Friday, July 29, 2016

A long-dead star

Credit: ESA/Hubble & NASA, Y. Chu

This NASA/ESA Hubble Space Telescope image captures the remnants of a long-dead star. These rippling wisps of ionised gas, named DEM L316A, are located some 160 000 light-years away within one of the Milky Way’s closest galactic neighbours — the Large Magellanic Cloud (LMC).

The explosion that formed DEM L316A was an example of an especially energetic and bright variety of supernova, known as a Type Ia. Such supernova events are thought to occur when a white dwarf star steals more material than it can handle from a nearby companion, and becomes unbalanced. The result is a spectacular release of energy in the form of a bright, violent explosion, which ejects the star’s outer layers into the surrounding space at immense speeds. As this expelled gas travels through the interstellar material, it heats it up and ionise it, producing the faint glow that Hubble’s Wide Field Camera 3 has captured here.

The LMC orbits the Milky Way as a satellite galaxy and is the fourth largest in our group of galaxies, the Local Group. DEM L316A is not alone in the LMC; Hubble came across another one in 2010 with SNR 0509 (heic1018), and in 2013 it snapped SNR 0519 (potw1317a).

Thursday, July 28, 2016

GJ 3253: Astronomers Gain New Insight into Magnetic Field of Sun and its Kin

Illustration of Low-mass Star
An artist's illustration depicts the interior of a low-mass star, such as the one seen in an X-ray image from Chandra in the image below. Such stars have different interior structures than our Sun. A new study looking at four of these low-mass stars shows the strength of magnetic fields of these stars - which is revealed by the amount of X-ray emission from the stars - are similar to those of more massive ones like the Sun. This discovery may have profound implications for understanding how the magnetic field in the Sun and stars like it are generated.  (Credit: NASA/CXC/M.Weiss)

Illustration of Sun-like star
 This artist's impression shows the internal structure of the sun and stars with a similar mass to the sun. These stars have a divided internal structure with an inner radiation zone, where energy moves outward, and an outer convection zone shown by loops with arrows. Similar to the circulation of warm air inside an oven, the process of convection in a star distributes heat from the interior of the star to its surface in a circulating pattern of rising cells of hot gas and descending cooler gas. A difference in the speed of rotation between the radiation and convection zones was thought to generate most of the magnetic field in the sun by causing magnetic fields along the border between the two zones to wind up and strengthen.  Credit: NASA/CXC/M.Weiss).  More Images 

Magnetic fields on the Sun and stars like it are responsible for much of their behavior, including the generation of powerful storms that can produce spectacular auroras on Earth, damage electrical power systems, knock out communications satellites, and affect astronauts in space. As discussed in our latest press release, new research relying on data from NASA's Chandra X-ray Observatory is helping astronomers better understand how these magnetic fields are produced.

By comparing the X-ray emission, an excellent indicator of a star's magnetic field strength, between low-mass stars and the Sun, a pair of astronomers was able to find an important clue about how stellar magnetic fields are generated.

The Sun and stars with approximately the same mass have a divided internal structure with an inner radiation zone (energy moves outward) and an outer convection zone (the energy circulates). Stars with significantly lower masses, however, do not have such a differentiated structure. Instead, the process of convection is dominant throughout the star, which is depicted in the artist's illustration in the main panel of the graphic.

The researchers in this latest study looked at four low-mass stars - two with Chandra and two with archival data from the ROSAT satellite - and found their X-ray emission was similar to that of stars like the Sun. (The inset in the graphic shows Chandra's data of one of these low-mass stars, GJ 3253).

This result was surprising because many scientists think the boundary between the radiation and convection zones in the Sun and Sun-like stars contributes to the strength of its magnetic field. If stars without such a boundary have relatively powerful magnetic fields, then this theory may need to be re-examined.

A paper describing these results by Wright and Drake appears in the July 28th issue of the journal Nature. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Fast Facts for GJ 3253:

Credit X-ray: NASA/CXC/Keele Univ/N.Wright et al; Illustration: NASA/CXC/M.Weiss
Scale: X-ray image is 20 arcsec across (about 0.003 light years)
Category: Normal Stars & Star Clusters
Coordinates (J2000): RA 03h 52m 41.70s | Dec +17° 01’ 05.70"
Constellation: Taurus
Observation Date: 25 Sep 2013
Observation Time: 5 hours 45 min.
Obs. ID: 14603
Instrument: ACIS
References: Wright, N. et al, 2016, Nature (accepted)
Color Code: X-ray (Pink)
About: 31 light years (z=0.003)

Loneliest Young Star Seen by Spitzer and WISE

An unusual celestial object called CX330 was first detected as a source of X-ray light in 2009. It has been launching "jets" of material into the gas and dust around it. Credit: NASA/JPL-Caltech.  › Full image and caption

Alone on the cosmic road, far from any known celestial object, a young, independent star is going through a tremendous growth spurt.

The unusual object, called CX330, was first detected as a source of X-ray light in 2009 by NASA's Chandra X-Ray Observatory while it was surveying the bulge in the central region of the Milky Way. Further observations indicated that this object was emitting optical light as well. With only these clues, scientists had no idea what this object was.

But when Chris Britt, postdoctoral researcher at Texas Tech University in Lubbock, and colleagues were examining infrared images of the same area taken with NASA's Wide-field Infrared Survey Explorer (WISE), they realized this object has a lot of warm dust around it, which must have been heated by an outburst.

Comparing WISE data from 2010 with Spitzer Space Telescope data from 2007, researchers determined that CX330 is likely a young star that had been outbursting for several years. In fact, in that three-year period its brightness had increased by a few hundred times.

Astronomers looked at data about the object from a variety of other observatories, including the ground-based SOAR, Magellan, and Gemini telescopes. They also used the large telescope surveys VVV and the OGLE-IV to measure the intensity of light emitted from CX330. By combining all of these different perspectives on the object, a clearer picture emerged.

"We tried various interpretations for it, and the only one that makes sense is that this rapidly growing young star is forming in the middle of nowhere," said Britt, lead author of a study on CX330 recently published in the Monthly Notices of the Royal Astronomical Society.

The lone star's behavior has similarities to FU Orionis, a young outbursting star that had an initial three-month outburst in 1936-7. But CX330 is more compact, hotter and likely more massive than the FU Orionis-like objects known. The more isolated star launches faster "jets," or outflows of material that slam into the gas and dust around it.

"The disk has probably heated to the point where the gas in the disk has become ionized, leading to a rapid increase in how fast the material falls onto the star," said Thomas Maccarone, study co-author and associate professor at Texas Tech.

Most puzzling to astronomers, FU Orionis and the rare objects like it -- there are only about 10 of them -- are located in star-forming regions. Young stars usually form and feed from their surrounding gas and dust-rich regions in star-forming clouds. By contrast, the region of star formation closest to CX330 is over a thousand light-years away.

"CX330 is both more intense and more isolated than any of these young outbursting objects that we've ever seen," said Joel Green, study co-author and researcher at the Space Telescope Science Institute in Baltimore. "This could be the tip of the iceberg -- these objects may be everywhere."

In fact, it is possible that all stars go through this dramatic stage of development in their youth, but that the outbursts are too short in cosmological time for humans to observe many of them.

How did CX330 become so isolated? One idea is that it may have been born in a star-forming region, but was ejected into its present lonely pocket of the galaxy. But this is unlikely, astronomers say.

Because CX330 is in a youthful phase of its development -- likely less than 1 million years old -- and is still eating its surrounding disk, it must have formed near its present location in the sky.

"If it had migrated from a star-forming region, it couldn't get there in its lifetime without stripping its disk away entirely," Britt said.

CX330 may also help scientists study the way stars form under different circumstances. One scenario is that stars form through turbulence. In this "hierarchical" model, a critical density of gas in a cloud causes the cloud to gravitationally collapse into a star. A different model, called "competitive accretion," suggests that stars begin as low-mass cores that fight over the mass of material left in the cloud. CX330 more naturally fits into the first scenario, as the turbulent circumstances would theoretically allow for a lone star to form.

It is still possible that other intermediate- to low-mass stars are in the immediate vicinity of CX330, but have not been detected yet.

When CX330 was last viewed in August 2015, it was still outbursting. Astronomers plan to continue studying the object, including with future telescopes that could view it in other wavelengths of light.

Outbursts from a young star change the chemistry of the star's disk, from which planets may eventually form. If the phenomenon is common, that means that planets, including our own, may carry the chemical signatures of an ancient disk of gas and dust scarred by stellar outbursts.

But as CX330 is continuing to devour its disk with increasing voracity, astronomers do not expect that planets are forming in its system.

"If it's truly a massive star, its lifetime is short and violent, and I wouldn't recommend being a planet around it," Green said. "You could experience some pretty intense heat for a few centuries."

For more information on WISE, visit:

For more information on Spitzer, visit:

News Media Contact

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.

 Source: JPL-Caltech

Wednesday, July 27, 2016

White Dwarf Lashes Red Dwarf with Mystery Ray

Artist’s impression of the exotic binary star system AR Scorpii

AR Scorpii in the constellation of Scorpius

Wide-field view of the sky around the exotic binary star system AR Scorpii


Artist’s impression video of the exotic binary star system AR Scorpii
Artist’s impression video of the exotic binary star system AR Scorpii

Zooming in on the exotic binary star AR Scorpii
Zooming in on the exotic binary star AR Scorpii

Astronomers using ESO’s Very Large Telescope, along with other telescopes on the ground and in space, have discovered a new type of exotic binary star. In the system AR Scorpii a rapidly spinning white dwarf star powers electrons up to almost the speed of light. These high energy particles release blasts of radiation that lash the companion red dwarf star, and cause the entire system to pulse dramatically every 1.97 minutes with radiation ranging from the ultraviolet to radio. The research will be published in the journal Nature on 28 July 2016.

In May 2015, a group of amateur astronomers from Germany, Belgium and the UK came across a star system that was exhibiting behaviour unlike anything they had ever encountered. Follow-up observations led by the University of Warwick and using a multitude of telescopes on the ground and in space [1], have now revealed the true nature of this previously misidentified system.

The star system AR Scorpii, or AR Sco for short, lies in the constellation of Scorpius, 380 light-years from Earth. It comprises a rapidly spinning white dwarf [2], the size of Earth but containing 200 000 times more mass, and a cool red dwarf companion one third the mass of the Sun [3], orbiting one another every 3.6 hours in a cosmic dance as regular as clockwork.

In a unique twist, this binary star system is exhibiting some brutal behaviour. Highly magnetic and spinning rapidly, AR Sco’s white dwarf accelerates electrons up to almost the speed of light. As these high energy particles whip through space, they release radiation in a lighthouse-like beam which lashes across the face of the cool red dwarf star, causing the entire system to brighten and fade dramatically every 1.97 minutes. These powerful pulses include radiation at radio frequencies, which has never been detected before from a white dwarf system.

Lead researcher Tom Marsh of the University of Warwick’s Astrophysics Group commented: “AR Scorpii was discovered over 40 years ago, but its true nature was not suspected until we started observing it in 2015. We realised we were seeing something extraordinary within minutes of starting the observations.”

The observed properties of AR Sco are unique. They are also mysterious. The radiation across a broad range of frequencies is indicative of emission from electrons accelerated in magnetic fields, which can be explained by AR Sco’s spinning white dwarf. The source of the electrons themselves, however, is a major mystery — it is not clear whether it is associated with the white dwarf itself, or its cooler companion.

AR Scorpii was first observed in the early 1970s and regular fluctuations in brightness every 3.6 hours led it to be incorrectly classified as a lone variable star [4]. The true source of AR Scorpii’s varying luminosity was revealed thanks to the combined efforts of amateur and professional astronomers. Similar pulsing behaviour has been observed before, but from neutron stars — some of the densest celestial objects known in the Universe  — rather than white dwarfs.

Boris Gänsicke, co-author of the new study, also at the University of Warwick, concludes: "We've known pulsing neutron stars for nearly fifty years, and some theories predicted white dwarfs could show similar behaviour. It's very exciting that we have discovered such a system, and it has been a fantastic example of amateur astronomers and academics working together."


[1] The observations underlying this research were carried out on: ESO’s Very Large Telescope (VLT) located at Cerro Paranal, Chile; the William Herschel and Isaac Newton Telescopes of the Isaac Newton Group of telescopes sited on the Spanish island of La Palma in the Canaries; the Australia Telescope Compact Array at the Paul Wild Observatory, Narrabri, Australia; the NASA/ESA Hubble Space Telescope; and NASA's Swift satellite.

[2]  White dwarfs form late in the life cycles of stars with masses up to about eight times that of our Sun. After hydrogen fusion in a star’s core is exhausted, the internal changes are reflected in a dramatic expansion into a red giant, followed by a contraction accompanied by the star’s outer layers being blown off in great clouds of dust and gas. Left behind is a white dwarf, Earth-sized but 200 000 times more dense. A single spoonful of the matter making up a white dwarf would weigh about as much as an elephant here on Earth.

[3] This red dwarf is an M type star. M type stars are the most common class in the Harvard classification system, which uses single letters to group stars according their spectral characteristics. The famously awkward to remember sequence of classes runs: OBAFGKM, and is often remembered using the mnemonic Oh Be A Fine Girl/Guy, Kiss Me.

[4] A variable star is one whose brightness fluctuates as seen from Earth. The fluctuations may be due to the intrinsic properties of the star itself changing. For instance some stars noticeably expand and contract. It could also be due to another object regularly eclipsing the star. AR Scorpii was mistaken for a single variable star as the orbiting of two stars also results in regular fluctuations in observed brightness.

More Information

This research was presented in a paper entitled “A radio pulsing white dwarf binary star”, by T. Marsh et al., to appear in the journal Nature on 28 July 2016.

The team is composed of  T.R. Marsh (University of Warwick, Coventry, UK), B.T. Gänsicke (University of Warwick, Coventry, UK),  S. Hümmerich (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany; American Association of Variable Star Observers (AAVSO), USA) , F.-J. Hambsch (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany; American Association of Variable Star Observers (AAVSO), USA; Vereniging Voor Sterrenkunde (VVS), Belgium), K. Bernhard (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany; American Association of Variable Star Observers (AAVSO),USA), C.Lloyd (University of Sussex, UK), E. Breedt (University of Warwick, Coventry, UK), E.R. Stanway (University of Warwick, Coventry, UK), D.T. Steeghs (University of Warwick, Coventry, UK), S.G. Parsons (Universidad de Valparaiso, Chile), O. Toloza (University of Warwick, Coventry, UK), M.R. Schreiber (Universidad de Valparaiso, Chile), P.G. Jonker (Netherlands Institute for Space Research, The Netherlands; Radboud University Nijmegen, The Netherlands), J. van Roestel (Radboud University Nijmegen, The Netherlands), T. Kupfer (California Institute of Technology, USA), A.F. Pala (University of Warwick, Coventry, UK) , V.S. Dhillon (University of Sheffield, UK; Instituto de Astrofisica de Canarias, Spain; Universidad de La Laguna, Spain), L.K. Hardy (University of Warwick, Coventry, UK; University of Sheffield, UK), S.P. Littlefair (University of Sheffield, UK), A. Aungwerojwit (Naresuan University, Thailand),  S. Arjyotha (Chiang Rai Rajabhat University, Thailand), D. Koester (University of Kiel, Germany),  J.J. Bochinski (The Open University, UK), C.A. Haswell (The Open University, UK), P. Frank (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V., Germany) and P.J. Wheatley (University of Warwick, Coventry, UK).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.



Tom Marsh
Department of Physics, University of Warwick
Coventry, United Kingdom
Tel: +44 24765 74739

Boris Gänsicke
Department of Physics, University of Warwick
Coventry, United Kingdom
Tel: +44 24765 74741

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591

Source: ESO

An Extremely Weak Magnetic Field in a White Dwarf

 A team of astronomers reports the discovery of one of the very weakest magnetic fields ever securely detected in a white dwarf. The observation was made using the ISIS spectropolarimeter on the William Herschel Telescope (WHT), in just one hour of exposure time and using the red and the blue arms of the spectrograph. This is part of a large survey of bright white dwarfs to search for such weak magnetic fields.

The strength of the magnetic field found in LTT 16093 = WD2047+372 is only about 60 kilogauss (6 teslas), 2 or 3 orders of magnitude smaller than the typical fields of tens of megagauss found in a few percent of white dwarfs. The field was marginally detected in polarimetery, but clear Zeeman splitting into a triplet was present in the sharp core of Hydrogen alpha. This first detection using ISIS was confirmed by a spectropolarimetric observation a month later with the higher resolving power spectropolarimeter ESPaDOnS on the Canada-France-Hawaii Telescope.

First observation of Zeeman splitting in the core of Hydrogen alpha due to a field of about 60 kilogauss in WD2047+372. The ISIS observation is in blue, the ESPaDOnS observation (at higher resolving power) is shown in red. The circular polarisation spectrum is shown below the intensity profile, shifted up by +0.4 to facilitate comparison with the spectral line profile. The green lines bracketing the circular polarisation are ± one sigma. Figure extracted from Landstreet et al. (2016). Large format: PNG.

It is not yet understood how the magnetic fields of white dwarfs are formed, or how they evolve during white dwarf cooling. In spite of many detections of megagauss fields in white dwarfs, mostly very faint, little is known about the low-field regime, and very little modelling of the fields of individual white dwarfs is available. This current ISIS survey is intended to increase the very small sample and to provide data for detailed modelling, and ultimately to provide data to constrain field formation scenarios. 

It is found that ISIS is a very powerful tool for searches for such weak fields; it is able to detect fields of tens of kilogauss using either Hydrogen-alpha spectroscopy or spectropolarimetry of Hydrogen or Helium line wings, or both, in white dwarfs fainter than V = 15.

More information:

J. D. Landstreet, S. Bagnulo, A. Martin, and G. Valyavin, 2016, "Discovery of an extremely weak magnetic field in the white dwarf LTT 16093 WD2047+372", A&A, 591, A80 [ADS ]. 


(Public Relations Officer)

Tuesday, July 26, 2016

Ancient Eye in the Sky

Fig.1: Eye of Horus in pseudo color. Enlarged image to the right (field of view of 23 arcseconds x 19 arcseconds) show two arcs/rings with different colors. The inner arc has a reddish hue, while the outer arc has a blue tint. There are also the lensed images of the background galaxies which are originally the same galaxies as the inner and the outer arcs. The yellow-ish object at the center is a massive galaxy at z = 0.79 (distance 7 billion light years), which bends the light from the two background galaxies. (Credit: NAOJ)

Fig. 2: A schematic diagram showing the location of galaxies creating the gravitational lens effect of Eye of Horus. A galaxy at 7 billion light years from the Earth bends the light from the two galaxies behind it, one at 9 billion light years, and the other at 10.5 billion light years. (Credit: NAOJ)

In a rare discovery, the National Astronomical Observatory of Japan (NAOJ) together with an international team of researchers from the University of Tokyo’s Graduate School of Science and the Institute of Advanced Studies’ Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) advanced knowledge of how light from a distant galaxy can be bent greatly by the gravitational effect of a foreground galaxy. The effect is known as strong gravitational lensing.

Usually, multiple lensed images of a single background galaxy are seen. In theory, the foreground galaxy can lens multiple background galaxies at the same time. The data showed a rare gravitational lensing effect, which suggests lensing by a foreground galaxy of two background galaxies at different distances (Fig. 1). Such systems, called “Double Source Plane (DSP) Lenses,” offer unique opportunities to examine the fundamental physics of galaxies while extending our knowledge of cosmology.

Based on data from the Sloan Digital Sky Survey, the lensing galaxy has a spectroscopic redshift of z = 0.79 (or 7.0 billion light-years away, Note 1). Further observations of the lensed objects using the infrared-sensitive FIRE spectrometer on the Magellan Telescope confirmed the existence of two galaxies behind the lens—one at z = 1.30 and the other at z = 1.99 (9.0 and 10.5 billion light-years away, respectively). This is the first DSP lens for which the distances to all the three galaxies are known accurately, which enables more accurate understanding of the mass distribution of the foreground galaxy.

Researchers and undergraduates made the discovery while visually inspecting images at the NOAJ headquarters in Mitaka, Tokyo as part of a Subaru Telescope invitation for students in September 2015. The images were gathered from the Subaru Telescope’s Hyper Suprime-Cam (HSC), which is mounted in Hawaii. Japan is conducting a widespread survey with the HSC of large areas of the sky at an unprecedented depth as part of the Subaru Strategic Program.

“When I was looking at HSC images with the students, we came across a ring-like galaxy and we immediately recognized it as a strong lens system-lens,” said lead author of the paper Masayuki Tanaka. “The discovery would not have been possible without the large survey data to find such a rare object, as well as the deep, high quality images to detect light from distant objects.”

The rare finding has been dubbed the “Eye of Horus” because of its eye-like appearance (including bright knots, an arc, and a complete Einstein ring), which is due to an alignment of the central lens galaxy and both sources, and resembles the eye of Horus, the ancient Egyptian sky god. The survey expects to find 10 more systems of the same kind.

“With the HSC survey, we expect to find about 10 DSP lens systems, providing new insights in the physics of galaxies and the expansion of the universe over the last several billion years,” said Anupreeta More, a researcher at the Kavli IPMU and a co-author of the paper.

Researchers involved in the discovery include Kavli IPMU Project Researcher Anupreeta More and Project Researcher Alessandro Sonnenfeld as well as Associate Scientist Masamune Oguri, who is also affiliated to the University of Tokyo Graduate School of Science, Department of Physics.


1. Conversion of the distance from the redshift uses the following cosmological parameters - H0=67.3km/s/Mpc, Ωm=0.315, Λ=0.685, based on Planck 2013 Results.

For more information, please see the press release of the National Astronomical Observatory of Japan Hawaii Observation.

Paper Details:

The Astrophysical Journal Letters (ApJ, 826, L19)

A Spectroscopically Confirmed Double Source Plane Lens System in the Hyper Suprime-Cam Subaru Strategic Program

DOI: 10.3847/2041-8205/826/2/L19 (2016/7/25)

Authors and Affiliations:

Masayuki Tanaka, National Astronomical Observatory of Japan, Japan Kenneth Wong, National Astronomical Observatory of Japan, Japan Anupreeta More, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), University of Tokyo, Japan Arsha Dezuka, Department of Astronomy, University of Kyoto, Japan Eiichi Egami, Steward Observatory, University of Arizona, USA Masamune Oguri, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), University of Tokyo, Japan; Department of Physics, University of Tokyo, Japan; Research Center for the Early Universe, University of Tokyo, Japan Sherry H. Suyu, Max Planck Institute for Astrophysics, Germany; Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan Alessandro Sonnenfeld, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), Universi-ty of Tokyo, Japan Ryou Higuchi, Institute for Cosmic Ray Research, The University of Tokyo, Japan Yutaka Komiyama, National Astronomical Observatory of Japan, Japan Satoshi Miyazaki, National Astronomical Observatory of Japan, Japan; SOKENDAI (The Graduate University for Ad-vanced Studies), Japan Masafusa Onoue, SOKENDAI (The Graduate University for Advanced Studies), Japan; National Astronomical Obser-vatory of Japan, Japan Shuri Oyamada, Japan Women’s University, Japan Yousuke Utsumi, Hiroshima Astrophysical Science Center, Hiroshima University, Japan.

Paper abstract:

The Astrophysical Journal Letters Pre-print


John Amari
Press Office
Kavli Institute for the Physics and Mathematics of the Universe
Institutes for Advanced Study
The University of Tokyo
TEL: +81-04-7136-5980

The University of Tokyo, Institutes for Advanced Study

Monday, July 25, 2016

Astronomers Discover Dizzying Spin of the Milky Way Galaxy’s “Halo”

Astronomers at the University of Michigan’s College of Literature, Science, and the Arts (LSA) discovered for the first time that the hot gas in the halo of the Milky Way galaxy is spinning in the same direction and at comparable speed as the galaxy's disk, which contains our stars, planets, gas, and dust. This new knowledge sheds light on how individual atoms have assembled into stars, planets, and galaxies like our own, and what the future holds for these galaxies.

Our Milky Way galaxy and its small companions are surrounded by a giant halo of million-degree gas (seen in blue in this artists' rendition) that is only visible to X-ray telescopes in space. University of Michigan astronomers discovered that this massive hot halo spins in the same direction as the Milky Way disk and at a comparable speed. Credits: NASA/CXC/M.Weiss/Ohio State/A Gupta et al

“This flies in the face of expectations,” says Edmund Hodges-Kluck, assistant research scientist. 

“People just assumed that the disk of the Milky Way spins while this enormous reservoir of hot gas is stationary – but that is wrong. This hot gas reservoir is rotating as well, just not quite as fast as the disk.”

The new NASA-funded research using the archival data obtained by XMM-Newton, a European Space Agency telescope, was recently published in the Astrophysical Journal. The study focuses on our galaxy’s hot gaseous halo, which is several times larger than the Milky Way disk and composed of ionized plasma.

Because motion produces a shift in the wavelength of light, the U-M researchers measured such shifts around the sky using lines of very hot oxygen. What they found was groundbreaking: The line shifts measured by the researchers show that the galaxy’s  halo spins in the same direction as the disk of the Milky Way and at a similar speed—about 400,000 mph for the halo versus 540,000 mph for the disk.

“The rotation of the hot halo is an incredible clue to how the Milky Way formed,” said Hodges Kluck. “It tells us that this hot atmosphere is the original source of a lot of the matter in the disk.”

Scientists have long puzzled over why almost all galaxies, including the Milky Way, seem to lack most of the matter that they otherwise would expect to find. Astronomers believe that about 80% of the matter in the universe is the mysterious “dark matter” that, so far, can only be detected by its gravitational pull. But even most of the remaining 20% of “normal” matter is missing from galaxy disks. More recently, some of the “missing” matter has been discovered in the halo. The U-M researchers say that learning about the direction and speed of the spinning halo can help us learn both how the material got there in the first place, and the rate at which we expect the matter to settle into the galaxy.

“Now that we know about the rotation, theorists will begin to use this to learn how our Milky Way galaxy formed – and its eventual destiny,” says Joel Bregman, a U-M LSA professor of astronomy.

“We can use this discovery to learn so much more – the rotation of this hot halo will be a big topic of future X-ray spectrographs,” Bregman says.

For more information, please visit:

By Felicia Chou
NASA Headquarters, Washington, D.C.

Editor: Ashley Morrow

Source: NASA/Galaxies

Saturday, July 23, 2016

X Marks the Spot for Milky Way Formation

Researchers used data from NASA's Wide-field Infrared Survey Explorer (WISE) mission to highlight the X-shaped structure in the bulge of the Milky Way. Credit: NASA/JPL-Caltech/D.Lang.   › Full image and caption

To reveal the X shape in the Milky Way's central bulge, researchers took WISE observations and subtracted a model of how stars would be distributed in a symmetrical bulge. Credit: NASA/JPL-Caltech/D.Lang.  › Larger image

A new understanding of our galaxy's structure began in an unlikely way: on Twitter. A research effort sparked by tweets led scientists to confirm that the Milky Way's central bulge of stars forms an "X" shape. The newly published study uses data from NASA's Wide-field Infrared Survey Explorer (WISE) mission.

The unconventional collaboration started in May 2015 when Dustin Lang, an astronomer at the Dunlap Institute of the University of Toronto, posted galaxy maps to Twitter, using data from WISE's two infrared surveys of the entire sky in 2010. Infrared light allows astronomers to see the structures of galaxies in spite of dust, which blocks crucial details in visible light. Lang was using the WISE data in a project to map the web of galaxies far outside our Milky Way, which he made available through an interactive website.

But it was the Milky Way's appearance in the tweets that got the attention of other astronomers. Some chimed in about the appearance of the bulge, a football-shaped central structure that is three-dimensional compared to the galaxy's flat disk. Within the bulge, the WISE data seemed to show a surprising X structure, which had never been as clearly demonstrated before in the Milky Way. Melissa Ness, a postdoctoral researcher at the Max Planck Institute for Astronomy in Heidelberg, Germany, recognized the significance of the X shape, and contacted Lang.

The two met a few weeks later at a conference in Michigan, and decided to collaborate on analyzing the bulge using Lang's WISE maps. Their work resulted in a new study published in the Astronomical Journal confirming an X-shaped distribution of stars in the bulge.

"The bulge is a key signature of formation of the Milky Way," said Ness, the study's lead author. "If we understand the bulge we will understand the key processes that have formed and shaped our galaxy."

The Milky Way is an example of a disk galaxy -- a collection of stars and gas in a rotating disk. In these kinds of galaxies, when the thin disk of gas and stars is sufficiently massive, a "stellar bar" may form, consisting of stars moving in a box-shaped orbit around the center. Our own Milky Way has a bar, as do nearly two-thirds of all nearby disk galaxies.

Over time, the bar may become unstable and buckle in the center. The resulting "bulge" would contain stars that move around the galactic center, perpendicular to the plane of the galaxy, and in and out radially. When viewed from the side, the stars would appear distributed in a box-like or peanut-like shape as they orbit. Within that structure, according to the new study, there is a giant X-shaped structure of stars crossing at the center of the galaxy.

A bulge can also form when galaxies merge, but the Milky Way has not merged with any large galaxy in at least 9 billion years.

"We see the boxy shape, and the X within it, clearly in the WISE image, which demonstrates that internal formation processes have driven the bulge formation," Ness said. "This also reinforces the idea that our galaxy has led a fairly quiet life, without major merging events since the bulge was formed, as this shape would have been disrupted if we had any major interactions with other galaxies."

The Milky Way's X-shaped bulge had been reported in previous studies. Images from the NASA Cosmic Background Explorer (COBE) satellite's Diffuse Infrared Background Experiment suggested a boxy structure for the bulge. In 2013, scientists at the Max Planck Institute for Extraterrestrial Physics published 3-D maps of the Milky Way that also included an X-shaped bulge, but these studies did not show an actual image of the X shape. Ness and Lang's study uses infrared data to show the clearest indication yet of the X shape.

Additional research is ongoing to analyze the dynamics and properties of the stars in the Milky Way's bulge.
Collaborating on this study was unusual for Lang -- his expertise is in using computer science to understand large-scale astronomical phenomena, not the dynamics and structure of the Milky Way. But he was able to enter a new field of research because he posted maps to social media and used openly accessible WISE data.

"To me, this study is an example of the interesting, serendipitous science that can come from large data sets that are publicly available," he said. "I'm very pleased to see my WISE sky maps being used to answer questions that I didn't even know existed."

NASA's Jet Propulsion Laboratory, Pasadena, California, manages and operates WISE for NASA's Science Mission Directorate in Washington. The spacecraft was put into hibernation mode in 2011, after it scanned the entire sky twice, thereby completing its main objectives. In September 2013, WISE was reactivated, renamed NEOWISE and assigned a new mission to assist NASA's efforts to identify potentially hazardous near-Earth objects.

For more information on WISE, visit:

News Media Contact

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.

Friday, July 22, 2016

Space... the final frontier

Abell S1063, the final frontier

PR Image heic1615b
Parallel field of Abell S1063 

PR Image heic1615c
Wide-field image of Abell S1063 (ground-based image)


Zoom into Abell S1063
Zoom into Abell S1063

Pan across the galaxy cluster Abell S1063

Pan across the galaxy cluster Abell S1063

Abell S1063 in fulldome
Abell S1063 in fulldome

Fifty years ago Captain Kirk and the crew of the starship Enterprise began their journey into space — the final frontier. Now, as the newest Star Trek film hits cinemas, the NASA/ESA Hubble space telescope is also exploring new frontiers, observing distant galaxies in the galaxy cluster Abell S1063 as part of the Frontier Fields programme.

Space... the final frontier. These are the stories of the Hubble Space Telescope. Its continuing mission, to explore strange new worlds and to boldly look where no telescope has looked before.

The newest target of Hubble’s mission is the distant galaxy cluster Abell S1063, potentially home to billions of strange new worlds.

This view of the cluster, which can be seen in the centre of the image, shows it as it was four billion years ago. But Abell S1063 allows us to explore a time even earlier than this, where no telescope has really looked before. The huge mass of the cluster distorts and magnifies the light from galaxies that lie behind it due to an effect called gravitational lensing. This allows Hubble to see galaxies that would otherwise be too faint to observe and makes it possible to search for, and study, the very first generation of galaxies in the Universe. “Fascinating”, as a famous Vulcan might say.

The first results from the data on Abell S1063 promise some remarkable new discoveries. Already, a galaxy has been found that is observed as it was just a billion years after the Big Bang.

Astronomers have also identified sixteen background galaxies whose light has been distorted by the cluster, causing multiple images of them to appear on the sky. This will help astronomers to improve their models of the distribution of both ordinary and dark matter in the galaxy cluster, as it is the gravity from these that causes the distorting effects. These models are key to understanding the mysterious nature of dark matter.

Abell S1063 is not alone in its ability to bend light from background galaxies, nor is it the only one of these huge cosmic lenses to be studied using Hubble. Three other clusters have already been observed as part of the Frontier Fields programme, and two more will be observed over the next few years, giving astronomers a remarkable picture of how they work and what lies both within and beyond them [1].

Data gathered from the previous galaxy clusters were studied by teams all over the world, enabling them to make important discoveries, among them galaxies that existed only hundreds of million years after the Big Bang (heic1523) and the first predicted appearance of a gravitationally lensed supernova (heic1525).

Such an extensive international collaboration would have made Gene Roddenberry, the father of Star Trek, proud. In the fictional world Roddenberry created, a diverse crew work together to peacefully explore the Universe. This dream is partially achieved by the Hubble programme in which the European Space Agency (ESA), supported by 22 member states, and NASA collaborate to operate one of the most sophisticated scientific instruments in the world. Not to mention the scores of other international science teams that cross state, country and continental borders to achieve their scientific aims.


[1] The Hubble Frontier Fields is a three-year, 840-orbit programme which will yield the deepest views of the Universe to date, combining the power of Hubble with the gravitational amplification of light around six different galaxy clusters to explore more distant regions of space than could otherwise be seen.

More Information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
Image credit: NASA, ESA, and J. Lotz (STScI)



Mathias Jäger
ESA/Hubble Public Information Officer
Garching bei München, Germany
Tel: +49 176 62397500

A galaxy fit to burst

Credit: ESA/Hubble & NASA
Acknowledgement: Judy Schmidt (Geckzilla)

This NASA/ESA Hubble Space Telescope image reveals the vibrant core of the galaxy NGC 3125. Discovered by John Herschel in 1835, NGC 3125 is a great example of a starburst galaxy — a galaxy in which unusually high numbers of new stars are forming, springing to life within intensely hot clouds of gas.
Located approximately 50 million light-years away in the constellation of Antlia (The Air Pump), NGC 3125 is similar to, but unfathomably brighter and more energetic than, one of the Magellanic Clouds.    Spanning 15 000 light-years, the galaxy displays massive and violent bursts of star formation, as shown by the hot, young, and blue stars scattered throughout the galaxy’s rose-tinted core. Some of these clumps of stars are notable — one of the most extreme Wolf–Rayet star clusters in the local Universe, NGC 3125-A1, resides within NGC 3125.

Despite their appearance, the fuzzy white blobs dotted around the edge of this galaxy are not stars, but globular clusters. Found within a galaxy’s halo, globular clusters are ancient collections of hundreds of thousands of stars. They orbit around galactic centres like satellites — the Milky Way, for example, hosts over 150 of them.

Thursday, July 21, 2016

1.2 Million Galaxies in 3D

This is one slice through the map of the large-scale structure of the Universe from the Sloan Digital Sky Survey and its Baryon Oscillation Spectroscopic Survey. Each dot in this picture indicates the position of a galaxy 6 billion years into the past. The image covers about 1/20th of the sky, a slice of the Universe 6 billion light-years wide, 4.5 billion light-years high, and 500 million light-years thick. Colour indicates distance from Earth, ranging from yellow on the near side of the slice to purple on the far side. Galaxies are highly clustered, revealing superclusters and voids whose presence is seeded in the first fraction of a second after the Big Bang. This image contains 48,741 galaxies, about 3% of the full survey dataset. Grey patches are small regions without survey data. Image credit: Daniel Eisenstein and SDSS-III. Hi-res image

This is a section of the three-dimensional map constructed by BOSS. The rectangle on the left shows a cut-out of 1000 sq. degrees in the sky containing nearly 120,000 galaxies, or roughly 10% of the total survey. The spectroscopic measurements of each galaxy - every dot in that cut-out - transform the two-dimensional picture into a three-dimensional map, extending our view out to 7 billion years in the past. The brighter regions in this map correspond to the regions of the Universe with more galaxies and therefore more dark matter. The extra matter in those regions creates an excess gravitational pull, which makes the map a test of Einstein’s theory of gravity. © Jeremy Tinker und SDSS-III. Hi-res image

What are the properties of Dark Energy? This question is one of the most intriguing ones in astronomy and scientists are one step closer in answering this question with the largest three-dimensional map of the universe so far: This map contains 1.2 million galaxies in a volume spanning 650 cubic billion light years. Hundreds of scientists from the Sloan Digital Sky Survey III (SDSS-III) – including researchers at the Max Planck Institutes for Extraterrestrial Physics and for Astrophyics - used this map to make one of the most precise measurements yet of dark energy. They found excellent agreement with the standard cosmological model and confirmed that dark energy is highly consistent with a cosmological constant.

"We have spent a decade collecting measurements of 1.2 million galaxies over one quarter of the sky to map out the structure of the Universe over a volume of 650 cubic billion light years,” says Jeremy Tinker of New York University, a co-leader of the scientific team that led this effort. Hundreds of scientists are part of the Sloan Digital Sky Survey III (SDSS-III) team.

These new measurements were carried out by the Baryon Oscillation Spectroscopic Survey (BOSS) programme of SDSS-III. Shaped by a continuous tug-of-war between dark matter and dark energy, the map revealed by BOSS allows astronomers to measure the expansion rate of the Universe by determining the size of the so-called baryonic acoustic oscillations (BAO) in the three-dimensional distribution of galaxies.

Pressure waves travelled through the young Universe up to when it was only 400,000 years old at which point they became frozen in the matter distribution of the Universe. The end result is that galaxies are preferentially separated by a characteristic distance, which astronomers call the BAO scale. The primordial size of the BAO scale is exquisitely determined from observations of the cosmic microwave background.

Ariel Sanchez of the Max-Planck Institute of Extraterrestrial Physics (MPE) led the effort to estimate the exact amount of dark matter and dark energy based on the BOSS data and explains: "Measuring the acoustic scale across cosmic history gives a direct ruler with which to measure the Universe’s expansion rate.  With BOSS, we have traced the BAO’s subtle imprint on the distribution of galaxies spanning a range of time from 2 to 7 billion years ago."

For the very precise measurements, however, the data had to be painstakingly analysed. Especially the determination of distances to the galaxies posed a big challenge. This is inferred from the galaxy spectra, which show that a galaxy’s light is shifted to the red part of the spectrum because it moves away from us. This so-called redshift is correlated with a galaxy’s distance: The farther a galaxy is away from us, the faster it moves.

“However, galaxies also have peculiar motions and the peculiar velocity component along the line-of-sight leads to the so-called redshift space distortion,” explains Shun Saito from the Max Planck Institute for Astrophysics (MPA), who contributed sophisticated models to the BOSS data analysis. “This makes the galaxy distribution anisotropic because the line-of-sight direction is now special – only along this direction the distance is measured through a redshift, which is contaminated by peculiar velocity. In other words, the characteristic anisotropic pattern allows us to measure the peculiar velocity of galaxies – and because the motion of galaxies is governed by gravity, we can use this measurement to constrain to what level Einstein’s general relativity is correct at cosmological scales. In order to properly interpret the data, we have developed a refined model to describe the galaxy distribution.”

Another approach, used by a junior MPE researcher for his PhD thesis, is to use the angular positions of galaxies on the sky instead of physical 3D positions. “This method uses only observables,” explains Salvador Salazar. “We make no prior assumptions about the cosmological model.”

Around the world, other groups all used slightly different models and methodologies to analyse the huge BOSS data set. “We now have seven measurements, which are slightly different, but highly correlated,” Ariel Sanchez points out. “To extract the most information about the cosmological parameters, we had to find not only the best methods and models for data analysis but also the optimal combination of these measurements.”

This analysis has now born fruit: the BOSS data show that dark energy, which is driving the cosmological expansion, is consistent with a cosmological constant within an error of only 5%. This constant, called Lambda, was introduced by Albert Einstein to counter the attractive force of matter, i.e. it has a repellent effect. Moreover, all results are fully consistent with the standard cosmological model, giving further strength to this still relatively young theory.

In particular, the map also reveals the distinctive signature of the coherent movement of galaxies toward regions of the Universe with more matter, due to the attractive force of gravity. Crucially, the observed amount of infall matches well to the predictions of general relativity. This supports the idea that the acceleration of the expansion rate is driven by a phenomenon at the largest cosmic scales, such as dark energy, rather than a breakdown of our gravitational theory.


Saito, Shun
Phone: 2225

Hämmerle, Hannelore
Hämmerle, Hannelore
Press officer
Phone: 3980

Original Publication 

1. Jan Niklas Grieb, Ariel G. Sánchez, Salvador Salazar-Albornoz et al. (the BOSS collaboration)
The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Cosmological implications of the Fourier space wedges of the final sample
submitted to MNRAS

2. Salvador Salazar-Albornoz, Ariel G. Sanchez, Jan Niklas Grieb et al.
The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Angular clustering tomography and its cosmological implications
submitted to MNRAS

3. Ariel G. Sanchez, Jan Niklas Grieb, Salvador Salazar-Albornoz et al.
The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: combining correlated Gaussian posterior distributions
submitted to MNRAS

4. Ariel G. Sanchez, Roman Scoccimarro, Martin Crocce et al.
The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological implications of the configuration-space clustering wedges
submitted to MNRAS

5. Florian Beutler, Hee-Jong Seo, Shun Saito et al.
The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Anisotropic galaxy clustering The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in Fourier-space
submitted to MNRAS

Wednesday, July 20, 2016

NASA's Hubble Telescope Makes First Atmospheric Study of Earth-Sized Exoplanets

Artist's View of Planets Transiting Red Dwarf Star in TRAPPIST-1 System  
Illustration Credit: NASA, ESA, and G. Bacon (STScI)
Science Credit: NASA, ESA, and J. de Wit (MIT)

Using NASA's Hubble Space Telescope, astronomers have conducted the first search for atmospheres around temperate, Earth-sized planets beyond our solar system and found indications that increase the chances of habitability on two exoplanets.

Specifically, they discovered that the exoplanets TRAPPIST-1b and TRAPPIST-1c, approximately 40 light-years away, are unlikely to have puffy, hydrogen-dominated atmospheres usually found on gaseous worlds.

"The lack of a smothering hydrogen-helium envelope increases the chances for habitability on these planets," said team member Nikole Lewis of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. "If they had a significant hydrogen-helium envelope, there is no chance that either one of them could potentially support life because the dense atmosphere would act like a greenhouse."

Julien de Wit of the Massachusetts Institute of Technology in Cambridge, Massachusetts, led a team of scientists to observe the planets in near-infrared light using Hubble's Wide Field Camera 3. They used spectroscopy to decode the light and reveal clues to the chemical makeup of an atmosphere. While the content of the atmospheres is unknown and will have to await further observations, the low concentration of hydrogen and helium has scientists excited about the implications.

"These initial Hubble observations are a promising first step in learning more about these nearby worlds, whether they could be rocky like Earth, and whether they could sustain life," said Geoff Yoder, acting associate administrator for NASA's Science Mission Directorate in Washington, D.C. "This is an exciting time for NASA and exoplanet research."

The planets orbit a red dwarf star at least 500 million years old, in the constellation of Aquarius. They were discovered in late 2015 through a series of observations by the TRAnsiting Planets and PlanetesImals Small Telescope (TRAPPIST), a Belgian robotic telescope located at the European Southern Observatory’s (ESO’s) La Silla Observatory in Chile.

TRAPPIST-1b completes a circuit around its red dwarf star in 1.5 days and TRAPPIST-1c in 2.4 days. The planets are between 20 and 100 times closer to their star than Earth is to the sun. Because their star is so much fainter than our sun, researchers think that at least one of the planets, or possibly both, may be within the star's habitable zone, where moderate temperatures could allow for liquid water to pool.

On May 4, astronomers took advantage of a rare simultaneous transit, when both planets crossed the face of their star within minutes of each other, to measure starlight as it filtered through any existing atmosphere. This double-transit, which occurs only every two years, provided a combined signal that offered simultaneous indicators of the atmospheric characteristics of the planets.

The researchers hope to use Hubble to conduct follow-up observations to search for thinner atmospheres, composed of elements heavier than hydrogen, like those of Earth and Venus.

"With more data, we could perhaps detect methane or see water features in the atmospheres, which would give us estimates of the depth of the atmospheres," said Hannah Wakeford, the paper's second author, at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Observations from future telescopes, including NASA's James Webb Space Telescope, will help determine the full composition of these atmospheres and hunt for potential biosignatures, such as carbon dioxide and ozone, in addition to water vapor and methane. Webb also will analyze a planet's temperature and surface pressure — key factors in assessing its habitability.

These planets are the first Earth-sized worlds found in the Search for habitable Planets EClipsing ULtra-cOOl Stars (SPECULOOS) survey, which will search more than 1,000 nearby red dwarf stars for Earth-sized worlds. So far, the survey has analyzed only 15 of those stars.

"These Earth-sized planets are the first worlds that astronomers can study in detail with current and planned telescopes to determine whether they are suitable for life," said de Wit. "Hubble has the ability to play the central atmospheric pre-screening role to tell astronomers which of these Earth-sized planets are prime candidates for more detailed study with the Webb telescope."

The results of the study appear in the July 20 issue of the journal Nature.


Felicia Chou
NASA Headquarters, Washington, D.C

Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4493 / 410-338-4514 /

Julien de Wit
Massachusetts Institute of Technology, Cambridge, Massachusetts

Hannah Wakeford
NASA Goddard Spaceflight Center, Greenbelt, Maryland

Nikole Lewis
Space Telescope Science Institute, Baltimore, Maryland

Source: HubbleSite