Friday, December 29, 2017

Comparison image: Hubble and HAWK-I explore a cluster with the mass of two quadrillion Suns

Hubble and HAWK-I explore a cluster with the mass of two quadrillion Suns 

Galaxy cluster RCS2 J2327

This image shows something spectacular: a galaxy cluster so massive that it is warping the space around it! The cluster, whose heart is at the centre of the frame, is named RCS2 J2327, and is one of the most massive clusters known as its distance or beyond.

Massive objects such as RCS2 J2327 have such a strong influence on their surroundings that they actually warp the space around them — this effect is known as gravitational lensing, and can cause light from more distant objects to be bent, distorted, and amplified, allowing us to see galaxies that would otherwise be far too distant for us to detect. Gravitational lensing is one of the predictions of Albert Einstein's General Theory of Relativity and can be observed in three different regimes: strong lensing, weak lensing, and microlensing. Unlike strong lensing, which produces stunning images of distorted galaxies, sweeping arcs, and phenomena known as Einstein rings, weak gravitational lensing is mostly studied statistically — but offers a way to measure the masses of cosmic objects, as shown here.

This image is a composite of observations from the HAWK-I instrument on ESO’s Very Large Telescope and the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys, and demonstrates an impressively detailed collaborative approach to studying weak lensing in the cosmos. The study found RCS2 J2327 to contain the mass of two quadrillion Suns!

Using the slider a mass map becomes visible, showing the amount of mass thought to be contained within each part of the cluster. The creation of the map was only possible due to the exact measurements on the amount of gravitational lensing in the different areas of the cluster.
Link

Credit
  • ESO & ESA/Hubble & NASA


Thursday, December 28, 2017

Radio Observations Point to Likely Explanation for Neutron-Star Merger Phenomena

Different scenarios for the aftermath of the collision of two neutron stars. At left (in the short gamma-ray burst [SGRB] scenario), a jet of material moving at nearly the speed of light is propelled from the collision site into a sphere of material initially blown out by the resulting explosion. If viewed from an angle away (off-axis) from the center of the jet, the long-term emission of X-rays and radio waves would be getting weaker. At right, the jet cannot punch out of the shell of explosion debris, but instead sweeps up material into a broad "cocoon," which absorbs the jet's energy and emits X-rays and radio waves over a wider angle. In this case, such emission is still growing in intensity, as now observed with both radio and X-ray telescopes. Credit: NRAO/AUI/NSF: D. Berry. Hi-Res File



Three months of observations with the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) have allowed astronomers to zero in on the most likely explanation for what happened in the aftermath of the violent collision of a pair of neutron stars in a galaxy 130 million light-years from Earth. What they learned means that astronomers will be able to see and study many more such collisions.

On August 17, 2017, the LIGO and VIRGO gravitational-wave observatories combined to locate the faint ripples in spacetime caused by the merger of two superdense neutron stars. It was the first confirmed detection of such a merger and only the fifth direct detection ever of gravitational waves, predicted more than a century ago by Albert Einstein.

The gravitational waves were followed by outbursts of gamma rays, X-rays, and visible light from the event. The VLA detected the first radio waves coming from the event on September 2. This was the first time any astronomical object had been seen with both gravitational waves and electromagnetic waves.

The timing and strength of the electromagnetic radiation at different wavelengths provided scientists with clues about the nature of the phenomena created by the initial neutron-star collision. Prior to the August event, theorists had proposed several ideas — theoretical models — about these phenomena. As the first such collision to be positively identified, the August event provided the first opportunity to compare predictions of the models to actual observations.

Astronomers using the VLA, along with the Australia Telescope Compact Array and the Giant Metrewave Radio Telescope in India, regularly observed the object from September onward. The radio telescopes showed the radio emission steadily gaining strength. Based on this, the astronomers identified the most likely scenario for the merger’s aftermath.

“The gradual brightening of the radio signal indicates we are seeing a wide-angle outflow of material, traveling at speeds comparable to the speed of light, from the neutron star merger,” said Kunal Mooley, now a National Radio Astronomy Observatory (NRAO) Jansky Postdoctoral Fellow hosted by Caltech.

The observed measurements are helping the astronomers figure out the sequence of events triggered by the collision of the neutron stars.

The initial merger of the two superdense objects caused an explosion, called a kilonova, that propelled a spherical shell of debris outward. The neutron stars collapsed into a remnant, possibly a black hole, whose powerful gravity began pulling material toward it. That material formed a rapidly-spinning disk that generated a pair of narrow, superfast jets of material flowing outward from its poles.

If one of the jets were pointed directly toward Earth, we would have seen a short-duration gamma-ray burst, like many seen before, the scientists said.

“That clearly was not the case,” Mooley said.

Some of the early measurements of the August event suggested instead that one of the jets may have been pointed slightly away from Earth. This model would explain the fact that the radio and X-ray emission were seen only some time after the collision.

“That simple model — of a jet with no structure (a so-called top-hat jet) seen off-axis — would have the radio and X-ray emission slowly getting weaker. As we watched the radio emission strengthening, we realized that the explanation required a different model,” said Alessandra Corsi, of Texas Tech University.

The astronomers looked to a model published in October by Mansi Kasliwal of Caltech, and colleagues, and further developed by Ore Gottlieb, of Tel Aviv University, and his colleagues. In that model, the jet does not make its way out of the sphere of explosion debris. Instead, it gathers up surrounding material as it moves outward, producing a broad “cocoon” that absorbs the jet’s energy.

The astronomers favored this scenario based on the information they gathered from using the radio telescopes. Soon after the initial observations of the merger site, the Earth’s annual trip around the Sun placed the object too close to the Sun in the sky for X-ray and visible-light telescopes to observe. 

For weeks, the radio telescopes were the only way to continue gathering data about the event.

“If the radio waves and X-rays both are coming from an expanding cocoon, we realized that our radio measurements meant that, when NASA’s Chandra X-ray Observatory could observe once again, it would find the X-rays, like the radio waves, had increased in strength,” Corsi said.

Mooley and his colleagues posted a paper with their radio measurements, their favored scenario for the event, and this prediction online on November 30. Chandra was scheduled to observe the object on December 2 and 6.

“On December 7, the Chandra results came out, and the X-ray emission had brightened just as we predicted,” said Gregg Hallinan, of Caltech.

“The agreement between the radio and X-ray data suggests that the X-rays are originating from the same outflow that’s producing the radio waves,” Mooley said.

“It was very exciting to see our prediction confirmed,” Hallinan said. He added, “An important implication of the cocoon model is that we should be able to see many more of these collisions by detecting their electromagnetic, not just their gravitational, waves.”

Mooley, Hallinan, Corsi, and their colleagues reported their findings in the scientific journal Nature.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.



Media Contact:

Dave Finley, Public Information Officer
(575) 835-7302

dfinley@nrao.edu




Monday, December 25, 2017

ERC Grant for Sherry Suyu: Cosmic Fireworks Première

The first and only spatially-resolved strongly lensed Type Ia Supernova, iPTF16geu, discovered by Goobar et al. (2017). Left: HST image taken on 28 October 2016, showing four images of the same source around the foreground galaxy. Middle and right: Two different reconstructions from lens mass models of the system by More, Suyu, Oguri et al. (2017).  From More, Suyu et al.


Unravelling Enigmas of Type Ia SuperUnravelling Enigmas of Type Ia Supernova Progenitors and Cosmology through Strong Lensingnova Progenitors and Cosmology through Strong Lensing

End of November, the European Research Council announced that Sherry Suyu, research group leader at the Max Planck Institute for Astrophysics and member of the Max-Planck@TUM programme, is one of the awardees of the 2017 ERC Consolidator Grants. With this funding, Suyu can expand her group to study gravitationally lensed supernovae and find out more about their progenitors. Strongly lensed supernovae also provide an independent way of measuring the Hubble constant, which tells scientists about the rate of expansion of the Universe.

Gravitational lensing of the Type Ia Supernova iPTF16geu. The spacetime between the supernova (marked with a star symbol) and the observer (on Earth) is disturbed by the gravity of the lensing galaxy (in orange). The observer will see the host galaxy of the supernova form a ring-like structure in the background, and the supernova split into four images. As Type Ia Supernovae have a distinct light-curve shape, the time delay between the four images can easily be determined (bottom image).


The LENSNOVA project proposed by Sherry Suyu plans to capitalize on her experience in the field of strong lensing time delays. With the aid of lensing, SNe can be observed in their entirety with unprecedented temporal sampling. Observations of the beginning of SN explosions are key to revealing SN progenitors that have been under debate for decades. Strongly lensed SNe Ia also allow an independent measurement of the Hubble constant (H0) that sets the cosmic expansion rate. The independent measurement is important to ascertain the possible need of new physics beyond the standard cosmological model, given the tensions in current H0 measurements. Thus, the LENSNOVA project will shed light on the natures of SNe Ia progenitors and dark energy, two of the greatest puzzles in the present era.

The advent of new, powerful telescopes such as the Large Synoptic Survey Telescope and the Euclid mission makes LENSNOVA particularly timely for building the first sample of a handful of strongly lensed SNe Ia. The ERC grant now enables Sherry Suyu to recruit further researchers for her team and to acquire the computing resources needed to capitalise on the new data. Thus, the project could potentially revolutionise both the fields of stellar physics and cosmology.


The ERC Consolidator Grants are awarded to outstanding researchers of any nationality and age in any field of research, with at least seven and up to twelve years of experience after PhD, and a scientific track record showing great promise. Research must be conducted in a public or private research organisation located in one of the EU Member States or Associated Countries. The funding (maximum of €2 million per grant), is provided for up to five years and mostly covers the employment of researchers and other staff to consolidate the grantees' teams. Proposals are evaluated by selected international peer reviewers who assess them on the basis of excellence as the sole criterion. 




More Information

Cosmology and extragalactic astrophysics with gravitational lensing

Max Planck Research Group at the Max Planck Institute for Astrophysics
 


ERC Consolidator Grants 2017
 


1. More, Suyu, Oguri et al.
 
Interpreting the Strongly Lensed Supernova iPTF16geu: Time Delay Predictions,
Microlensing, and Lensing Rates
 


Sunday, December 24, 2017

A snowstorm of stars

Credit:NASA and ESA
Acknowledgement: S. Djorgovski (Caltech) and F. Ferraro (University of Bologna)


It’s beginning to look a lot like Christmas in this NASA/ESA Hubble Space Telescope image of a blizzard of stars, which resembles a swirling storm in a snow globe.

These stars make up the globular cluster Messier 79, located about 40 000 light-years from Earth in the constellation of Lepus (The Hare). Globular clusters are gravitationally bound groupings of up to one million stars. These giant “star globes” contain some of the oldest stars in our galaxy. Messier 79 is no exception; it contains about 150 000 stars, packed into an area measuring just roughly 120 light-years across.

This 11.7-billion-year-old star cluster was first discovered by French astronomer Pierre Méchain in 1780. Méchain reported the finding to his colleague Charles Messier, who included it in his catalogue of non-cometary objects: The Messier catalogue. About four years later, using a larger telescope than Messier’s, William Herschel was able to resolve the stars in Messier 79 and described it as a “globular star cluster.”

In this sparkling Hubble image, Sun-like stars appear yellow-white and the reddish stars are bright giants that are in the final stages of their lives. Most of the blue stars sprinkled throughout the cluster are aging “helium-burning” stars, which have exhausted their hydrogen fuel and are now fusing helium in their cores.



Saturday, December 23, 2017

Cosmic Filament Probes Our Galaxy’s Giant Black Hole

In 2016, Farhad Yusef-Zadeh of Northwestern University reported the discovery of an unusual filament near the center of the Milky Way Galaxy using the NSF’s Karl G. Jansky Very Large Array (VLA). The filament is about 2.3 light years long and curves around to point at the supermassive black hole, called Sagittarius A* (Sgr A*), located in the Galactic center.

Now, another team of astronomers has employed a pioneering technique to produce the highest-quality image yet obtained of this curved object.

“With our improved image, we can now follow this filament much closer to the Galaxy’s central black hole, and it is now close enough to indicate to us that it must originate there,” said Mark Morris of the University of California, Los Angeles, who led the study. “However, we still have more work to do to find out what the true nature of this filament is.”

The researchers have considered three main explanations for the filament. The first is that it is caused by high-speed particles kicked away from the supermassive black hole. A spinning black hole coupled with gas spiraling inwards can produce a rotating, vertical tower of magnetic field that approaches or even threads the event horizon, the point of no return for infalling matter. Within this tower, particles would be sped up and produce radio emission as they spiral around magnetic field lines and stream away from the black hole.

The second, more fantastic, possibility is that the filament is a cosmic string, theoretical, as-yet undetected objects that are long, extremely thin objects that carry mass and electric currents. Previously, theorists had predicted that cosmic strings, if they exist, would migrate to the centers of galaxies. If the string moves close enough to the central black hole it might be captured once a portion of the string crosses the event horizon.

The final option is that the position and the direction of the filament aligning with the black hole are merely coincidental superpositions, and there is no real association between the two. This would imply it is like dozens of other known filaments found farther away from the center of the Galaxy. However, such a coincidence is quite unlikely to happen by chance.

“Part of the thrill of science is stumbling across a mystery that is not easy to solve,” said co-author Jun-Hui Zhao of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “While we don’t have the answer yet, the path to finding it is fascinating. This result is motivating astronomers to build next generation radio telescopes with cutting edge technology.”

Each of the scenarios being investigated would provide intriguing insight if proven true. For example, if the filament is caused by particles being ejected by Sgr A*, this would reveal important information about the magnetic field in this special environment, showing that it is smooth and orderly rather than chaotic.

The second option, the cosmic string, would provide the first evidence for a highly speculative idea with profound implications for understanding gravity, space-time and the Universe itself.

Evidence for the idea that particles are being magnetically kicked away from the black hole would come from observing that particles further away from Sgr A* are less energetic than those close in. A test for the cosmic string idea will capitalize on the prediction by theorists that the string should move at a high fraction of the speed of light. Follow-up observations with the VLA should be able to detect the corresponding shift in position of the filament.

Even if the filament is not physically tied to Sgr A*, the bend in the shape of this filament is still unusual. The bend coincides with, and could be caused by, a shock wave, akin to a sonic boom, where the blast wave from an exploded star is colliding with the powerful winds blowing away from massive stars surrounding the central black hole.

“We will keep hunting until we have a solid explanation for this object,” said co-author Miller Goss, from the National Radio Astronomy Observatory in Socorro, New Mexico. “And we are aiming to next produce even better, more revealing images.”

A paper describing these results appeared in the December 1st, 2017 issue of The Astrophysical Journal Letters.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

Megan Watzke
Harvard-Smithsonian Center for Astrophysics
+1 617-496-7998
mwatzke@cfa.harvard.edu

Peter Edmonds
Harvard-Smithsonian Center for Astrophysics
+1 617-571-7279
pedmonds@cfa.harvard.edu


Friday, December 22, 2017

Astronomers Shed Light on Formation of Black Holes and Galaxies

Image of the quasar host galaxy from the UC San Diego research team’s data. The distance to this quasar galaxy is ~9.3 billion light years. The four-color image shows findings from use of the Keck Observatory and ALMA. As seen from Keck Observatory, the green colors highlight the energetic gas across the galaxy that is being illuminated by the quasar. The blue color represents powerful winds blowing throughout the galaxy. The red-orange colors represent the cold molecular gas in the system as seen from ALMA. The supermassive black hole sits at the center of the bright red-orange circular area slightly below the middle of the image. Credit: A. Vayner and Team



Maunakea, Hawaii – Stars forming in galaxies appear to be influenced by the supermassive black hole at the center of the galaxy, but the mechanism of how that happens has not been clear to astronomers until now.

“Supermassive black holes are captivating,” says lead author Shelley Wright, a University of California San Diego Professor of Physics. “Understanding why and how galaxies are affected by their supermassive black holes is an outstanding puzzle in their formation.” 

In a study published today in The Astrophysical Journal, Wright, graduate student Andrey Vayner, and their colleagues examined the energetics surrounding the powerful winds generated by the bright, vigorous supermassive black hole (known as a “quasar”) at the center of the 3C 298 host galaxy, located approximately 9.3 billion light years away.

“We study supermassive black holes in the very early universe when they are actively growing by accreting massive amounts of gaseous material,” says Wright. “While black holes themselves do not emit light, the gaseous material they chew on is heated to extreme temperatures, making them the most luminous objects in the universe.”

The UC San Diego team’s research revealed that the winds blow out through the entire galaxy and impact the growth of stars. 

“This is remarkable that the supermassive black hole is able to impact stars forming at such large distances,” says Wright.

Today, neighboring galaxies show that the galaxy mass is tightly correlated with the supermassive black hole mass. Wright’s and Vayner’s research indicates that 3C 298 does not fall within this normal scaling relationship between nearby galaxies and the supermassive black holes that lurk at their center. But, in the early universe, their study shows that the 3C 298 galaxy is 100 times less massive than it should be given its behemoth supermassive black hole mass.

This implies that the supermassive black hole mass is established well before the galaxy, and potentially the energetics from the quasar are capable of controlling the growth of the galaxy.

To conduct the study, the UC San Diego researchers utilized multiple state-of-the-art astronomical facilities. The first of these was Keck Observatory’s instrument OSIRIS (OH-Suppressing Infrared Imaging Spectrograph) and its advanced adaptive optics (AO) system. An AO system allows ground-based telescopes to achieve higher quality images by correcting for the blurring caused by the Earth’s atmosphere. The resulting images are as good as those obtained from space. 

The second major facility was the Atacama Large Millimeter/submillimeter Array, known as “ALMA,” an international observatory in Chile that is able to detect millimeter wavelengths using up to 66 antennae to achieve high-resolution images of the gas surrounding the quasar.

“The most enjoyable part of researching this galaxy has been putting together all the data from different wavelengths and techniques,” said Vayner. “Each new dataset that we obtained on this galaxy answered one question and helped us put some of the pieces of the puzzle together. However, at the same time, it created new questions about the nature of galaxy and supermassive black hole formation.”

Wright agreed, saying that the data sets were “tremendously gorgeous” from both Keck Observatory and ALMA, offering a wealth of new information about the universe.

These findings are the first results from a larger survey of distant quasars and their energetics’ impact on star formation and galaxy growth. Vayner and the team will continue developing results on more distant quasars using the new facilities and capabilities from Keck Observatory and ALMA.



About OSIRIS


The OH-Suppressing Infrared Imaging Spectrograph (OSIRIS) is one of W. M. Keck Observatory’s "integral field spectrographs." The instrument works behind the adaptive optics system, and uses an array of lenslets to sample a small rectangular patch of the sky at resolutions approaching the diffraction limit of the 10-meter Keck Telescope. OSIRIS records an infrared spectrum at each point within the patch in a single exposure, greatly enhancing its efficiency and precision when observing small objects such as distant galaxies. It is used to characterize the dynamics and composition of early stages of galaxy formation.

About W.M. Keck Observatory


The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two, 10-meter optical/infrared telescopes on the summit of Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems.

Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. 

Article Summary


Latest findings using the W. M. Keck Observatory on Maunakea, Hawaii increase scientific understanding of how powerful winds generated by supermassive black holes impact and regulate the growth of 3C 298 Quasar Host Galaxy.


Thursday, December 21, 2017

Perseus Cluster: A New Twist in the Dark Matter Tale A Quick Look at the Perseus Cluster

Perseus Cluster
Credit: X-ray: NASA/CXO/Oxford University/J. Conlon et al. Radio: NRAO/AUI/NSF/Univ. of Montreal/Gendron-Marsolais et al.
Optical: NASA/ESA/IoA/A. Fabian et al.; DSS

Tour of Perseus Cluster - More Animations




An innovative interpretation of X-ray data from a galaxy cluster could help scientists understand the nature of dark matter, as described in our latest press release. The finding involves a new explanation for a set of results made with NASA's Chandra X-ray Observatory, ESA's XMM-Newton and Hitomi, a Japanese-led X-ray telescope. If confirmed with future observations, this may represent a major step forward in understanding the nature of the mysterious, invisible substance that makes up about 85% of matter in the Universe.

The image shown here contains X-ray data from Chandra (blue) of the Perseus galaxy cluster, which has been combined with optical data from the Hubble Space Telescope (pink) and radio emission from the Very Large Array (red). In 2014, researchers detected an unusual spike of intensity, known as an emission line, at a specific wavelength of X-rays (3.5 keV) in the hot gas within the central region of the Perseus cluster. They also reported the presence of this same emission line in a study of 73 other galaxy clusters.

In the subsequent months and years, astronomers have tried to confirm the existence of this 3.5 keV line. They are eager to do so because it may give us important clues about the nature of dark matter. However, it has been debated in the astronomical community exactly what the original and follow-up observations have revealed.

Credit: NASA/CXC/M. Weiss

A new analysis of Chandra data by a team from Oxford University, however, is providing a fresh take on this debate. The latest work shows that absorption of X-rays at an energy of 3.5 keV is detected when observing the region surrounding the supermassive black hole at the center of Perseus. This suggests that dark matter particles in the cluster are both absorbing and emitting X-rays (see our artist's impression above for a diagram helping to explain this behavior, where 3.5 keV X-rays are shown). If the new model turns out to be correct, it could provide a path for scientists to one day identify the true nature of dark matter. For next steps, astronomers will need further observations of the Perseus cluster and others like it with current X-ray telescopes and those being planned for the next decade and beyond.

A paper describing these results was published in Physical Review D on December 19, 2017 and a preprint is available online. The authors of the paper are Joseph Conlon, Francesca Day, Nicolas Jennings, Sven Krippendorf and Markus Rummel, all from Oxford University in the UK. 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 Perseus Cluster:

Scale: Image is 3.87 arcmin (about 280,000 light years) across
Category:   Groups & Clusters of Galaxies, Cosmology/Deep Fields/X-ray Background
Coordinates (J2000): RA 03h 19m 47.60s | Dec +41° 30´ 37.00"
Constellation: Perseus
Observation Date: 2009
Observation Time: 55 hours 33 minutes (2 days 7 hours 33 minutes)
Obs. ID: 11713,12025,12044, 12036
Instrument: ACIS
Also Known As: Abell 426
References: Conlon et al. 2017 Physical Review D, 90, 123009; arXiv: 1086.01684
Color Code: X-ray (Blue); Optical (Pink); Radio (Red)
Distance Estimate: About 250 million light years



Wednesday, December 20, 2017

Giant Bubbles on Red Giant Star’s Surface

The surface of the red giant star π1 Gruis from PIONIER on the VLT

PR Image eso1741b
Widefield image of the sky around π1 Gruis

PR Image eso1741c
The red giant star π1 Gruis in the constellation of Grus



Videos
 
ESOcast 144 Light: Giant Bubbles on Red Giant Star’s Surface (4K UHD)
ESOcast 144 Light: Giant Bubbles on Red Giant Star’s Surface (4K UHD) 

Zooming in on the red giant star π1 Gruis
Zooming in on the red giant star π1 Gruis 



Astronomers using ESO’s Very Large Telescope have for the first time directly observed granulation patterns on the surface of a star outside the Solar System — the ageing red giant π1 Gruis. This remarkable new image from the PIONIER instrument reveals the convective cells that make up the surface of this huge star, which has 350 times the diameter of the Sun. Each cell covers more than a quarter of the star’s diameter and measures about 120 million kilometres across. These new results are being published this week in the journal Nature.

Located 530 light-years from Earth in the constellation of Grus (The Crane), π1 Gruis is a cool red giant. It has about the same mass as our Sun, but is 350 times larger and several thousand times as bright [1]. Our Sun will swell to become a similar red giant star in about five billion years.

An international team of astronomers led by Claudia Paladini (ESO) used the PIONIER instrument on ESO’s Very Large Telescope to observe π1 Gruis in greater detail than ever before. They found that the surface of this red giant has just a few convective cells, or granules, that are each about 120 million kilometres across — about a quarter of the star’s diameter [2]. Just one of these granules would extend from the Sun to beyond Venus. The surfaces  — known as photospheres —  of many giant stars are obscured by dust, which hinders observations. However, in the case of π1 Gruis, although dust is present far from the star, it does not have a significant effect on the new infrared observations [3].

When π1 Gruis ran out of hydrogen to burn long ago, this ancient star ceased the first stage of its nuclear fusion programme. It shrank as it ran out of energy, causing it to heat up to over 100 million degrees. These extreme temperatures fueled the star’s next phase as it began to fuse helium into heavier atoms such as carbon and oxygen. This intensely hot core then expelled the star’s outer layers, causing it to balloon to hundreds of times larger than its original size. The star we see today is a variable red giant. Until now, the surface of one of these stars has never before been imaged in detail.

By comparison, the Sun’s photosphere contains about two million convective cells, with typical diameters of just 1500 kilometres. The vast size differences in the convective cells of these two stars can be explained in part by their varying surface gravities. π1 Gruis is just 1.5 times the mass of the Sun but much larger, resulting in a much lower surface gravity and just a few, extremely large, granules.

While stars more massive than eight solar masses end their lives in dramatic supernovae explosions, less massive stars like this one gradually expel their outer layers, resulting in beautiful planetary nebulae. Previous studies of π1 Gruis found a shell of material 0.9 light-years away from the central star, thought to have been ejected around 20 000 years ago. This relatively short period in a star's life lasts just a few tens of thousands of years – compared to the overall lifetime of several billion – and these observations reveal a new method for probing this fleeting red giant phase.



Notes

[1] π1 Gruis is named following the Bayer designation system. In 1603 the German astronomer Johann Bayer classified 1564 stars, naming them by a Greek letter followed by the name of their parent constellation. Generally, stars were assigned Greek letters in rough order of how bright they appeared from Earth, with the brightest designated Alpha (α). The brightest star of the Grus constellation is therefore Alpha Gruis.


π1 Gruis is one of an attractive pair of stars of contrasting colours that appear close together in the sky, the other one naturally being named π2 Gruis. They are bright enough to be well seen in a pair of binoculars. Thomas Brisbane realised in the 1830s that π1 Gruis was itself also a much closer binary star system. Annie Jump Cannon, credited with the creation of the Harvard Classification Scheme, was the first to report the unusual spectrum of π1 Gruis in 1895.

[2] Granules are patterns of convection currents in the plasma of a star. As plasma heats up at the centre of the star it expands and rises to the surface, then cools at the outer edges, becoming darker and more dense, and descends back to the centre. This process continues for billions of years and plays a major role in many astrophysical processes including energy transport, pulsation, stellar wind and dust clouds on brown dwarfs.

[3] π1 Gruis is one of the brightest members of the rare S class of stars that was first defined by the American astronomer Paul W. Merrill to group together stars with similarly unusual spectra. π1 Gruis, R Andromedae and R Cygni became prototypes of this type. Their unusual spectra is now known to be the result of the “s-process” or “slow neutron capture process” — responsible for the creation of half the elements heavier than iron.



More Information


This research was presented in a paper “Large granulation cells on the surface of the giant star π1 Gruis”, by C. Paladini et al., published in the journal Nature on 21 December 2017.

The team is composed of C. Paladini (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium; ESO, Santiago, Chile), F. Baron (Georgia State University, Atlanta, Georgia, USA), A. Jorissen (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), J.-B. Le Bouquin (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), B. Freytag (Uppsala University, Uppsala, Sweden), S. Van Eck (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), M. Wittkowski (ESO, Garching, Germany), J. Hron (University of Vienna, Vienna, Austria), A. Chiavassa (Laboratoire Lagrange, Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, Nice, France), J.-P. Berger (Université Grenoble Alpes, CNRS, IPAG, Grenoble, France), C. Siopis (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), A. Mayer (University of Vienna, Vienna, Austria), G. Sadowski (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), K. Kravchenko (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), S. Shetye (Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles, Brussels, Belgium), F. Kerschbaum (University of Vienna, Vienna, Austria), J. Kluska (University of Exeter, Exeter, UK) and S. Ramstedt (Uppsala University, Uppsala, Sweden).

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”.



Links


Contacts 

Claudia Paladini
ESO
Santiago, Chile
Email:
cpaladin@eso.org

Alain Jorissen
Institut d’Astronomie et d’Astrophysique, Université libre de Bruxelles
Brussels, Belgium
Tel: +32 (0) 2 6502834
Email:
Alain.Jorissen@ulb.ac.be

Fabien Baron
Georgia State University
Atlanta, Georgia, USA
Email:
fbaron@gsu.edu

Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email:
rhook@eso.org

Source: ESO

Tuesday, December 19, 2017

Habitable planets around pulsars theoretically possible

Artistic impression of a habitable planet (centre) near a pulsar (right). Such a planet must have an enormous atmosphere that convert the deadly X-rays and high energy particles of the pulsar into heat. (c) Institute of Astronomy, University of Cambridge.  Hi-res image

It is theoretically possible that habitable planets exist around pulsars. Such planets must have an enormous atmosphere that convert the deadly X-rays and high energy particles of the pulsar into heat. That is stated in a scientific paper by astronomers Alessandro Patruno and Mihkel Kama, working in the Netherlands and the United Kingdom. The paper appears today in the journal Astronomy & Astrophysics.

Pulsars are known for their extreme conditions. They are neutron stars of only 10 to 30 kilometers in diameter. They have enormous magnetic fields, they accrete matter and they regularly burst out large amounts of X-rays and other energetic particles. Nevertheless, Alessandro Patruno (Leiden University and ASTRON) and Mihkel Kama (Leiden University and Cambridge University) suggest that there could be life in the vicinity of these stars. 

It is the first time that astronomers try to calculate so-called habitable zones near neutron stars. The calculations show that the habitable zone around a neutron star can be as large as the distance from our Earth to our Sun. An important premise is that the planet must be a super-Earth with a mass between one and ten times of our Earth. A smaller planet will lose its atmosphere within a few thousand years. Furthermore, the atmosphere must be a million times as thick as that of the Earth. The conditions on the pulsar planet surface might resemble those of the deep sea at Earth.

The astronomers studied the pulsar PSR B1257+12 about 2300 light-years away in the constellation Virgo. They used the Chandra space telescope that is specially made to observe X-rays. Three planets orbit the pulsar. Two of them are super-Earths with a mass of four to five times our Earth. The planets orbit close enough around the pulsar to warm up. Patruno: "According to our calculations, the temperature of the planets might be suitable for the presence of liquid water on their surface. Though, we don't know yet if the two super-Earths have the right, extremely dense atmosphere." 

In the future, the astronomers would love to observe the pulsar in more detail and compare it with other pulsars. The ALMA telescope of the European Southern Observatory would be able to show dust discs around neutron stars. Such disks are good predictors of planets. 

Probably our Milky Way contains about 1 billion neutron stars of which about 200,000 pulsars. So far, 3000 pulsars have been studied and only 5 pulsar planets have been found. PSR B1257+12 is a much-studied pulsar. In 1992, the first exoplanets ever were discovered around this object. 

Article:

Neutron Star Planets: Atmospheric processes and irradiation  
By: A. Patruno & M. Kama. In Astronomy & Astrophysics (free preprint



Friday, December 15, 2017

Cosmic fireflies

Credit: ESA/Hubble & NASA


Galaxies glow like fireflies in this spectacular NASA/ESA Hubble Space Telescope image! This flickering swarm of cosmic fireflies is a rich cluster of galaxies called Abell 2163. Abell 2163 is a member of the Abell catalogue, an all-sky catalogue of over 4000 galaxy clusters. It is particularly well-studied because the material sitting at its core (its intracluster medium) exhibits exceptional properties, including a large and bright radio halo and extraordinarily high temperatures and X-ray luminosities. It is the hottest cluster in the catalogue! Observing massive clusters like Abell 2163 can contribute to the study of dark matter, and provide a new perspective on the distant Universe via phenomena such as gravitational lensing

This image was taken by Hubble’s Advanced Camera for Surveys and Wide-Field Camera 3, partially for an extensive observing programme called RELICS. The programme is imaging 41 massive galaxy clusters to find the brightest distant galaxies, which will be studied in more detail using both current telescopes and the future NASA/ESA/CSA James Webb Space Telescope (JWST).



Thursday, December 14, 2017

Mars Mission Sheds Light on Habitability of Distant Planets

This illustration depicts charged particles from a solar storm stripping away charged particles of Mars' atmosphere, one of the processes of Martian atmosphere loss studied by NASA's MAVEN mission, beginning in 2014. Unlike Earth, Mars lacks a global magnetic field that could deflect charged particles emanating from the Sun. Image credit: NASA/GSFC.  › Full image and caption


To receive the same amount of starlight as Mars receives from our Sun, a planet orbiting an M-type red dwarf would have to be positioned much closer to its star than Mercury is to the Sun. Image credit: NASA/GSFC.  › Full image and caption


How long might a rocky, Mars-like planet be habitable if it were orbiting a red dwarf star? It's a complex question but one that NASA's Mars Atmosphere and Volatile Evolution mission can help answer.

"The MAVEN mission tells us that Mars lost substantial amounts of its atmosphere over time, changing the planet's habitability," said David Brain, a MAVEN co-investigator and a professor at the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder. "We can use Mars, a planet that we know a lot about, as a laboratory for studying rocky planets outside our solar system, which we don't know much about yet."

At the fall meeting of the American Geophysical Union on Dec. 13, 2017, in New Orleans, Louisiana, Brain described how insights from the MAVEN mission could be applied to the habitability of rocky planets orbiting other stars. 

MAVEN carries a suite of instruments that have been measuring Mars' atmospheric loss since November 2014. The studies indicate that Mars has lost the majority of its atmosphere to space over time through a combination of chemical and physical processes. The spacecraft's instruments were chosen to determine how much each process contributes to the total escape.

In the past three years, the Sun has gone through periods of higher and lower solar activity, and Mars also has experienced solar storms, solar flares and coronal mass ejections. These varying conditions have given MAVEN the opportunity to observe Mars' atmospheric escape getting cranked up and dialed down.

Brain and his colleagues started to think about applying these insights to a hypothetical Mars-like planet in orbit around some type of M-star, or red dwarf, the most common class of stars in our galaxy.

The researchers did some preliminary calculations based on the MAVEN data. As with Mars, they assumed that this planet might be positioned at the edge of the habitable zone of its star. But because a red dwarf is dimmer overall than our Sun, a planet in the habitable zone would have to orbit much closer to its star than Mercury is to the Sun.

The brightness of a red dwarf at extreme ultraviolet (UV) wavelengths combined with the close orbit would mean that the hypothetical planet would get hit with about 5 to 10 times more UV radiation than the real Mars does. That cranks up the amount of energy available to fuel the processes responsible for atmospheric escape. Based on what MAVEN has learned, Brain and colleagues estimated how the individual escape processes would respond to having the UV cranked up.

Their calculations indicate that the planet's atmosphere could lose 3 to 5 times as many charged particles, a process called ion escape. About 5 to 10 times more neutral particles could be lost through a process called photochemical escape, which happens when UV radiation breaks apart molecules in the upper atmosphere.

Because more charged particles would be created, there also would be more sputtering, another form of atmospheric loss. Sputtering happens when energetic particles are accelerated into the atmosphere and knock molecules around, kicking some of them out into space and sending others crashing into their neighbors, the way a cue ball does in a game of pool.

Finally, the hypothetical planet might experience about the same amount of thermal escape, also called Jeans escape. Thermal escape occurs only for lighter molecules, such as hydrogen. Mars loses its hydrogen by thermal escape at the top of the atmosphere. On the exo-Mars, thermal escape would increase only if the increase in UV radiation were to push more hydrogen to the top of the atmosphere.

Altogether, the estimates suggest that orbiting at the edge of the habitable zone of a quiet M-class star, instead of our Sun, could shorten the habitable period for the planet by a factor of about 5 to 20. For an M-star whose activity is amped up like that of a Tasmanian devil, the habitable period could be cut by a factor of about 1,000 -- reducing it to a mere blink of an eye in geological terms. The solar storms alone could zap the planet with radiation bursts thousands of times more intense than the normal activity from our Sun.

However, Brain and his colleagues have considered a particularly challenging situation for habitability by placing Mars around an M-class star. A different planet might have some mitigating factors -- for example, active geological processes that replenish the atmosphere to a degree, a magnetic field to shield the atmosphere from stripping by the stellar wind, or a larger size that gives more gravity to hold on to the atmosphere. 

"Habitability is one of the biggest topics in astronomy, and these estimates demonstrate one way to leverage what we know about Mars and the Sun to help determine the factors that control whether planets in other systems might be suitable for life," said Bruce Jakosky, MAVEN's principal investigator at the University of Colorado Boulder.

MAVEN's principal investigator is based at the University of Colorado's Laboratory for Atmospheric and Space Physics, Boulder. The university provided two science instruments and leads science operations, as well as education and public outreach, for the mission. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the MAVEN project and provided two science instruments for the mission. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Exploration Program for NASA's Science Mission Directorate, Washington. 

For more information about MAVEN, visit: https://www.nasa.gov/maven


News Media Contact

Laurie Cantillo / Dwayne Brown
NASA Headquarters, Washington
202-358-1077 / 202-358-1726

laura.l.cantillo@nasa.gov / dwayne.c.brown@nasa.gov

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



Wednesday, December 13, 2017

Stellar Nursery Blooms into View

Stellar Nursery Blooms into View

The star formation region NGC 6559 in the constellation of Sagittarius

The rich surroundings of Sharpless 29



Videos

ESOcast 142 Light: Stellar Nursery Blooms into View (4K UHD)
ESOcast 142 Light: Stellar Nursery Blooms into View (4K UHD)

Zooming in on the star-forming region Sharpless 29
Zooming in on the star-forming region Sharpless 29

Panning across the VST’s view of Sharpless 29
Panning across the VST’s view of Sharpless 29



The OmegaCAM camera on ESO’s VLT Survey Telescope has captured this glittering view of the stellar nursery called Sharpless 29. Many astronomical phenomena can be seen in this giant image, including cosmic dust and gas clouds that reflect, absorb, and re-emit the light of hot young stars within the nebula.

The region of sky pictured is listed in the Sharpless catalogue of H II regions: interstellar clouds of ionised gas, rife with star formation. Also known as Sh 2-29, Sharpless 29 is located about 5500 light-years away in the constellation of Sagittarius (The Archer), next door to the larger Lagoon Nebula. It contains many astronomical wonders, including the highly active star formation site of NGC 6559, the nebula at the centre of the image.

This central nebula is Sharpless 29’s most striking feature. Though just a few light-years across, it showcases the havoc that stars can wreak when they form within an interstellar cloud. The hot young stars in this image are no more than two million years old and are blasting out streams of high-energy radiation. This energy heats up the surrounding dust and gas, while their stellar winds dramatically erode and sculpt their birthplace. In fact, the nebula contains a prominent cavity that was carved out by an energetic binary star system. This cavity is expanding, causing the interstellar material to pile up and create the reddish arc-shaped border.

When interstellar dust and gas are bombarded with ultraviolet light from hot young stars, the energy causes them to shine brilliantly. The diffuse red glow permeating this image comes from the emission of hydrogen gas, while the shimmering blue light is caused by reflection and scattering off small dust particles. As well as emission and reflection, absorption takes place in this region. Patches of dust block out the light as it travels towards us, preventing us from seeing the stars behind it, and smaller tendrils of dust create the dark filamentary structures within the clouds.

The rich and diverse environment of Sharpless 29 offers astronomers a smorgasbord of physical properties to study. The triggered formation of stars, the influence of the young stars upon dust and gas, and the disturbance of magnetic fields can all be observed and examined in this single area.
But young, massive stars live fast and die young. They will eventually explosively end their lives in a supernova, leaving behind rich debris of gas and dust. In tens of millions of years, this will be swept away and only an open cluster of stars will remain.

Sharpless 29 was observed with ESO’s OmegaCAM on the VLT Survey Telescope (VST) at Cerro Paranal in Chile. OmegaCAM produces images that cover an area of sky more than 300 times greater than the largest field of view imager of the NASA/ESA Hubble Space Telescope, and can observe over a wide range of wavelengths from the ultraviolet to the infrared. Its hallmark feature is its ability to capture the very red spectral line H-alpha, created when the electron inside a hydrogen atom loses energy, a prominent occurrence in a nebula like Sharpless 29.




More Information


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, 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 Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.



Links


Contacts

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


Email: rhook@eso.org


Source: ESO

Tuesday, December 12, 2017

Chandra Reveals the Elementary Nature of Cassiopeia A

 Cassiopeia A
 Credit  NASA/CXC/SAO



 
Where do most of the elements essential for life on Earth come from? The answer: inside the furnaces of stars and the explosions that mark the end of some stars' lives.

Astronomers have long studied exploded stars and their remains — known as "supernova remnants" — to better understand exactly how stars produce and then disseminate many of the elements observed on Earth, and in the cosmos at large.

Due to its unique evolutionary status, Cassiopeia A (Cas A) is one of the most intensely studied of these supernova remnants. A new image from NASA's Chandra X-ray Observatory shows the location of different elements in the remains of the explosion: silicon (red), sulfur (yellow), calcium (green) and iron (purple). Each of these elements produces X-rays within narrow energy ranges, allowing maps of their location to be created. The blast wave from the explosion is seen as the blue outer ring.

Location of elements in Cassiopeia A. 
Credit: NASA/CXC/SAO 

X-ray telescopes such as Chandra are important to study supernova remnants and the elements they produce because these events generate extremely high temperatures — millions of degrees — even thousands of years after the explosion. This means that many supernova remnants, including Cas A, glow most strongly at X-ray wavelengths that are undetectable with other types of telescopes.

Chandra's sharp X-ray vision allows astronomers to gather detailed information about the elements that objects like Cas A produce. For example, they are not only able to identify many of the elements that are present, but how much of each are being expelled into interstellar space.

The Chandra data indicate that the supernova that produced Cas A has churned out prodigious amounts of key cosmic ingredients. Cas A has dispersed about 10,000 Earth masses worth of sulfur alone, and about 20,000 Earth masses of silicon. The iron in Cas A has the mass of about 70,000 times that of the Earth, and astronomers detect a whopping one million Earth masses worth of oxygen being ejected into space from Cas A, equivalent to about three times the mass of the Sun. (Even though oxygen is the most abundant element in Cas A, its X-ray emission is spread across a wide range of energies and cannot be isolated in this image, unlike with the other elements that are shown.)

Astronomers have found other elements in Cas A in addition to the ones shown in this new Chandra image. Carbon, nitrogen, phosphorus and hydrogen have also been detected using various telescopes that observe different parts of the electromagnetic spectrum. Combined with the detection of oxygen, this means all of the elements needed to make DNA, the molecule that carries genetic information, are found in Cas A.

Periodic Table of Elements
Credit: NASA/CXC/K. Divona

Oxygen is the most abundant element in the human body (about 65% by mass), calcium helps form and maintain healthy bones and teeth, and iron is a vital part of red blood cells that carry oxygen through the body. All of the oxygen in the Solar System comes from exploding massive stars. About half of the calcium and about 40% of the iron also come from these explosions, with the balance of these elements being supplied by explosions of smaller mass, white dwarf stars.

While the exact date is not confirmed (PDF), many experts think that the stellar explosion that created Cas A occurred around the year 1680 in Earth's timeframe. Astronomers estimate that the doomed star was about five times the mass of the Sun just before it exploded. The star is estimated to have started its life with a mass about 16 times that of the Sun, and lost roughly two-thirds of this mass in a vigorous wind blowing off the star several hundred thousand years before the explosion.

Earlier in its lifetime, the star began fusing hydrogen and helium in its core into heavier elements through the process known as "nucleosynthesis." The energy made by the fusion of heavier and heavier elements balanced the star against the force of gravity. These reactions continued until they formed iron in the core of the star. At this point, further nucleosynthesis would consume rather than produce energy, so gravity then caused the star to implode and form a dense stellar core known as a neutron star.

Pre-Supernova Star: As it nears the end of its evolution, heavy elements produced by nuclear fusion inside the star are concentrated toward the center of the star. Illustration Credit: NASA/CXC/S. Lee 

The exact means by which a massive explosion is produced after the implosion is complicated, and a subject of intense study, but eventually the infalling material outside the neutron star was transformed by further nuclear reactions as it was expelled outward by the supernova explosion.

Chandra has repeatedly observed Cas A since the telescope was launched into space in 1999. The different datasets have revealed new information about the neutron star in Cas A, the details of the explosion, and specifics of how the debris is ejected into space.

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 Cassiopeia A:

Scale: Image is 8.91 arcmin across (about 29 light years)
Category: Supernovas & Supernova Remnants
Observation Date: 16 pointings between Jan. 2000-Nov. 2010
Observation Time: 353 hours (14 days, 17 hours)
Obs. ID: 114, 1952, 4634-4639, 5196, 5319, 5320, 6690, 10935, 10936, 12020, 13177
Instrument: ACIS
Also Known As: Cas A
References: Hwang and Laming, 2012, ApJ, 746, 130; arXiv:1111.7316; Lee, et al. 2014, ApJ, 789, 7; arXiv:1304.3973
Color Code: X-rays: Red: Silicon, Yellow: Sulphur, Green: Calcium, Purple: Iron, Blue: Blast Wave
Distance Estimate: About 11,000 light years