A dragon-shaped cloud of dust seems to fly out from a bright explosion in this infrared light image (bottom) from NASA's Spitzer Space Telescope, a creature that is entirely cloaked in shadow when viewed in visible part of the spectrum (top). Image credit: NASA/JPL-Caltech/Penn State/DSS. Full image and caption

A dragon-shaped cloud of dust seems to fly with the stars in a new image from NASA's Spitzer Space Telescope (bottom). In visible light (top), the creature disappears into the clouds -- perhaps it's "frolicking in the autumn mist" like Puff, the Magic Dragon, from the famous Peter, Paul and Mary song.

The infrared image has revealed that this creature, a dark cloud called M17 SWex, is forming stars at a furious rate but has not yet spawned the most massive type of stars, known as O stars. Such stellar behemoths, however, light up the M17 nebula at the image's center and have also blown a huge "bubble" in the gas and dust that forms M17's luminous left edge.

The stars and gas in this region are now passing though the Sagittarius spiral arm of the Milky Way (moving from right to left), touching off a galactic "domino effect." The youngest episode of star formation is playing out inside the dusty dragon as it enters the spiral arm. Over time, this area will flare up like the bright M17 nebula, glowing in the light of young massive stars. An older burst of star formation blew the bubble seen in the region to the far left, called M17 EB.

The visible-light view of the area clearly shows the bright M17 nebula, as well as the glowing hot gas filling the "bubble" to its left. However the M17 SWex "dragon" is hidden within dust clouds that are opaque to visible light. It takes an infrared view to catch the light from these shrouded regions and reveal the earliest stages of star formation.

The bottom image is a three-color composite that shows infrared observations from two Spitzer instruments. Blue represents 3.6-micron light and green shows light of 8 microns, both captured by Spitzer's infrared array camera. Red is 24-micron light detected by Spitzer's multiband imaging photometer. The bottom visible-light image is a composite of visible-light data from the Digitized Sky Survey (DSS) from the UK Schmidt telescope. The image combines two observations that represent the blue and red light from the region.

For a more detailed feature story about the science in this image, visit http://www.spitzer.caltech.edu/news/1143.

This image was taken before Spitzer ran out of its liquid coolant in May 2009, beginning its warm mission.

Since launch in 2002, INTEGRAL's imaging telescope, IBIS, has been used to assemble four iterations of the soft gamma-ray survey catalogue. Over the years astronomers have utilised IBIS to look at specific sources in the gamma-ray Universe. Whilst these dedicated observations are under way, the telescope also records gamma-ray photons from any source which happens to be within the field of view during the exposure, which can last anywhere from a few days up to a few weeks. As a result the catalogue now contains more than 700 sources.

This fourth edition represents a major expansion of scope compared to its three predecessors. Previous observations had concentrated on an area in the plane of the Milky Way known as the 'Zone of Avoidance', a murky area opaque in many other wavelengths due to the gas and dust towards the heart of our Galaxy. However, INTEGRAL's gamma-ray eyes can peer straight through the debris. Having completed a large survey of the galactic nucleus, many astronomers turned their attention, and that of INTEGRAL, to extragalactic sources; only 4% of first catalogue sources were beyond our Galaxy compared to 35% in this latest incarnation.

This broadening of their gamma-ray horizons allows researchers to better probe the secrets of galaxy formation. "Looking over the whole sky at high energies is an excellent way to test our models of how galaxies have formed and evolved throughout the life of the Universe," says Tony Bird, co-investigator for the IBIS imager at Southampton University. It has also had an effect on the relative numbers of different cosmic species which comprise the catalogue. In particular, a little under a third of the catalogue is now dominated by Active Galactic Nuclei (AGNs), accompanied by High Mass X-Ray Binaries (13%), Low Mass X-Ray Binaries (13%) and Cataclysmic Variables (5%).

This still leaves around a third of sources unknown. "There are still a significant number of sources that are unidentified because the comparatively large error circle of INTEGRAL makes it difficult to uniquely identify a counterpart," says INTEGRAL Project Scientist Chris Winkler. While INTEGRAL's wide field of view is good at flagging up the general location of a source, the arc-second accuracy provided by other telescopes, such as ESA's X-ray telescope, XMM-Newton, is needed to pinpoint their exact location. Once this precise location is known, astronomers can start to unveil the true nature of the source using observations over several wavelengths. Bird expects this process will be completed in the near future. "I expect many more of these new INTEGRAL sources to be identified in the coming year, as part of the ongoing multi-wavelength campaign," he said.

A prime example of such a multi-wavelength campaign success is the source IGR J17488-2338. Initially identified by the INTEGRAL catalogue, observations with XMM-Newton revealed it to be an AGN located 10 degrees from the plane of our own Galaxy. Similarly, IGR J13042-1020 was revealed as another AGN by the SWIFT X-ray satellite when it caught a glimpse of the source's core, this time at the heart of galaxy NGC 4939.

IGR J17488-2338 (left) and NGC 4939 (right) are two sources discovered in hard X-rays with INTEGRAL, which were later identified with multi-wavelength observations. Credit: ESA

In this way INTEGRAL is leading from the front by identifying sources which then demand the attention of the wider research community. In doing so the satellite is moving towards the mainstream of astronomical research. "The numbers of sources that we have now seen with INTEGRAL means that gamma-ray astronomy is able to contribute strongly in many of the current areas of astronomical research and is finally moving away from being 'niche' science," explains Bird.

Christoph Winkler, INTEGRAL Project Scientist
Research and Scientific Support Department
Directorate of Science and Robotic Exploration, ESA, The Netherlands
Email: cwinkler@rssd.esa.int
Phone: +31 71 565 3591

Tony Bird
School of Physics & Astronomy, University of Southampton, United Kingdom
Email: ajb@astro.soton.ac.uk
Phone: +44 23 8059 2190

Credit: NASA, ESA, R. O'Connell (University of Virginia), F. Paresce (National Institute for Astrophysics, Bologna, Italy), E. Young (Universities Space Research Association/Ames Research Center), the WFC3 Science Oversight Committee, and the Hubble Heritage Team (STScI/AURA). Larger image - Labeled image - Fast Facts

Like a July 4 fireworks display a young, glittering collection of stars looks like an aerial burst. The cluster is surrounded by clouds of interstellar gas and dust - the raw material for new star formation. The nebula, located 20,000 light-years away in the constellation Carina, contains a central cluster of huge, hot stars, called NGC 3603.

This environment is not as peaceful as it looks. Ultraviolet radiation and violent stellar winds have blown out an enormous cavity in the gas and dust enveloping the cluster, providing an unobstructed view of the cluster.

Most of the stars in the cluster were born around the same time but differ in size, mass, temperature, and color. The course of a star's life is determined by its mass, so a cluster of a given age will contain stars in various stages of their lives, giving an opportunity for detailed analyses of stellar life cycles. NGC 3603 also contains some of the most massive stars known. These huge stars live fast and die young, burning through their hydrogen fuel quickly and ultimately ending their lives in supernova explosions.

Star clusters like NGC 3603 provide important clues to understanding the origin of massive star formation in the early, distant universe. Astronomers also use massive clusters to study distant starbursts that occur when galaxies collide, igniting a flurry of star formation. The proximity of NGC 3603 makes it an excellent lab for studying such distant and momentous events.

This Hubble Space Telescope image was captured in August 2009 and December 2009 with the Wide Field Camera 3 in both visible and infrared light, which trace the glow of sulfur, hydrogen, and iron.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc. in Washington, D.C.

Planck has delivered its first image of the entire sky. By looking at microwave radiation, it not only provides new insight into the way stars and galaxies form, but also tells us how the Universe itself came to life after the Big Bang.

Professor George Efstathiou, at University of Cambridge and the Planck Survey Scientist, said “it has taken sixteen years of hard work by many scientists in Europe, the USA and Canada, to produce this new image of the early Universe. Planck is working brilliantly and we expect to learn a lot about the Big Bang and the creation of our Universe.”

Dr David Parker, Director of Space Science and Exploration for the UK Space Agency, added, “Planck has ‘painted’ us its first spectacular picture of the Universe. This single image captures both our own cosmic backyard – the Milky Way galaxy that we live in – but also the subtle imprint of the Big Bang from which the whole Universe emerged. We’re proud to be supporting this great new discovery machine and look forward to our scientists unravelling the deeper meaning behind the beauty of this first image.”

From the closest portions of the Milky Way to the furthest reaches of space and time, the new all-sky Planck image is an extraordinary treasure chest of new data for astronomers. The main disc of our Galaxy runs across the centre of the image. Immediately striking are the streamers of cold dust reaching above and below the Milky Way. This galactic web is where new stars are being formed, and Planck has found many locations where individual stars are edging toward birth or just beginning their cycle of development.

Less spectacular but perhaps more intriguing is the mottled backdrop at the top and bottom. This is the cosmic microwave background (CMB) radiation. It is the oldest light in the Universe, the remains of the fireball out of which our Universe sprang into existence 13.7 billion years ago.

While the Milky Way shows us what our local neighbourhood looks like now, those microwaves show us what the Universe looked like close to its time of creation, before there were stars or galaxies. The CMB radiation was released as the first atoms were forming, about 400 000 years after the Big Bang, and is at the heart of Planck’s mission to decode what happened in the primordial Universe.

The microwave pattern is the cosmic blueprint from which today’s clusters of galaxies were built. The different colours represent minute differences in the temperature and density of matter across the sky. Through the action of gravity, these small irregularities evolved into denser regions that became the galaxies of today.

The CMB covers the entire sky but most of it is hidden in this image by the Milky Way’s emission, which must be digitally removed from the final data in order to see the microwave background in its entirety. Planck looks at the sky in nine different bands, or colours, of microwave light, which have wavelengths thousands of times that of optical light. These nine different bands, ranging from frequencies of 30 to 850 GHz, are crucial for understanding which parts of the Planck data are from the early Universe, and which are from our own Galaxy. Clive Dickinson, of the University of Manchester, said “Planck has the unique ability to distinguish very cold dust at temperatures of just a few degrees above absolute zero (-273.15oC) from the warmer dust at tens of degrees above absolute zero. These regions of space are likely to be where stars form, and Planck will allow us to study such regions over large regions of sky for the first time.”

A number of UK institutions have been involved in the design and construction of the satellite, and are now working alongside colleagues from around the world to operate the satellite and analyse the data. Dr David Clements, of Imperial College London, said “just looking at the pictures you can tell we're seeing new things about the structure of our galaxy. Once we've done that, and stripped away these foregrounds, then it's on to the Cosmic Microwave Background and the glow of the Big Bang itself!”

The image shown here is constructed from data taken from the first ten months of Planck’s main mission, with observations beginning in August 2009. Planck continues to map the Universe, and by the end of its mission in 2012 it will have imaged the whole sky four times. The first full data release of the CMB is planned for 2012. Before then, a catalogue containing individual objects, both regions in our Galaxy and entire distant galaxies, will be released in January 2011.

Professor Peter Ade, at Cardiff University, has been involved with design, construction and operation of the High Frequency Instrument. He said “at last we can see the realisation of the full potential of Planck, showing in exquisite detail our own Milky Way galaxy superimposed on the relic fireball background. It is a fantastic result for this unique satellite, and demonstrates once again that you can only do pioneering science by using advanced and therefore high risk technologies.”

The Jodrell Bank Centre for Astrophysics at the University of Manchester is involved with the Low Frequency Instrument. Rod Davies, Emeritus Professor at Jodrell, said “it is particularly rewarding for me to see the culmination of a 30-year involvement in Cosmic Microwave Background research beginning with radio telescopes at Jodrell Bank in Cheshire, then under the clear dry skies on the high volcanic slopes of Tenerife and finally with the construction by Jodrell Bank of the radio receivers for Planck’s Low Frequency Instrument.”

Figure 1 First released in September of 2008: Gemini adaptive optics image of 1RXS J160929.1-210524 and its ~8 Jupiter-mass companion (within red circle). This image is a composite of J-, H- and K-band near-infrared images. All images obtained with the Gemini Altair adaptive optics system and the Near-Infrared Imager (NIRI) on the Gemini North telescope. Photo Credit: Gemini Observatory. JPG 89.39 KB | TIFF 18.7 MB

A planet only about eight times the mass of Jupiter has been confirmed orbiting a Sun-like star at over 300 times farther from the star than the Earth is from our Sun. The newly confirmed planet is the least massive planet known to orbit at such a great distance from its host star. The discovery utilized high-resolution adaptive optics technology at the Gemini Observatory to take direct images and spectra of the planet.

First reported in September 2008 by a team led by David Lafrenière (then at the University of Toronto, now at the University of Montreal and Center for Research in Astrophysics of Quebec), the suspected planetary system required further observations over time to confirm that the planet and star were indeed moving through space together. “Back in 2008 what we knew for sure was that there was this young planetary mass object sitting right next to a young Sun-like star on the sky,” says Lafrenière. The extremely close proximity of the two objects strongly suggested that they were associated with each other but it was still possible (but unlikely) that they were unrelated and only aligned by chance in the sky. According to Lafrenière, “Our new observations rule out this chance alignment possibility, and thus confirms that the planet and the star are related to each other.”

With this confirmation by Lafrenière and colleagues, the system, known as 1RXS J160929.1-210524 (or 1RXS 1609 for short), provides scientists with a unique specimen that challenges planetary formation theories due to its extreme separation from the star. "The unlikely locale of this alien world could be telling us that nature has more than one way of making planets," says co-author Ray Jayawardhana of the University of Toronto. "Or, it could be hinting at a violent youth when close encounters between newborn planets hurl some siblings out to the hinterlands," he adds.

With its initial detection by the team using the Gemini Observatory in April of 2008 this object became the first likely planet known to orbit a sun-like star that was revealed by direct imaging. At the time of its discovery the team also obtained a spectrum of the planet and was able to determine many of its characteristics, which are confirmed in this new work. “In retrospect, this makes our initial data the first spectrum of a confirmed exoplanet ever!” says Lafrenière. The spectrum shows absorption features due to water vapor, carbon monoxide, and molecular hydrogen in the planet’s atmosphere.

Since the initial observations several other worlds have been discovered using direct imaging, including a system of three planets around the star HR 8799 also discovered with Gemini. However, the planets around HR 8799 orbit much closer to their host star.

The team’s recent work on 1RXS 1609 also verified that no additional large planets (between 1-8 Jupiter masses) are present in the system closer to the star. Future observations may shed light on the origin of this mysterious far-out planet. In particular, in a few years, it should be to possible to detect a slight difference in motion between the planet and its star due to their mutual orbit. Co-author Marten van Kerkwijk (University of Toronto) notes that the difference will be “very small,” since the fastest possible orbital period is more than one thousand years. But he adds that by using Gemini it should be possible to measure a very precise velocity of the planet relative to its host. This will show whether the planet is likely on a roughly circular orbit, as would be expected if it really formed far from its host star, or whether it is in a very non-circular or even unbound orbit, as could be the case if it formed closer to its star, but was kicked out in a close encounter with another planet.

The host star is located about 500 light-years away in a group of young stars called the Upper Scorpius association that formed about five million years ago. The original survey studied more than 85 stars in this association. The planet has an estimated temperature of about 1800 Kelvin (about 1500 degrees Celsius) and is much hotter than Jupiter, which has a atmospheric cloud-top temperature of about 160 Kelvin (-110 degrees Celsius). The host star has an estimated mass of about 85% that of our Sun. The young age of the system explains the high temperature of the planet. The contraction of the planet under its own gravity during its formation quickly raised its temperature to thousands of degrees. Once this contraction phase is over, the planet slowly cools down by radiating infrared light. In billions of years, the planet will eventually reach a temperature similar to that of Jupiter.

The observations used the Near-Infrared Imager (NIRI) and the Altair adaptive optics system on the Gemini North telescope. Adaptive optics allows scientists to remove much of the distortions caused by our atmosphere and dramatically sharpen views of space. “Without adaptive optics, we would simply have been unable to see this planet,” says Lafrenière. “The atmosphere blurs the image of a star so much that it extends over and is much brighter than the image of a faint planet around it, rendering the planet undetectable. Adaptive optics removes this blurring and provides a better view of faint objects very close to stars.”

The result has been accepted for publication (see preprint here) in an upcoming issue of The Astrophysical Journal.

The Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located at Mauna Kea, Hawai'i (Gemini North) and the other telescope at Cerro Pachón in northern Chile (Gemini South), and hence provide full coverage of both hemispheres of the sky. Both telescopes incorporate new technologies that allow large, relatively thin mirrors under active control to collect and focus both optical and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in each partner country with state-of-the-art astronomical facilities that allocate observing time in proportion to each country's contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the US National Science Foundation (NSF), the UK Science and Technology Facilities Council (STFC), the Canadian National Research Council (NRC), the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT), the Australian Research Council (ARC), the Argentinean Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) and the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico CNPq). The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

The HerMES project is providing a view of the distant Universe at wavelengths which can only be observed from space. Because the SPIRE camera on board Herschel “sees” images in three sub-millimetre wavelength bands, or colours, which have hardly been used in astronomy until now, it shows a different aspect of galaxies, and is able to view cool objects previously invisible to astronomers. The appearance of an object in these three colours provides information on its temperature, distance and luminosity.

One set of the data being released focusses on a massive cluster of galaxies called Abell 2218. At a distance of over 2 billion light years from Earth, the huge mass of the cluster warps the surrounding space, bending and magnifying light from background galaxies in a manner similar to light being magnified by a normal glass lens. Abell 2218 is famous for being one of the best known examples of this “gravitational lensing”. The effect, first predicted by Einstein in the early 20th century, means that the background galaxies are magnified, allowing a much clearer view of objects as they were over 11 billion years ago – less than 3 billion years after the Big Bang. Without the gravitational lensing these galaxies would be much fainter, and confused by the presence of the foreground galaxies, but this chance alignment provides the opportunity to explore a tiny part of the early Universe in much more detail. The Herschel observations of these distant galaxies tell astronomers how fast they were forming stars at these early times, and help to build up a picture of how galaxies have evolved over the course of billions of years.

The image above shows the Abell 2218 cluster as seen by the SPIRE instrument on Herschel, in relation to an iconic image from the Hubble Space Telescope. The three wavelength bands are first shown as individual red, green and blue images, and then combined into a colour image. The centre of the cluster is marked as a white cross-hair, and the bright yellow object just below is the lensed galaxy. Most of the other galaxies shown are much bluer, and are in the foreground cluster. The properties of the cluster are also of great interest to other astronomers, such as those using the Hubble Space Telescope. Observing at many wavelengths not only helps work out the precise effect of the lensing, but also shows the nature and behaviour of galaxies within large clusters.

Dr. Michael Zemcov of California Institute of Technology says "Images like this show that SPIRE has opened up the possibility of observing at sub-mm wavelengths in a way which was just not possible before; this kind of clarity is unprecedented at these wavelengths. Now that these data are available to the entire astronomical community, we will really be able to test our understanding of objects like galaxy clusters and, more profoundly, the formation of structure in the Universe from soon after the Big Bang right up to the present day."

Richard Ellis, Steele Professor of Astronomy at the California Institute of Technology, who is not a member of the HerMES team but has exploited gravitational lensing in cosmology for over 20 years, added: "It is wonderful to see these first HerMES images which demonstrate the phenomenal power of the Herschel mission. The magnification provided by the rich cluster Abell 2218 and other clusters will provide astronomers worldwide with an unique view of the evolution of early galaxies."

Dr. Evanthia Hatziminaoglou, at the European Southern Observatory, has been using the HerMES data to study the connection between galaxies and the super-massive black holes that lie at their centre. These super-massive black holes grow by accreting gas, with some radiating vast quantities of power as quasars or “Active Galactic Nuclei” (AGN). This is the most efficient energy conversion process known. Looking at these objects with Herschel, Dr Hatziminaoglou discovered that their sub-millimetre emission comes almost entirely from star formation and that their properties, in these wavelengths, are indistinguishable from those of non-active galaxies. This result, which will be published next month, confirms independently that super-massive black holes grow in size along with the galaxies in which they reside. Dr Hatziminaoglou said "it is surprising to see that these two highly energetic astrophysical phenomena co-exist in such harmony”.

The HerMES team hope that by releasing catalogues of their galaxies to the whole astronomical community, telescopes around the world will be trained on these kinds of exotic distant beasts to help our understanding of how galaxies and AGN have evolved over the lifetime of the Universe. Professor Ian Smail, an astronomer at Durham University, is not a member of the HerMES team, but uses surveys of galaxies at different wavelengths to study their formation and evolution. Discussing the release of the HerMES catalogues, Prof. Smail said "These first sub-millimetre views of young galaxies in the distant Universe clearly show that huge numbers of new stars are being formed, but cloaked by dust and so missed by optical observatories such as the Hubble Space Telescope. It is already clear that we live in a changing Universe and, thanks to Herschel and SPIRE, few things are changing faster than our perception of it."

Professor Oliver adds “we have made these images and lists of galaxies available to all astronomers sooner than we were obliged to because Herschel is a fantastic mission but has a limited lifetime, and it is vital that it is used for the best science. We hope that other astronomers will want to use Herschel and many other telescopes to study the galaxies we have discovered”.

The Herschel Project Scientist, Göran Pilbratt, said “it is very gratifying that Herschel data are being publicly released. The more people get access to the data, the more productive the mission will be, and the greater its science return. This is a win-win situation for the entire astronomical community.”

XTE J1550-564 is a binary system in which an evolved star orbits -- and donates matter to -- a black hole estimated at 10 times the sun's mass. Credit: ESO/L. Calçada - View Hi-Res

In April 2000, XTE J1550-564 erupted. The blue line indicates the energy and brightness of X-rays from the system as detected by NASA's Rossi X-ray Timing Explorer. Insets show where the X-rays are thought to originate in the vicinity of the black hole. From June to September, the system's particle jets produced most of the X-rays. Credit: NASA/RXTE. View Hi-Res - Print Resolution

The Rossi X-ray Timing Explorer spacecraft undergoes pre-launch tests in 1995. Credit: NASA/GSFC - View Hi-Res

For decades, X-ray astronomers have studied the complex behavior of binary systems pairing a normal star with a black hole. In these systems, gas from the normal star streams toward the black hole and forms a disk around it. Friction within the disk heats the gas to millions of degrees -- hot enough to produce X-rays. At the disk's inner edge, near the black hole, strong magnetic fields eject some of the gas into dual, oppositely directed jets that blast outward at about half the speed of light.

That's the big picture, but the details have been elusive. For example, do most of the X-rays arise from the jets? The disk? Or from a high-energy region on the threshold of the black hole?

Now, astronomers using NASA's Rossi X-ray Timing Explorer (RXTE) satellite, together with optical, infrared and radio data, find that, at times, most of the X-rays come from the jets.

"Theoretical models have suggested this possibility for several years, but this is the first time we've confirmed it through multiwavelength analysis," said David Russell, lead author of the study and a post-doctoral researcher at the University of Amsterdam.

Russell and his colleagues looked at a well-studied outburst of the black-hole binary XTE J1550-564. The system lies 17,000 light-years away in the southern constellation of Norma and contains a black hole with about 10 times the sun's mass. The usually inconspicuous binary was discovered by RXTE in 1998, when the system briefly became one of the brightest X-ray sources in the sky.

Between April and July 2000, the system underwent another outburst. RXTE monitored the event in X-rays, with some additional help from NASA's Chandra X-ray Observatory. Optical and infrared observations covering the outburst came from the YALO 1-meter telescope at Cerro Tololo Inter-American Observatory in Chile, while radio observations were collected by the Australia Telescope Compact Array.

Drawing on these data, Russell and his team reconstructed a detailed picture of X-ray emission during the outburst. The study appears in the July 1 edition of Monthly Notices of the Royal Astronomical Society.

"We suspect that these outbursts are tied to increases in the amount of mass falling onto the black hole," explained Russell. "Where and how the emission occurs are the only clues we have to what's going on."

As the outburst began in mid-April 2000, the system's brightest X-ray emission was dominated by higher-energy ("hard") X-rays from a region very close to the black hole.

"We think the source of these X-rays is a region of very energetic electrons that form a corona around the innermost part of the disk," Russell said. When these electrons run into photons of visible light, the collision boosts the photons to hard X-ray energies, a process known as inverse Compton scattering. The jets were present, but only minor players.

Over the next couple of weeks, the peak X-ray emission moved to lower ("softer") energies and seems to have come from the dense gas in the accretion disk. At the same time, the hot disk quenched whatever process powers the jets and shut them down.

By late May 2000, XTE J1550-564's accretion disk was cool enough that the jets switched on again. Most of the X-rays, which were fainter but higher in energy, again came from scattering off of energetic electrons close to the black hole.

In early June, as the system faded and its peak emission gradually softened, the jets emerged as the main X-ray source. In the jet, electrons and positrons moving at a substantial fraction of light speed emit the radiation as they encounter magnetic fields, a process called synchrotron emission.

The jets require a continuous supply of particles with energies of a trillion electron volts -- billions of times the energy of visible light. "The total energy bound up in the jet is enormous, much larger than previously thought," Russell said.

As summer wore on, the jets gradually faded and their X-ray emission softened. By September, the system's brightest X-rays came from high-speed blobs of matter that the jets had hurled into space during previous eruptions.

"We're really beginning to get a handle on the 'ecology' of these extreme systems, thanks in large part to RXTE," Russell added. "We can apply what we've learned in nearby binaries like XTE J1550 to the supersized black holes and jets found at the centers of galaxies."

Launched in 1995, RXTE is still going strong. "Of currently operating NASA missions, only Hubble has been working longer," said Tod Strohmayer, the mission's project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. RXTE's unique capabilities provide insight into accreting black holes and neutron stars and allow it to detect short, faint outbursts that are easily missed by other current missions exploring the X-ray regime.

Evidence for a recoiling black hole has been found using data from the Chandra X-ray Observatory, XMM-Newton, the Hubble Space Telescope (HST), and several ground-based telescopes. This black hole kickback was caused either by a slingshot effect produced in a triple black hole system, or from the effects of gravitational waves produced after two supermassive black holes merged a few million years earlier.

The discovery of this object, located in this composite image, comes from a large, multi-wavelength survey, known as the Cosmic Evolution Survey (COSMOS). This survey includes data from Chandra, HST, XMM- Newton, as well as ground-based observatories. Of the 2,600 X-ray sources found in COSMOS, only one -- named CID-42 and located in a galaxy about 3.9 billion light years away -- coincides with two very close, compact optical sources (The two sources are seen in the HST data, but they are too close for Chandra to resolve separately.) In this image, the X-ray source detected by Chandra is colored blue, while the Hubble data are seen in gold.

The galaxy's long tail suggests that a merger between galaxies has occurred relatively recently, only a few million years earlier. Data from the Very Large Telescope and the Magellan telescope give evidence that the difference in speed of the two optical sources is at least three million miles an hour.

The X-ray spectra from Chandra and XMM-Newton provide extra information about CID-42. Absorption from iron-rich gas shows that gas is moving rapidly away from us in the rest frame of the galaxy. This could be gas in the galaxy between us and one of the black holes that is falling into the black hole, or it could be gas on the far side of the black hole that is blowing away.

Taken together, these pieces of information allow for two different scenarios for what is happening in this system. In the first scenario, the researchers surmise that a triple black hole encounter was produced by a two-step process. First, a collision between two galaxies created a galaxy with a pair of black holes in a close orbit. Before these black holes could merge, another galaxy collision occurred, and another supermassive black hole spiraled toward the existing black hole pair.

The interaction among the three black holes resulted in the lightest one being ejected. In this case, the optical source in the lower left of the image is an active galactic nucleus (AGN) powered by material being pulled along by, and falling onto, the escaping supermassive black hole. The source in the upper right is an AGN containing the black hole that resulted from a merger between the two remaining black holes.

In this slingshot scenario, the high-speed X-ray absorption can be explained as a high-speed wind blowing away from the AGN in the upper right that absorbs light from the AGN in the lower left. Based on its optical spectrum, the AGN in the upper right is thought to be obscured by a torus of dust and gas. In nearly all cases a wind from such an AGN would be undetectable, but here it is illuminated by the other AGN, giving the first evidence that fast winds exist in obscured AGN.

An alternative explanation posits a merger between two supermassive black holes in the center of the galaxy. The asymmetry of the gravitational waves emitted in this process caused the merged black hole to be kicked away from the center of the galaxy. In this scenario, the ejected black hole is the point source in the lower left and a cluster of stars left behind in the center of the galaxy is in the upper right. The observed X-ray absorption would be caused by gas falling onto the recoiling black hole.

Future observations may help eliminate or further support one of these scenarios. A team of researchers led by Francesca Civano and Martin Elvis of the Harvard-Smithsonian Center for Astrophysics (CfA) will publish their work on CID-42 in the July 1st edition of The Astrophysical Journal.

The second scenario, concerning the recoil of a supermassive black hole caused by a gravitational wave kick, has recently been proposed by Peter Jonker from the Netherlands Institute for Space Research in Utrecht as a possible explanation for a source in a different galaxy. In this study, led by Peter Jonker from the Netherlands Institute for Space Research in Utrecht, a Chandra X-ray source was discovered about ten thousand light years, in projection, away from the center of a galaxy. Three possible explanations for this object are that it is an unusual type of supernova, or an ultraluminous X- ray source with a very bright optical counterpart or a recoiling supermassive black hole resulting from a gravitational wave kick.

Scale Image is 0.5 arcmin across (about 570,000 light years).
Category: Quasars & Active Galaxies, Black Holes
Coordinates: (J2000) RA 10h 00m 29.06s | Dec +02° 05' 31.33"
Constellation: Sextans
Observation Date: Jan 4, 2007
Observation Time: 14 hours
Obs. ID: 8012
Color Code: X-ray (Blue); Optical (Yellow, White)
Instrument: ACIS
References: Civano, F. et al, 2010, ApJ 717:209-222
Distance Estimate: About 3.92 billion light years

Full size image - Full size image without galaxy identification