X-Ray Emissions from Dwarf Galaxy J1329+3234

This image depicts the X-ray emission from dwarf galaxy J1329+3234 (center in this image), and from a background AGN (lower right), measured by XMM-Newton in June 2013.

Located over 200 million light-years away, the dwarf galaxy contains a few hundred million stars and is similar in size to the Small Magellanic Cloud, one of our nearest neighboring galaxies.

Astronomers were intrigued to discover infrared signatures of an accreting black hole when they studied this galaxy with NASA's WISE spacecraft in 2013. When they subsequently observed the galaxy with ESA's XMM-Newton X-ray observatory they were surprised to detect X-ray emission over 100 times stronger than expected for this galaxy.

The combined X-ray and infrared properties of this galaxy can only be explained by the presence of a massive black hole residing in J1329+3234, similar to the super-massive black holes found at the centers of much more massive galaxies.

The image is constructed from 2-10 keV X-ray emission and has been smoothed. The color code represents the intensity of X-ray emission with blue being more intense and red less intense. The white bar indicates a width of 10 arcseconds, equivalent to 3.3 kpc at the distance of this galaxy. North is up, east to the left.

Image credit: ESA/XMM-Newton/N. Secrest, et al. (2015)

Note: For more information, see XMM-Newton Spots Monster Black Hole Hidden in Tiny Galaxy.

SNR Puppis A

Puppis A: A supernova remnant located about 7,000 light years from Earth.

The destructive results of a powerful supernova explosion are seen in a delicate tapestry of X-ray light in this new image. The remnant is called Puppis A, which could have been witnessed on Earth about 3,700 years ago and is about 10 light years across. This image is the most complete and detailed X-ray view of Puppis A ever obtained, made by combining a mosaic of different Chandra and XMM-Newton observations. In this image, low-energy X-rays are shown in red, medium-energy X-rays are in green and high energy X-rays are colored blue.

Scale: Image is about 1.5 degrees across (About 180 light years).

Image credit: X-ray: NASA/CXC/IAFE/G.Dubner et al & ESA/XMM-Newton

Note: For more information, see Puppis A: An X-Ray Tapestry.

Magnetar 3XMM J185246.6+003317 Below Supernova Remnant Kesteven 79

Massive stars end their life with a bang, exploding as supernovas and releasing massive amounts of energy and matter. What remains of the star is a small and extremely dense remnant: a neutron star or a black hole.

Neutron stars come in several flavors, depending on properties such as their ages, the strength of the magnetic field concealed beneath their surface, or the presence of other stars nearby. Some of the energetic processes taking place around neutron stars can be explored with X-ray telescopes, like ESA's XMM-Newton.

This image depicts two very different neutron stars that were observed in the same patch of the sky with XMM-Newton. The green and pink bubble dominating the image is Kesteven 79, the remnant of a supernova explosion located about 23,000 light-years away from us.

From the properties of the hot gas in Kesteven 79 and from its size, astronomers estimate that it is between 5000 and 7000 years old. Taking account of the time needed for light to travel to Earth, this means that the supernova that created it must have exploded almost 30,000 years ago. The explosion left behind a young neutron star with a weak magnetic field, which can be seen as the blue spot at the center of Kesteven 79.

Beneath it, a blue splotch indicates an entirely different beast: a neutron star boasting an extremely strong magnetic field, known as a magnetar. Astronomers discovered this magnetar, named 3XMM J185246.6+003317, in 2013 by looking at images that had been taken in 2008 and 2009. After the discovery, they looked at previous images of the same patch of the sky, taken before 2008, but did not find any trace of the magnetar. This suggests that the detection corresponded to an outburst of X-rays released by the magnetar, likely caused by a dramatic change in the structure of its magnetic field.

While the neutron star in the supernova remnant is relatively young, the magnetar is likely a million years old; the age difference means that it is very unlikely that the magnetar arose from the explosion that created Kesteven 79, but must have formed much earlier.

This false-color image is a composite of 15 observations performed between 2004 and 2009 with the EPIC MOS camera on board XMM-Newton. The image combines data collected at energies from 0.3 to 1.2 keV (shown in red), 1.2 to 2 keV (shown in green) and 2 to 7 keV (shown in blue).

Image credit: ESA/XMM-Newton/ Ping Zhou, Nanjing University, China

Supernova Remnant Puppis A

The destructive results of a mighty supernova explosion reveal themselves in a delicate blend of infrared and X-ray light, as seen in this image from NASA's Spitzer Space Telescope and Chandra X-Ray Observatory, and the European Space Agency's XMM-Newton.

The bubbly cloud is an irregular shock wave, generated by a supernova that would have been witnessed on Earth 3,700 years ago. The remnant itself, called Puppis A, is around 7,000 light-years away, and the shock wave is about 10 light-years across.

The pastel hues in this image reveal that the infrared and X-ray structures trace each other closely. Warm dust particles are responsible for most of the infrared light wavelengths, assigned red and green colors in this view. Material heated by the supernova's shock wave emits X-rays, which are colored blue. Regions where the infrared and X-ray emissions blend together take on brighter, more pastel tones.

The shock wave appears to light up as it slams into surrounding clouds of dust and gas that fill the interstellar space in this region.

From the infrared glow, astronomers have found a total quantity of dust in the region equal to about a quarter of the mass of our sun. Data collected from Spitzer's infrared spectrograph reveal how the shock wave is breaking apart the fragile dust grains that fill the surrounding space.

Supernova explosions forge the heavy elements that can provide the raw material from which future generations of stars and planets will form. Studying how supernova remnants expand into the galaxy and interact with other material provides critical clues into our own origins.

Infrared data from Spitzer's multiband imaging photometer (MIPS) at wavelengths of 24 and 70 microns are rendered in green and red. X-ray data from XMM-Newton spanning an energy range of 0.3 to 8 kiloelectron volts are shown in blue.

Image credit: NASA/ESA/JPL-Caltech/GSFC/IAFE

Artist's Conception of an Exploding Blue Supergiant Star

This artist’s impression depicts a region of an exploding blue supergiant. These stars are quite rare in the relatively nearby Universe, but are thought to have been very common in the early Universe, with almost all of the first stars having evolved into them over the course of their short lives.

Astronomers used a number of space- and ground-based observatories, including ESA's XMM-Newton to study the gamma-ray burst GRB130925A – a flash of very energetic radiation streaming from a blue supergiant in a galaxy 5.6 billion light years from Earth. They found evidence that this star contained very little in the way of elements heavier than hydrogen and helium. The same was true for the first stars to form in the Universe, making GRB130925A a remarkable analogue for similar explosions that occurred just a few hundred million years after the Big Bang.

The illustration shows a hot cocoon of gas (shown in red) surrounding a relativistic jet emerging from the blue supergiant.

Illustration credit: NASA/Swift/A. Simonnet, Sonoma State University

Note: For more information, see Bizarre Nearby Blast Mimics Universe's Most Ancient Stars.

Perseus Galaxy Cluster in X-Rays

A new study of the Perseus galaxy cluster, shown in this image, and others using Chandra and XMM-Newton has revealed a mysterious X-ray signal in the data. The signal is also seen in over 70 other galaxy clusters using XMM-Newton. This unidentified signal requires further investigation to confirm both its existence and nature, but one possibility is that it represents the decay of ‘sterile neutrinos’, one proposed candidate to explain dark matter.

Image credit: Chandra: NASA/CXC/SAO/E.Bulbul, et al.; XMM-Newton: ESA)

Note: For more information, see Puzzling X-Rays Point to Dark Matter, Perseus Galaxy Cluster, Perseus A: Mysterious X-ray Signal Intrigues Astronomers, and Mystery in the Perseus Cluster.

X-Ray Pulsar SXP 1062

Massive stars end their lives with a bang: exploding as spectacular supernovas, they release huge amounts of mass and energy into space. These explosions sweep up any surrounding material, creating bubble remnants that expand into interstellar space. At the heart of bubbles like these are small, dense neutron stars or black holes, the remains of what once shone brightly as a star.

Since supernova-carved bubbles shine for only a few tens of thousands of years before dissolving, it is rare to come across neutron stars or black holes that are still enclosed within their expanding shell. This image captures such an unusual scene, featuring both a strongly magnetized, rotating neutron star – known as a pulsar – and its cosmic cloak, the remains of the explosion that generated it.

This pulsar, named SXP 1062, lies in the outskirts of the Small Magellanic Cloud, one of the satellite galaxies of our Milky Way galaxy. It is an object known as an X-ray pulsar: it hungrily gobbles up material from a nearby companion star and burps off X-rays as it does so. In the future, this scene may become even more dramatic, as SXP 1062 has a massive companion star that has not yet exploded as a supernova.

Most pulsars whirl around incredibly quickly, spinning many times per second. However, by exploring the expanding bubble around this pulsar and estimating its age, astronomers have noticed something intriguing: SXP 1062 seems to be rotating far too slowly for its age. It is actually one of the slowest pulsars known.

While the cause of this weird sluggishness is still a mystery, one explanation may be that the pulsar has an unusually strong magnetic field, which would slow the rotation.

The diffuse blue glow at the center of the bubble in this image represents X-ray emission from both the pulsar and the hot gas that fills the expanding bubble. The other fuzzy blue objects visible in the background are extragalactic X-ray sources.

This image combines X-ray data from ESA’s XMM-Newton (shown in blue) with optical observations from the Cerro Tololo Inter-American Observatory in Chile. The optical data were obtained using two special filters that reveal the glow of oxygen (shown in green) and hydrogen (shown in red). The size of the image is equivalent to a distance of 457 light-years on a side.

This image was first published on ESA’s Science and Technology website in 2011. It is based on data from the paper “Discovery of a Be/X-ray pulsar binary and associated supernova remnant in the Wing of the Small Magellanic Cloud” by V. Hénault-Brunet, et al. 2012.

Image credit: ESA/XMM-Newton/ L. Oskinova/M. Guerrero; CTIO/R. Gruendl/Y.H. Chu

Note: The above image was first published on this blog in December 2011; however, the above text is different and provides additional information.

The Bullet Group

This image shows the Bullet Group, a group of galaxies also known as SL2S J08544-0121.

The galaxies belonging to the group are visible in the central part of the image, embedded in the diffuse dark matter (shown in blue). Hot gas, which fills the space between galaxies and comprises the bulk of ordinary (baryonic) matter in the group, is shown in pink, as imaged by ESA's XMM-Newton X-ray observatory.

The light from galaxies and hot gas belonging to the group, which lies at a redshift of z=0.351, has been traveling for almost four billion years before reaching us. Other galaxies, either in the foreground or background of the Bullet Group, are sprinkled across the image, as well as bright foreground stars that belong to our Galaxy.

The group's components appear to be clearly separated, with the hot gas partitioned from the rest of the mass within the group. This is the smallest object ever found to show such an effect, which was caused by a merger in the group's past.

Astronomers were able to map the extent of the Bullet Group's dark matter through its gravitational lensing of background galaxies. This effect is particularly evident in the center-right part of this image, where a round, bright galaxy that belongs to the Bullet Group is circled by curious arcs of light – the distorted image of another galaxy lying much farther away.

By exploring the contents of these cosmic wrecks, astronomers can learn more about the properties of dark matter. In particular, from the split between the dark matter and the hot gas, they can constrain how much dark matter does – or does not – interact with normal matter.

This image is a composite of an X-ray image (shown in pink) from ESA's XMM-Newton observatory, a three-color (red, green, blue) optical image from the Canada-France-Hawaii Telescope (CFHT), and a dark matter overlay (indicated in blue) based on data from CFHT, the NASA/ESA Hubble Space Telescope, and the W. M. Keck Observatory.

Image credit: ESA / XMM-Newton / F. Gastaldello (INAF/IASF, Milano, Italy) / CFHTLS

Note: For more information, see Cosmic Collision in the Bullet Group and Cosmic collision in the Bullet Group.

Xi1 Canis Majoris

X-ray emission from the B-type star Xi1 Canis Majoris (Xi1 CMa) – seen in the center of this image - has been measured using ESA's XMM-Newton observatory.

Xi1 CMa was observed continuously with XMM-Newton in October 2012 for almost 29 hours. These observations resulted in the first detection of pulsed X-ray emission from a non-degenerate, massive star.

Xi1 CMa is an extremely bright star with a surface temperature of approximately 27,500K, and a mass of approximately 15 times that of the Sun. It lies some 1400 light years away in the constellation Canis Major. The star has a notably strong magnetic field, about 5000 times stronger than our Sun's.

This 3-colour image of the field was made by mapping 0.2-1.0 keV emission to red, 1.0-2.5 keV emission to green, and 2.5-10.0 keV emission to blue. The field of view of this image is 19 arcmin × 19 arcmin (approximately 7.6 light years × 7.6 light years).

Image credit: ESA/XMM-Newton/L. Oskinova (University of Potsdam)

Note: For more information, see Pulsating X-Rays Allow XMM-Newton to Unmask a Mysterious Star.

X-Ray View of the COSMOS Survey

When we gaze up at the night sky, we are only seeing part of the story. Unfortunately, some of the most powerful and energetic events in the Universe are invisible to our eyes – and to even the best optical telescopes.

Luckily, these events are not lost; they appear vividly in the high-energy sky, making them visible to space-based telescopes like ESA's XMM-Newton, which observes the Universe in the X-ray part of the spectrum.

This image shows a patch of sky from the COSMOS survey, as viewed by XMM-Newton. COSMOS is a project studying how galaxies form and evolve, gathering observations using a variety of ground- and space-based telescopes. This image alone features about two thousand supermassive black holes, and over a hundred clusters of galaxies.

Small point sources dotted across the frame show supermassive black holes that are hungrily devouring matter from their surroundings. All massive galaxies host a black hole at their core, but not all of these are actively accreting, dragging in surrounding matter and releasing high-energy radiation and powerful jets in the process. As they are so energetic, one of the best ways to hunt these extreme bodies is by using X-ray telescopes.

The larger blobs in this image, mainly red and yellow, reveal another class of cosmic behemoths: galaxy clusters. Containing up to several thousand galaxies, galaxy clusters are the largest cosmic structures to be held together by gravity. The galaxies within these clusters are enveloped by hot gas, which releases a diffuse X-ray glow that can be detected by telescopes like XMM-Newton.

The image combines data collected by the EPIC instrument on board XMM-Newton at energies from 0.5 to 2 keV (shown in red), 2 to 4.5 keV (shown in green) and 4.5 to 10 keV (shown in blue). The observations were taken between 2003 and 2005, and the image spans 1.4 degrees on each side, corresponding to almost three times the diameter of the full Moon.

This image was first published in the paper “The XMM-Newton Wide-Field Survey in the COSMOS Field. I. Survey Description” by G. Hasinger et al. in 2007.

Image credit: ESA/XMM-Newton/Gunther Hasinger, Nico Cappelluti, and the XMM-COSMOS collaboration.

Unique Pair of Hidden Black Holes Discovered by XMM-Newton

A pair of supermassive black holes in orbit around one another have been spotted by XMM-Newton. This is the first time such a pair have been seen in an ordinary galaxy. They were discovered because they ripped apart a star when the space observatory happened to be looking in their direction.

Most massive galaxies in the Universe are thought to harbor at least one supermassive black hole at their center. Two supermassive black holes are the smoking gun that the galaxy has merged with another. Thus, finding binary supermassive black holes can tell astronomers about how galaxies evolved into their present-day shapes and sizes.

To date, only a few candidates for close binary supermassive black holes have been found. All are in active galaxies where they are constantly ripping gas clouds apart, in the prelude to crushing them out of existence.

In the process of destruction, the gas is heated so much that it shines at many wavelengths, including X-rays. This gives the galaxy an unusually bright center, and leads to it being called active. The new discovery, reported by Fukun Liu, Peking University, Beijing, China, and colleagues, is important because it is the first to be found in a galaxy that is not active.

"There might be a whole population of quiescent galaxies that host binary black holes in their centers," says co-author Stefanie Komossa, Max-Planck-Institut für Radioastronomie, Bonn, Germany. But finding them is a difficult task because in quiescent galaxies, there are no gas clouds feeding the black holes, and so the cores of these galaxies are truly dark.

The only hope that the astronomers have is to be looking in the right direction at the moment one of the black holes goes to work, and rips a star to pieces. Such an occurrence is called a 'tidal disruption event'. As the star is pulled apart by the gravity of the black hole, it gives out a flare of X-rays.

In an active galaxy, the black hole is continuously fed by gas clouds. In a quiescent galaxy, the black hole is fed by tidal disruption events that occur sporadically and are impossible to predict. So, to increase the chances of catching such an event, researchers use ESA's X-ray observatory, XMM-Newton, in a novel way.

Usually, the observatory collects data from designated targets, one at a time. Once it completes an observation, it slews to the next. The trick is that during this movement, XMM-Newton keeps the instruments turned on and recording. Effectively this surveys the sky in a random pattern, producing data that can be analyzed for unknown or unexpected sources of X-rays.

On 10 June 2010, a tidal disruption event was spotted by XMM-Newton in galaxy SDSS J120136.02+300305.5. Komossa and colleagues were scanning the data for such events and scheduled follow-up observations just days later with XMM-Newton and NASA's Swift satellite.

The galaxy was still spilling X-rays into space. It looked exactly like a tidal disruption event caused by a supermassive black hole but as they tracked the slowly fading emission day after day something strange happened.

The X-rays fell below detectable levels between days 27 and 48 after the discovery. Then they re-appeared and continued to follow a more expected fading rate, as if nothing had happened.

Now, thanks to Fukun Liu, the behavior can be explained. "This is exactly what you would expect from a pair of supermassive black holes orbiting one another," says Liu.

Liu had been working on models of black hole binary systems that predicted a sudden plunge to darkness and then the recovery because the gravity of one of the black holes disrupted the flow of gas onto the other, temporarily depriving it of fuel to fire the X-ray flare. He found that two possible configurations were possible to reproduce the observations of J120136.

In the first, the primary black hole contained 10 million solar masses and was orbited by a black hole of about a million solar masses in an elliptical orbit. In the second solution, the primary black hole was about a million solar masses and in a circular orbit.

In both cases, the separation between the black holes was relatively small: 0.6 milliparsecs, or about 2 thousandths of a light year. This is about the width of our Solar System.

Being this close, the fate of this newly discovered black hole pair is sealed. They will radiate their orbital energy away, gradually spiraling together, until in about two million years time they will merge into a single black hole.

Now that astronomers have found this first candidate for a binary black hole in a quiescent galaxy, the search is inevitably on for more. XMM-Newton will continue its slew survey. This detection will also spur interest in a network of telescopes that search the whole sky for tidal disruption events.

"Once we have detected thousands of tidal disruption events, we can begin to extract reliable statistics about the rate at which galaxies merge," says Komossa.

There is another hope for the future as well. When binary black holes merge, they are predicted to release a massive burst of energy into the Universe but not mostly in X-rays. "The final merger is expected to be the strongest source of gravitational waves in the Universe," says Liu.

Gravitational waves are ripples in the space-time continuum. Astronomers around the world are currently building a new type of observatory to detect these ripples. ESA are also involved in opening this new window on the Universe. In 2015, ESA will launch LISA Pathfinder, which will test the necessary technology for building a space-based gravitational wave detector that must be placed in space. The search for elusive gravitational waves is also the theme for one of ESA's next large science missions, the L3 mission in the Cosmic Vision program.

In the meantime, XMM-Newton will continue to look out for the tidal disruption events that betray the presence of binary supermassive black holes candidates.

"The innovative use of XMM-Newton's slew observations made the detection of this binary supermassive black hole system possible," says Norbert Schartel, ESA's XMM-Newton Project Scientist. "This demonstrates the important role that long-lasting space observatories have in detecting rare events that can potentially open new areas in astronomy."


Background Information

The results described in this article are reported in "A milli-parsec supermassive black hole binary candidate in the galaxy SDSS J120136.02+300305.5", by F.K. Liu, Shuo Li, and S. Komossa, published in the May 10 issue of The Astrophysical Journal, 2014, Volume 786; doi:10.1088/0004-637X/786/2/103

Illustration credit: ESA - C. Carreau

Open Cluster Berkeley 87 and Star-Forming Region ON2

Massive stars are born in tumultuous clouds of gas and dust. They lead a brief but intense life, blowing powerful winds of particles and radiation that strike their surroundings, before their explosive demise as supernovas.

The interplay between massive stars and their environment is revealed in this image of the star-forming region ON2. It combines X-ray coverage from ESA’s XMM-Newton X-ray observatory with an infrared view from NASA’s Spitzer Space Telescope.

This stellar cradle is associated with the open cluster of stars named Berkeley 87, some 4000 light-years from Earth. The cluster is home to over 2000 stars, most of which are low-mass stars like our Sun or smaller, but some – a few dozen – are stellar monsters weighing 10–80 times more.

Two glowing clouds of gas and dust – the raw material from which stars form – dominate the center of the image and are shown in red. Scattered across the image are a multitude of protostars – seeds of future stellar generations; these are shown in green. The bright yellow star in the upper part of the image is BC Cygni, a massive star that has puffed up enormously and will eventually explode as a supernova.

Shown in blue is XMM-Newton’s X-ray view of ON2: it reveals individual sources – young, massive stars as well as protostars – and more diffuse regions of X-rays. Two ‘bubbles’ of X-rays can be seen in the upper and lower clouds, respectively, pink against the red background. These two bubbles conceal the cumulative emissions from many protostars, but also light radiated by very energetic particles – a signature of shockwaves triggered by massive stars and their winds.

The image combines observations performed in the X-ray energy range of 0.25–12 keV (blue) and at infrared wavelengths of 3.6 microns (green) and 8 microns (red). It spans about 15 arcminutes on each side; north is up and east is to the left.

This image was first published in the paper “Hard X-Ray Emission in the Star-Forming Region ON 2: Discovery with XMM-Newton” by Oskinova et al. in April 2010.

Image credit: L.M. Oskinova, R.A. Gruendl, Spitzer Space Telescope, JPL, NASA & ESA

Quasar RX J1131-1231

RX J1131-1231: A quasar located about 6 billion light years from Earth.

Multiple images of a distant quasar known as RX J1131-1231 are visible in this combined view from Chandra (pink) and Hubble (red, green, and blue). The Chandra data, along with data from ESA’s XMM-Newton, were used to directly measure the spin of the supermassive black hole powering this quasar. Black holes are defined by just two simple characteristics: mass and spin. At a distance of 6 billion light years, this is the most distant black hole where such a measurement has been made, allowing for an important advance in understanding how black holes grow over time.

Scale: Image is 1.2 arcmin across (about 1.6 million light years).

Image credit: X-ray: NASA/CXC/Univ of Michigan/R.C.Reis et al; Optical: NASA/STScI

Note: For more information, see RX J1131-1231: Chandra & XMM-Newton Provide Direct Measurement of Distant Black Hole's Spin.

Messier 51 - The Whirlpool Galaxy

The Whirlpool Galaxy, also known as M51 or NGC 5194, is one of the most spectacular examples of a spiral galaxy. With two spiral arms curling into one another in a billowing swirl, this galaxy hosts over a hundred billion stars and is currently merging with its companion, the smaller galaxy NGC 5195.

Around 30 million light-years away, the Whirlpool Galaxy is close enough to be easily spotted even with binoculars. Using the best telescopes available both on the ground and in space, astronomers can scrutinize its population of stars in extraordinary detail.

In this image, observations performed at three different wavelengths with ESA’s Herschel and XMM-Newton space telescopes are combined to reveal how three generations of stars coexist in the Whirlpool Galaxy.

The infrared light collected by Herschel – shown in red and yellow – reveals the glow of cosmic dust, which is a minor but crucial ingredient in the interstellar material in the galaxy’s spiral arms. This mixture of gas and dust provides the raw material from which the Whirlpool Galaxy’s future generations of stars will take shape.

Observing in visible and ultraviolet light, astronomers can see the current population of stars in the Whirlpool Galaxy, since stars in their prime shine most brightly at shorter wavelengths than infrared. Seen at ultraviolet wavelengths with XMM-Newton and portrayed in green in this composite image are the galaxy’s fiercest stellar inhabitants: young and massive stars pouring powerful winds and radiation into their surroundings.

The image also shows the remains of previous stellar generations, which shine brightly in X-rays and were detected by XMM-Newton. Shown in blue, these sources of X-rays are either the sites where massive stars exploded as supernovae in the past several thousand years, or binary systems that host neutron stars or black holes, the compact objects left behind by supernovae.

Image credit: ESA / Herschel / XMM-Newton. Acknowledgements: "Physical Processes in the Interstellar Medium of Very Nearby Galaxies" Key Programme, Christine Wilson

NGC 5044

Galaxies are social beasts that are mostly found in groups or clusters – large assemblies of galaxies that are permeated by even larger amounts of diffuse gas. With temperatures of 10 million degrees or more, the gas in galaxy groups and clusters is hot enough to shine brightly in X-rays and be detected by ESA’s XMM-Newton X-ray observatory.

As galaxies speed through these gigantic cauldrons, they occasionally jumble the gas and forge it into lop-sided shapes. An example is revealed in this composite image of the galaxy group NGC 5044, the brightest group in X-rays in the entire sky.

The group is named after the massive and bright elliptical galaxy at its center, surrounded by tens of smaller spiral and dwarf galaxies. The galaxies are shown in a combination of optical images from the Digitized Sky Survey with infrared and ultraviolet images from NASA’s WISE and Galex satellites, respectively. Foreground stars are also sprinkled across the image.

The large blue blob shows the distribution of hot gas filling the space between NGC 5044’s galaxies as imaged by XMM-Newton. From the X-ray observations, astronomers can also see the glow of iron atoms that were forged in stellar explosions within the galaxies of the group but streamed beyond. The distribution of iron atoms is shown in purple.

Embedded within the hot gas are clouds of even more energetic plasma that emit radio waves – a reminder of the past activity of a supermassive black hole lurking at the center of the group. These are the green filament extending from the central galaxy to the lower right and the larger green region to its lower left, which were imaged with the Giant Metrewave Radio Telescope, near Pune in India.

The distribution of the intergalactic gas and its ingredients is asymmetric, with a larger splotch in the upper right part of the image and a smaller one in the lower left.

Astronomers believe that gas in NGC 5044 is sloshing as a consequence of a galaxy that passed through it several millions of years ago. The culprit is the spiral galaxy NGC 5054, which is not visible here, instead hiding beyond its lower left corner.

The transit of NGC 5054 through the center of the group may have also caused the twisted shape of the radio-bright filament.

This image was first published in the XMM-Newton Image Gallery in October 2013. The analysis is reported in the paper by E. O’Sullivan et al. “The impact of sloshing on the intra-group medium and old radio lobe of NGC 5044.”

Image credit: E. O’Sullivan & ESA

Black Hole with Accretion Disk and Binary Jets

Artist's impression of a black hole feasting on matter from its companion star in a binary system. Matter flows from the star towards the black hole and forms an accretion disc with a temperature so high that it emits X-rays. The black hole can be a fussy eater: instead of swallowing all of the material, it sometimes pushes a fraction of it away in the form of two powerful jets of particles.

A team of astronomers studying the jets of the binary system 4U1630-47 have confirmed that black hole jets not only consist of electrons but also contain heavier particles, like protons or atomic nuclei. This means that jets can carry mass and energy away from the black hole in much larger amounts than previously thought.

Illustration credit: ESA/ATG Medialab

Note: For more information, see Black Hole Boasts Heavyweight Jets and Black Hole with Disc and Jets.

An Ordinary Pulsar Evolving Into a Millisecond Pulsar

This animation shows an artist's impression of the evolutionary process that is believed to turn pulsars into millisecond pulsars.

The emission mechanism of pulsars transforms kinetic rotational energy into radiation: as this energy is radiated over time, the rotation is slowed down. Whilst pulsars spin rapidly at birth, they tend to rotate more slowly – with periods of up to a few seconds – as they age.

The mysterious millisecond pulsars – old but extremely quickly rotating pulsars with periods of a few thousandths of a second – are explained through a theoretical model known as the 'recycling' scenario. If a pulsar is part of a binary system and is accreting matter from a stellar companion via an accretion disc, then it may also gain angular momentum. This process can 'rejuvenate' old pulsars, boosting their rotation and making their periods as short as a few milliseconds.

Using data from INTEGRAL and XMM-Newton, astronomers have discovered IGR J18245-2452, a millisecond pulsar that within only a few weeks switched from being accretion-powered and X-ray bright to rotation-powered and bright in radio waves. As the evolutionary link between these two categories of sources, this millisecond pulsar brings conclusive evidence to the 'recycling' scenario.

The animation shows a pulsar in a binary system, with a low-mass, red star as a companion. The two objects orbit around their mutual center of gravity; for clarity, this motion is not shown in the animation.

At the beginning of the animation, the pulsar spins very fast, then its rotation gradually slows down. At this stage, the pulsar's emission is entirely supported by its rotation and results in two narrow beams of radio waves (shown in purple). The slowing down process may last several millions of years.

Eventually, the gravitational pull of the pulsar – which is a very dense object – starts drawing matter from the companion star. As the pulsar accretes matter via an accretion disc, it gains angular momentum and its rotation becomes extremely rapid again.

During the accretion process, the high density of accreted matter inhibits the acceleration of particles that cause radio emission, so the pulsar is not visible in radio waves but only in X-rays (shown as wide, white beams). When the accretion rate decreases, the magnetosphere expands and pushes matter away from the pulsar: as a consequence, the X-ray emission becomes weaker and weaker, while the radio emission intensifies.

Over a period of at least several hundreds of millions of years, the pulsar keeps swinging back and forth between the two states several times, emitting alternately X-rays and radio waves. When the accretion process stops, the pulsar becomes a purely rotation-powered, radio-emitting millisecond pulsar, while its companion star has evolved into a white dwarf.

Video credit: ESA; text credit: ESA

Note: For more information, see Volatile Pulsar Reveals Millisecond Missing Link.

Coma Cluster

Coma Cluster: A collection of thousands of galaxies about 320 million light years from Earth.

Enormous arms of hot gas have been revealed in the Coma galaxy cluster in data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton. A specially processed Chandra image (pink) has been combined with optical data from the Sloan Digital Sky Survey (white and blue) to highlight these spectacular arms. Researchers think that these arms -- which span at least a half million light years -- were most likely formed when smaller galaxy clusters had their gas stripped away by the head wind created by the motion of the clusters through the hot gas.

Scale: Image is 23 arcmin on a side (about 2 million light years).

Image credit: X-ray: NASA/CXC/MPE/J.Sanders et al, Optical: SDSS

Note: For more information, see Coma Cluster: Clues to the Growth of the Colossus in Coma

Magnetar SGR 0418+5729 With a Magnetic Loop

This image shows an artist's impression of the magnetar SGR 0418+5729.

Magnetars are peculiar pulsars – the spinning remnants of massive stars – that are characterised by unusually intense magnetic fields. Astronomers discovered them through their exceptional behavior at X-ray wavelengths, including sudden outbursts of radiation and occasional giant flares. These peculiar features of magnetars are caused by their extremely strong magnetic fields, which range between 1014 and 1015 Gauss (G) and are hundreds or thousands of times more intense than those of regular pulsars.

Since it was discovered in 2009, SGR 0418+5729 has been puzzling astronomers. Its dipolar magnetic field – the most direct manifestation of a magnetar's average magnetic field, which can be estimated from its spin-down rate – is about two orders of magnitude lower than other magnetars. Astronomers believed that this magnetar concealed, in its interior, a very strong magnetic field. A study based on data from ESA's XMM-Newton X-ray Observatory has found evidence to confirm this, revealing that the magnetar's internal field may even exceed 1015 G, removing any lingering doubts about the object's true identity.

The strong internal magnetic field of this magnetar reveals itself only in a small feature emerging from its surface, where protons absorb some of the X-rays emitted by the magnetar. The protons are confined in this region by a strong and localized magnetic field, with lines that are probably shaped like a series of adjacent arcs, resembling the appearance of loops on the surface of the Sun.

Illustration credit: ESA/ATG medialab

Note: For more information, see Weakling Magnetar Reveals Hidden Strength; also, Magnetic Loop on Magnetar SGR 0418.

HD 189733: NASA's Chandra Sees Eclipsing Planet in X-rays for First Time

This graphic depicts HD 189733b, the first exoplanet caught passing in front of its parent star in X-rays. As described in our press release, NASA's Chandra X-ray Observatory and the European Space Agency's XMM Newton Observatory have been used to observe a dip in X-ray intensity as HD 189733b transits its parent star.

The main figure is an artist’s impression showing the HD 189733 system, containing a Sun-like star orbited by HD 189733b, an exoplanet about the size of Jupiter. This "hot Jupiter" is over 30 times closer to its star than Earth is to the Sun and goes around the star once every 2.2 days, as determined from previous observations. Also in the illustration is a faint red companion star, which was detected for the first time in X-rays with these observations (roll your mouse over the image above). This star orbits the main star about once every 3,200 years.

The inset contains the Chandra image of HD 189733. The source in the middle is the main star and the source in the lower right is the faint companion star. The source at the bottom of the image is a background object not contained in the HD 189733 system.

The exoplanet itself cannot be seen in the Chandra image, as the transits involve measuring small decreases in X-ray emission from the main star. The authors estimate that the percentage decrease in X-ray light during the transits is about three times greater than the corresponding decrease in optical light. This tells them that the region blocking X-rays from the star is substantially larger than the region blocking optical light from the star, helping to determine the size of the planet's atmosphere. The extended atmosphere implied by these results is shown by the light blue color around the planet. Recent observations of HD 189733b with the Hubble Space Telescope have confirmed that the lower atmosphere of the planet has a deep blue color, due to the preferential scattering of blue light by silicate particles in its atmosphere.

For about a decade astronomers have known that ultraviolet and X-ray radiation from the main star in HD 189733 are evaporating the atmosphere of its closely orbiting planet over time. The authors of the new study estimate that HD 189733b is losing between 100 million and 600 million kilograms per second. This rate is about 25% to 65% higher than it would be if the planet's atmosphere were not extended.

At a distance of just 63 light years, HD 189733b is the closest hot Jupiter to Earth, which makes it a prime target for astronomers who want to learn more about this type of exoplanet and the atmosphere around it.

Chandra was used to make observations of six transits by HD 189733b and the team also used archival data from XMM-Newton for one transit. These results are available online and will appear in a future issue of The Astrophysical Journal.

Illustration credit: X-ray: NASA/CXC/SAO/K.Poppenhaeger et al; Illustration: NASA/CXC/M.Weiss

Note: For more information, see Hubble Spots Azure Blue Planet - True Color of Exoplanet Measured for the First Time and The Strange Attraction of Hot Jupiters.