Friday, January 19, 2018

NASA Team Studies Middle-aged Sun by Tracking Motion of Mercury

Mercury’s proximity to the Sun and small size make it exquisitely sensitive to the dynamics of the Sun and its gravitational pull. 
Credits: NASA/SDO

Like the waistband of a couch potato in midlife, the orbits of planets in our solar system are expanding. It happens because the Sun’s gravitational grip gradually weakens as our star ages and loses mass. Now, a team of NASA and MIT scientists has indirectly measured this mass loss and other solar parameters by looking at changes in Mercury’s orbit.

The new values improve upon earlier predictions by reducing the amount of uncertainty. That’s especially important for the rate of solar mass loss, because it’s related to the stability of G, the gravitational constant. Although G is considered a fixed number, whether it’s really constant is still a fundamental question in physics.

“Mercury is the perfect test object for these experiments because it is so sensitive to the gravitational effect and activity of the Sun,” said Antonio Genova, the lead author of the study published in Nature Communications and a Massachusetts Institute of Technology researcher working at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

The study began by improving Mercury’s charted ephemeris — the road map of the planet’s position in our sky over time. For that, the team drew on radio tracking data that monitored the location of NASA’s MESSENGER spacecraft while the mission was active. Short for Mercury Surface, Space Environment, Geochemistry, and Ranging, the robotic spacecraft made three flybys of Mercury in 2008 and 2009 and orbited the planet from March 2011 through April 2015. The scientists worked backward, analyzing subtle changes in Mercury’s motion as a way of learning about the Sun and how its physical parameters influence the planet’s orbit.

NASA and MIT scientists analyzed subtle changes in Mercury’s motion to learn about the Sun and how its dynamics influence the planet’s orbit. The position of Mercury over time was determined from radio tracking data obtained while NASA’s MESSENGER mission was active. Credits: NASA's Goddard Space Flight Center

For centuries, scientists have studied Mercury’s motion, paying particular attention to its perihelion, or the closest point to the Sun during its orbit. Observations long ago revealed that the perihelion shifts over time, called precession. Although the gravitational tugs of other planets account for most of Mercury’s precession, they don’t account for all of it.

The second-largest contribution comes from the warping of space-time around the Sun because of the star’s own gravity, which is covered by Einstein’s theory of general relativity. The success of general relativity in explaining most of Mercury’s remaining precession helped persuade scientists that Einstein’s theory was right.

Other, much smaller contributions to Mercury’s precession, are attributed to the Sun’s interior structure and dynamics. One of those is the Sun’s oblateness, a measure of how much it bulges at the middle — its own version of a “spare tire” around the waist — rather than being a perfect sphere. The researchers obtained an improved estimate of oblateness that is consistent with other types of studies.
The researchers were able to separate some of the solar parameters from the relativistic effects, something not accomplished by earlier studies that relied on ephemeris data. The team developed a novel technique that simultaneously estimated and integrated the orbits of both MESSENGER and Mercury, leading to a comprehensive solution that includes quantities related to the evolution of Sun’s interior and to relativistic effects.

“We’re addressing long-standing and very important questions both in fundamental physics and solar science by using a planetary-science approach,” said Goddard geophysicist Erwan Mazarico. “By coming at these problems from a different perspective, we can gain more confidence in the numbers, and we can learn more about the interplay between the Sun and the planets.”

The team’s new estimate of the rate of solar mass loss represents one of the first times this value has been constrained based on observations rather than theoretical calculations. From the theoretical work, scientists previously predicted a loss of one-tenth of a percent of the Sun’s mass over 10 billion years; that’s enough to reduce the star’s gravitational pull and allow the orbits of the planets to spread by about half an inch, or 1.5 centimeters, per year per AU (an AU, or astronomical unit, is the distance between Earth and the Sun: about 93 million miles).

The new value is slightly lower than earlier predictions but has less uncertainty. That made it possible for the team to improve the stability of G by a factor of 10, compared to values derived from studies of the motion of the Moon.

“The study demonstrates how making measurements of planetary orbit changes throughout the solar system opens the possibility of future discoveries about the nature of the Sun and planets, and indeed, about the basic workings of the universe,” said co-author Maria Zuber, vice president for research at MIT.

By Elizabeth Zubritsky
NASA's Goddard Space Flight Center, Greenbelt, Md.

Editor: Rob Garner

Thursday, January 18, 2018

Odd Behaviour of Star Reveals Lonely Black Hole Hiding in Giant Star Cluster

Hubble image of the globular star cluster NGC 3201 (annotated)

Hubble image of the globular star cluster NGC 3201 (annotated)

Wide-field image of the sky around the globular star cluster NGC 3201 

The globular cluster NGC 3201

Hubble image of the globular star cluster NGC 3201 (unannotated)

The globular cluster NGC 3201 in the constellation of Vela (The Sails)


ESOcast 146 Light: Odd Behaviour of Star Reveals Black Hole in Giant Star Cluster (4K UHD)
ESOcast 146 Light: Odd Behaviour of Star Reveals Black Hole in Giant Star Cluster (4K UHD)

Zooming in on the globular star cluster NGC 3201
Zooming in on the globular star cluster NGC 3201

Artist’s impression video of the black hole binary system in NGC 3201
Artist’s impression video of the black hole binary system in NGC 3201

Artist’s impression video of the black hole binary system in NGC 3201
Artist’s impression video of the black hole binary system in NGC 3201

Artist’s impression video of the black hole binary system in NGC 3201
Artist’s impression video of the black hole binary system in NGC 3201

Astronomers using ESO’s MUSE instrument on the Very Large Telescope in Chile have discovered a star in the cluster NGC 3201 that is behaving very strangely. It appears to be orbiting an invisible black hole with about four times the mass of the Sun — the first such inactive stellar-mass black hole found in a globular cluster and the first found by directly detecting its gravitational pull. This important discovery impacts on our understanding of the formation of these star clusters, black holes, and the origins of gravitational wave events.

Globular star clusters are huge spheres of tens of thousands of stars that orbit most galaxies. They are among the oldest known stellar systems in the Universe and date back to near the beginning of galaxy growth and evolution. More than 150 are currently known to belong to the Milky Way.

One particular cluster, called NGC 3201 and situated in the southern constellation of Vela (The Sails), has now been studied using the MUSE instrument on ESO’s Very Large Telescope in Chile. An international team of astronomers has found that one of the stars [1] in NGC 3201 is behaving very oddly — it is being flung backwards and forwards at speeds of several hundred thousand kilometres per hour, with the pattern repeating every 167 days [2].

Lead author Benjamin Giesers (Georg-August-Universität Göttingen, Germany) was intrigued by the star’s behaviour: “It was orbiting something that was completely invisible, which had a mass more than four times the Sun — this could only be a black hole! The first one found in a globular cluster by directly observing its gravitational pull.

The relationship between black holes and globular clusters is an important but mysterious one. Because of their large masses and great ages, these clusters are thought to have produced a large number of stellar-mass black holes — created as massive stars within them exploded and collapsed over the long lifetime of the cluster [3][4].

ESO’s MUSE instrument provides astronomers with a unique ability to measure the motions of thousands of far away stars at the same time. With this new finding, the team have for the first time been able to detect an inactive black hole at the heart of a globular cluster — one that is not currently swallowing matter and is not surrounded by a glowing disc of gas. They could estimate the black hole’s mass through the movements of a star caught up in its enormous gravitational pull [5].

From its observed properties the star was determined to be about 0.8 times the mass of our Sun, and the mass of its mysterious counterpart was calculated at around 4.36 times the Sun’s mass — almost certainly a black hole [6].
Recent detections of radio and X-ray sources in globular clusters, as well as the 2016 detection of gravitational-wave signals produced by the merging of two stellar-mass black holes, suggest that these relatively small black holes may be more common in globular clusters than previously thought.

Giesers concludes: “Until recently, it was assumed that almost all black holes would disappear from globular clusters after a short time and that systems like this should not even exist! But clearly this is not the case — our discovery is the first direct detection of the gravitational effects of a stellar-mass black hole in a globular cluster. This finding helps in understanding the formation of globular clusters and the evolution of black holes and binary systems — vital in the context of understanding gravitational wave sources.”


[1] The star found is a main sequence turn-off star, meaning it is at the end of the main sequence phase of its life. Having exhausted its primary hydrogen fuel supply it is now on the way to becoming a red giant.

[2] A large survey of 25 globular clusters around the Milky Way is currently being conducted using ESO’s MUSE instrument with the support of the MUSE consortium. It will provide astronomers with the spectra of 600 to 27 000 stars in each cluster. The study includes analysis of the “radial velocity” of individual stars — the speed at which they move away from and toward the Earth, along the line of sight of the observer. With radial velocity measurements the orbits of stars can be determined, as well as the properties of any massive object they may be orbiting.

[3] In the absence of continuous star formation, as is the case for globular clusters, stellar-mass black holes soon become the most massive objects present. Generally, stellar-mass black holes in globular clusters are about four times as massive as the surrounding low-mass stars. Recent theories have concluded that black holes form a dense nucleus within the cluster, which then becomes detached from the rest of the globular material. Movements at the centre of the cluster are then thought to eject the majority of black holes, meaning only a few would survive after a billion years.

[4] Stellar-mass black holes — or collapsars — are formed when massive stars die, collapsing under their own gravity and exploding as powerful hypernovae. Left behind is a black hole with most of the mass of the former star, which can range from a few times the mass of our Sun to several tens of times as massive.

[5] As no light is able to escape black holes because of their tremendous gravity, the primary method of detecting them is through observations of radio or X-ray emissions coming from hot material around them. But when a black hole is not interacting with hot matter and so not accumulating mass or emitting radiation, as in this case, the black hole is “inactive” and invisible, so another method of detection is required.

[6] Because the non-luminous object in this binary system cannot be directly observed there are alternative, although much less persuasive, explanations for what it could be. It is perhaps a triple star system made up of two tightly bound neutron stars, with the observed star orbiting around them. This scenario would require each tightly bound star to be at least twice the mass of our Sun, a binary system that has never been observed before.

More Information

This research was presented in a paper entitled “A detached stellar-mass black hole candidate in the globular cluster NGC 3201”, by B. Giesers et al., to appear in the journal Monthly Notices of the Royal Astronomical Society.

The team is composed of Benjamin Giesers (Georg-August-Universität Göttingen, Germany), Stefan Dreizler (Georg-August-Universität Göttingen, Germany), Tim-Oliver Husser (Georg-August-Universität Göttingen, Germany), Sebastian Kamann (Georg-August-Universität Göttingen, Germany; Liverpool John Moores University, Liverpool, United Kingdom), Guillem Anglada Escudé (Queen Mary University of London, United Kingdom), Jarle Brinchmann (Leiden Observatory, Leiden University, Leiden, The Netherlands; Universidade do Porto, CAUP, Porto, Portugal), C. Marcella Carollo (Swiss Federal Institute of Technology, ETH, Zurich, Switzerland) Martin M. Roth (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Peter M. Weilbacher (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany) and Lutz Wisotzki (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany).

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 and by Australia as a strategic partner. 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 and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.



Benjamin Giesers
Georg-August-Universität Göttingen
Göttigen, Germany

Stefan Dreizler
Georg-August-Universität Göttingen
Göttigen, Germany

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

 Source: ESO

Wednesday, January 17, 2018

NASA Space Telescopes Provide a 3D Journey Through the Orion Nebula

Visible and Infrared Visualization of the Orion Nebula
Credit: Image: NASA, ESA, F. Summers, G. Bacon, Z. Levay, J. DePasquale, L. Hustak, L. Frattare, M. Robberto and M. Gennaro (STScI), and R. Hurt (Caltech/IPAC).   Release Images - Release Videos

Astronomers and visualization specialists from NASA’s Universe of Learning program have combined visible and infrared vision of the Hubble and Spitzer space telescopes to create an unprecedented, three-dimensional, fly-through view of the picturesque Orion Nebula, a nearby star-forming region.

Viewers experience this nearby stellar nursery “close up and personally” as the new digital visualization ferries them among newborn stars, glowing clouds heated by intense radiation, and tadpole-shaped gaseous envelopes surrounding protoplanetary disks.

Using actual scientific imagery and other data, combined with Hollywood techniques, a team at the Space Telescope Science Institute in Baltimore, Maryland, and the Caltech/IPAC in Pasadena, California, has created the best and most detailed multi-wavelength visualization yet of this photogenic nebula. The fly-through enables people to experience and learn about the universe in an exciting new way.

The three-minute movie, which shows the Orion Nebula in both visible and infrared light, was released to the public today. It is available to planetariums and other centers of informal learning worldwide to help audiences explore fundamental questions in science such as, “How did we get here?”

“Being able to fly through the nebula’s tapestry in three dimensions gives people a much better sense of what the universe is really like,” explained the Space Telescope Science Institute’s visualization scientist Frank Summers, who led the team that developed the movie. “By adding depth and structure to the amazing images, this fly-through helps elucidate the universe for the public, both educating and inspiring,” added Summers.

“Looking at the universe in infrared light gives striking context for the more familiar visible-light views. This movie provides a uniquely immersive chance to see how new features appear as we shift to wavelengths of light normally invisible to our eyes,” said Robert Hurt, lead visualization scientist at IPAC.

One of the sky’s brightest nebulas, the Orion Nebula is visible to the naked eye. It appears as the middle “star” in the sword of the constellation Orion, the Hunter, and is located about 1,350 light-years away. At only 2 million years old, the nebula is an ideal laboratory for studying young stars and stars that are still forming. It offers a glimpse of what might have happened when the Sun was born 4.6 billion years ago.

The three-dimensional video provides a look at the fantastic topography of the nebula. A torrent of ultraviolet radiation and stellar winds from the massive, central stars of the Trapezium star cluster have carved out a cavernous bowl-like cavity in the wall of a giant cloud of cold molecular hydrogen laced with dust.

Astronomers and visualizers worked together to make a three-dimensional model of the depths of this cavernous region, like plotting mountains and valleys on the ocean floor. Colorful Hubble and Spitzer images were then overlaid on the terrain.

The scientific visualization video takes the viewer on a breathtaking flight through the nebula, following the contours of the gas and dust. By toggling between the Hubble and Spitzer’s views, the movie shows strikingly different details of the Orion Nebula.

Hubble sees objects that glow in visible light, which are typically in the thousands of degrees. Spitzer is sensitive to cooler objects with temperatures of just hundreds of degrees. Spitzer’s infrared vision pierces through obscuring dust to see stars embedded deep into the nebula, as well as fainter and less massive stars, which are brighter in the infrared than in visible light. The new visualization helps people experience how the two telescopes provide a more complex and complete picture of the nebula.

The visualization is one of a new generation of products and experiences being developed by the NASA’s Universe of Learning program. The effort combines a direct connection to the science and scientists of NASA’s Astrophysics missions with attention to audience needs to enable youth, families, and lifelong learners to explore fundamental questions in science, experience how science is done, and discover the universe for themselves.

The three-dimensional interpretation is guided by scientific knowledge and scientific intuition. Starting with the two-dimensional Hubble and Spitzer images, Summers and Hurt worked with experts to analyze the structure inside the nebula. They first created a visible-light surface, and then an underlying structure of the infrared features.

To give the nebula its ethereal feel, Summers wrote a special rendering code for efficiently combining the tens of millions of semi-transparent elements of the gas. The customized code allows Summers to run this and other visualizations on desktop workstations, rather than on a supercomputing cluster.

The other components of the nebula were isolated into image layers and modeled separately. These elements included stars, protoplanetary disks, bow shocks, and the thin gas in front of the nebula called “the veil.” After rendering, these layers and the gaseous nebula are brought back together to create the visualization.

The three-dimensional structures serve as scientifically reasonable approximations for imagining the nebula. “The main thing is to give the viewer an experiential understanding, so that they have a way to interpret the images from telescopes,” explained Summers. “It’s a really wonderful thing when they can build a mental model in their head to transform the two-dimensional image into a three-dimensional scene.”

This movie demonstrates the power of multi-wavelength astronomy. It helps audiences understand how science is done — how and why astronomers use multiple regions of the electromagnetic spectrum to explore and learn about our universe. It is also whetting astronomers’ appetites for what they will see with NASA’s James Webb Space Telescope, which will show much finer details of the deeper, infrared features.

More visualizations and connections between the science of nebulas and learners can be explored through other products produced by NASA’s Universe of Learning such as ViewSpace. ViewSpace is a video exhibit currently at almost 200 museums and planetariums across the United States. Visitors can go beyond video to explore the images produced by space telescopes with interactive tools now available for museums and planetariums.

NASA’s Universe of Learning materials are based upon work supported by NASA under award number NNX16AC65A to the Space Telescope Science Institute, working in partnership with Caltech/IPAC, Jet Propulsion Laboratory, Smithsonian Astrophysical Observatory, and Sonoma State University.

Source:  HubbleSite

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Space Telescope Science Institute, Baltimore, Maryland
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Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, California

Tuesday, January 16, 2018

Game Over for Supernovae Hide & Seek

SN 2013if with GeMS/GSAOI, from left to right with linear scaling: Reference image (June 2015), discovery image (April 2013) and the image subtraction. SN 2013if had a projected distance from the nucleus as small as 600 light years (200 pc), which makes it the second most nuclear CCSN discovery in a LIRG to date in the optical and near-IR after SN 2010cu.

The Core-collapse Supernova Rate Problem, or the fact that we don’t see as many core-collapse supernovae as we would expect, has a solution, thanks to research using the Gemini South telescope. The research team concludes that the majority of core collapse supernovae, exploding in luminous infrared galaxies, have previously not been found due to dust obscuration and poor spatial resolution. 

Core-collapse supernovae are spectacular explosions that mark the violent deaths of massive stars. An international team of astronomers, led by PhD student Erik Kool of Macquarie University in Australia, used laser guide star imaging on the Gemini South telescope to study why we don’t see as many of these core-collapse supernovae as expected. The study began in 2015 with the Supernova UNmasked By InfraRed detection (SUNBIRD) project which has shown that dust obscuration and limited spatial resolution can explain the small number of detections to date.

In this, the first results of the SUNBIRD project, the team discovered three core-collapse supernovae, and one possible supernova that could not be confirmed with subsequent imaging. Remarkably, these supernovae were spotted as close as 600 light years from the bright nuclear regions of these galaxies – despite being at least 150 million light years from the Earth. “Because we observed in the near-infrared, the supernovae are less affected by dust extinction compared to optical light,” said Kool.

According to Kool the results coming from SUNBIRD reveal that their new approach provides a powerful tool for uncovering core-collapse supernova in nuclear regions of galaxies. They also conclude that this methodology is crucial in characterizing these supernova that are invisible through other means. Kool adds, “The supernova rate problem can be resolved using the unique multi-conjugate adaptive optics capability provided by Gemini, which allows us to achieve the highest spatial resolution in order to probe very close to the nuclear regions of galaxies.” This work is published in the Monthly Notices of the Royal Astronomical Society.

This research is also highlighted in the January 2018 GeminiFocus (p.11).


Core collapse supernova (CCSN) rates suffer from large uncertainties as many CCSNe exploding in regions of bright background emission and significant dust extinction remain unobserved. Such a shortfall is particularly prominent in luminous infrared galaxies (LIRGs), which have high star formation (and thus CCSN) rates and host bright and crowded nuclear regions, where large extinctions and reduced search detection efficiency likely lead to a significant fraction of CCSNe remaining undiscovered. We present the first results of project SUNBIRD (Supernovae UNmasked By InfraRed Detection), where we aim to uncover CCSNe that otherwise would remain hidden in the complex nuclear regions of LIRGs, and in this way improve the constraints on the fraction that is missed by optical seeing-limited surveys. We observe in the near-infrared 2.15 µm Ks-band, which is less affected by dust extinction compared to the optical, using the multi-conjugate adaptive optics imager GeMS/GSAOI on Gemini South, allowing us to achieve a spatial resolution that lets us probe close in to the nuclear regions. During our pilot program and subsequent first full year we have discovered three CCSNe and one candidate with projected nuclear offsets as small as 200 pc. When compared to the total sample of LIRG CCSNe discovered in the near-IR and optical, we show that our method is singularly effective in uncovering CCSNe in nuclear regions and we conclude that the majority of CCSNe exploding in LIRGs are not detected as a result of dust obscuration and poor spatial resolution.

Monday, January 15, 2018

What Stars Will Hatch From The Tarantula Nebula? NASA’s Flying Observatory Seeks to Find Out

The Tarantula Nebula as seen on SOFIA’s visible light guide camera during observations from Christchurch, New Zealand.
Credits: NASA/SOFIA/Nicholas A. Veronico

To have a full picture of the lives of massive stars, researchers need to study them in all stages – from when they’re a mass of unformed gas and dust, to their often dynamic end-of-life explosions.

NASA's flying telescope, the Stratospheric Observatory for Infrared Astronomy, or SOFIA, is particularly well-suited for studying the pre-natal stage of stellar development in star-forming regions, such as the Tarantula Nebula, a giant mass of gas and dust located within the Large Magellanic Cloud, or LMC.  

Researchers from the Minnesota Institute for Astrophysics, led by Michael Gordon, went aboard SOFIA to identify and characterize the brightness, ages and dust content of three young star-forming regions within the LMC.

The Large Magellanic Cloud has always been an interesting and excellent laboratory for massive star formation,” said Gordon. “The chemical properties of star-forming regions in the LMC are significantly different than in the Milky Way, which means the stars forming there potentially mirror the conditions of star formation in dwarf galaxies at earlier times in the universe.”

In our galactic neighborhood, which includes the LMC, massive stars – generally classified as stars more than eight times the mass of Earth’s Sun – are believed to form exclusively in very dense molecular clouds. The dark dust and gas absorb background light, which prevents traditional optical telescopes from imaging these areas.

“The mid-infrared capabilities of SOFIA are ideal for piercing through infrared dark clouds to capture images of potential massive star-forming regions,” Gordon said.

The observations were completed with the Faint Object infrared Camera for the SOFIA Telescope, known as FORCAST. This infrared camera also performs spectroscopy, which identifies the elements present.

Astronomers study stars evolving in both the optical and the infrared to learn more about the photosphere, and the population of stars in the photosphere. The mid- and far-infrared data from SOFIA reaffirm dust temperature and mass accretion rates that are consistent with prior research of the LMC.

"We want to combine as many observations as we can from the optical, as seen through images from the Hubble Space Telescope, all the way out to the far infrared, imaged using the Spitzer Space Telescope and the Herschel Space Observatory, to get as broad a picture as possible," Gordon continued. "No previous researchers have used FORCAST’s wavelength range to effectively study massive star formations. We needed SOFIA to fill in the 20- to 40-micron gap to give us the whole picture of what’s taking place."

In summer 2017, further research of the Tarantula Nebula was accomplished aboard SOFIA during the observatory’s six-week science campaign operating from Christchurch, New Zealand, to study the sky in the Southern Hemisphere. Gordon and his team are hopeful that when analyzed, data obtained from the Christchurch flights will reveal previously undiscovered young massive stars forming in the region, which have never been observed outside of the Milky Way.

SOFIA is a Boeing 747SP jetliner modified to carry a 100-inch diameter telescope. It is a joint project of NASA and the German Aerospace Center, DLR. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science and mission operations in cooperation with the Universities Space Research Association headquartered in Columbia, Maryland, and the German SOFIA Institute (DSI) at the University of Stuttgart. The aircraft is based at NASA’s Armstrong Flight Research Center's Hangar 703, in Palmdale, California.


Media Point of Contact

Nicholas A. Veronico • SOFIA Science Center
NASA Ames Research Center, Moffett Field, California

Editor: Kassandra Bell

Sunday, January 14, 2018

NASA's Great Observatories Team Up to Find Magnified and Stretched Image of Distant Galaxy

This Hubble Space Telescope image shows the farthest galaxy yet seen in an image that has been stretched and amplified by a phenomenon called gravitational lensing. Credits: NASA , ESA, and B. Salmon (STScI). › Full image and caption

An intensive survey deep into the universe by NASA's Hubble and Spitzer space telescopes has yielded the proverbial needle-in-a-haystack: the farthest galaxy yet seen in an image that has been stretched and amplified by a phenomenon called gravitational lensing.

The embryonic galaxy named SPT0615-JD existed when the universe was just 500 million years old.

Though a few other primitive galaxies have been seen at this early epoch, they have essentially all looked like red dots, given their small size and tremendous distances. However, in this case, the gravitational field of a massive foreground galaxy cluster not only amplified the light from the background galaxy but also smeared the image of it into an arc (about 2 arcseconds long).

"No other candidate galaxy has been found at such a great distance that also gives you the spatial information that this arc image does. By analyzing the effects of gravitational lensing on the image of this galaxy, we can determine its actual size and shape," said the study's lead author, Brett Salmon of the Space Telescope Science Institute in Baltimore. He is presenting his research at the 231st meeting of the American Astronomical Society in Washington.

First predicted by Albert Einstein a century ago, the warping of space by the gravity of a massive foreground object can brighten and distort the images of far more distant background objects. Astronomers use this "zoom lens" effect to go hunting for amplified images of distant galaxies that otherwise would not be visible with today's telescopes.

SPT0615-JD was identified in Hubble's Reionization Lensing Cluster Survey (RELICS) and companion S-RELICS Spitzer program. "RELICS was designed to discover distant galaxies like these that are magnified brightly enough for detailed study," said Dan Coe, principal investigator of RELICS. RELICS observed 41 massive galaxy clusters for the first time in infrared with Hubble to search for such distant lensed galaxies. One of these clusters was SPT-CL J0615-5746, which Salmon analyzed to make this discovery. Upon finding the lens-arc, Salmon thought, "Oh, wow! I think we're on to something!"

By combining the Hubble and Spitzer data, Salmon calculated the lookback time to the galaxy of 13.3 billion years. Preliminary analysis suggests the diminutive galaxy weighs in at no more than 3 billion solar masses (roughly 1/100th the mass of our fully grown Milky Way galaxy). It is less than 2,500 light-years across, half the size of the Small Magellanic Cloud, a satellite galaxy of our Milky Way. The object is considered prototypical of young galaxies that emerged during the epoch shortly after the big bang.

The galaxy is right at the limits of Hubble's detection capabilities, but just the beginning for the upcoming NASA James Webb Space Telescope's powerful capabilities, said Salmon. "This galaxy is an exciting target for science with the Webb telescope as it offers the unique opportunity for resolving stellar populations in the very early universe." Spectroscopy with Webb will allow for astronomers to study in detail the firestorm of starbirth activity taking place at this early epoch, and resolve its substructure.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington, D.C. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Spacecraft operations are based at Lockheed Martin Space, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA.

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

News Media Contact

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland

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NASA Headquarters, Washington
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No Planets Needed: NASA Study Shows Disk Patterns Can Self-Generate

When exoplanet scientists first spotted patterns in disks of dust and gas around young stars, they thought newly formed planets might be the cause. But a recent NASA study cautions that there may be another explanation — one that doesn’t involve planets at all.

Exoplanet hunters watch stars for a few telltale signs that there might be planets in orbit, like changes in the color and brightness of the starlight. For young stars, which are often surrounded by disks of dust and gas, scientists look for patterns in the debris — such as rings, arcs and spirals — that might be caused by an orbiting world.

“We’re exploring what we think is the leading alternative contender to the planet hypothesis, which is that the dust and gas in the disk form the patterns when they get hit by ultraviolet light,” said Marc Kuchner, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Kuchner presented the findings of the new study on Thursday, Jan. 11, at the American Astronomical Society meeting in Washington. A paper describing the results has been submitted to The Astrophysical Journal.

When high-energy UV starlight hits dust grains, it strips away electrons. Those electrons collide with and heat nearby gas. As the gas warms, its pressure increases and it traps more dust, which in turn heats more gas. The resulting cycle, called the photoelectric instability (PeI), can work in tandem with other forces to create some of the features astronomers have previously associated with planets in debris disks.

Kuchner and his colleagues designed computer simulations to better understand these effects. The research was led by Alexander Richert, a doctoral student at Penn State in University Park, Pennsylvania, and includes Wladimir Lyra, a professor of astronomy at California State University, Northridge and research associate at NASA’s Jet Propulstion Laboratory in Pasadena, California. The simulations were run on the Discover supercomputing cluster at the NASA Center for Climate Simulation at Goddard.

In 2013, Lyra and Kuchner suggested that PeI could explain the narrow rings seen in some disks. Their model also predicted that some disks would have arcs, or incomplete rings, which were first directly observed in 2016.

“People very often model these systems with planets, but if you want to know what a disk with a planet looks like, you first have to know what a disk looks like without a planet,” Richert said.

Richert is lead author on the new study, which builds on Lyra and Kuchner’s previous simulations by including an additional new factor: radiation pressure, a force caused by starlight striking dust grains.

Light exerts a minute physical force on everything it encounters. This radiation pressure propels solar sails and helps direct comet tails so they always point away from the Sun. The same force can push dust into highly eccentric orbits, and even blow some of the smaller grains out of the disk entirely.

The researchers modeled how radiation pressure and PeI work together to affect the movement of dust and gas. They also found that the two forces manifest different patterns depending on the physical properties of the dust and gas.

The 2013 simulations of PeI revealed how dust and gas interact to create rings and arcs, like those observed around the real star HD 141569A. With the inclusion of radiation pressure, the 2017 models show how these two factors can create spirals like those also observed around the same star. While planets can also cause these patterns, the new models show scientists should avoid jumping to conclusions.

“Carl Sagan used to say extraordinary claims require extraordinary evidence,” Lyra said. “I feel we are sometimes too quick to jump to the idea that the structures we see are caused by planets. That is what I consider an extraordinary claim. We need to rule out everything else before we claim that.”

Kuchner and his colleagues said they would continue to factor other parameters into their simulations, like turbulence and different types of dust and gas. They also intend to model how these factors might contribute to pattern formation around different types of stars.

A NASA-funded citizen science project spearheaded by Kuchner, called Disk Detective, aims to discover more stars with debris disks. So far, participants have contributed more than 2.5 million classifications of potential disks. The data has already helped break new ground in this research.

By Jeanette Kazmierczak
NASA's Goddard Space Flight Center, Greenbelt, Md.

Editor: Rob Garner

Saturday, January 13, 2018

A Quick Look at SDSS J1354+1327

 SDSS J1354+1327
Credit: X-ray NASA/CXC/University of Colorado/J. Comerford et al.; Optical: NASA/STScI

Using data from several telescopes including NASA's Chandra X-ray Observatory, astronomers have caught a supermassive black hole snacking on gas and then "burping" — not once but twice, as described in our latest press release.

This graphic shows the galaxy, called SDSS J1354+1327 (J1354 for short) in a composite image with data from Chandra (purple), and the Hubble Space Telescope (HST; red, green and blue). The inset box contains a close-up view of the central region around J1354's supermassive black hole. A companion galaxy to J1354 is shown to the north. Researchers also used data from the W.M. Keck Observatory atop Mauna Kea, Hawaii and the Apache Point Observatory (APO) in New Mexico for this finding.

Chandra detected a bright, point-like source of X-ray emission from J1354, a telltale sign of the presence of a supermassive black hole millions or billions of times more massive than our sun. The X-rays are produced by gas heated to millions of degrees by the enormous gravitational and magnetic forces near the black hole. Some of this gas will fall into the black hole, while a portion will be expelled in a powerful outflow of high-energy particles.

By comparing images from Chandra and HST, the team determined that the black hole is located in the center of the galaxy, the expected location for such an object. The X-ray data also provide evidence that the supermassive black hole is embedded in a heavy veil of dust and gas.

The two-course meal for the black hole comes from a companion galaxy that collided with J1354 in the past. This collision produced a stream of stars and gas that links J1354 and the other galaxy. The separate outbursts from the black hole are caused by different clumps from this stream being consumed by the supermassive black hole. The researchers determined these two "burps" happened about 100,000 years apart.

The team used optical data from HST, Keck and APO to show that electrons had been stripped from atoms in a cone of gas (the green emission in the lower left of the inset) extending some 30,000 light years south from the galaxy's center. This stripping was likely caused by a burst of radiation from the vicinity of the black hole, indicating that the first of the two feasting events had occurred. Evidence for the second, more recent feast comes from the small source of green emission located at the northern tip of the Chandra source in the inset.

Julie Comerford from the University of Colorado at Boulder presented the team's findings in a January 11th, 2018 press briefing at the 231st meeting of the American Astronomical Society held in Washington D.C. A paper on the subject was published in a recent issue of The Astrophysical Journal and is available online. Co-authors on the new study include postdoctoral fellows Rebecca Nevin, Scott Barrows and Francisco Muller-Sanchez of CU Boulder, Jenny Greene of Princeton University, David Pooley from Trinity University, Daniel Stern from the Jet Propulsion Laboratory in Pasadena, California, and Fiona Harrison from the California Institute of Technology.

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.

A Quick Look at SDSS J1354+1327

Fast Facts for SDSS J1354+1327:

Scale: Full field image: 37 arcsec (About 160,000 light years) across; Inset image: 3 arcsec (About 13,000 light years) across
Category: Quasars & Active Galaxies
Constellation: Boötes
Observation Date: June 25, 2014 
Observation Time 2 hours 37 minutes
Instrument: ACIS
Obs ID:  16115
References: J Comerford et al. 2017, ApJ, 849,102; arXiv:1710.00825
Distance Estimate: About 800 million light years (z=0.06)

Friday, January 12, 2018

Galactic Center: Scientists Take Viewers to the Center of the Milky Way

 Galactic Center
Credit: NASA/CXC/Pontifical Catholic Univ. of Chile /C.Russell et al.

A new visualization provides an exceptional virtual trip — complete with a 360-degree view — to the center of our home galaxy, the Milky Way. This project, made using data from NASA's Chandra X-ray Observatory and other telescopes, allows viewers to control their own exploration of the fascinating environment of volatile massive stars and powerful gravity around the monster black hole that lies in the center of the Milky Way.

The Earth is located about 26,000 light years, or about 150,000 trillion miles, from the center of the Galaxy. While humans cannot physically travel there, scientists have been able to study this region by using data from powerful telescopes that can detect light in a variety of forms, including X-ray and infrared light.

This visualization builds on infrared data with the European Southern Observatory's Very Large Telescope of 30 massive stellar giants called Wolf-Rayet stars that orbit within about 1.5 light years of the center of our Galaxy. Powerful winds of gas streaming from the surface of these stars are carrying some of their outer layers into interstellar space.

When the outflowing gas collides with previously ejected gas from other stars, the collisions produce shock waves, similar to sonic booms, which permeate the area. These shock waves heat the gas to millions of degrees, which causes it to glow in X-rays. Extensive observations with Chandra of the central regions of the Milky Way have provided critical data about the temperature and distribution of this multimillion-degree gas.

Sagittarius A*
 Credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI 

Astronomers are interested in better understanding what role these Wolf-Rayet stars play in the cosmic neighborhood at the Milky Way's center. In particular, they would like to know how the stars interact with the Galactic center's most dominant resident: the supermassive black hole known as Sagittarius A* (abbreviated Sgr A*). Pre-eminent yet invisible, Sgr A* has the mass equivalent to some four million Suns.

The Galactic Center visualization is a 360-degree movie that immerses the viewer into a simulation of the center of our Galaxy. The viewer is at the location of Sgr A* and is able to see about 25 Wolf-Rayet stars (white, twinkling objects) orbiting Sgr A* as they continuously eject stellar winds (black to red to yellow color scale). These winds collide with each other, and then some of this material (yellow blobs) spirals towards Sgr A*. The movie shows two simulations, each of which start around 350 years in the past and span 500 years. The first simulation shows Sgr A* in a calm state, while the second contains a more violent Sgr A* that is expelling its own material, thereby turning off the accretion of clumped material (yellow blobs) that is so prominent in the first portion.

Scientists have used the visualization to examine the effects Sgr A* has on its stellar neighbors. As the strong gravity of Sgr A* pulls clumps of material inwards, tidal forces stretch the clumps as they get closer to the black hole. Sgr A* also impacts its surroundings through occasional outbursts from its vicinity that result in the expulsion of material away from the giant black hole, as shown in the later part of the movie. These outbursts can have the effect of clearing away some of the gas produced by the Wolf-Rayet winds.

The researchers, led by Christopher Russell of the Pontifical Catholic University of Chile, used the visualization to understand the presence of previously detected X-rays in the shape of a disk that extend about 0.6 light years outward from Sgr A*. Their work shows that the amount of X-rays generated by these colliding winds depends on the strength of outbursts powered by Sgr A*, and also the amount of time that has elapsed since an eruption occurred. Stronger and more recent outbursts result in weaker X-ray emission.

The information provided by the theoretical modeling and a comparison with the strength of X-ray emission observed with Chandra led Russell and his colleagues to determine that Sgr A* most likely had a relatively powerful outburst that started within the last few centuries. Moreover, their findings suggest the outburst from the supermassive black hole is still affecting the region around Sgr A* even though it ended about one hundred years ago. 

The 360-degree video of the Galactic Center is ideally viewed in virtual reality (VR) goggles, such as Samsung Gear VR or Google Cardboard. The video can also be viewed on smartphones using the YouTube app. Moving the phone around pans to show a different portion of the movie, mimicking the effect in the VR goggles. Finally, most browsers on a computer also allow 360-degree videos to be shown on YouTube. To look around, either click and drag the video, or click the direction pad in the corner. 

Christopher Russell presented this new visualization and the related scientific findings at the 231st meeting of the American Astronomical Society in Washington, DC. Some of the results are based on a paper by Russell et al published in 2017 in the Monthly Notices of the Royal Astronomical Society. An online version is here. The co-authors of this paper are Daniel Wang from University of Massachusetts in Amherst, Mass. and Jorge Cuadra from Pontifical Catholic University of Chile. 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.

A Quick Look at the Galactic Center

Fast Facts for Galactic Center:

Category: Normal Galaxies & Starburst Galaxies, Milky Way Galaxy, Black Holes
Coordinates (J2000): RA 17h 45m 40s | Dec -29° 00´ 28.00"
Constellation: Sagittarius
Instrument: ACIS
References: Russell, C. et al. 2017, MNRAS, 464, 4958, arXiv:1607.01562
Distance Estimate: About 26,000 light years

Thursday, January 11, 2018

The long and short of it: Iron-rich stars host shorter-period planets

An artist’s rendering of how the iron content of a star can impact its planets. A normal star (green label) is more likely to host a longer-period planet (green orbit), while an iron-rich star (yellow label) is more likely to host a shorter-period planet (yellow orbit).  Image Credit: Dana Berry/SkyWorks Digital Inc.; SDSS collaboration.   Image Credit: Dana Berry/SkyWorks Digital Inc.; SDSS collaboration.  Click on the image for a larger version

Astronomers with the Sloan Digital Sky Survey (SDSS) have learned that the chemical composition of a star can exert unexpected influence on its planetary system — a discovery made possible by an ongoing SDSS survey of stars seen by NASA’s Kepler spacecraft, and one that promises to expand our understanding of how extrasolar planets form and evolve.

“Without these detailed and accurate measurements of the iron content of stars, we could have never made this measurement,” says Robert Wilson, a graduate student in astronomy at the University of Virginia and lead author of the paper announcing the results.

The team presented their results today at the American Astronomical Society (AAS) meeting in National Harbor, Maryland. Using SDSS data, they found that stars with higher concentrations of iron tend to host planets that orbit quite close to their host star — often with orbital periods of less than about eight days — while stars with less iron tend to host planets with longer periods that are more distant from their host star. Further investigation of this effect may help us understand the full variety of extrasolar planetary systems in our Galaxy, and shed light on why planets are found where they are.

The story of planets around Sun-like stars began in 1995, when a team of astronomers discovered a single planet orbiting a Sun-like star 50 light years from Earth. The pace of discovery accelerated in 2009, when NASA launched the Kepler spacecraft, a space telescope designed to look for extrasolar planets. During its four-year primary mission, Kepler monitored thousands of stars at a time, watching for the tiny dimming of starlight that indicates a planet passing in front its host star. And because Kepler looked at the same stars for years, it saw their planets over and over again, and was thus able to measure the time the planet takes to orbit its star. This information reveals the distance to from star to planet, with closer planets orbiting faster than farther ones. Thanks to Kepler’s tireless monitoring, the number of exoplanets with known orbital periods increased dramatically, from about 400 in 2009 to more than 3,000 today.

Although Kepler was perfectly designed to spot extrasolar planets, it was not designed to learn about the chemical compositions of the stars around which those planets orbit. That knowledge comes from the SDSS’s Apache Point Observatory Galactic Evolution Experiment (APOGEE), which has studied hundreds of thousands of stars all over the Milky Way Galaxy. APOGEE works by collecting a spectrum for each star — a measurement of how much light the star gives off at different wavelengths (colors) of light. Because atoms of each chemical element interact with light in their own characteristic way, a spectrum allows astronomers to determine not only which elements a star contains, but also how much — for all elements including the key element iron.

“All Sun-like stars are mostly hydrogen, but some contain more iron than others,” says Johanna Teske of the Carnegie Institution for Science, a member of the research team. “The amount of iron a star contains is an important clue to how it formed and how it will evolve over its lifetime.”

By combining data from these two sources — planetary orbits from Kepler and stellar chemistry from APOGEE — astronomers have learned about the relationships between these “iron-enriched” stars and the planetary systems they hold.

“We knew that the element enrichment of a star would matter for its own evolution,” says Teske, “But we were surprised to learn that it matters for the evolution of its planetary system as well.”

The work presented today builds on previous work, led by Gijs Mulders of the University of Arizona, using a larger but less precise sample of spectra from the LAMOST-Kepler project. (LAMOST, the Large-Area Multi-Object fiber Spectroscopic Telescope, is a Chinese sky survey.) Mulders and collaborators found a similar trend — closer-in planets orbiting more iron-rich stars — but did not pin down the critical period of eight days. 

“It is encouraging to see an independent confirmation of the trend we found in 2016,” says Mulders. “The identification of the critical period really shows that Kepler is the gift that keeps on giving.”

What is particularly surprising about the new result, Wilson explained, is that the iron-enriched stars have only about 25 percent more iron than the others in the sample. “That’s like adding five-eighths of a teaspoon of salt into a cupcake recipe that calls for half a teaspoon of salt, among all its other ingredients. I’d still eat that cupcake,” he says. “That really shows us how even small differences in stellar composition can have profound impacts on planetary systems.”

But even with this new discovery, astronomers are left with many unanswered questions about how extrasolar planets form and evolve, especially planets Earth-sized or slightly larger (“super-Earths”). 

Do iron-rich stars intrinsically form planets with shorter orbits? Or are planets orbiting iron-rich stars more likely to form farther out and then migrate to shorter period, closer-in orbits? Wilson and collaborators hope to work with other astronomers to create new models of protoplanetary disks to test both of these explanations.

“I’m excited that we still have much to learn about how the chemical compositions of stars impact their planets, particularly about how small planets form,” Teske says. “Plus, APOGEE provides many more stellar chemical abundances besides iron, so there are likely other trends buried within this rich dataset that we have yet to explore.”

About Sloan Digital Sky Survey

Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is

SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofísica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU) / University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut für Extraterrestrische Physik (MPE), National Astronomical Observatories of China, New Mexico State University, New York University, University of Notre Dame, Observatório Nacional / MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University, and Yale University.


Robert Wilson, 
The University  

Johanna Teske, 
Carnegie Institution for Science,,   

Karen Masters, 
SDSS Scientific Spokesperson, Haverford College/University of Portsmouth,,   
+44 (0)7590 5266005,   

Jordan Raddick, 
SDSS Public Information Officer, Johns Hopkins University,  

Wednesday, January 10, 2018

How massive is Supermassive? Astronomers measure more black holes, farther away

An artist’s rendering of the inner regions of an active galaxy/quasar, with a supermassive black hole at the center surrounded by a disk of hot material falling in. The inset at the bottom right shows how the brightness of light coming from the two different regions changes with time. 

The top panel of the plot shows the “continuum” region, which originates close in to the black hole (the general vicinity is indicated by the “swoosh” shape). The bottom panel shows the H-beta emission line region, which comes from fast-moving hydrogen gas farther away from the black hole (the general vicinity is indicated by the other “swoosh”). The time span covered by these two light curves is about six months. 

The bottom plot “echoes” the top, with a slight time delay of about 10 days indicated by the vertical line. This means that the distance between these two regions is about 10 light-days (about 150 billion miles, or 240 million kilometers). Image Credit: Nahks Tr’Ehnl ( and Catherine Grier (The Pennsylvania State University) and the SDSS collaboration.  Hi-res image

A graph of known supermassive black hole masses at various “lookback times,” which measures the time into the past we see when we look at each quasar. 

More distant quasars have longer lookback times (since their light takes longer to travel to Earth), so we see them as they appeared in the more distant past. The Universe is about 13.8 billion years old, so the graph goes back to when the Universe was about half of its current age. 

The black hole masses measured in this work are shown as purple circles, while gray squares show black hole masses measured by prior reverberation mapping projects. The sizes of the squares and circles are related to the masses of the black holes they represent. The graph shows black holes from 5 million to 1.7 billion times the mass of the Sun.  Image Credit: Catherine Grier (The Pennsylvania State University) and the SDSS collaboration

Today, astronomers from the Sloan Digital Sky Survey (SDSS) announced new measurements of the masses of a large sample of supermassive black holes far beyond the local Universe.

The results, being presented at the American Astronomical Society (AAS) meeting in National Harbor, Maryland and published in the Astrophysical Journal, represent a major step forward in our ability to measure supermassive black hole masses in large numbers of distant quasars and galaxies.
“This is the first time that we have directly measured masses for so many supermassive black holes so far away,” says Catherine Grier, a postdoctoral fellow at the Pennsylvania State University and the lead author of this work. “These new measurements, and future measurements like them, will provide vital information for people studying how galaxies grow and evolve throughout cosmic time.”

Supermassive Black Holes (SMBHs) are found in the centers of nearly every large galaxy, including those in the farthest reaches of the Universe. The gravitational attraction of these supermassive black holes is so great that nearby dust and gas in the host galaxy is inexorably drawn in. The infalling material heats up to such high temperatures that it glows brightly enough to be seen all the way across the Universe. These bright disks of hot gas are known as “quasars,” and they are clear indicators of the presence of supermassive black holes. By studying these quasars, we learn not only about SMBHs, but also about the distant galaxies that they live in. But to do all of this requires measurements of the properties of the SMBHs, most importantly their masses.

The problem is that measuring the masses of SMBHs is a daunting task. Astronomers measure SMBH masses in nearby galaxies by observing groups of stars and gas near the galaxy center — however, these techniques do not work for more distant galaxies, because they are so far away that telescopes cannot resolve their centers. Direct SMBH mass measurements in galaxies farther away are made using a technique called “reverberation mapping.”

Reverberation mapping works by comparing the brightness of light coming from gas very close in to the black hole (referred to as the “continuum” light) to the brightness of light coming from fast-moving gas farther out. Changes occurring in the continuum region impact the outer region, but light takes time to travel outwards, or “reverberate.” This reverberation means that there is a time delay between the variations seen in the two regions. By measuring this time delay, astronomers can determine how far out the gas is from the black hole. Knowing that distance allows them to measure the mass of the supermassive black hole — even though they can’t see the details of the black hole itself.

Over the past 20 years, astronomers have used the reverberation mapping technique to laboriously measure the masses of around 60 SMBHs in nearby active galaxies. Reverberation mapping requires getting observations of these active galaxies, over and over again for several months — and so for the most part, measurements are made for only a handful of active galaxies at a time. Using the reverberation mapping technique on quasars, which are farther away, is even more difficult, requiring years of repeated observations. Because of these observational difficulties, astronomers had only successfully used reverberation mapping to measure SMBH masses for a handful of more distant quasars — until now.


Grier et al. 2017, Astrophysical Journal 851, 21

About this research

This research was supported by funding from the National Science Foundation (NSF) grant AST-1517113 and the Penn State Willaman Endowment. The SDSS-RM team would also like to acknowledge support from the Alfred P. Sloan Research Fellowship, NSF grants AST-1715579, AST-1515427, AST 15-15115, and AST-1302093, the STFC grant ST/ M001296/1, the National Key R&D Program of China (2016YFA0400702), and the National Science Foundation of China (11473002, 11721303).
This work is also based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France–Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

About Sloan Digital Sky Survey

Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is

SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofísica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU) / University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut für Extraterrestrische Physik (MPE), National Astronomical Observatories of China, New Mexico State University, New York University, University of Notre Dame, Observatório Nacional / MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University, and Yale University.


Catherine Grier, 
The Pennsylvania State University

Jon Trump, 
University of Connecticut, 

Yue Shen, 
University of Illinois at Urbana-Champaign, 

Niel Brandt, 
The Pennsylvania State University, 

Karen Masters, 
SDSS Scientific Spokesperson, Haverford College/University of Portsmouth,
+44 (0)7590 5266005, 

Jordan Raddick, 
SDSS Public Information Officer, Johns Hopkins University,