enough to narrow down the gamma-ray-emitting region within the galaxy.

The VLBA offered a millionfold improvement in resolving power, allowing the scientists to determine that the gamma rays are coming from the immediate vicinity of the black hole. Though gamma rays are the most energetic form of electromagnetic radiation and radio waves the least energetic, both often arise from the same regions. This was shown clearly when M87's most energetic gamma-ray flares were accompanied by the largest flare of radio waves seen from that galaxy by the VLBA.

The radio flare began at about the time of the gamma-ray flares, but continued to increase in brightness for at least two months. "This tells us that energetic material burst out very close to the black hole, causing the gamma rays to be emitted and the radio flare to begin. As that material traveled down the jet, expanding and losing energy, the gamma-ray emission ceased, but the radio continued to increase in brightness," Walker explained. "The VLBA showed us with great precision where the radio emission came from, so we know the gamma rays came from closer in toward the black hole," he added.

M87 is the largest galaxy in the Virgo Cluster of galaxies, at the center of a supercluster of galaxies that includes the Local Group, of which our own Milky Way is a member. The black hole in M87 has an "event horizon," from which matter cannot escape, roughly twice the size of our Solar System, or a tiny fraction of the size of the entire galaxy. The new measurements indicate that the gamma rays are coming from an area no larger than 50 times the size of the event horizon.

The telescope systems that detected the gamma-ray flares are the VERITAS array in Arizona, the H.E.S.S. system in Namibia, Africa, and the MAGIC system on La Palma in the Canary Islands.

The VLBA is a system of ten radio-telescope antennas stretching from Hawaii to the Caribbean, operated by the NRAO from Socorro, New Mexico. The VLBA offers resolving power equal to the ability to read a newspaper in New York while standing in Los Angeles.

Walker and Beilicke worked with Fred Davies of NRAO and New Mexico Tech, Henric Krawczynski of Washington University, Phil Hardee of the University of Alabama, Bill Junor of Los Alamos National Laboratory, Chun Ly of UCLA, and large research teams from VERITAS, H.E.S.S., and MAGIC. The scientists reported their findings in the July 2 online edition of the journal Science.

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

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Dave Finley, Public Information Officer
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