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

View other resolutions

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.

Contact:
Dave Finley, Public Information Officer
Socorro, NM
(575) 835-7302
dfinley@nrao.edu

XMM-Newton discovers a new class of black holes

Illustration of HLX-1 (blue star to the upper left hand side of the galactic bulge). HLX-1, located on the outskirts of the spiral galaxy ESO 243-49, is the strongest candidate to- date of intermediate-mass black holes. Credits: Heidi Sagerud

Astronomers using ESA’s XMM-Newton X-ray observatory have discovered a black hole weighing more than 500 solar masses, a missing link between lighter stellar-mass and heavier supermassive black holes, in a distant galaxy. This discovery is the best detection to date of a new class that has long been searched for: intermediate mass black holes.

Due to appear tomorrow in the journal Nature, the discovery has been made by an international team of researchers working with XMM-Newton data, led by Sean Farrell from the Centre d’Etude Spatiale des Rayonnements, now based at the University of Leicester.

Stellar-mass black holes (about three to twenty times as massive as the Sun) and supermassive black holes (several million to several thousand million times as massive as the Sun) have long been known to exist. Because of the large gap between these two extremes, scientists have speculated the existence of a third, intermediate class of black holes, with masses between a hundred and several hundred thousand solar masses.

Up until now, scientists were unable to confirm that this elusive intermediate class actually existed.

Farrell’s team were analysing archived data obtained by XMM-Newton, looking for neutron stars and white dwarves, when they stumbled upon a most peculiar object that was observed on 23 November 2004.

Called HLX-1 (Hyper-Luminous X-ray source 1), it lies towards the outskirts of the galaxy ESO 243-49, approximately 290 million light-years from Earth. If it is indeed located in this distant galaxy, HLX-1 is very luminous in X-rays; peaking at 260 million times the luminosity of the Sun.

On analysing the light originating from HLX-1, the team found that the X-ray signature was inconsistent with any object other than a feeding black hole. The measured brightness was too low for it to be in our own Galaxy, and the lack of observed radio or optical emission from the location of HLX-1 in addition to the observed X-ray signature indicates that it is unlikely to be a background galaxy.

This means that the source of the X-ray emission must lie in ESO 243-49. Its location is too far away from the galactic centre for it to be a supermassive black hole, and too bright for a stellar-mass black hole feeding at the maximum rate.

To be sure that this really was a single astronomical object, and not a cluster of several fainter sources that was shining brightly, the team used XMM-Newton to observe it again on 28 November 2008.

Comparing the two observations, they found that the signature of X-rays originating from HLX-1 varied significantly in time and concluded from this that it must be a single object. They found that the only way to explain its intense luminosity was if HLX-1 harboured a black hole greater than 500 solar masses. No other physical explanation could account for what they had seen.


The few intermediate-mass black hole candidates that have been discovered so far could be accounted for by other theories, but this one stood out as it was brighter than all the previous candidates by a factor of almost 10. The team had their hands on the best detection of an intermediate mass black holes to-date.

While it is already known that stellar-mass black holes are the remnants of massive stars, how supermassive black holes form is still unknown. One of the possible scenarios involves mergers of intermediate mass black holes. To ratify such a theory, it is essential to prove their existence in the first place.

This is why detections such as this by XMM-Newton are essential. It will help to understand just how supermassive black holes, such as that at the centre of our Galaxy, form.

The team have planned further observations in X-ray, ultraviolet, optical, infrared and radio wavelengths in the near future to better understand this unique object and the environment around it.

For more information:

Sean Farrell, University of Leicester
Email: saf28@star.le.ac.uk

Didier Barret, Centre d’Etude Spatiale des Rayonnements
Email: didier.barret@cesr.fr

Intense heat killed the Universe's would-be galaxies, researchers say

Computer generated image of Gas around young galaxy
Credit:Jim Geach (Durham University)
and Rob Crain (CAS/Swinburne University of Technology)

Image of simulated dark matter
Credit:Virgo Consortium

Millions of would-be galaxies failed to develop after being exposed to intense heat from the first stars and black holes formed in the early Universe, according to new research funded by Science and Technology Facilities Council (STFC) and the Japanese Society for the Promotion of Science.

Our Milky Way galaxy only survived because it was already immersed in a large clump of dark matter which trapped gases inside it, scientists led by Durham University’s Institute for Computational Cosmology (ICC) found.

The research, to be presented at an international conference today (Wednesday, July 1), also forms a core part of a new ICC movie charting the evolution of the Milky Way to be shown at the Royal Society.

The researchers said that the early Milky Way, which had begun forming stars, held on to the raw gaseous material from which further stars would be made. This material would otherwise have been evaporated by the high temperatures generated by the “ignition” of the Universe about half-a-billion years after the Big Bang.

Tiny galaxies, inside small clumps of dark matter, were blasted away by the heat which reached approximate temperatures of between 20,000 and 100,000 degrees centigrade, the scientists, including experts at Japan’s University of Tsukuba, said.

Dark matter is thought to make up 85 per cent of the Universe’s mass and is believed to be one of the building blocks of galaxy formation.

Using computer simulations carried out by the international Virgo Consortium (which is led by Durham) the scientists examined why galaxies like the Milky Way have so few companion galaxies or satellites.

Astronomers have found a few dozen small satellites around the Milky Way, but the simulations revealed that hundreds of thousands of small clumps of dark matter should be orbiting our galaxy.

The scientists said the heat from the early stars and black holes rendered this dark matter barren and unable to support the development of satellite star systems.

The findings will be presented to The Unity of the Universe conference to be held at the Institute of Cosmology and Gravitation, at the University of Portsmouth on Wednesday, July 1.

The simulations also form part of a new ICC movie – called Our Cosmic Origins – which combines ground-breaking simulations with observations of galaxies to track the evolution of the Milky Way over the 13-billion-year history of the Universe.

The movie is part of the ICC’s exhibit at The Royal Society’s annual Summer Science Exhibition which runs until this Saturday (July 4).

Joint lead investigator Professor Carlos Frenk, Director of the Institute for Computational Cosmology, at Durham University, said: “The validity of the standard model of our Universe hinges on finding a satisfactory explanation for why galaxies like the Milky Way have so few companions.

“The simulations show that hundreds of thousands of small dark matter clumps should be orbiting the Milky Way, but they didn’t form galaxies.

“We can demonstrate that it was almost impossible for these potential galaxies to survive the extreme heat generated by the first stars and black holes.

“The heat evaporated gas from the small dark matter clumps, rendering them barren. Only a few dozen front-runners which had a head start on making stars before the Universe ignited managed to survive.”

By providing a natural explanation for the origin of galaxies, the simulations support the view that cold dark matter is the best candidate for the mysterious material believed to make up the majority of our Universe, the scientists added.

It is now up to experimental physicists to either find this dark matter directly or to make it in a particle accelerator such as the Large Hadron Collider at CERN.

Professor Frenk, added: “Identifying the dark matter is not only one of the most pressing problems in science today, but also the key to understanding the formation of galaxies.”

Joint lead investigator Dr Takashi Okamoto from the University of Tsukuba said: “These are still early days in trying to make realistic galaxies in a computer, but our results are very encouraging.”

Notes for editors

Interviews

Professor Carlos Frenk, Director of the Institute for Computational Cosmology, at Durham University, is available for interview on Tuesday, June 30, and Wednesday, July 1.

However please note that as Professor Frenk is attending a conference his availability could be infrequent. He will be travelling between Portsmouth and London on the afternoon of Wednesday, July 1

Professor Frenk can be contacted on +44 (0)7808 726080 or alternatively please contact Durham University Media Relations Office, tel: +44 (0)191 334 6075.

Images

Copy of The International Virgo Consortium/Durham University Institute for Computational Cosmology movie

Additional information

The dark matter simulations were carried out at the Leibniz-Rechenzentrum München (LRZ) supercomputer as part of the “Aquarius Programme” by the Virgo Consortium

The gas simulations were carried out at the Cosmology Machine at Durham University’s Institute for Computational Cosmology and the Center for Computational Sciences at the University of Tsukuba, Japan.

The Cosmic Origins movie was made at the Visualization Laboratory of Durham University

Timeline of evolution of Universe (11.76mb - poster)

About dark matter ( 10.29mb): Most of the matter in the Universe is invisible. Scientists call this dark matter – though no one knows exactly what this is.

About STFC

by Julia Short
Science and Technology Facilities Council
Switchboard: 01793 442000

Astronomer's new guide to the galaxy: largest map of cold dust revealed

ESO PR Photo 24a/09
View of the Galactic Plane from
the ATLASGAL survey
(annotated and in five sections)

ESO PR Photo 24b/09
View of the Galactic Plane from
the ATLASGAL survey
(annotated)

ESO PR Photo 24c/09
ESO PR Photo 24d/09

ESO PR Photo 24e/09
The Galactic Centre
and Sagittarius B2

ESO PR Photo 24f/09
The NGC 6357 and
NGC 6334 nebulae

ESO PR Photo 24g/09
The RCW120 nebula

ESO PR Video 24a/09
Annotated pan as seen by
the ATLASGAL survey

Astronomers have unveiled an unprecedented new atlas of the inner regions of the Milky Way, our home galaxy, peppered with thousands of previously undiscovered dense knots of cold cosmic dust — the potential birthplaces of new stars. Made using observations from the APEX telescope in Chile, this survey is the largest map of cold dust so far, and will prove an invaluable map for observations made with the forthcoming ALMA telescope, as well as the recently launched ESA Herschel space telescope.

This new guide for astronomers, known as the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) shows the Milky Way in submillimetre-wavelength light (between infrared light and radio waves [1]). Images of the cosmos at these wavelengths are vital for studying the birthplaces of new stars and the structure of the crowded galactic core.

“ATLASGAL gives us a new look at the Milky Way. Not only will it help us investigate how massive stars form, but it will also give us an overview of the larger-scale structure of our galaxy”, said Frederic Schuller from the Max Planck Institute for Radio Astronomy, leader of the ATLASGAL team.

The area of the new submillimetre map is approximately 95 square degrees, covering a very long and narrow strip along the galactic plane two degrees wide (four times the width of the full Moon) and over 40 degrees long. The 16 000 pixel-long map was made with the LABOCA submillimetre-wave camera on the ESO-operated APEX telescope. APEX is located at an altitude of 5100 m on the arid plateau of Chajnantor in the Chilean Andes — a site that allows optimal viewing in the submillimetre range. The Universe is relatively unexplored at submillimetre wavelengths, as extremely dry atmospheric conditions and advanced detector technology are required for such observations.

The interstellar medium — the material between the stars — is composed of gas and grains of cosmic dust, rather like fine sand or soot. However, the gas is mostly hydrogen and relatively difficult to detect, so astronomers often search for these dense regions by looking for the faint heat glow of the cosmic dust grains.

Submillimetre light allows astronomers to see these dust clouds shining, even though they obscure our view of the Universe at visible light wavelengths. Accordingly, the ATLASGAL map includes the denser central regions of our galaxy, in the direction of the constellation of Sagittarius — home to a supermassive black hole (ESO 46/08) — that are otherwise hidden behind a dark shroud of dust clouds.

The newly released map also reveals thousands of dense dust clumps, many never seen before, which mark the future birthplaces of massive stars. The clumps are typically a couple of light-years in size, and have masses of between ten and a few thousand times the mass of our Sun. In addition, ATLASGAL has captured images of beautiful filamentary structures and bubbles in the interstellar medium, blown by supernovae and the winds of bright stars.

Some striking highlights of the map include the centre of the Milky Way, the nearby massive and dense cloud of molecular gas called Sagittarius B2, and a bubble of expanding gas called RCW120, where the interstellar medium around the bubble is collapsing and forming new stars (see ESO 40/08).

“It’s exciting to get our first look at ATLASGAL, and we will be increasing the size of the map over the next year to cover all of the galactic plane visible from the APEX site on Chajnantor, as well as combining it with infrared observations to be made by the ESA Herschel Space Observatory. We look forward to new discoveries made with these maps, which will also serve as a guide for future observations with ALMA”, said Leonardo Testi from ESO, who is a member of the ATLASGAL team and the European Project Scientist for the ALMA project.

Note

[1] The map was constructed from individual APEX observations in radiation at 870 µm (0.87 mm) wavelength.

More information:

The ATLASGAL observations are presented in a paper by Frederic Schuller et al., ATLASGAL — The APEX Telescope Large Area Survey of the Galaxy at 870 µm, published in Astronomy & Astrophysics. ATLASGAL is a collaboration between the Max Planck Institute for Radio Astronomy, the Max Planck Institute for Astronomy, ESO, and the University of Chile.

LABOCA (Large APEX Bolometer Camera), one of APEX’s major instruments, is the world’s largest bolometer camera (a "thermometer camera", or thermal camera that measures and maps the tiny changes in temperature that occur when sub-millimetre wavelength light falls on its absorbing surface; see ESO 35/07). LABOCA’s large field of view and high sensitivity make it an invaluable tool for imaging the “cold Universe”. LABOCA was built by the Max Planck Institute for Radio Astronomy.

The Atacama Pathfinder Experiment (APEX) telescope is a 12-metre telescope, located at 5100 m altitude on the arid plateau of Chajnantor in the Chilean Andes. APEX operates at millimetre and submillimetre wavelengths. This wavelength range is a relatively unexplored frontier in astronomy, requiring advanced detectors and an extremely high and dry observatory site, such as Chajnantor. APEX, the largest submillimetre-wave telescope operating in the southern hemisphere, is a collaboration between the Max Planck Institute for Radio Astronomy, the Onsala Space Observatory and ESO. Operation of APEX at Chajnantor is entrusted to ESO. APEX is a “pathfinder” for ALMA — it is based on a prototype antenna constructed for the ALMA project, it is located on the same plateau and will find many targets that ALMA will be able to study in extreme detail.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ESO is the European partner in ALMA. ALMA, the largest astronomical project in existence, is a revolutionary telescope, comprising an array of 66 giant 12-metre and 7-metre diameter antennas observing at millimetre and submillimetre wavelengths. ALMA will start scientific observations in 2011.

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”.

Links

The ATLASGAL paper referred to is available online at :
http://www.aanda.org/10.1051/0004-6361/200811568/pdf

More about APEX: http://www.eso.org/apex

APEX handout:
http://www.eso.org/public/outreach/products/publ/handouts/pdf/apex-lr.pdf

Max-Planck Press Release in German:
http://www.mpifr-bonn.mpg.de/public/pr/pr-atlasgal-dt.html

Contacts
Frederic Schuller
Max Planck Institute for Radio Astronomy, Bonn, Germany
Phone: +49 228 525 126
E-mail: schuller@mpifr-bonn.mpg.de

Leonardo Testi
European Project Scientist for ALMA
ESO, Garching, Germany
Phone: +49 89 3200 6541
E-mail: ltesti@eso.org

Douglas Pierce-Price
ESO ALMA/APEX Public Information Officer
ESO, Garching, Germany
Phone: +49 89 3200 6759
E-mail: dpiercep@eso.org

ESO ALMA-APEX Public Information Officer:
Dr. Douglas Pierce-Price - +49 89 3200 6759 - dpiercep@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/

Dating young star clusters in starburst galaxy M82

Figure 1: Existing dataset of star cluster spectroscopy (16 hours of GMOS on-target integration time in all), with slit positions plotted over HST-ACS imaging of M82 (Hubble Heritage ACS mosaic of 6 WFC images, Mutchler et al. 2007). The dataset samples individual star clusters across the entire galaxy disk and cluster associations in the nucleus.

Full Resolution TIF | 607KB

Figure 2: Cluster age dating. Each of these three image-spectrum pairs represents a BVI composite image and part of its optical spectrum. The spatial scale of the images is a square of side 175 pc. In the spectra, the top panel shows the age fit, with the solid line and dashed lines representing the observed spectrum and best fitting model respectively. The dashed blue boxes indicate the spectral regions where the fit takes place. The bottom panel shows the probability distribution of the fit across age-space, with a vertical line indicating the best fitting age and a horizontal line to delimit a confidence region.

Figure 3: A ground- and space-based HST/WIYN composite image of M82 and its optically bright superwind. This has been colour-coded to show its supergalactic wind running left-right (north-south) and a nearly vertical disk of stars. Broad blue, green and red filters were used to render the relatively smooth stellar disk. Purple represents emission from hydrogen.

Credit: Mark Westmoquette (UCL), Jay Gallagher (Wisconsin-Madison), Linda Smith (STScI/UCL)

Aimed at deciphering the secrets of archetypal starburst galaxy M82, the Gemini Multi-Object Spectrograph (GMOS) on Gemini North was employed by a team of UK- and US-based astronomers, led by Iraklis Konstantopoulos of University College London (UCL). The astronomers assembled key data for the largest sample of young extragalactic star clusters to date. M82 presents a gas, dust and stellar system that has intrigued scientists for decades due to its irregular, dusty appearance and extravagant super-galactic wind (see Figure 1).

Konstantopoulos et al. used the Gemini spectra to derive the age of 49 clusters in the disk, nucleus and halo of the galaxy (Figure 2). The resulting demographics were used to investigate the starburst history of M82, thus demonstrating the usefulness of star clusters as probes of star formation in environments where stars are too faint to be observed. On this basis, the observations were compared to theoretical models of starburst evolution in M82 (Förster Schreiber et al., 2003) and simulations that studied the interaction between M82 and its massive neighbour, M81, and the consequent burst of star formation (Yun et al., 1999).

In addition to deriving clusters ages, the group were able to establish a clear picture of this dusty, edge-on galaxy by combining radial velocity information with optical and near-IR imaging from the HST as well as CO observations from the Owens Valley Radio Observatory millimeter interferometer (Walter, Weiss & Scoville, 2002).

The combination and interpretation of the multi-wavelength data-set shows that the galaxy is far simpler than had previously been thought: it has a regular, two-armed spiral structure that is obscured in a highly irregular fashion by gas and dust perturbedby the recent interaction of the last ~220 million years. This is exemplified by the finding that the bright region 'B' (comparable to the nucleus in terms of apparent luminosity) is no more than an “artefact”: a hole in the dust distribution.

For more details, see the full article “A spectroscopic census of the M82 stellar cluster population”, by Iraklis S. Konstantopoulos, Nate Bastian, Linda J. Smith, Mark S. Westmoquette, Gelys Trancho and Jay S. Gallagher, The Astrophysical Journal, 2009, in press [or astro-ph/0906.2006].

The content of the article represents a large part of Konstantopoulos (UCL) PhD thesis. This work falls under two large Gemini projects: one is an investigation of M82 (led by Linda Smith) with respect to its star cluster content (presented here), the interstellar medium and super-galactic wind of M82 (led by Mark Westmoquette, University College London). The other, headed by Gelys Trancho (Gemini Observatory), is focussed on the study of star cluster formation in interacting and merging galaxies.

Source: Gemini Observatory

Milky Way's super-efficient particle accelerators caught in the act

ESO PR Photo 23a/09

The rim of RCW 86

Image of part of a stellar remnant whose explosion was recorded in 185 AD. By studying this remnant in detail, a team of astronomers was able to solve the mystery of the Milky Way’s super-efficient particle accelerators. The team shows that the shock wave visible in this area is very efficient at accelerating particles and the energy used in this process matches the number of cosmic rays observed on Earth. North is toward the top right and east to the top left. The image is about 6 arc minutes across.

ESO PR Photo 23b/09

DSS + insert, annotated

This wide-field image contains the area where a team of researchers confirmed that cosmic rays from our galaxy are very efficiently accelerated in the remnants of exploded stars. The red line guides the eye to various regions where the remnants of the stellar explosion are most visible. The boxed area contains an insert of data from the VLT and Chandra. This region, named RCW 86, is centered on the position where a star exploded in 185 AD. The field of view is 4 degrees across with north to the top and east to the left.

ESO PR Photo 23c/09

DSS image

A wide-field image of the area of the sky where the mystery of the Milky Way’s super-efficient particle accelerators was solved by studying the ancient RCW 86 supernova remnant.

This image in full resolution (TIF format, 649 MB) is available on this link.

ESO PR Video 23a/09
Zoom-in RCW 86

Thanks to a unique "ballistic study" that combines data from ESO's Very Large Telescope and NASA's Chandra X-ray Observatory, astronomers have now solved a long-standing mystery of the Milky Way’s particle accelerators. They show in a paper published today on Science Express that cosmic rays from our galaxy are very efficiently accelerated in the remnants of exploded stars.

During the Apollo flights astronauts reported seeing odd flashes of light, visible even with their eyes closed. We have since learnt that the cause was cosmic rays — extremely energetic particles from outside the Solar System arriving at the Earth, and constantly bombarding its atmosphere. Once they reach Earth, they still have sufficient energy to cause glitches in electronic components.

Galactic cosmic rays come from sources inside our home galaxy, the Milky Way, and consist mostly of protons moving at close to the speed of light, the “ultimate speed limit” in the Universe. These protons have been accelerated to energies exceeding by far the energies that even CERN’s Large Hadron Collider will be able to achieve.

“It has long been thought that the super-accelerators that produce these cosmic rays in the Milky Way are the expanding envelopes created by exploded stars, but our observations reveal the smoking gun that proves it”, says Eveline Helder from the Astronomical Institute Utrecht of Utrecht University in the Netherlands, the first author of the new study.

“You could even say that we have now confirmed the calibre of the gun used to accelerate cosmic rays to their tremendous energies”, adds collaborator Jacco Vink, also from the Astronomical Institute Utrecht.

For the first time Helder, Vink and colleagues have come up with a measurement that solves the long-standing astronomical quandary of whether or not stellar explosions produce enough accelerated particles to explain the number of cosmic rays that hit the Earth’s atmosphere. The team’s study indicates that they indeed do and it directly tells us how much energy is removed from the shocked gas in the stellar explosion and used to accelerate particles.

“When a star explodes in what we call a supernova a large part of the explosion energy is used for accelerating some particles up to extremely high energies”, says Helder. “The energy that is used for particle acceleration is at the expense of heating the gas, which is therefore much colder than theory predicts”.

The researchers looked at the remnant of a star that exploded in AD 185, as recorded by Chinese astronomers. The remnant, called RCW 86, is located about 8200 light-years away towards the constellation of Circinus (the Drawing Compass). It is probably the oldest record of the explosion of a star.

Using ESO’s Very Large Telescope, the team measured the temperature of the gas right behind the shock wave created by the stellar explosion. They measured the speed of the shock wave as well, using images taken with NASA’s X-ray Observatory Chandra three years apart. They found it to be moving at between 10 and 30 million km/h, between 1 and 3 percent the speed of light.

The temperature of the gas turned out to be 30 million degrees Celsius. This is quite hot compared to everyday standards, but much lower than expected, given the measured shock wave’s velocity. This should have heated the gas up to at least half a billion degrees.

“The missing energy is what drives the cosmic rays”, concludes Vink.

More Information
This research was presented in a paper to appear in Science: Measuring the cosmic ray acceleration efficiency of a supernova remnant, by E. A. Helder et al.

The team is composed of E.A. Helder, J. Vink and F. Verbunt (Astronomical Institute Utrecht, Utrecht University, The Netherlands), C.G. Bassa and J.A.M. Bleeker (SRON, Netherlands Institute for Space Research, The Netherlands), A. Bamba (ISAS/JAXA Department of High Energy Astrophysics, Kanagawa, Japan), S. Funk (Kavli Institute for Particle Astrophysics and Cosmology, Stanford, USA), P. Ghavamian (Space Telescope Science Institute, Baltimore, USA), K. J. van der Heyden (University of Cape Town, South Africa), and R. Yamazaki (Department of Physical Science, Hiroshima University, Japan). C.G. Bassa is also affiliated with the Radboud University Nijmegen, the Netherlands.

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”.

Links
To request the Science paper: http://www.sciencemag.org/help/about/contact_info.dtl

Contacts
Eveline Helder, Jacco Vink
Astronomical Institute Utrecht
The Netherlands
Phone: +31 30 253 5221, +31 30 253 2513
E-mail: E.A.Helder@uu.nl, j.vink@uu.nl

Stefan Funk
Kavli Institute for Particle Astrophysics and Cosmology, Stanford, USA
Phone: +1 650 926 8979
E-mail: funk@slac.stanford.edu

Ryo Yamazaki
Hiroshima University, Japan
Phone: +81-82-424-7362
E-mail: ryo@theo.phys.sci.hiroshima-u.ac.jp

Aya Bamba
ISAS/JAXA Department of High Energy Astrophysics
Kanagawa, Japan
Phone: +81-42-759-8138
E-mail : bamba@astro.isas.jaxa.jp

ESO La Silla - Paranal - ELT Press Officer:
Dr. Henri Boffin - +49 89 3200 6222 - hboffin@eso.org

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

National contacts for the media:
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STScI Joins the Search for Other Earths in Space

Credit: NASA
Credit:NASA

The Space Telescope Science Institute (STScI) in Baltimore, Md., is partnering on a historic search for Earth-size planets around other stars. STScI is the data archive center for NASA's Kepler mission, a spacecraft that is undertaking a survey for Earth-size planets in our region of the galaxy. The spacecraft sent its first raw science data to STScI on June 19.

The Institute was the logical choice for storing the anticipated flood of data because its scientists have processed enough observations from NASA's Hubble Space Telescope over the past 19 years to fill almost two collections of material in the U.S. Library of Congress.

The Institute's role is to convert the raw science data into files that can be analyzed by Kepler researchers and to store the files every three months in an archive.

"We are part of this mission because of our experience with Hubble data processing and archiving," explained David Taylor, project manager for the development of Kepler's Data Management Center at the Institute. "NASA's Ames Research Center [the home of Kepler's science operations] had not done a science mission like this one. Building the Data Management Center from scratch would have been more costly, and it would have taken longer to get up to speed."

Launched on March 6 on a Delta II rocket from Cape Canaveral, Fla., the Kepler spacecraft will spend the next 3 1/2 years searching for habitable planets by staring nonstop at more than 100,000 Sun-like stars out of about 4.5 million catalogued stars in the spacecraft's field-of-view, located in the summer constellations Cygnus and Lyra.

The spacecraft simultaneously measures the variations in brightness of the more than 100,000 stars every 30 minutes, searching for periodic dips in a star's brightness that happen when an orbiting planet crosses in front of it and partially blocks the light. These fluctuations are tiny compared with the brightness of the star. For an Earth-size planet transiting a solar-type star, the change in brightness is less than 1/100 of 1 percent. This event is similar to the dimming one might see if a flea were to crawl across a car's headlight viewed from several miles away.

When the mission is completed in several years, the survey should tell astronomers how common Earth-size planets are around stars.

Once a month, the Kepler spacecraft will send its science data, about 50 gigabytes, back to Kepler's Mission Operations Center at the Laboratory for Atmospheric and Space Physics at the University of Colorado. Raw science data will then be relayed to the Institute's Data Management Center (DMC). DMC Operations will convert the information into Flexible Image Transport System (FITS) files, a digital file format used to store, transmit, and manipulate scientific information. FITS is the most commonly used digital file format in astronomy.

The FITS files will be sent to the Kepler Scientific Operations Center (SOC) at Ames Research Center in California, where the science data analysis will be carried out.

Kepler mission scientists will turn the data into 30-minute snapshots of light from each of the 100,000 or more stars. From these snapshots, the scientists will construct a light curve for each star, which details any brightness fluctuations. They will review the light curves to look for any periodic decrease in brightness, an indication of a possible transiting planet.

The mission scientists also will use the light curves to study the stars and their interiors. Because of the quality of the Kepler data and the large number of stars the spacecraft will observe, scientists hope to improve their understanding of stellar evolution.

"The mission's main purpose is to find planets that are the same distance from its solar-type star as Earth is from the Sun," said Daryl Swade, who directed the systems engineering development of Kepler's Data Management Center at the Institute. "So that means that the planet would cross in front of its star every year. We would need three or four of these transits to confirm the detection, which will take about three or four years."

A planet at an Earth-like distance from its star would be in the star's "habitable zone," where temperatures are just right for liquid oceans to exist on the surface without freezing over or evaporating away. On Earth, a liquid ocean was needed to nurture the chemical processes that lead to the appearance of life. This is considered an important prerequisite for life as we know it to appear elsewhere in the galaxy.

Kepler's science data also will be archived at the Institute. Every three months the SOC at Ames will ship FITS files in a 500-gigabyte computer hard drive to the Institute for storage in the Multimission Archive, or MAST. The archive houses data from about 14 missions, including Hubble, the Far Ultraviolet Spectroscopic Explorer (FUSE), and the Galaxy Evolution Explorer (GALEX).

Based on its strong track record in processing and archiving data, the Institute could earn a role in many future missions.

"Partnering with other institutions to share the duties of a mission may be a trend for future missions," Taylor said.

The Space Telescope Science Institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc., Washington, D.C.

Kepler is a NASA Discovery mission. NASA Ames Research Center, Moffett Field, Calif., is the home organization of the science principal investigator and is responsible for the ground system development, mission operations, and science data analysis. NASA Jet Propulsion Laboratory, Pasadena, Calif., managed the Kepler mission development. Ball Aerospace & Technologies Corp. of Boulder, Colo., was responsible for developing the Kepler flight system and is supporting mission operations.

CONTACT
Donna Weaver
Space Telescope Science Institute, Baltimore, Md.
410-338-4493
dweaver@stsci.edu

Lyman Alpha Blobs: Galaxies Coming of Age in Cosmic Blobs

bCredit: Left panel: X-ray (NASA/CXC/Durham Univ./D.Alexander et al.); Optical (NASA/ESA/STScI/IoA/S.Chapman et al.); Lyman-alpha Optical (NAOJ/Subaru/Tohoku Univ./T.Hayashino et al.); Infrared (NASA/JPL-Caltech/Durham Univ./J.Geach et al.); Right, Illustration: NASA/CXC/M.Weiss

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A deep study of 29 gigantic blobs of hydrogen gas has been carried out with NASA's Chandra X-ray Observatory to identify the source of immense energy required to illuminate these structures. These mysterious blobs - called "Lyman-alpha blobs" by astronomers because of the light they emit - are several hundred thousand light years across and are seen when the Universe is only about two billion years old, or about 15% of its current age.

The composite image on the left shows one of the largest blobs observed in this study. Glowing hydrogen gas in the blob is shown by a Lyman-alpha optical image (colored yellow) from the National Astronomy Observatory of Japan's Subaru telescope. A galaxy located in the blob is visible in a broadband optical image (white) from the Hubble Space Telescope and an infrared image from the Spitzer Space Telescope (red). Finally, the Chandra X-ray Observatory image in blue shows evidence for a growing supermassive black hole in the center of the galaxy. Radiation and outflows from this active black hole are powerful enough to light up and heat the gas in the blob. Radiation and winds from rapid star formation occurring in the galaxy is believed to have similar effects. Clear evidence for four other active black holes in blobs is also seen.

The artist's representation on the right shows what one of the galaxies inside a blob might look like if viewed at a relatively close distance. A two-sided outflow powered by the supermassive black hole buried inside the middle of the galaxy is shown in bright yellow, above and below the spiral arms of the galaxy. This outflow illuminates and heats gas surrounding the galaxy. Radiation from regions close to the black hole will also play a significant role in lighting up and heating the blob. Stars are forming at a rapid rate in this galaxy, and young stars are being destroyed in supernova explosions. The three bright stars above the central bulge of the galaxy are examples of such supernovas (a companion illustration shows the effects of such explosions).

These new results show how blobs fit into the cosmic story of how galaxies and black holes evolve. Galaxies are believed to form when gas flows inwards under the pull of gravity and cools by emitting radiation. This process should stop when the gas is heated by radiation and outflows from galaxies and their black holes. Blobs could be a sign of this first stage, or of the second.

Based on the new data and theoretical arguments, Geach and his colleagues show that heating of gas by growing supermassive black holes and bursts of star formation, rather than cooling of gas, most likely powers the blobs. The implication is that blobs represent a stage when the galaxies and black holes are just starting to switch off their rapid growth because of these heating processes. This is a crucial stage of the evolution of galaxies and black holes -- known as "feedback" -- and one that astronomers have long been trying to understand.

Fast Facts for Lyman Alpha Blobs:

Scale: Left panel is 38 arcsec across
Category: Cosmology/Deep Fields/X-ray Background
Coordinates: (J2000) RA 22h 17m 39s | Dec +00° 13' 27.5
Constellation: Aquarius
Observation Date: 08/01/2007 - 12/30/2007
Observation Time: 4 days15 hours
Obs. ID: 8034-8036, 9717
Color Code: X-ray (Blue); Optical (White, Yellow); Infrared (Red)
Instrument: ACIS
References: J. Geach et al. 2009, ApJ, in press
Distance Estimate: About 11.5 billion light years