The SZ effect: Big black holes can block new stars

Elliptical galaxy NGC 1132, as seen by NASA's Chandra X-Ray Observatory; the blue/purple in the image is the X-ray glow from hot, diffuse gas that is not forming into stars. 

Credit: NASA, ESA, M. West (ESO, Chile), and CXC /Penn State University /G. Garmire, et al.

Massive black holes spewing out radio-frequency-emitting particles at near-light speed can block formation of new stars in aging galaxies, a study has found.

The research provides crucial new evidence that it is these jets of "radio-frequency feedback" streaming from mature galaxies' central black holes that prevent hot free gas from cooling and collapsing into baby stars.

"When you look into the past history of the universe, you see these galaxies building stars," said Tobias Marriage, assistant professor of physics and astronomy at Johns Hopkins and co-lead author of the study.

"At some point, they stop forming stars and the question is: Why? Basically, these active black holes give a reason for why stars stop forming in the universe."

The findings have been published in the journal Monthly Notices of the Royal Astronomical Society.

They were made possible by adaptation of a well-known research technique for use in solving a new problem.

Johns Hopkins postdoctoral fellow Megan Gralla found that the Sunyaev–Zel'dovich effect signature, typically used to study large galaxy clusters, can also be used to learn a great deal about smaller formations.

The SZ effect occurs when high-energy electrons in hot gas interact with faint light in the cosmic microwave background, light left over from earliest times when the universe was a thousand times hotter and a billion times denser than today.

"The SZ is usually used to study clusters of hundreds of galaxies but the galaxies we're looking for are much smaller and have just a companion or two," Gralla said.

"What we're doing is asking a different question than what has been previously asked," Gralla said.

"We're using a technique that's been around for some time and that researchers have been very successful with, and we're using it to answer a totally different question in a totally different subfield of astronomy."

"I was stunned when I saw this paper, because I've never thought that detecting the SZ effect from active galactic nuclei was possible," said Eiichiro Komatsu, director of the Max Planck Institute for Astrophysics in Germany and an expert in the field who was not involved in the research.

"I was wrong. ... It makes those of us who work on the SZ effect from galaxy clusters feel old; research on the SZ effect has entered a new era."

In space, hot gas drawn into a galaxy can cool and condense, forming stars. Some gas also funnels down into the galaxy's black hole, which grows together with the stellar population.

This cycle can repeat continuously; more gas is pulled in to cool and condense, more stars begin to shine and the central black hole grows more massive.

But in nearly all mature galaxies, the big galaxies called "elliptical" because of their shape – that gas doesn't cool any more. "If gas is kept hot, it can't collapse," Marriage said. When that happens: No new stars.

Marriage, Gralla and their collaborators found that the elliptical galaxies with radio-frequency feedback, relativistic radio-frequency-emitting particles shooting from the massive central black holes at their center at close to the speed of light, all contain hot gas and a dearth of infant stars.

That provides crucial evidence for their hypothesis that this radio-frequency feedback is the "off switch" for star-making in mature galaxies.

Marriage said, however, that it is still not known just why black holes in mature elliptical galaxies begin to emit radio-frequency feedback.

"The exact mechanism behind this is not fully understood and there are still debates," he said.

Komatsu said that the new Johns Hopkins-led study, combined with others detecting SZ signals from more ordinary galaxies, "pose new challenges to the theory of galaxy formation, as there were hardly any data which told us how much hot gas there is around galaxies."

More information: Monthly Notices of the Royal Astronomical Society, mnras.oxfordjournals.org/content/445/1/460.full

Huge Alien Planet Forcing Host Star Age Prematurely

A nearby star is not acting its age, thanks to the influence of a massive exoplanet.

The close-orbiting alien planet, known as WASP-18b, is apparently disrupting the magnetic field of its host star so much that the object is behaving like a much older star, researchers said.

"WASP-18b is an extreme exoplanet," study lead author Ignazio Pillitteri, of the Instituto Nazionale di Astrofisica (INAF)-Osservatorio Astronomico di Palermo in Italy, said in a statement.

"It is one of the most massive hot Jupiters known and one of the closest to its host star, and these characteristics lead to unexpected behaviour. The planet is causing its host star to act old before its time."

Artist's concept depicting the giant alien planet WASP-18b and its star, which are about 330 light-years away. 

Credit: NASA/CXC/M. Weiss

The star WASP-18, which lies about 330 light-years away, is about as massive as our own sun.

The gas giant WASP-18b weighs in at more than 10 times the mass of Jupiter and completes one orbit around the star in less than 23 hours, leading scientists to classify it as a "hot Jupiter."

WASP-18b's tight orbit has led scientists to estimate that it may have only one million years of life or so remaining before it's destroyed by the parent star.

Pillitteri's team targeted WASP-18 with NASA's Chandra X-ray Observatory and found it to be relatively quiet, a characteristic of older stars.

Young stars tend to be more active, with stronger magnetic fields, larger flares and more intense X-ray emission.

Stellar activity is connected to rotation, a process that slows with age.

Observations of WASP-18 using Chandra revealed no X-ray emission.

This by itself would suggest that the star has an age similar to the sun's 5 billion years, researchers said.

However, Pillitteri and his team used other data as well as theoretical models to calculate that WASP-18 is actually just 500 million to 2 billion years old, and thus approximately 100 times less active than a star its age should be.

"We think the planet is aging the star by wreaking havoc on its innards," said co-author Scott Wolk, of the Harvard-Smithsonian Center for Astrophysics (CfA) in Massachusetts.

WASP-18b's strong gravitational pull may be disrupting the star's magnetic field, researchers said.

The planet's tug exerts forces similar to those imposed on Earth's tides by the moon, but on a much larger scale.

Puppis A: Supernova remnant seen in Two LIghts

Credit: NASA/ESA/JPL-Caltech/GSFC/IAFE

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 colours 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.

NASA Chandra: Supernova SN 2014J Explosion

Image Credit: NASA/CXC/SAO/R.Margutti et al

New data from NASA’s Chandra X-ray Observatory has provided stringent constraints on the environment around one of the closest supernovas discovered in decades.

The Chandra results provide insight into possible cause of the explosion, as described in our press release.

On January 21, 2014, astronomers witnessed a supernova soon after it exploded in the Messier 82, or M82, galaxy.

Telescopes across the globe and in space turned their attention to study this newly exploded star, including Chandra.

Astronomers determined that this supernova, dubbed SN 2014J, belongs to a class of explosions called “Type Ia” supernovas.

These supernovas are used as cosmic distance-markers and played a key role in the discovery of the Universe’s accelerated expansion, which has been attributed to the effects of dark energy.

Scientists think that all Type Ia supernovas involve the detonation of a white dwarf.

One important question is whether the fuse on the explosion is lit when the white dwarf pulls too much material from a companion star like the Sun, or when two white dwarf stars merge.

This image contains Chandra data, where low, medium, and high-energy X-rays are red, green, and blue respectively.

Raffaella Margutti

The boxes in the bottom of the image show close-up views of the region around the supernova in data taken prior to the explosion (left), as well as data gathered on February 3, 2014, after the supernova went off (right).

The lack of the detection of X-rays detected by Chandra is an important clue for astronomers looking for the exact mechanism of how this star exploded.

The non-detection of X-rays reveals that the region around the site of the supernova explosion is relatively devoid of material.

This finding is a critical clue to the origin of the explosion. Astronomers expect that if a white dwarf exploded because it had been steadily collecting matter from a companion star prior to exploding, the mass transfer process would not be 100% efficient, and the white dwarf would be immersed in a cloud of gas.

If a significant amount of material were surrounding the doomed star, the blast wave generated by the supernova would have struck it by the time of the Chandra observation, producing a bright X-ray source.

Since they do not detect any X-rays, the researchers determined that the region around SN 2014J is exceptionally clean.

A viable candidate for the cause of SN 2014J must explain the relatively gas-free environment around the star prior to the explosion.

One possibility is the merger of two white dwarf stars, in which case there might have been little mass transfer and pollution of the environment before the explosion.

Another is that several smaller eruptions on the surface of the white dwarf cleared the region prior to the supernova.

Further observations a few hundred days after the explosion could shed light on the amount of gas in a larger volume, and help decide between these and other scenarios.

A paper describing these results was published in the July 20 issue of The Astrophysical Journal and is available online.

More Information: "No X-rays from the very nearby Type Ia SN2014J: constraints on its environment" The first author is Raffaella Margutti from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, MA, and the co-authors are Jerod Parrent (CfA), Atish Kamble (CfA), Alicia Soderberg (CfA), Ryan Foley (University of Illinois at Urbana-Champaign), Dan Milisavljevic (CfA), Maria Drout (CfA), and Robert Kirshner (CfA). 

NASA Chandra: Signal from Dark Matter

An X-ray image of the hot gas in the central region of the Perseus Cluster of galaxies, taken by the Chandra X-ray Observatory. 

The Perseus Cluster is one of the most massive objects in the Universe with thousands of galaxies immersed in an enormous cloud of superheated gas. 

The image shows enormous bright loops, ripples, and jet-like streaks throughout the cluster. 

Astronomers may have detected an emission line from a form of dark matter, the sterile neutrino, in the spectrum of galaxy clusters like Perseus. 

Credit: Chandra/NASA/ESA

Galaxies are often found in groups or clusters, the largest known aggregations of matter and dark matter.

The Milky Way, for example, is a member of the "Local Group" of about three dozen galaxies, including the Andromeda Galaxy located about 2 million light-years away.

Very large clusters can contain thousands of galaxies, all bound together by gravity.

The closest large cluster of galaxies to us, the Virgo Cluster with about 2000 members, is about 50 million light-years away.

The space between galaxies is not empty. It is filled with hot intergalactic gas whose temperature is of order ten million kelvin, or even higher.

The gas is enriched with heavy elements that escape from the galaxies and accumulate in the intracluster medium over billions of years of galactic and stellar evolution.

These intracluster gas elements can be detected from their emission lines in X-ray, and include oxygen, neon, magnesium, silicon, sulphur, argon, calcium, iron, nickel, and even chromium and manganese.

The relative abundances of these elements contain valuable information on the rate of supernovae in the different types of galaxies in the clusters since supernovae make and/or disburse them into the gas.

Therefore it came as something of a surprise when CfA astronomers and their colleagues discovered a faint line corresponding to no known element.

Esra Bulbul, Adam Foster, Randall Smith, Scott Randall and their team were studying the averaged X-ray spectrum of a set of seventy-three clusters (including Virgo) looking for emission lines too faint to be seen in any single one when they uncovered a line with no known match in a particular spectral interval not expected to have any features.

The scientists propose a tantalizing suggestion: the line is the result of the decay of a putative, long-sought-after dark matter particle, the so-called sterile neutrino.

It had been suggested that the hot X-ray emitting gas in a galaxy cluster might be a good place to look for dark matter signatures, and if the sterile neutrino result is confirmed it would mark a breakthrough in dark matter research (it is of course possible that it is a statistical or other error).

Recent unpublished results from another group tend to support the detection of this feature; the team suggests that observations with the planned Japanese Astro-H X-ray mission in 2015 will be critical to confirm and resolve the nature of this line.

More information: "Detection of an Unidentified Emission Line in the Stacked X-Ray Spectrum of Galaxy Clusters," Esra Bulbul, Maxim Markevitch, Adam Foster, Randall K. Smith, Michael Loewenstein, and Scott W. Randall, ApJ 789, 13, 2014.

NASA NuSTAR: Celebrating two years of science in space

Artist's concept of NuSTAR on orbit.

NuSTAR has a 10-m (30') mast that deploys after launch to separate the optics modules (right) from the detectors in the focal plane (left). 

The spacecraft, which controls NuSTAR's pointings, and the solar panels are with the focal plane. 

NuSTAR has two identical optics modules to increase sensitivity. The background is an image of the Galactic center obtained with the Chandra X-ray Observatory. 

Credit: NASA/JPL-Caltech

NASA's Nuclear Spectroscopic Telescope Array (NuSTAR), a premier black-hole hunter among other talents, has finished up its two-year prime mission, and will be moving onto its next phase, a two-year extension.

"It's hard to believe it's been two years since NuSTAR launched," said Fiona Harrison, the mission's principal investigator at the California Institute of Technology in Pasadena.

"We achieved all the mission science objectives and made some amazing discoveries I never would have predicted two years ago."

In this new chapter of NuSTAR's life, it will continue to examine the most energetic objects in space, such as black holes and the pulsating remains of dead stars.

In addition, outside observers, astronomers not on the NuSTAR team, will be invited to compete for time on the telescope.

"NuSTAR will initiate a general observer program, which will start execution next spring and will take 50 percent of the observatory time," said Suzanne Dodd, the NuSTAR project manager at NASA's Jet Propulsion Laboratory in Pasadena, California.

"We are very excited to see what new science the community will propose to execute with NuSTAR."

NuSTAR blasted into space above the Pacific Ocean on June 13, 2012, with the help of a plane that boosted the observatory and its rocket to high altitudes.

After a 48-day checkout period, the telescope began collecting X-rays from black holes, supernova remnants, galaxy clusters and other exotic objects.

With its long mast - the length of a school bus, NuSTAR has a unique design that allows it to capture detailed data in the highest-energy range of X-rays, the same type used by dentists.

It is the most sensitive high-energy X-ray mission every flown.

In its prime mission, NuSTAR made the most robust measurements yet of the mind-bending spin rate of black holes and provided new insight into how massive stars slosh around before exploding.

Other observations include: the discovery of a highly magnetized neutron star near the center of our Milky Way galaxy, measurements of luminous active black holes enshrouded in dust, and serendipitous discoveries of supermassive black holes.

Galaxy's Huge Black Hole Puts on Spectacular Fireworks Show - Video

The supermassive black hole at the center of a far-off galaxy is putting on a fireworks display of cosmic proportions.

Scientists captured the brilliant display in new images and a video tour of the spiral galaxy Messier 106 (also called NGC 4258).

NSF Karl Janksy Very Large Array

An amazing composite picture was created by combining data from three NASA telescopes and a National Science Foundation (NSF) Karl Janksy Very Large Array trained on Messier 106, which is about 23 million light-years away.

While the galaxy is spiral in shape, like the Milky Way, Messier 106 has two extra swirling arms that glow in X-ray, optical and radio light.

These features are called anomalous arms and intersect the galaxy at an angle instead of aligning with the main galactic disk.

The combination of data from multiple telescopes revealed that the swirling arms of Messier 106 are streams of shock waves and superheated gas.

The NSF telescope picked up radio waves from high-energy particles streaming from the supermassive black hole at the center of the galaxy.

NASA's Spitzer Space Telescope

Infrared light data gathered by NASA's Spitzer Space Telescope shows that these bursts of particles create shock waves, similar to sonic booms, when they strike the main disk of the galaxy.

The shock waves heat up huge pockets of hydrogen gas to thousands of degrees.

Spiral Galaxy Messier 106

Spiral Galaxy Messier 106 has two extra swirling arms that glow in X-ray, optical and radio light. 

Credit: X-ray: NASA /CXC /Caltech /P.Ogle et al; Optical: NASA /STScI; IR: NASA /JPL-Caltech; Radio: NSF /NRAO /VLA

The new composite image released by NASA earlier this month shows X-rays seen by NASA's Chandra X-Ray Observatory in blue; radio waves captured by the NSF's Karl Janksy Very Large Array are shown in purple; visible light data from the Hubble telescope can be seen in yellow and blue; and infrared light from the Spitzer telescope in red.

Chandra X-Ray images reveal huge, superheated gas bubbles above and below the plane of the galaxy.

This suggests that much of the gas inside the galaxy is heated to millions of degrees and then rides along the shock waves streaming from the black hole to the outer regions of the galaxy.

Researchers predict all the gas from the galaxy will be cast out within the next 300 million years unless it is somehow replenished. Since most of the gas is already gone, less gas is available for star formation.

Researchers using Spitzer estimate that stars are forming in Messier 106 almost 10 times more slowly than they are in the Milky Way.

The black hole at the center of Messier 106 is about 10 times larger than the black hole in the Milky Way and is sucking in material much more quickly.

Researchers hope to learn more about how the black hole is influencing the galaxy. The results of the new galaxy study were published June 20 in The Astrophysical Journal Letters.

Chandra X-Ray Observatory Deployed by Space Shuttle Crew Fifteen Years Ago

Image Credit: NASA

On July 23, 1999, a little more than seven hours after Space Shuttle Columbia and its five astronauts were launched from the Kennedy Space Center, NASA's Chandra X-Ray Observatory was successfully deployed by the STS-93 crew.

Chandra was spring-ejected from a cradle in the shuttle’s cargo bay at 6:47 a.m. Central time, as Columbia flew over the Indonesian island chain.

Inertial Upper Stage (IUS)

Commander Eileen Collins, the first female Shuttle Commander, maneuvered Columbia to a safe distance away from the telescope as an internal timer counted down to the first of a two-phase ignition of the solid-fuel Inertial Upper Stage (IUS).

The IUS lit up as scheduled at 7:47 a.m., and a few minutes later, shut down as planned, sending Chandra on a highly elliptical orbit which was refined over the next few weeks by a series of firings of telescope thrusters, designed to place Chandra in an orbit about 6900 x 87,000 statute miles above the Earth.

Since its deployment, Chandra has helped revolutionise our understanding of the universe through its unrivaled X-ray vision.

Chandra, one of NASA's current "Great Observatories," along with the Hubble Space Telescope and Spitzer Space Telescope, is specially designed to detect X-ray emission from hot and energetic regions of the universe.

In this photograph, the five STS-93 astronauts pose for the traditional inflight crew portrait on Columbia's middeck.

In front are astronauts Eileen Collins, mission commander, and Michel Tognini, mission specialist representing France's Centre National d'Etudes Spatiales (CNES).

Behind them are (from the left) astronauts Steven A. Hawley, mission specialist; Jeffrey S. Ashby, pilot; and Catherine G. (Cady) Coleman, mission specialist.

In the background is a large poster depicting the Chandra X-Ray Observatory.

NASA's Chandra X-ray Observatory celebrates 15th anniversary

Credit: NASA/CXC/SAO

Fifteen years ago, NASA's Chandra X-ray Observatory was launched into space aboard the Space Shuttle Columbia.

Since its deployment on July 23, 1999, Chandra has helped revolutionize our understanding of the universe through its unrivaled X-ray vision.

Chandra, one of NASA's current "Great Observatories," along with the Hubble Space Telescope and Spitzer Space Telescope, is specially designed to detect X-ray emission from hot and energetic regions of the universe.

With its superb sensitivity and resolution, Chandra has observed objects ranging from the closest planets and comets to the most distant known quasars.

It has imaged the remains of exploded stars, or supernova remnants, observed the region around the supermassive black hole at the center of the Milky Way, and discovered black holes across the universe.

Chandra also has made a major advance in the study of dark matter by tracing the separation of dark matter from normal matter in collisions between galaxy clusters. It is also contributing to research on the nature of dark energy.

To celebrate Chandra's 15th anniversary, four new images of supernova remnants; the Crab Nebula, Tycho, G292.0+1.8, and 3C58 – are being released.

These supernova remnants are very hot and energetic and glow brightly in X-ray light, which allows Chandra to capture them in exquisite detail.

"Chandra changed the way we do astronomy. It showed that precision observation of the X-rays from cosmic sources is critical to understanding what is going on," said Paul Hertz, NASA's Astrophysics Division director in Washington.

"We're fortunate we've had 15 years, so far, to use Chandra to advance our understanding of stars, galaxies, black holes, dark energy, and the origin of the elements necessary for life."

Chandra orbits far above Earth's X-ray absorbing atmosphere at an altitude up to 139,000 km (86,500 mi), allowing for long observations unobscured by Earth's shadow.

When it was carried into space in 1999, it was the largest satellite ever launched by the shuttle.

"We are thrilled at how well Chandra continues to perform," said Belinda Wilkes, director of the Chandra X-ray Center (CXC) in Cambridge, Massachusetts.

"The science and operations teams work very hard to ensure that Chandra delivers its astounding results, just as it has for the past decade and a half."

"We are looking forward to more ground-breaking science over the next decade and beyond."

Originally called the Advanced X-ray Astrophysics Facility (AXAF), the telescope was first proposed to NASA in 1976.

Prior to its launch aboard the shuttle, the observatory was renamed in honour of the late Indian-American Nobel laureate, Subrahmanyan Chandrasekhar.

Known to the world as Chandra (which means "moon" or "luminous" in Sanskrit), he was widely regarded as one of the foremost astrophysicists of the 20th century.

"Chandra continues to be one of the most successful missions that NASA has ever flown as measured against any metric, cost, schedule, technical success and, most of all, scientific discoveries," said Martin Weisskopf, Chandra Project Scientist at the Marshall Space Flight Center in Huntsville, Ala.

"It has been a privilege to work on developing and maintaining this scientific powerhouse, and we look forward to many years to come."

Black hole fireworks in nearby galaxy Messier 106

A galaxy about 23 million light-years away is the site of impressive, ongoing, fireworks. 

Rather than paper, powder, and fire, this galactic light show involves a giant black hole, shock waves, and vast reservoirs of gas. 

Credit: NASA /CXC /JPL-Caltech /STScI /NSF /NRAO /VLA

Celebrants this Fourth of July will enjoy the dazzling lights and booming shock waves from the explosions of fireworks.

A similarly styled event is taking place in the galaxy Messier 106 (NGC 4258), as seen by NASA's Spitzer Space Telescope, Chandra X-ray Observatory and the Herschel Space Observatory. Herschel is a European Space Agency mission with important NASA contributions.

Energetic jets, which blast from Messier 106's central black hole, are heating up material in the galaxy and thus making it glow, like the ingredients in a firework.

The jets also power shock waves that are driving gases out of the galaxy's interior.

Those gases constitute the fuel for churning out new stars. A new study estimates the shock waves have already warmed and ejected two-thirds of the gas from the center of Messier 106.

With a reduced ability to birth new stars, Messier 106 appears to be transitioning into a barren, so-called lenticular galaxy full of old, red stars. Lenticular galaxies are flat disks without prominent spiral arms.

"Jets from the supermassive black hole at the center of Messier 106 are having a profound influence on the available gas for making stars in this galaxy," said Patrick Ogle, an astrophysicist at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, and lead author of a new paper describing the results.

"This process may eventually transform the spiral galaxy Messier 106 into a lenticular galaxy, depriving it of the raw material to form stars."

Many galaxies contain a central black hole that actively "feeds" upon nearby gas.

Some of the material, as it draws toward the black hole, dramatically speeds up and violently spews out as twin jets near the black hole's poles.

As one of the Milky Way's closest galactic neighbors, Messier 106 offers a great opportunity for investigating these high-powered jets.

Messier 106 is 23.5 million light-years distant, and visible with binoculars in the constellation Canes Venatici.

For the new study, researchers used data obtained with the Spitzer infrared telescope before the observatory ran out of coolant in 2009, as planned.

The data amount to a map of the infrared light emitted by heated-up hydrogen molecules in Messier 106.

The warmed hydrogen is a signature of the jet from the central black hole energizing the surrounding disk of the galaxy.

'Sterile neutrinos' re-ignites and excites Dark Matter debate - video

Astro-physicists remain cautiously excited about an unexpected X-ray signal discovered in a survey of galactic clusters.

Having first put their findings in the public sphere in March, the work has now passed peer review to hit the presses in the prestigious Astrophysical Journal, and re-ignite discussion about whether the rays represent at least a chunk of the missing stuff in the cosmos.

It's the frequency of the signal that's excited the astronomers' imaginations, since spectroscopy even at high energies is sufficiently familiar that something new demands attention.

The emission line occurs at an energy of (3.55-3.57)+/-0.03 keV – let's say “between 3.55 and 3.57 kilo-electron-volts.

Perhaps cautious after the recent BICEP-CMB 'Big Bang' controversy, which still hasn't been completely resolved, the news from ESA and NASA has been given a much more muted reception saying that “this will be huge if it's right”.

It will be huge: the missing matter in the universe remains one of astrophysics' biggest puzzles along with the search for dark energy.

The world is host to a number of sophisticated instruments designed to track down dark matter, but without positively identifying the source.

What the analysis of data from NASA's Chandra X-ray observatory and the ESA's XMM-Newton instrument has turned up is an unexpected line in the X-ray spectrum, while looking at the Perseus cluster.

Galactic clusters are among the largest-scale structures in the universe, consisting of galaxies interacting via gravity, along with the hot gas filling the space between them.

They're also one of the reasons we believe in dark matter, since the observable mass of clusters makes up only 20 per cent of the mass needed to provide the necessary gravity. The rest is presumed to be dark matter.

NASA's press release stated: there's a faint X-ray emission line discovered in the analysis of the Perseus cluster, which is matched by the same line in an analysis of another 73 galactic clusters.

ESA's release explains that while a single image of Perseus showed the line, composite images were needed to detect it in the other galactic clusters.

The research has been posted at Arxiv. NASA stated: “The authors suggest this emission line could be a signature from the decay of a 'sterile neutrino.'

Sterile neutrinos are a hypothetical type of neutrino that is predicted to interact with normal matter only via gravity. Some scientists have proposed that sterile neutrinos may at least partially explain dark matter”.

NASA goes on to point out that 55 other papers offering theories about the X-ray line already cite the original work.

Perseus, about 250 million light years away, has sparked a search for an X-ray emission. 

Credit: NASA

Co-author Maxim Markevitch from Goddard Space Flight Center says the mere possibility that a signature of sterile neutrinos is exciting, but cautions: “We have a lot of work to do before we can claim, with any confidence, that we’ve found sterile neutrinos”.

At ESA, lead author Dr Esra Bulbul from the Harvard-Smithsonian Center for Astrophysics in Cambridge explains: “If this strange signal had been caused by a known element present in the gas, it should have left other signals in the X-ray light at other well-known wavelengths, but none of these were recorded.”

Dr Bulbul doesn't say that sterile neutrinos might make up all of the missing matter in the universe, only that they could be part of it.

Check out more information on this story at NASA Chandra site

Mysterious X-ray signal intrigues astronomers

Credit: X-ray: NASA/CXC/SAO/E.Bulbul, et al.

A mysterious X-ray signal has been found in a detailed study of galaxy clusters using NASA's Chandra X-ray Observatory and ESA's XMM-Newton.

One intriguing possibility is that the X-rays are produced by the decay of sterile neutrinos, a type of particle that has been proposed as a candidate for dark matter.

While holding exciting potential, these results must be confirmed with additional data to rule out other explanations and determine whether it is plausible that dark matter has been observed.

Astronomers think dark matter constitutes 85% of the matter in the Universe, but does not emit or absorb light like "normal" matter such as protons, neutrons and electrons that make up the familiar elements observed in planets, stars, and galaxies. Because of this, scientists must use indirect methods to search for clues about dark matter.

The latest results from Chandra and XMM-Newton consist of an unidentified X-ray emission line, that is, a spike of intensity at a very specific wavelength of X-ray light.

Astronomers detected this emission line in the Perseus galaxy cluster using both Chandra and XMM-Newton.

They also found the line in a combined study of 73 other galaxy clusters with XMM-Newton.

"We know that the dark matter explanation is a long shot, but the pay-off would be huge if we're right," said Esra Bulbul of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. who led the study. "So we're going to keep testing this interpretation and see where it takes us."

The authors suggest this emission line could be a signature from the decay of a "sterile neutrino." Sterile neutrinos are a hypothetical type of neutrino that is predicted to interact with normal matter only via gravity. Some scientists have proposed that sterile neutrinos may at least partially explain dark matter.

"We have a lot of work to do before we can claim, with any confidence, that we've found sterile neutrinos," said Maxim Markevitch, a co-author from NASA's Goddard Space Flight Center in Greenbelt, Maryland. "But just the possibility of finding them has us very excited."

One source of uncertainty is that the detection of this emission line is pushing the capabilities of the two observatories in terms of sensitivity. Also, there may be explanations other than sterile neutrinos if this X-ray emission line is deemed to be real.

There are ways that normal matter in the cluster could have produced the line, although the team's analysis suggested that all of these would involve unlikely changes to our understanding of physical conditions in the galaxy cluster or the details of the atomic physics of extremely hot gases.

The authors note that even if the sterile neutrino interpretation is correct, their detection does not necessarily imply that all of dark matter is composed of these particles.

More information: The paper describing the new Chandra and XMM-Newton observations appears in the June 20, 2014, issue of The Astrophysical Journal: dx.doi.org/10.1088/0004-637X/789/1/13

A violent, complex scene of colliding galaxy clusters

Colliding galaxy clusters MACS J0717+3745, more than 5 billion light-years from Earth. Background is Hubble Space Telescope image; blue is X-ray image from Chandra, and red is VLA radio image. 

Credit: Van Weeren, et al.; Bill Saxton, NRAO /AUI /NSF; NASA.

Astronomers using the Karl G. Jansky Very Large Array (VLA) and the Chandra X-Ray Observatory have produced a spectacular image revealing new details of violent collisions involving at least four clusters of galaxies.

Combined with an earlier image from NASA's Hubble Space Telescope (HST), the new observations show a complex region more than 5 billion light-years from Earth where the collisions are triggering a host of phenomena that scientists still are working to understand.

The HST image forms the background of this composite, with the X-ray emission detected by Chandra in blue and radio emission seen by the VLA in red.

The X-rays indicate hot, tenuous gas that pervades the region containing the galaxy clusters.

The large, oddly-shaped red feature at the center probably is a region where shocks caused by the collisions are accelerating particles that then interact with magnetic fields and emit the radio waves.

"The complex shape of this region is unique; we've never spotted anything like this before," said Reinout van Weeren, an Einstein Fellow at the Harvard-Smithsonian Center for Astrophysics (CfA).

"The shape probably is the result of the multiple ongoing collisions," he added.

The new radio and X-ray observations are much more sensitive than previous ones, the scientists said. The combination of these images will make this region one of the best-studied examples of cluster-cluster collisions yet known, and can yield new insights on the complex interactions during cluster mergers.

Together, the merging clusters are called MACS J0717+3745, which also is one of the HST Frontier Fields for which HST will produce the deepest observations ever.

The scientists presented their findings to the American Astronomical Society's meeting in Boston, Mass.

The straight, elongated radio-emitting object is a foreground galaxy whose central black hole is accelerating jets of particles in two directions. The red object at bottom-left is a radio galaxy that probably is falling into the cluster.

NASA Chandra: Inside the Flame Nebula - NGC 2024

Image credit: X-ray: NASA /CXC /PSU /K.Getman, E.Feigelson, M.Kuhn & the MYStIX team; Infrared:NASA /JPL-Caltech

Stars are often born in clusters, in giant clouds of gas and dust.

Astronomers have studied two star clusters using NASA's Chandra X-ray Observatory and infrared telescopes and the results show that the simplest ideas for the birth of these clusters cannot work, as described in our latest press release.

This composite image shows one of the clusters, NGC 2024, which is found in the center of the so-called Flame Nebula about 1,400 light years from Earth.

In this image, X-rays from Chandra are seen as purple, while infrared data from NASA's Spitzer Space Telescope are coloured red, green, and blue.

A study of NGC 2024 and the Orion Nebula Cluster, another region where many stars are forming, suggest that the stars on the outskirts of these clusters are older than those in the central regions.

This is different from what the simplest idea of star formation predicts, where stars are born first in the center of a collapsing cloud of gas and dust when the density is large enough.

The research team developed a two-step process to make this discovery. First, they used Chandra data on the brightness of the stars in X-rays to determine their masses.

Next, they found out how bright these stars were in infrared light using data from Spitzer, the 2MASS telescope, and the UK Infrared Telescope (UKIRT).

By combining this information with theoretical models, the ages of the stars throughout the two clusters could be estimated.

According to the new results, the stars at the center of NGC 2024 were about 200,000 years old while those on the outskirts were about 1.5 million years in age.

In Orion, the age spread went from 1.2 million years in the middle of the cluster to nearly 2 million years for the stars toward the edges.

Professional and amateur astronomers join forces: Pro-Am Venture

Starting in the upper left and moving clockwise, the galaxies are M101 (the "Pinwheel Galaxy"), M81, Centaurus A, and M51 (the "Whirlpool Galaxy"). 

M101 is a spiral galaxy like our Milky Way, but about 70% bigger. 

Credit: X-ray: NASA /CXC /SAO; Optical: Detlef Hartmann; Infrared: NASA /JPL-Caltech

Long before the term "citizen science" was coined, the field of astronomy has benefited from countless men and women who study the sky in their spare time.

These amateur astronomers devote hours exploring the cosmos through a variety of telescopes that they acquire, maintain, and improve on their own.

Some of these amateur astronomers specialise in capturing what is seen through their telescopes in images and are astrophotographers.

What happens when the work of amateur astronomers and astrophotographers is combined with the data from some of the world's most sophisticated space telescopes?

Collaborations between professional and amateur astronomers reveal the possibilities and are intended to raise interest and awareness among the community of the wealth of data publicly available in NASA's various mission archives.

This effort is particularly appropriate for this month because April marks Global Astronomy Month, the world's largest global celebration of astronomy.

The images in this quartet of galaxies represent a sample of composites created with X-ray data from NASA's Chandra X-ray Observatory, infrared data from the Spitzer Space Telescope, and optical data collected by an amateur astronomer.

In these images, the X-rays from Chandra are shown in pink, infrared emission from Spitzer is red, and the optical data are in red, green, and blue.

The two astrophotographers who donated their images for these four images, Detlef Hartmann and Rolf Olsen, used their personal telescopes of 17.5 inches and 10 inches in diameter respectively.

More details on how these images were made can be found in this blog post.

However, the long exposures of these objects may help to reveal phenomena that may otherwise be missed in the relatively short snapshots taken by major telescopes, which are tightly scheduled and often oversubscribed by professional astronomers.

Therefore, projects like this Astro Pro-Am collaboration might prove useful not only for producing spectacular images, but also contributing to the knowledge of what is happening in each of these cosmic vistas.