Suzaku satellite reveals the average chemical composition of our Universe

JAXA logo.

October 22, 2015

Suzaku satellite reveals the average chemical composition of our Universe on
the largest scales to be the same as that of our Sun

All of the chemical elements that are heavier than carbon, the oxygen we breathe, the silicon that makes up the sand on the beach, were produced inside stars through nuclear fusion and released by stellar explosions called supernovae. By measuring the chemical composition of the Universe, scientists are trying to reconstruct the history of how, when, and where each of the chemical elements so necessary for the evolution of life were produced.

X-ray Astronomy Satellite "Suzaku" (ASTRO-EII). Image Credit: JAXA

Very generally speaking, there are two ways that a supernova explosion can take place, and the proportion of chemical elements that are produced depend on the supernova type. Lighter elements, like oxygen and magnesium, originate mainly from the explosions of very massive stars, more than 10 times the size of our Sun, at the end of their lifetimes. These are known as “core-collapse supernovae”. Smaller stars instead usually end their life cycles as “white dwarves”, a small fraction of which can explode as a “thermonuclear” or “type Ia” supernova if they later accrete matter from a companion star, causing the white dwarf to become unstable to the pull of its own gravity. Heavier atoms like iron and nickel mostly come from this latter type of supernovae. To make up the chemical composition of our Solar System, for instance, we require a mixture of roughly one thermonuclear for every five core-collapse supernova explosions. JAXA research fellow Aurora Simionescu wanted to find out whether the average chemical composition of the Universe was similar to that of our Solar System, or whether our local neighborhood was, after all, a special place.

Actually, perhaps counterintuitively, the answer to this question is best found not by looking at the stars themselves, but rather looking at the intergalactic space. That is because most of the normal matter in the universe, and thus also most of the metals, are presently not contained in stars, but rather in a very hot, diffuse gas that fills the space between galaxies, and is so hot that it shines in X-ray light. The brightest X-rays come from so-called clusters of galaxies, the places in the Universe where the galaxies are packed closest together.

“I’ve found this idea fascinating ever since the first year of my PhD: X-raying the chemical content of our Universe”, says Aurora Simionescu. But back then, almost 10 years ago, it was very hard to obtain reliable measurements of the metal abundances except for the very densest, brightest parts of the intergalactic medium, due to a lack of X-ray photons and high background noise. So we could only really probe the chemical composition of roughly the central one-thousandths of the typical volume of any given galaxy cluster.

Perseus Cluster. Image Credits: NASA/CXC/IoA/A.Fabian et al.

JAXA’s Suzaku X-ray satellite dedicated a great amount of observing time, collecting data over many weeks, to address this problem. The first such deep observations, targeting the brightest system, the Perseus Cluster, allowed remarkably detailed measurements of the iron abundance in the intra-cluster medium on large scales. However, information about chemical elements predominantly produced by core collapse supernovae was still missing.

For such measurements, observations of a galaxy cluster with a lower average temperature were needed, in order for the emission from lighter elements to be comparatively stronger than in the Perseus Cluster. Suzaku therefore spent about two weeks looking at the Virgo Cluster, the nearest and second brightest cluster in the X-ray sky, which has such a suitably low temperature. With this new data set, Simionescu and her colleagues at JAXA and Stanford University succeeded to detect not only iron but for the first time also magnesium, silicon and sulphur all the way to the edge of this galaxy cluster. Their results are reported in a study published recently in the Astrophysical Journal.

“What we found was that the ratios between the abundances of iron, silicon, sulphur, and magnesium, are constant throughout the entire volume of the Virgo Cluster, and indeed roughly consistent with the composition of our own Sun and most of the stars in our Galaxy”, explains Dr. Norbert Werner from Stanford University, a co-author of the article. Galaxy clusters cover such a large volume that the content of each such object is believed to be representative for the rest of the Universe as well. The new Suzaku finding means that the chemical elements in the cosmos are very well mixed, with a chemical composition that remains the same from scales of the solar radius (hundreds of thousands of kilometers) to the size of a cluster of galaxies (several million light years). Although there may still be a few special places in the Universe that retain a different chemical make-up, on average, the bulk of the Universe has a very similar composition to our local neighbourhood — the same raw soup of elements that is necessary for life like ours is found, wherever you look.

“The Suzaku satellite has opened a brand new window on the Universe and shown us that wherever you look, over vast scales, the mix of chemical elements is essentially the same" said Steven Allen, Professor of Physics at Stanford University and co-author of the study. "It's a beautifully simple result, and another step in understanding how the Universe around us came to be.”

Magazine name：
The Astrophysical Journal Letters

Thesis title：
A UNIFORM CONTRIBUTION OF CORE-COLLAPSE AND TYPE Ia SUPERNOVAE TO THE CHEMICAL ENRICHMENT PATTERN IN THE OUTSKIRTS OF THE VIRGO CLUSTER

Authors：
A. Simionescu, N. Werner, O. Urban, S. W. Allen, Y. Ichinohe, I. Zhuravleva

DOI number：
10.1088/2041-8205/811/2/L25

Related link:

X-ray Astronomy Satellite "Suzaku" (ASTRO-EII): http://global.jaxa.jp/projects/sat/astro_e2/

Images (mentioned),  Text, Credits: Japan Aerospace Exploration Agency (JAXA)/National Research and Development Agency.

Sayonara, Orbiter.ch

Landing site recommended for ExoMars 2018

ESA / ROSCOSMOS - ExoMars Mission logo.

22 October 2015

Oxia Planum has been recommended as the primary candidate for the landing site of the ExoMars 2018 mission.

ExoMars 2018, comprising a rover and surface platform, is the second of two missions making up the ExoMars programme, a joint endeavour between ESA and Russia’s Roscosmos. Launch is planned for May 2018, with touchdown on the Red Planet in January 2019.

Oxia Planum. Image Credits: ESA/DLR/FU Berlin & NASA MGS MOLA Science Team

Meanwhile, the Trace Gas Orbiter and the Schiaparelli entry, descent and landing demonstrator module will be launched in March 2016, arriving at Mars around this time next year.

Schiaparelli will land in Meridiani Planum. The orbiter will study the atmosphere and act as a relay for the second mission.

The search for a suitable landing site for the second mission began in December 2013, when the science community was asked to propose candidates. In October 2014, the Landing Site Selection Working Group chose four sites. The last year has been spent evaluating these sites, taking into account the engineering constraints of descent and landing, and the best possible scientific return of the mission

The main goal for the rover is to search for evidence of martian life, past or present, in an area with ancient rocks where liquid water was once abundant. A drill is capable of extracting samples from up to 2 m below the surface. This is crucial, because the present surface of Mars is a hostile place for living organisms owing to the harsh solar and cosmic radiation. By searching underground, the rover has more chance of finding preserved evidence.

Scientists believe that primitive life could have gained a foothold when the surface environment was wetter, more than 3.6 billion years ago. Buried or recently exhumed layered sedimentary deposits thus offer the best window into this important period of Mars history.

All four sites under study – Aram Dorsum, Hypanis Vallis, Mawrth Vallis and Oxia Planum – show evidence of having been influenced by water in the past, and are likely representative of global processes operating in the Red Planet’s early history.

ExoMars 2018 landing site candidates. Image Credits: ESA/CartoDB

All locations offer the opportunity of landing at a scientifically interesting site or finding one within a 1 km drive from the touchdown point, with numerous targets accessible along a typical 2 km traverse planned for the mission of 218 martian days (each 24 hours 37 minutes).

The sites must also conform to strict engineering constraints to ensure the safe entry, descent and landing of the entry module. These include the need for a relatively low-lying site, in order that the module passes through enough atmosphere for the completion of key events such as parachute opening and deceleration.

The horizontal and vertical wind speeds expected during the descent must also be also considered – it will land at the end of the planet’s global dust storm season in 2019.

Aram Dorsum. Image Credits: ESA/DLR/FU Berlin & NASA MGS MOLA Science Team

Knowledge of how the terrain slopes over various scales is important, because the lander uses radar to monitor its velocity and altitude. Slopes can alter the degree of certainty in the measured distance to the ground, with implications for fuel consumption and landing.

Steep slopes and boulders taller than 35 cm – the clearance beneath the landing module – need to be avoided, although the rover will be able navigate around local hazards after egress.

Taking into account these requirements and the individual science cases put forward for each site, the Landing Site Selection Working Group today recommended that Oxia Planum be the primary focus for further detailed evaluation for the 2018 mission.

A further recommendation was made to also consider Oxia Planum as one of the two candidate landing sites for the backup launch opportunity in 2020, with a second to be selected from Aram Dorsum and Mawrth Vallis.

Schiaparelli separating from the Trace Gas Orbiter. Image Credits: ESA/ATG medialab

“Our preliminary analysis shows that Oxia Planum appears to satisfy the strict engineering constraints while also offering some very interesting opportunities to study, in situ, places where biosignatures might best be preserved,” says Jorge Vago, ESA’s project scientist.

Oxia Planum contains one of the largest exposures of rocks on Mars that are around 3.9 billion years old and clay-rich, indicating that water once played a role here.

The site sits in a wide catchment area of valley systems with the exposed rocks exhibiting different compositions, indicating a variety of deposition and wetting environments.

A period of volcanic activity may have covered early clays and other aqueous deposits, offering preservation for biosignatures against the planet's harsh radiation and oxidation environment, and have only been exposed by erosion within the last few hundred million years.

ExoMars 2018 landing site constraints. Image Credits: ESA-Roscosmos/LSSWG/D. Loizeau

“Compared with landing site selection for previous missions, which relied primarily on the morphology of candidate sites alone, we are today in a much better position to understand the mineralogy of the various sites,” adds Jorge.

“This puts us in the best position to choose sites that offer access to the most ancient, pristine material that not only preserves a record of early Mars but which is globally representative of processes occurring across the planet.

“It made for a challenging decision today, given the quality of the cases for all sites, but we are looking forward to the next stage of analysis as we move closer to the launch of our exciting mission: our rover will search for molecular biosignatures in the subsurface for the very first time.”

Selection of the final landing site by ESA and Roscosmos is planned to occur six months before launch.

Notes for Editors:

Detailed descriptions of all four candidates are available here:

Aram Dorsum: http://exploration.esa.int/mars/54722-aram-dorsum/

Hypanis Vallis: http://exploration.esa.int/mars/54723-hypanis-vallis/

Mawrth Vallis: http://exploration.esa.int/mars/54721-mawrth-vallis/

Oxia Planum: http://exploration.esa.int/mars/54724-oxia-planum/

More information about the Landing Site Selection Working Group is available here: http://exploration.esa.int/mars/53454-exomars-2018-landing-site-selection-working-group/

For more information about ExoMars mission, visit: http://exploration.esa.int/mars/

Images (mentioned), Text, Credits: ESA Science and Robotic Exploration Communication Officer/Markus Bauer/ESA ExoMars 2018 project scientist/Jorge Vago.

Best regards, Orbiter.ch

NASA Spots the ‘Great Pumpkin’: Halloween Asteroid a Treat for Radar Astronomers

Asteroid Watch logo.

Oct. 21, 2015

NASA scientists are tracking the upcoming Halloween flyby of asteroid 2015 TB145 with several optical observatories and the radar capabilities of the agency's Deep Space Network at Goldstone, California. The asteroid will fly past Earth at a safe distance slightly farther than the moon's orbit on Oct. 31 at 10:05 a.m. PDT (1:05 p.m. EDT). Scientists are treating the flyby of the estimated 1,300-foot-wide (400-meter) asteroid as a science target of opportunity, allowing instruments on "spacecraft Earth" to scan it during the close pass.

Image above: This is a graphic depicting the orbit of asteroid 2015 TB145. The asteroid will safely fly past Earth slightly farther out than the moon's orbit on Oct. 31 at 10:05 a.m. Pacific (1:05 p.m. EDT and 17:05 UTC). Image Credits: NASA/JPL-Caltech.

Asteroid 2015 TB145 was discovered on Oct. 10, 2015, by the University of Hawaii's Pan-STARRS-1 (Panoramic Survey Telescope and Rapid Response System) on Haleakala, Maui, part of the NASA-funded Near-Earth Object Observation (NEOO) Program. According to the catalog of near-Earth objects (NEOs) kept by the Minor Planet Center, this is the closest currently known approach by an object this large until asteroid 1999 AN10, at about 2,600 feet (800 meters) in size, approaches at about 1 lunar distance (238,000 miles from Earth) in August 2027.

“The trajectory of 2015 TB145 is well understood," said Paul Chodas, manager of the Center for Near Earth Object Studies at NASA's Jet Propulsion Laboratory, Pasadena, California. "At the point of closest approach, it will be no closer than about 300,000 miles -- 480,000 kilometers or 1.3 lunar distances. Even though that is relatively close by celestial standards, it is expected to be fairly faint, so night-sky Earth observers would need at least a small telescope to view it."

The gravitational influence of the asteroid is so small it will have no detectable effect on the moon or anything here on Earth, including our planet's tides or tectonic plates.

The Center for NEO Studies at JPL is a central node for NEO data analysis in NASA’s Near-Earth Object Observation Program and a key group involved with the international collaboration of astronomers and scientists who keep watch on the sky with their telescopes, looking for asteroids that could be a hazard to impact our planet and predicting their paths through space for the foreseeable future.

"The close approach of 2015 TB145 at about 1.3 times the distance of the moon’s orbit, coupled with its size, suggests it will be one of the best asteroids for radar imaging we’ll see for several years," said Lance Benner, of JPL, who leads NASA's asteroid radar research program. "We plan to test a new capability to obtain radar images with two-meter resolution for the first time and hope to see unprecedented levels of detail."

Artist's interpretation of the close pass of the Earth by an asteroid. Image Credit: NASA

During tracking, scientists will use the 34-meter (110-foot) DSS 13 antenna at Goldstone to bounce radio waves off the asteroid. Radar echoes will in turn be collected by the National Radio Astronomy Observatory’s Green Bank Telescope in Green Bank, West Virginia, and the National Astronomy and Ionosphere Center's Arecibo Observatory, Puerto Rico. NASA scientists hope to obtain radar images of the asteroid as fine as about 7 feet (2 meters) per pixel. This should reveal a wealth of detail about the object's surface features, shape, dimensions and other physical properties.

“The asteroid's orbit is very oblong with a high inclination to below the plane of the solar system," said Benner. "Such a unique orbit, along with its high encounter velocity -- about 35 kilometers or 22 miles per second -- raises the question of whether it may be some type of comet. If so, then this would be the first time that the Goldstone radar has imaged a comet from such a close distance."

NASA’s Near-Earth Object Observations Program detects, tracks and characterizes asteroids and comets passing within 30 million miles of Earth using both ground- and space-based telescopes. The NEOO Program, sometimes called "Spaceguard," discovers these objects, characterizes the physical nature of a subset of them, and predicts their paths to determine if any could be potentially hazardous to our planet. There are no known credible impact threats to date -- only the ongoing and harmless in-fall of meteoroids, tiny asteroids that burn up in the atmosphere.

JPL hosts the Center for Near-Earth Object Studies for NASA's Near-Earth Object Observations Program within the agency's Science Mission Directorate. JPL is a division of the California Institute of Technology in Pasadena.

More information about asteroids and near-Earth objects is at: http://neo.jpl.nasa.gov and http://www.jpl.nasa.gov/asteroidwatch

Images (mentioned), Text, Credits: NASA/Tony Greicius/JPL/DC Agle.

Greetings, Orbiter.ch

GPM Satellite Sees Typhoon Champi Still Going Strong

NASA / JAXA - Global Precipitation Measurement (GPM) logo.

Oct. 21, 2015

Champi - Northwest Pacific Ocean

Image above: On Oct. 21 at 01:15 UTC the MODIS instrument aboard NASA's Terra satellite captured this visible image of Typhoon Champi in the western Pacific Ocean. Image Credits: NASA Goddard MODIS Rapid Response Team.

The Global Precipitation Measurement mission, or GPM, core satellite is getting a workout in the western North Pacific Ocean as it gathered rainfall and cloud height data on Typhoon Champi.

Both Typhoon Champi and Super-typhoon Koppu formed on Oct. 13, 2015. Champi is still a typhoon because it stayed over the open waters of the Pacific Ocean, but Super-typhoon Koppu's strength was sapped by its travel over the rugged terrain of the Philippines.

The GPM core observatory satellite passed above Typhoon Champi on Oct. 21, 2015 at 0110 UTC (7:01 a.m. EDT). Maximum sustained winds were still about 75 knots (86 mph) at the time GPM passed overhead.

Rainfall data derived from data captured by GPM's Microwave Imager (GMI) instrument reveal that Typhoon Champi had a large eye. Rain was measured in the eyewall falling at a rate of 56.7 mm (2.23 inches) per hour.

GPM's Dual-Frequency Precipitation Radar (DPR) instrument made 3-D measurements of precipitation on Typhoon Champi's eastern side. Those measurements showed that some storm top heights there were reaching altitudes of 13.7 km (8.5 miles).

Image above: GPM saw that Typhoon Champi had a large eye and rain was measured in the eyewall falling at a rate of 56.7 mm (2.23 inches) per hour. Some storm top heights there were reaching altitudes of 13.7 km (8.5 miles). Image Credits: NASA/JAXA/SSAI, Hal Pierce.

At 1500 UTC (11 a.m. EDT), Typhoon Champi's maximum sustained winds were near 75 knots (86.3 mph/138.9 kph). It was centered near 23.2 degrees north latitude and 140.4 degrees east longitude, about 108 miles south-southwest of Iwo To, Japan. It was moving to the north at 4 knots (4.6 mph/7.4 kph) and generating wave heights to 30 feet (9.1 meters).

The Joint Typhoon Warning Center (JTWC) has predicted that Typhoon Champi will become a little more powerful with peak winds of 85 knots (98 mph) tomorrow, October 22. Within a few days increasing vertical wind shear and colder sea surface temperatures are expected to weaken the system.

For more information about Global Precipitation Measurement mission, visit: http://www.nasa.gov/mission_pages/GPM/main/ and http://www.eorc.jaxa.jp/GPM/index_e.htm

Images (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Hal Pierce/SSAI.

Greetings, Orbiter.ch

NASA’s K2 Finds Dead Star Vaporizing a Mini “Planet”

NASA - Kepler Space Telescope patch.

Oct. 21, 2015

Scientists using NASA’s repurposed Kepler space telescope, known as the K2 mission, have uncovered strong evidence of a tiny, rocky object being torn apart as it spirals around a white dwarf star. This discovery validates a long-held theory that white dwarfs are capable of cannibalizing possible remnant planets that have survived within its solar system.

“We are for the first time witnessing a miniature “planet” ripped apart by intense gravity, being vaporized by starlight and raining rocky material onto its star,” said Andrew Vanderburg, graduate student from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, and lead author of the paper published in Nature.

As stars like our sun age, they puff up into red giants and then gradually lose about half their mass, shrinking down to 1/100th of their original size to roughly the size of Earth. This dead, dense star remnant is called a white dwarf.

Image above: In this artist’s conception, a tiny rocky object vaporizes as it orbits a white dwarf star. Astronomers have detected the first planetary object transiting a white dwarf using data from the K2 mission. Slowly the object will disintegrate, leaving a dusting of metals on the surface of the star. Image Credits: CfA/Mark A. Garlick.

The devastated planetesimal, or cosmic object formed from dust, rock, and other materials, is estimated to be the size of a large asteroid, and is the first planetary object to be confirmed transiting a white dwarf. It orbits its white dwarf, WD 1145+017, once every 4.5 hours. This orbital period places it extremely close to the white dwarf and its searing heat and shearing gravitational force.

During its first observing campaign from May 30, 2014 to Aug. 21, 2014, K2 trained its gaze on a patch of sky in the constellation Virgo, measuring the minuscule change in brightness of the distant white dwarf. When an object transits or passes in front of a star from the vantage point of the space telescope, a dip in starlight is recorded. The periodic dimming of starlight indicates the presence of an object in orbit about the star.

A research team led by Vanderburg found an unusual, but vaguely familiar pattern in the data. While there was a prominent dip in brightness occurring every 4.5 hours, blocking up to 40 percent of the white dwarf's light, the transit signal of the tiny planet did not exhibit the typical symmetric U-shaped pattern. It showed an asymmetric elongated slope pattern that would indicate the presence of a comet-like tail. Together these features indicated a ring of dusty debris circling the white dwarf, and what could be the signature of a small planet being vaporized.

“The eureka moment of discovery came on the last night of observation with a sudden realization of what was going around the white dwarf. The shape and changing depth of the transit were undeniable signatures,” said Vanderburg.

In addition to the strangely shaped transits, Vanderburg and his team found signs of heavier elements polluting the atmosphere of WD 1145+017, as predicted by theory.

Diagram above: The diagram depicts a model of light curve shapes. The red line indicates the symmetric shape of a typical planet transit while the blue line is the asymmetric shape of a disintegrating planet. The black dots are measurements recorded by the K2 mission of WD 1145+017. Diagram Credits: CfA/A. Vanderburg.

Due to intense gravity, white dwarfs are expected to have chemically pure surfaces, covered only with light elements of helium and hydrogen. For years, researchers have found evidence that some white dwarf atmospheres are polluted with traces of heavier elements such as calcium, silicon, magnesium and iron. Scientists have long suspected that the source of this pollution was an asteroid or a small planet being torn apart by the white dwarf's intense gravity.

Analysis of the star's atmospheric composition was conducted using observations made by the University of Arizona's MMT Observatory.

“For the last decade we’ve suspected that white dwarf stars were feeding on the remains of rocky objects, and this result may be the smoking gun we’re looking for,” said Fergal Mullally, staff scientist of K2 at SETI and NASA’s Ames Research Center in Moffett Field, California. “However, there's still a lot more work to be done figuring out the history of this system.”

“This discovery highlights the power and serendipitous nature of K2. The science community has full access to K2 observations and is using these data to make a wide range of unique discoveries across the full range of astrophysics phenomena,” said Steve Howell, K2 project scientist at Ames.

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

For more information about the Kepler and K2 missions, visit: http://www.nasa.gov/kepler

Image (mentioned), Diagram (mentioned), Text, Credits: NASA/Ames Research Center/Michele Johnson.

Greetings, Orbiter.ch

Black hole caught feasting on a star

ESA - XMM-Newton Mission patch.

21 October 2015

Astronomers have detected the last 'cry' from a star that passed too close to the central black hole of its host galaxy and was being destroyed and 'swallowed' – a phenomenon known as a tidal disruption event. The study, based on the observations of X-rays emitted by leftover material from the star in the vicinity of the black hole, allowed the astronomers to measure, for the first time, the physical properties of a newly formed accretion disc, enabling them to investigate the initial phases of such a powerful event.

Artist's impression of a tidal disruption event. Image Credit: ESA/C. Carreau

At the core of most galaxies sits a supermassive black hole, whose gravity influences the motions of stars and gas in the central regions of the galaxy. A small fraction of these black holes actively feed on the material in their surroundings through a disc, releasing powerful jets of particles and giving rise to intense emission across the electromagnetic spectrum.

The majority of these supermassive black holes, however, are not as active: an example is the one at the centre of our Milky Way, which has a mass of a few million times that of the Sun and is relatively inactive. These 'dormant' black holes have a much quieter feeding routine, only occasionally devouring a star or cloud of gas that dares to venture too close to the galaxy's centre.

On such occasions, when a star starts feeling the gravitational pull of the black hole, it experiences a stronger force on one side than on the other – something that eventually breaks the star up. In the process, stellar material starts flowing onto the black hole, where part of it is accreted and the rest ejected, producing a sudden boost in the luminosity of the galaxy, especially in X-rays.

Astronomers have been studying this phenomenon, known as tidal disruption, for over three decades, and in that time have detected dozens of black holes tearing apart and devouring stars in many galaxies, near and far.

Now, a new study led by Jon Miller of the University of Michigan, USA, offers the first close-up look into the formation of a black-hole accretion disc after a tidal disruption event. The results are published on 22 October 2015 in the journal Nature.

"All previous observations of tidal disruption events revealed an already formed disc around the black hole," says Miller, "but this is the first time that we catch such a disc in its infancy, so we can study the details of how matter starts flowing from the shattered star towards the black hole and settles in circular orbits around it."

Optical image of PGC 043234 galaxy. Image Credit: Sloan Digital Sky Survey

This source, called ASASSN-14li, was discovered on 22 November 2014 as part of an optical survey to detect supernovae, the explosive death throes of massive stars, in galaxies across the sky. Further observations revealed that this sudden spike of light was extremely close to the centre of its host galaxy, located some 300 million light-years away from us.

Soon after that, astronomers started observing this object with X-ray telescopes: ESA's XMM-Newton X-ray Observatory, and NASA's Swift X-ray Telescope (XRT) and Chandra X-ray Observatory. These data provided clear evidence of a disc of hot material flowing towards the galaxy's central black hole, which has a mass around one million solar masses and up until that time had never shown any signs of steady, active accretion.

"We immediately realised that this was a star being disrupted by the black hole, but there was more: it was the closest to be discovered in the past ten years," adds Miller.

"Given the host galaxy's relative vicinity to us, we could study the physics of this system in ever greater detail: a very rewarding outcome for a team who had been trying to decipher the puzzle of tidal disruption events for many years."

XMM-Newton X-ray Observatory spacecraft. Image Credit: ESA

The astronomers collected light curves of this source – monitoring its luminosity over time – with Swift, and high-resolution spectra with XMM-Newton and Chandra.

"In particular, the excellent spectral resolution and large collecting area of the Reflection Grating Spectrometer on XMM-Newton enabled us to pin down the velocity of the material in the disc, its density and ionisation properties for the first time in a tidal disruption event," adds co-author Jelle Kaastra from the Netherlands Institute for Space Research – SRON.

The data also revealed signs of X-ray absorbing material beyond the disc. This could either be outflowing gas, leaving the disc via a wind, or a stream of gas flowing towards the black hole but temporarily set on a different orbit, not having settled yet in the disc with most of the leftover matter from the destroyed star.

With this new discovery, astronomers can finally study tidal disruption events with similar tools to those that have been used for many years to investigate the steadily accreting supermassive black holes at the centre of active galaxies.

"Tidal disruption events provide us a unique window onto the onset of black hole accretion, and we are looking forward to exploiting this to understand the history of supermassive black holes and their host galaxies," says Norbert Schartel, ESA XMM-Newton Project Scientist.

More information:

"Flows of X-ray gas reveal the disruption of a star by a massive black hole" by Jon M. Miller, et al., is published in the 22 October 2015 issue of the journal Nature: http://www.nature.com/nature/journal/v526/n7574/full/nature15708.html

The study is based on observations of a transient source, ASASSN-14li, which was discovered on 22 November 2014 by the All-Sky Automated Survey for Supernovae (ASAS-SN). Follow up observations were performed with NASA's Swift X-ray Telescope (XRT) and Chandra X-ray Observatory, and with ESA's XMM-Newton.

The source is located in a small galaxy, PGC 043234, belonging to the Coma supercluster of galaxies. The galaxy is at a redshift of z=0.0206 and its light has travelled about 300 million years before reaching Earth.

The European Space Agency's X-ray Multi-Mirror Mission, XMM-Newton, was launched in December 1999. The largest scientific satellite to have been built in Europe, it is also one of the most sensitive X-ray observatories ever flown. More than 170 wafer-thin, cylindrical mirrors direct incoming radiation into three high-throughput X-ray telescopes. XMM-Newton's orbit takes it almost a third of the way to the Moon, allowing for long, uninterrupted views of celestial objects.

For more information about XMM-Newton mission, visit: http://sci.esa.int/xmm-newton/

Images (mentioned), Text, Credits: ESA XMM-Newton Project Scientist/Norbert Schartel/SRON – Netherlands Institute for Space Research/Jelle S. Kaastra/Department of Astronomy, The University of Michigan/Jon M. Miller.

Best regards, Orbiter.ch

New Perspective on a Galaxy Cluster

NASA - Chandra X-ray Observatory patch.

Oct. 21, 2015

The galaxy cluster MS 0735.6+7421 is home to one of the most powerful eruptions ever observed. X-rays detected by NASA's Chandra X-Ray Observatory (blue) show the hot gas that comprises much of the mass of this enormous object. Within the Chandra data, holes, or cavities, can be seen. These cavities were created by an outburst from a supermassive black hole at the center of the cluster, which ejected the enormous jets detected in radio waves (pink) detected by the Very Large Array. These data have been combined with optical data from the Hubble Space Telescope of galaxies in the cluster and stars in the field of view (orange).

This image is part of a collection of new images released from the Chandra archive to celebrate American Archive Month. Archives, in their many forms, save information from today that people will want to access and study in the future. This is a critical function of all archives, but it is especially important when it comes to storing data from today's modern telescopes. Chandra has collected data for over sixteen years on thousands of different objects throughout the universe. Once the data is processed, all of the data goes into an archive and is available to the public.

Related link:

Chandra archive: http://www.nasa.gov/mission_pages/chandra/banking-x-ray-data-for-the-future.html

For more information about Chandra X-Ray Observatory, visit: http://www.nasa.gov/mission_pages/chandra/main/index.html

Image, Text, Credits: X-ray: NASA/CXC/Univ. of Waterloo/A.Vantyghem et al; Optical: NASA/STScI; Radio: NRAO/VLA/Sarah Loff.

Greetings, Orbiter.ch