ESA : A monster in the Milky Way

A monster in the Milky Way

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This image, not unlike a pointillist painting, shows the star-studded centre of the Milky Way towards the constellation of Sagittarius. The crowded centre of our galaxy contains numerous complex and mysterious objects that are usually hidden at optical wavelengths by clouds of dust — but many are visible here in these infrared observations from Hubble.

However, the most famous cosmic object in this image still remains invisible: the monster at our galaxy’s heart called Sagittarius A*. Astronomers have observed stars spinning around this supermassive black hole (located right in the centre of the image), and the black hole consuming clouds of dust as it affects its environment with its enormous gravitational pull.

Infrared observations can pierce through thick obscuring material to reveal information that is usually hidden to the optical observer. This is the best infrared image of this region ever taken with Hubble, and uses infrared archive data from Hubble’s Wide Field Camera 3, taken in September 2011. It was posted to Flickr by Gabriel Brammer, a fellow at the European Southern Observatory based in Chile. He is also an ESO photo ambassador

ESA
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com

NASA - NASA'S Chandra Turns up Black Hole Bonanza in Galaxy Next Door

The Remarkable Remains of a Recent Supernova

June 26, 2013

Astronomers estimate that a star explodes as a supernova in our Galaxy, on average, about twice per century. In 2008, a team of scientists announced they discovered the remains of a supernova that is the most recent, in Earth's time frame, known to have occurred in the Milky Way.

The explosion would have been visible from Earth a little more than a hundred years ago if it had not been heavily obscured by dust and gas. Its likely location is about 28,000 light years from Earth near the center of the Milky Way. A long observation equivalent to more than 11 days of observations of its debris field, now known as the supernova remnant G1.9+0.3, with NASA's Chandra X-ray Observatory is providing new details about this important event.

The source of G1.9+0.3 was most likely a white dwarf star that underwent a thermonuclear detonation and was destroyed after merging with another white dwarf, or pulling material from an orbiting companion star. This is a particular class of supernova explosions (known as Type Ia) that are used as distance indicators in cosmology because they are so consistent in brightness and incredibly luminous.

The explosion ejected stellar debris at high velocities, creating the supernova remnant that is seen today by Chandra and other telescopes. This new image is a composite from Chandra where low-energy X-rays are red, intermediate energies are green and higher-energy ones are blue. Also shown are optical data from the Digitized Sky Survey, with appearing stars in white. The new Chandra data, obtained in 2011, reveal that G1.9+0.3 has several remarkable properties.

The Chandra data show that most of the X-ray emission is "synchrotron radiation," produced by extremely energetic electrons accelerated in the rapidly expanding blast wave of the supernova. This emission gives information about the origin of cosmic rays - energetic particles that constantly strike the Earth's atmosphere - but not much information about Type Ia supernovas.

In addition, some of the X-ray emission comes from elements produced in the supernova, providing clues to the nature of the explosion. The long Chandra observation was required to dig out those clues.

Most Type Ia supernova remnants are symmetrical in shape, with debris evenly distributed in all directions. However, G1.9+0.3 exhibits an extremely asymmetric pattern. The strongest X-ray emission from elements like silicon, sulfur, and iron is found in the northern part of the remnant, giving an extremely asymmetric pattern.

Another exceptional feature of this remnant is that iron, which is expected to form deep in the doomed star's interior and move relatively slowly, is found far from the center and is moving at extremely high speeds of over 3.8 million miles per hour. The iron is mixed with lighter elements expected to form further out in the star.

Because of the uneven distribution of the remnant's debris and their extreme velocities, the researchers conclude that the original supernova explosion also had very unusual properties. That is, the explosion itself must have been highly non-uniform and unusually energetic.

By comparing the properties of the remnant with theoretical models, the researchers found hints about the explosion mechanism. Their favorite concept for what happened in G1.9+0.3 is a "delayed detonation," where the explosion occurs in two different phases. First, nuclear reactions occur in a slowly expanding wavefront, producing iron and similar elements. The energy from these reactions causes the star to expand, changing its density and allowing a much faster-moving detonation front of nuclear reactions to occur.

If the explosion were highly asymmetric, then there should be large variations in expansion rate in different parts of the remnant. These should be measurable with future observations with X-rays using Chandra and radio waves with the NSF's Karl G. Jansky Very Large Array.

Observations of G1.9+0.3 allow astronomers a special, close-up view of a young supernova remnant and its rapidly changing debris. Many of these changes are driven by the radioactive decay of elements ejected in the explosion. For example, a large amount of antimatter should have formed after the explosion by radioactive decay of cobalt. Based on the estimated mass of iron, which is formed by radioactive decay of nickel to cobalt to iron, over a hundred million trillion (i.e. ten raised to the power of twenty) pounds of positrons, the antimatter counterpart to electrons, should have formed. However, nearly all of these positrons should have combined with electrons and been destroyed, so no direct observational signature of this antimatter should remain.

A paper describing these results is available online and will be published in the July 1, 2013 issue of The Astrophysical Journal Letters. The first author is Kazimierz Borkowski of North Carolina State University (NCSU), in Raleigh, NC and his co-authors are Stephen Reynolds, also of NCSU; Una Hwang from NASA's Goddard Space Flight Center (GSFC) in Greenbelt, MD; David Green from Cavendish Laboratory in Cambridge, UK; Robert Petre, also from GSFC; Kalyani Krishnamurthy from Duke University in Durham, NC and Rebecca Willett, also from Duke University. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Credits: X-ray: NASA/CXC/NCSU/K. Borkowski et al.; Optical: DSS

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NASA'S Chandra Turns up Black Hole Bonanza in Galaxy Next Door

WASHINGTON - Using data from NASA's Chandra X-ray Observatory, astronomers have discovered an unprecedented bonanza of black holes in the Andromeda Galaxy, one of the nearest galaxies to the Milky Way.

Using more than 150 Chandra observations, spread over 13 years, researchers identified 26 black hole candidates, the largest number to date, in a galaxy outside our own. Many consider Andromeda to be a sister galaxy to the Milky Way. The two ultimately will collide, several billion years from now.

"While we are excited to find so many black holes in Andromeda, we think it's just the tip of the iceberg," said Robin Barnard of Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., and lead author of a new paper describing these results. "Most black holes won't have close companions and will be invisible to us."

The black hole candidates belong to the stellar mass category, meaning they formed in the death throes of very massive stars and typically have masses five to 10 times that of our sun. Astronomers can detect these otherwise invisible objects as material is pulled from a companion star and heated up to produce radiation before it disappears into the black hole.

The first step in identifying these black holes was to make sure they were stellar mass systems in the Andromeda Galaxy itself, rather than supermassive black holes at the hearts of more distant galaxies. To do this, the researchers used a new technique that draws on information about the brightness and variability of the X-ray sources in the Chandra data. In short, the stellar mass systems change much more quickly than the supermassive black holes.

To classify those Andromeda systems as black holes, astronomers observed that these X-ray sources had special characteristics: that is, they were brighter than a certain high level of X-rays and also had a particular X-ray color. Sources containing neutron stars, the dense cores of dead stars that would be the alternate explanation for these observations, do not show both of these features simultaneously. But sources containing black holes do.

The European Space Agency's XMM-Newton X-ray observatory added crucial support for this work by providing X-ray spectra, the distribution of X-rays with energy, for some of the black hole candidates. The spectra are important information that helps determine the nature of these objects.

"By observing in snapshots covering more than a dozen years, we are able to build up a uniquely useful view of M31," said co-author Michael Garcia, also of CfA. "The resulting very long exposure allows us to test if individual sources are black holes or neutron stars."

The research group previously identified nine black hole candidates within the region covered by the Chandra data, and the present results increase the total to 35. Eight of these are associated with globular clusters, the ancient concentrations of stars distributed in a spherical pattern about the center of the galaxy. This also differentiates Andromeda from the Milky Way as astronomers have yet to find a similar black hole in one of the Milky Way's globular clusters.

Seven of these black hole candidates are within 1,000 light-years of the Andromeda Galaxy's center. That is more than the number of black hole candidates with similar properties located near the center of our own galaxy. This is not a surprise to astronomers because the bulge of stars in the middle of Andromeda is bigger, allowing more black holes to form.

"When it comes to finding black holes in the central region of a galaxy, it is indeed the case where bigger is better," said co-author Stephen Murray of Johns Hopkins University and CfA. "In the case of Andromeda we have a bigger bulge and a bigger supermassive black hole than in the Milky Way, so we expect more smaller black holes are made there as well."

This new work confirms predictions made earlier in the Chandra mission about the properties of X-ray sources near the center of M31. Earlier research by Rasmus Voss and Marat Gilfanov of the Max Planck Institute for Astrophysics in Garching, Germany, used Chandra to show there was an unusually large number of X-ray sources near the center of M31. They predicted most of these extra X-ray sources would contain black holes that had encountered and captured low mass stars. This new detection of seven black hole candidates close to the center of M31 gives strong support to these claims.

"We are particularly excited to see so many black hole candidates this close to the center, because we expected to see them and have been searching for years," said Barnard.

These results will be published in the June 20 issue of The Astrophysical Journal. Many of the Andromeda observations were made within Chandra's Guaranteed Time Observer program.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra Program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

For Chandra images, multimedia and related materials, visit:
 


http://www.nasa.gov/chandra

For an additional interactive image, podcast, and video on the finding, visit:
 

http://chandra.si.edu

NASA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

NASA - NASA Chandra, Spitzer Study Suggests Black Holes Abundant Among The Earliest Stars

By comparing infrared and X-ray background signals across the same stretch of sky, an international team of astronomers has discovered evidence of a significant number of black holes that accompanied the first stars in the universe.

Using data from NASA's Chandra X-ray Observatory and NASA's Spitzer Space Telescope, which observes in the infrared, researchers have concluded one of every five sources contributing to the infrared signal is a black hole.

The cosmic microwave background, shown at left in this illustration, is a flash of light that occurred when the young universe cooled enough for electrons and protons to form the first atoms. It contains slight temperature fluctuations that correspond to regions of slightly different densities, representing the seeds of all cosmic structure we see around us today. The universe then went dark for hundreds of millions of years until the first stars shone and the first black holes began accreting gas. A portion of the infrared and X-ray signals from these sources is preserved in the cosmic infrared background, or CIB, and its X-ray equivalent, the CXB. At least 20 percent of the structure in these backgrounds changes in concert, indicating that black hole activity was hundreds of times more intense in the early universe than it is today.
Credit: Karen Teramura, UHIfA
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"Our results indicate black holes are responsible for at least 20 percent of the cosmic infrared background, which indicates intense activity from black holes feeding on gas during the epoch of the first stars," said Alexander Kashlinsky, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md.

The cosmic infrared background (CIB) is the collective light from an epoch when structure first emerged in the universe. Astronomers think it arose from clusters of massive suns in the universe's first stellar generations, as well as black holes, which produce vast amounts of energy as they accumulate gas.

Even the most powerful telescopes cannot see the most distant stars and black holes as individual sources. But their combined glow, traveling across billions of light-years, allows astronomers to begin deciphering the relative contributions of the first generation of stars and black holes in the young cosmos. This was at a time when dwarf galaxies assembled, merged and grew into majestic objects like our own Milky Way galaxy.

"We wanted to understand the nature of the sources in this era in more detail, so I suggested examining Chandra data to explore the possibility of X-ray emission associated with the lumpy glow of the CIB," said Guenther Hasinger, director of the Institute for Astronomy at the University of Hawaii in Honolulu, and a member of the study team.

Hasinger discussed the findings Tuesday at the 222nd meeting of the American Astronomical Society in Indianapolis. A paper describing the study was published in the May 20 issue of The Astrophysical Journal.

The work began in 2005, when Kashlinsky and his colleagues studying Spitzer observations first saw hints of a remnant glow. The glow became more obvious in further Spitzer studies by the same team in 2007 and 2012. The 2012 investigation examined a region known as the Extended Groth Strip, a single well-studied slice of sky in the constellation Bootes. In all cases, when the scientists carefully subtracted all known stars and galaxies from the data, what remained was a faint, irregular glow. There is no direct evidence this glow is extremely distant, but telltale characteristics lead researchers to conclude it represents the CIB.

In 2007, Chandra took especially deep exposures of the Extended Groth Strip as part of a multiwavelength survey. Along a strip of sky slightly larger than the full moon, the deepest Chandra observations overlap with the deepest Spitzer observations. Using Chandra observations, lead researcher Nico Cappelluti, an astronomer with the National Institute of Astrophysics in Bologna, Italy, produced X-ray maps with all of the known sources removed in three wavelength bands. The result, paralleling the Spitzer studies, was a faint, diffuse X-ray glow that constitutes the cosmic X-ray background (CXB).

Comparing these maps allowed the team to determine whether the irregularities of both backgrounds fluctuated independently or in concert. Their detailed study indicates fluctuations at the lowest X-ray energies are consistent with those in the infrared maps.

"This measurement took us some five years to complete and the results came as a great surprise to us," said Cappelluti, who also is affiliated with the University of Maryland, Baltimore County in Baltimore.

The process is similar to standing in Los Angeles while looking for signs of fireworks in New York. The individual pyrotechnics would be too faint to see, but removing all intervening light sources would allow the detection of some unresolved light. Detecting smoke would strengthen the conclusion at least part of this signal came from fireworks.

In the case of the CIB and CXB maps, portions of both infrared and X-ray light seem to come from the same regions of the sky. The team reports black holes are the only plausible sources that can produce both energies at the intensities required. Regular star-forming galaxies, even those that vigorously form stars, cannot do this.

By teasing out additional information from this background light, the astronomers are providing the first census of sources at the dawn of structure in the universe.

"This is an exciting and surprising result that may provide a first look into the era of initial galaxy formation in the universe," said another contributor to the study, Harvey Moseley, a senior astrophysicist at Goddard. "It is essential that we continue this work and confirm it."

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass. Data are archived at the Chandra X-ray Center in Cambridge.

NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., manages the Spitzer Space Telescope mission. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology (Caltech) in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

Related Links

› Paper: Cross-Correlating Cosmic Infrared and X-ray Background Fluctuations: Evidence of Significant Black Hole Populations Among the CIB Sources
› "NASA's Spitzer Finds First Objects Burned Furiously" (06.07.12)
› "NASA Telescope Picks Up Glow of Universe's First Objects" (12.18.06)
› NASA’s Chandra website
› NASA’s Spitzer website

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Francis Reddy
NASA's Goddard Space Flight Center, Greenbelt, Md.

(Text issued as NASA Headquarters release No. 13-170)

NASA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

NASA - Black Hole-Powered Jets Plow Into Galaxy

This composite image of a galaxy illustrates how the intense gravity of a supermassive black hole can be tapped to generate immense power. The image contains X-ray data from NASA's Chandra X-ray Observatory (blue), optical light obtained with the Hubble Space Telescope (gold) and radio waves from the NSF’s Very Large Array (pink).

This multi-wavelength view shows 4C+29.30, a galaxy located some 850 million light years from Earth. The radio emission comes from two jets of particles that are speeding at millions of miles per hour away from a supermassive black hole at the center of the galaxy. The estimated mass of the black hole is about 100 million times the mass of our Sun. The ends of the jets show larger areas of radio emission located outside the galaxy.

The X-ray data show a different aspect of this galaxy, tracing the location of hot gas. The bright X-rays in the center of the image mark a pool of million-degree gas around the black hole. Some of this material may eventually be consumed by the black hole, and the magnetized, whirlpool of gas near the black hole could in turn, trigger more output to the radio jet.

Most of the low-energy X-rays from the vicinity of the black hole are absorbed by dust and gas, probably in the shape of a giant doughnut around the black hole. This doughnut, or torus blocks all the optical light produced near the black hole, so astronomers refer to this type of source as a hidden or buried black hole. The optical light seen in the image is from the stars in the galaxy.

The bright spots in X-ray and radio emission on the outer edges of the galaxy, near the ends of the jets, are caused by extremely high energy electrons following curved paths around magnetic field lines. They show where a jet generated by the black hole has plowed into clumps of material in the galaxy (mouse over the image for the location of these bright spots). Much of the energy of the jet goes into heating the gas in these clumps, and some of it goes into dragging cool gas along the direction of the jet. Both the heating and the dragging can limit the fuel supply for the supermassive black hole, leading to temporary starvation and stopping its growth. This feedback process is thought to cause the observed correlation between the mass of the supermassive black hole and the combined mass of the stars in the central region or bulge or a galaxy.

These results were reported in two different papers. The first, which concentrated on the effects of the jets on the galaxy, is available online and was published in the May 10, 2012 issue of The Astrophysical Journal. It is led by Aneta Siemiginowska from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, MA and the co-authors are Łukasz Stawarz, from the Institute of Space and Astronautical Science in Yoshinodai, Japan; Teddy Cheung from the National Academy of Sciences in Washington, DC; Thomas Aldcroft from CfA; Jill Bechtold from University of Arizona in Tucson, AZ; Douglas Burke from CfA; Daniel Evans from CfA; Joanna Holt from Leiden University in Leiden, The Netherlands; Marek Jamrozy from Jagiellonian University in Krakow, Poland; and Giulia Migliori from CfA. The second, which concentrated on the supermassive black hole, is available online and was published in the October 20, 2012 issue of The Astrophysical Journal. It is led by Malgorzata Sobolewska from CfA, and the co-authors are Aneta Siemiginowska, Giulia Migliori, Łukasz Stawarz, Marek Jamrozy, Daniel Evans, and Teddy Cheung.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Credits: X-ray: NASA/CXC/SAO/A. Siemiginowska et al; Optical: NASA/STScI; Radio: NSF/NRAO/VLA

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J.D. Harrington, 202-358-0321
Headquarters, Washington
j.d.harrington@nasa.gov

Janet Anderson, 256-544-0034
Marshall Space Flight Center, Huntsville, Ala.
janet.l.anderson@nasa.gov

Megan Watzke 617-496-7998
Chandra X-ray Center, Cambridge, Mass.
mwatzke@cfa.harvard.edu

NASA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

NASA - Searching for the Best Black Hole Recipe

Ring Galaxy NGC 922

In this holiday season of home cooking and carefully-honed recipes, some astronomers are asking: what is the best mix of ingredients for stars to make the largest number of plump black holes?

They are tackling this problem by studying the number of black holes in galaxies with different compositions. One of these galaxies, the ring galaxy NGC 922, is seen in this composite image containing X-rays from NASA's Chandra X-ray Observatory (red) and optical data from the Hubble Space Telescope (pink, yellow and blue).

NGC 922 was formed by the collision between two galaxies – one seen in this image and another located outside the field of view. This collision triggered the formation of new stars in the shape of a ring. Some of these were massive stars that evolved and collapsed to form black holes.

Most of the bright X-ray sources in Chandra's image of NGC 922 are black holes pulling material in from the winds of massive companion stars. Seven of these are what astronomers classify as "ultraluminous X-ray sources" (ULXs). These are thought to contain stellar-mass black holes that are at least ten times more massive than the sun, which places them in the upper range for this class of black hole. They are a different class from the supermassive black holes found at the centers of galaxies, which are millions to billions of times the mass of the sun.

Theoretical work suggests that the most massive stellar-mass black holes should form in environments containing a relatively small fraction of elements heavier than hydrogen and helium, called “metals” by astronomers. In massive stars, the processes that drive matter away from the stars in stellar winds work less efficiently if the fraction of metals is smaller. Thus, stars with fewer of these metals among their ingredients should lose less of their mass through winds as they evolve. A consequence of this reduced mass loss is that a larger proportion of massive stars will collapse to form black holes when their nuclear fuel is exhausted. This theory appeared to be supported by the detection of a large number (12) of ULXs in the Cartwheel galaxy, where stars typically contain only about 30% of the metals found in the sun.

To test this theory, scientists studied NGC 922, which contains about the same fraction of metals as the sun, meaning that this galaxy is about three times richer in metals than the Cartwheel galaxy. Perhaps surprisingly, the number of ULXs found in NGC 922 is comparable to the number seen in the Cartwheel galaxy. Rather, the ULX tally appears to depend only on the rate at which stars are forming in the two galaxies, not on the fraction of metals they contain.

One explanation for these results is that the theory predicting the most massive stellar-mass black holes should form in metal poor conditions is incorrect. Another explanation is that the metal fraction in the Cartwheel galaxy is not low enough to have a clear effect on the production of unusually massive stellar-mass black holes, and therefore will not cause an enhancement in the number of ULXs. Recent models incorporating the evolution of stars suggest that a clear enhancement in the number of ULXs might only be seen when the metal fraction falls below about 15% of the Sun's value. Astronomers are investigating this possibility by observing galaxies with extremely low metal fractions using Chandra. The number of ULXs is being compared with the number found in galaxies with higher metal content. The results of this work will be published in a future paper.

A paper describing the results for NGC 922 was published in the March 10, 2012 issue of the Astrophysical Journal. The authors were Andrea Prestwich and Jose Luis Galache of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, MA; Tim Linden from University of Santa Cruz in Santa Cruz, CA; Vicky Kalogera from Northwestern University in Evanston, IL; Andreas Zezas from CfA and University of Crete in Crete, Greece; Tim Roberts from University of Durham in Durham, UK; Roy Kilgard from Wesleyan University in Middletown, CT; Anna Wolter and Ginevra Trinchieri from INAF in Milano, Italy. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Credits: X-ray: NASA/CXC/SAO/A. Prestwich et al; Optical: NASA/STScI

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› Chandra's Flickr photoset

 

 

J.D. Harrington, 202-358-0321
Headquarters, Washington
j.d.harrington@nasa.gov

Janet Anderson, 256-544-0034
Marshall Space Flight Center, Huntsville, Ala.
janet.l.anderson@nasa.gov

Megan Watzke 617-496-7998
Chandra X-ray Center, Cambridge, Mass.
mwatzke@cfa.harvard.edu

 NASA

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

ASTRONOMY: Cygnus X-1: A Stellar Mass Black Hole; NASA's Chandra Contributes to Black Hole Birth Announcement

Hi My Friends: AL VUELO DE UN QUINDE EL BLOG., New details about the birth of a famous black hole that took place millions of years ago have been uncovered, thanks to a team of scientists who used data from NASA's Chandra X-ray Observatory as well as from radio, optical and other X-ray telescopes. On the left, an optical image from the Digitized Sky Survey shows Cygnus X-1, outlined in a red box. Cygnus X-1 is located near large active regions of star formation in the Milky Way, as seen in this image that spans some 700 light years across. An artist's illustration on the right depicts what astronomers think is happening within the Cygnus X-1 system. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star. The black hole pulls material from a massive, blue companion star toward it. This material forms a disk (shown in red and orange) that rotates around the black hole before falling into it or being redirected away from the black hole in the form of powerful jets.

A trio of papers with data from radio, optical and X-ray telescopes, including NASA's Chandra X-ray Observatory, has revealed new details about the birth of this famous black hole that took place millions of years ago. Using X-ray data from Chandra, the Rossi X-ray Timing Explorer, and the Advanced Satellite for Cosmology and Astrophysics, scientists were able to determine the spin of Cygnus X-1 with unprecedented accuracy, showing that the black hole is spinning at very close to its maximum rate. Its event horizon -- the point of no return for material falling towards a black hole -- is spinning around more than 800 times a second.

Using optical observations of the companion star and its motion around its unseen companion, the team also made the most precise determination ever for the mass of Cygnus X-1, of 14.8 times the mass of the Sun. It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.

The researchers also announced that they have made the most accurate distance estimate yet of Cygnus X-1 using the National Radio Observatory's Very Long Baseline Array (VLBA). The new distance is about 6,070 light years from Earth. This accurate distance was a crucial ingredient for making the precise mass and spin determinations. Credits: X-ray: NASA/CXC; Optical: Digitized Sky Survey

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NASA's Chandra Contributes to Black Hole Birth Announcement:

New details about the birth of a famous black hole that took place millions of years ago have been uncovered, thanks to a team of scientists who used data from NASA's Chandra X-ray Observatory as well as from radio, optical and other X-ray telescopes.

Over three decades ago, Stephen Hawking placed -- and eventually lost -- a bet against the existence of a black hole in Cygnus X-1. Today, astronomers are confident the Cygnus X-1 system contains a black hole, and with these latest studies they have remarkably precise values of its mass, spin, and distance from Earth. With these key pieces of information, the history of the black hole has been reconstructed.

"This new information gives us strong clues about how the black hole was born, what it weighed and how fast it was spinning," said author Mark Reid of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass.

"This is exciting because not much is known about the birth of black holes." Reid led one of three papers -- all appearing in the November 10th issue of The Astrophysical Journal -- describing these new results on Cygnus X-1.

The other papers were led by Jerome Orosz from San Diego State University and Lijun Gou, also from CfA. Cygnus X-1 is a so-called stellar-mass black hole, a class of black holes that comes from the collapse of a massive star.

The black hole is in close orbit with a massive, blue companion star. Using X-ray data from Chandra, the Rossi X-ray Timing Explorer, and the Advanced Satellite for Cosmology and Astrophysics, a team of scientists was able to determine the spin of Cygnus X-1 with unprecedented accuracy, showing that the black hole is spinning at very close to its maximum rate.

Its event horizon -- the point of no return for material falling towards a black hole -- is spinning around more than 800 times a second. An independent study that compared the evolutionary history of the companion star with theoretical models indicates that the black hole was born some 6 million years ago.

In this relatively short time (in astronomical terms), the black hole could not have pulled in enough gas to ramp up its spin very much. The implication is that Cygnus X-1 was likely born spinning very quickly.

Using optical observations of the companion star and its motion around its unseen companion, the team made the most precise determination ever for the mass of Cygnus X-1, of 14.8 times the mass of the Sun. It was likely to have been almost this massive at birth, because of lack of time for it to grow appreciably.

"We now know that Cygnus X-1 is one of the most massive stellar black holes in the Galaxy," said Orosz. "And, it's spinning as fast as any black hole we've ever seen." Knowledge of the mass, spin and charge gives a complete description of a black hole, according to the so-called "No Hair" theorem.

This theory postulates that all other information aside from these parameters is lost for eternity behind the event horizon. The charge for an astronomical black hole is expected to be almost zero, so only the mass and spin are needed.

"It is amazing to me that we have a complete description of this asteroid-sized object that is thousands of light years away," said Gou. "This means astronomers have a more complete understanding of this black hole than any other in our Galaxy."

The team also announced that they have made the most accurate distance estimate yet of Cygnus X-1 using the National Radio Observatory's Very Long Baseline Array (VLBA). The new distance is about 6,070 light years from Earth. This accurate distance was a crucial ingredient for making the precise mass and spin determinations.

The radio observations also measured the motion of Cygnus X-1 through space, and this was combined with its measured velocity to give the three-dimensional velocity and position of the black hole.

This work showed that Cygnus X-1 is moving very slowly with respect to the Milky Way, implying it did not receive a large "kick" at birth. This supports an earlier conjecture that Cygnus X-1 was not born in a supernova, but instead may have resulted from the dark collapse of a progenitor star without an explosion.

The progenitor of Cygnus X-1 was likely an extremely massive star, which initially had a mass greater than about 100 times the sun before losing it in a vigorous stellar wind. In 1974, soon after Cygnus X-1 became a good candidate for a black hole, Stephen Hawking placed a bet with fellow astrophysicist Kip Thorne, a professor of theoretical physics at the California Institute of Technology, that Cygnus X-1 did not contain a black hole.

This was treated as an insurance policy by Hawking, who had done a lot of work on black holes and general relativity. By 1990, however, much more work on Cygnus X-1 had strengthened the evidence for it being a black hole.

With the help of family, nurses, and friends, Hawking broke into Thorne's office, found the framed bet, and conceded. "For forty years, Cygnus X-1 has been the iconic example of a black hole. However, despite Hawking's concession, I have never been completely convinced that it really does contain a black hole -- until now," said Thorne.

"The data and modeling described in these three papers at last provide a completely definitive description of this binary system." NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

More information is available at:
http://www.nasa.gov/chandra

http://www.nasa.gov/mission_pages/chandra/news/cygnusx1.html

Guillermo Gonzalo Sánchez Achutegui

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