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Chandra image of the star cluster RCW 38
The most recent Chandra image of a binary star system known as SS 433 shows two high-speed lobes of 50-million-degree gas that are 3 trillion miles apart on opposite sides of a binary black hole system. As shown in the illustration (lower right), the binary system, which has a diameter several million times smaller than the distance between the lobes, consists of a massive star and a black hole with a disk of hot matter. Material is ejected from this disk in narrow jets that slowly wobble (represented by blue circular arrow), or precess, around a fixed axis (dotted white line). The detection of the hot gas lobes so far away from the central black hole came as a surprise since earlier observations by Chandra and the Hubble Space Telescope had indicated that gas was cooling as it expanded away from the vicinity of the black hole in narrow jets. This led scientists to predict that no hot gas would be found farther than a few million kilometers from the black hole. This observation implies that the gas in the jets has been reheated, most likely by collisions between blobs of gas. Long-term optical monitoring observations have shown that matter is ejected every few minutes from the vicinity of the black hole in bullet-like gaseous blobs. The blobs apparently travel outward at about a quarter of the speed of light for several months without colliding until a faster blob collides with a slower one, causing a pileup that reheats the gas. SS 433 is similar to the XTE J1550-564 binary system, in that they both involve black holes that are producing high-speed jets of gas. However, there are significant differences. The X-ray emitting lobes in XTE J1550 are observed to be much farther from the black hole than those in SS 433, and the X-rays from the XTE J1550 lobes appear to be produced by a magnetized cloud of highly energetic electrons, not clouds of hot gas as in SS 433. These differences might be due to the mass of the companion stars, which are quite different. In XTE J1550, the companion star has a mass similar to that of the Sun, whereas in SS 433, the companion star's mass is estimated to be almost 20 times that of the Sun. Perhaps the rapid rate of evaporation of matter from the massive star could affect the behavior of the jets in SS 433. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (Credit: NASA/CXC/U. Amsterdam/S. Migliari et al.)
The Chandra X-ray Observatory image of NGC 6240 — a butterfly-shaped galaxy that is the product of the collision of two smaller galaxies — revealed that the central region of the galaxy (inset) contains not one, but two active giant black holes. Previous X-ray observatories had shown that the central region was an X-ray source, but astronomers did not know what was producing the X-rays. Radio, infrared, and optical observations had detected two bright nuclei, but their exact nature also remained a mystery. Chandra was able to show that the X-rays were coming from the two nuclei, and determine their X-ray spectra. These cosmic fingerprints revealed features that are characteristic of supermassive black holes — an excess of high energy photons from gas swirling around a black hole, and X-rays from fluorescing iron atoms in gas near black holes. Over the course of the next few hundred million years, the two supermassive black holes, which are about 3000 light years apart, will drift toward one another and merge to form one larger supermassive black hole. This detection of a binary black hole supports the idea that black holes grow to enormous masses in the centers of galaxies by merging with other black holes. NGC 6240 is a prime example of a "starburst" galaxy in which stars are forming, evolving, and exploding at an exceptionally rapid rate due to a relatively recent merger (30 million years ago). Heat generated by this activity created the extensive multimillion degree Celsius gas seen in this image. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (Credit: NASA/CXC/MPE/S.Komossa et al.)
Revealing Chandra image shows Mars glows in X-rays This remarkable image from the Chandra X-ray Observatory image gave scientists their first look at X-rays from Mars. In the sparse upper atmosphere of Mars, about 75 miles above its surface, the observed X-rays are produced by fluorescent radiation from oxygen atoms. X-rays from the Sun impact oxygen atoms, knock electrons out of the inner parts of their electron clouds, and excite the atoms to a higher energy level in the process. The atoms almost immediately return to their lower energy state and may emit a fluorescent X-ray in this process with an energy characteristic of the atom involved — oxygen in this case. A similar process involving ultraviolet light produces the visible light from fluorescent lamps. The X-ray power detected from the Martian atmosphere is very small, amounting to only 4 megawatts, comparable to the X-ray power of about ten thousand medical X-ray machines. Chandra was scheduled to observe Mars when it was only 43.5 million miles from Earth, and also near the point in its orbit when it is closest to the Sun. At the time of the Chandra observation, a huge dust storm developed on Mars that covered about one hemisphere, later to cover the entire planet. This hemisphere rotated out of view over the course of the 9-hour observation but no change was observed in the X-ray intensity, implying that the dust storm did not affect the upper atmosphere. The astronomers also found evidence for a faint halo of X-rays that extends out to 4,350 miles above the surface of Mars. Scientists believe the X-rays are produced by collisions of ions racing away from the Sun (the solar wind) with oxygen and hydrogen atoms in the tenuous exosphere of Mars. NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (Credit: NASA/CXC/MPE/K.Dennerl et al.)
Chandra casts cloud on alternative to dark matter An image from NASA's Chandra X-ray Observatory of galaxy NGC 720 shows the galaxy enveloped in a slightly flattened, or ellipsoidal cloud of hot gas that has an orientation different from that of the optical image of the galaxy. The flattening is too large to be explained by theories in which stars and gas are assumed to contain most of the mass in the galaxy. According to the standard theory of gravity, the X-ray producing cloud would need an additional source of gravity - a halo of dark matter - to keep the hot gas from expanding away. The mass of dark matter required would be about five to 10 times the mass of the stars in the galaxy. An alternative theory of gravity called MOND, for Modified Newtonian Dynamics, does away with the need for dark matter. However, MOND cannot explain the Chandra observation of NGC 720, which shows that the dark matter halo has a different shape from that of the stars and gas in the galaxy. This implies that dark matter is not just an illusion due to a shortcoming of the standard theory of gravity - it is real. The Chandra data also fit predictions of a cold dark matter model. According to this model, dark matter consists of slowly moving particles, which interact with each other and "normal" matter only through gravity. Other dark matter models, such as self-interacting dark matter, and cold molecular dark matter, are not consistent with the observation in that they require a dark matter halo that is too round or too flat, respectively. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. ( NASA/CXC/UCI/D.Buote et al.)
Chandra tracks evolution of X-ray jets A series of Chandra images has allowed scientists to trace the evolution of large-scale X-ray jets produced by a black hole in a binary star system. As the schematic shows, gaseous matter pulled from a normal star forms a disk around the black hole. The gas is heated to temperatures of millions of degrees, and intense electromagnetic forces in the disk can expel jets of high-energy particles. An outburst of X-rays from the source, XTE J1550-564, was detected by NASA's Rossi X-ray Timing Explorer (RXTE) in 1998. Further observations with Chandra and radio telescopes detected first one jet (left), then another opposing jet (right) of high-energy particles moving away from the black hole at about half the speed of light. Four years after the outburst, the jets had moved more than three light years apart with the left jet slowing down and disappearing. The observations indicate that the jet on the left is moving along a line tilted toward Earth, whereas the jet on the right is tilted away from Earth. This alignment explains why the left jet appears to have traveled farther from the black hole than the jet on the right, and why the left jet faded first. However, with this alignment, the relative brightness of the right jet is difficult to understand because it is receding, and should be dimmer than it appears. One explanation is that it is plowing into a dense cloud of gas. The resistance of the gas would slow down the jet, and produce a shock wave that could energize the electrons in the jet, causing it to brighten. The observed cometary shape of the right jet indicates that it is in fact interacting with interstellar gas. The ejection of jets from stellar black holes and supermassive black holes is a common occurrence in the universe, and appears to be one of the primary ways that black holes inject energy into their environment. Although all jets are assumed to decelerate because of the resistance of the gas through which they move, the process can take millions of years for jets from supermassive black holes. The XTE J1550 jets are the first ones caught in the act of slowing down. During the past four years astronomers have observed a process that would take as much as a million years to unfold for a supermassive black hole jet. This underscores the enormous value of studying black holes in our galaxy such as XTE J1550. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (Photo credit: X-ray (NASA/CXC); Illustration credit: (CXC/M.Weiss))
Crab Nebula: Space movie reveals shocking secrets of the Crab pulsar A wisp can be seen moving outward at half the speed of light from the upper right of the inner ring around the pulsar. The wisp appears to merge with a larger outer ring that is visible in both X-ray and optical images. The inner X-ray ring consists of about two-dozen knots that form, brighten and fade. As a high-speed wind of matter and antimatter particles from the pulsar plows into the surrounding nebula, it creates a shock wave and forms the inner ring. Energetic shocked particles move outward to brighten the outer ring and produce an extended X-ray glow. Enormous electrical voltages generated by the rotating, highly magnetized neutron star accelerate particles outward along its equator to produce the pulsar wind. These pulsar voltages also produce the polar jets seen spewing X-ray emitting matter and antimatter particles perpendicular to the rings. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (NASA/CXC/ASU/J. Hester et al.)
Abell 2104: Chandra Reveals Black Hole Activity in Old Galaxies A Chandra observation of the galaxy cluster A2104 revealed six bright X-ray sources that are associated with supermassive black holes in red galaxies in the cluster. Since red galaxies are thought to be composed primarily older stars, and to contain little gas, the observation came as a surprise to astronomers. Powerful X-ray emission from a supermassive black hole comes from gas heated as it falls toward the black hole, so an abundant supply of gas is needed to produce the bright X-ray sources detected by Chandra. It is generally believed that as galaxies move through the hot cluster gas at high speeds, they are stripped of their interstellar gas, much as a strong wind strips leaves from a tree. Galaxies can also lose gas through collisions with other galaxies in the cluster. The presence of these six X-ray sources indicates that these supermassive black holes have somehow retained a fuel source, despite the harsh environment of the clusters. It could be that galaxies are better at holding onto a supply of gas and dust than previously thought, particularly deep down at their cores near the supermassive black hole. Such gas and dust may explain why the centers of the galaxies are obscured at optical wavelengths. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (NASA/CXC/Carnegie Observatories/P. Martini et al.)
Chandra X-ray Observatory image of Tycho's Supernova Remnant This Chandra image reveals fascinating details of the turbulent debris created by a supernova explosion observed by the Danish astronomer Tycho Brahe in 1572. The colors show different X-ray energies, with red, green, and blue representing low, medium and high energies, respectively. The image is cut off at the bottom because the southernmost region of the remnant fell outside the field of view of the detector. A shock wave produced by the expanding debris is outlined by the strikingly sharp blue circular arcs of twenty million degree Celsius gas seen on the outer rim. The stellar debris, which has a temperature of about ten million degrees and is visible only in X-rays, shows up as mottled yellow, green and red fingers of gas. Tycho's supernova remnant presents several interesting contrasts with the Cassiopeia A (Cas A) supernova remnant. The debris for Tycho is distributed in clumps rather than knots as in Cas A, and its outer shock wave can be seen in smooth and continuous arcs rather than being fragmented, as in Cas A. Also, no central point source is detected in Tycho, in contrast to Cas A. The absence of a central point source is consistent with other evidence that Tycho is a Type Ia supernova, which is thought to signal the detonation and destruction of a white dwarf star. Theory predicts that a white dwarf star will explode when infalling matter from a companion star increases the mass of the white dwarf beyond a critical mass limit, known as the Chandrasekhar limit. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (NASA/CXC)
Chandra's composite image of the Centaurus A galaxy A composite X-ray (blue), radio (pink and green), and optical (orange and yellow) image of the galaxy Centaurus A presents a stunning tableau of a galaxy in turmoil. A broad band of dust and cold gas is bisected at an angle by opposing jets of high-energy particles blasting away from the supermassive black hole in the nucleus. Two large arcs of X-ray emitting hot gas were discovered in the outskirts of the galaxy on a plane perpendicular to the jets. The arcs of multimillion-degree gas appear to be part of a projected ring 25,000 light years in diameter. The size and location of the ring indicates that it may have been produced in a titanic explosion that occurred about ten million years ago. Such an explosion would have produced the high-energy jets, and a galaxy-sized shock wave moving outward at speeds of a million miles per hour. The age of 10 million years for the outburst is consistent with optical and infrared observations that indicate that the rate of star formation in the galaxy increased dramatically at about that time. Scientists have suggested that all this activity may have begun with the merger of a small spiral galaxy and Centaurus A about 100 million years ago. Such a merger could eventually trigger both the burst of star formation and the violent activity in the nucleus of the galaxy. The tremendous energy released when a galaxy becomes "active" can have a profound influence on the subsequent evolution of the galaxy and its neighbors. The mass of the central black hole can increase, the gas reservoir for the next generation of stars can be expelled, and the space between the galaxies can be enriched with heavier elements. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. Image Credits:
Chandra image of the dwarf galaxy NGC 1569 The Chandra image of NGC 1569, a dwarf galaxy 7 million light years from Earth, shows large hot bubbles, or lobes extending above and below a disk of gas along the equator of the galaxy. The 27-hour observation allowed scientists to measure for the first time the concentration of oxygen, neon, magnesium, and silicon in the bubbles and the disk. They found that bubbles contain oxygen equal to the oxygen contained in 3 million suns. For the last 10 million to 20 million years NGC 1569 has been undergoing a burst of star formation and supernova explosions, perhaps triggered by a collision with a massive gas cloud. The supernovas eject oxygen and other heavy elements at high velocity into the gas in the galaxy, heating it to millions of degrees. Hot gas boils off the gaseous disk of the galaxy to form the bubbles, which expand out of the galaxy at speeds of hundreds of thousands of miles per hour. Dwarf galaxies are much smaller than ordinary galaxies like our Milky Way. Because of their size, they have relatively low gravity and matter can escape from them more easily. This property, combined with the fact that dwarf galaxies are the most common type of galaxy in the universe, makes them very important in understanding how the universe was seeded with various elements billions of years ago, when galaxies were forming. (Credit: NASA/CXC/UCSB/C. Martin et al.)
High-energy activity heats up the whirlpool X-rays from a rare type of supernova in the Whirlpool Galaxy were recently observed, thanks to the fine resolution of NASA's Chandra X-ray Observatory. The team of researchers also detected a large number of point-like X-ray sources due to black holes and neutron stars in binary star systems. Chandra's image highlights the energetic central regions of the two interacting galaxies, NGC 5194 (center) and its smaller companion (upper left) NGC 5195, that are collectively called the Whirlpool Galaxy. The inset contains an expanded image of the central region of NGC 5194. Extending to the north and south of the bright nucleus are clouds of multimillion-degree gas, with diameters of about 1500 light years and 500 light years, respectively. The similarity of these features with ones observed at radio wavelengths suggests that the gas is heated by high-velocity jets produced near a supermassive black hole in the nucleus of the galaxy. On the lower left of the inset image is a faint source identified with a supernova discovered in 1994 by amateur astronomers in Georgia, and subsequently determined to be an unusual Type Ic supernova. The massive stars responsible for these supernovas are thought to have lost their outer layers of hydrogen and helium gas thousands of years before the explosion, either through evaporation or transfer to a companion. In the millennia before a doomed star explodes into a supernova, it loses mass. X-ray observations of the supernova shock wave provide a method to sensitively probe into this process. The Chandra data from SN 1994I and its surrounding area indicate that the progenitor star evaporated material into a cloud around the star that has a diameter at Andrew Wilson of the University of Maryland, in College Park, was the principal investigator for the Chandra observations of M51. Other scientists involved in the research were Yuichi Terashima of the University of Maryland, and Stefan Immler of the University of Massachusetts, Amherst. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (Credit: NASA/CXC/UMD/A. Wilson et al.)
SNR G54.1+0.3: Energetic ring narks spot that leads to discovery of neutron star The Chandra image of the distant supernova Remnant SNR G54.1+0.3 reveals a bright ring of high-energy particles with a central point-like source. This observation enabled scientists to use the giant Arecibo Radio Telescope to search for and locate the pulsar, or neutron star that powers the ring. The ring of particles and two jet-like structures appear to be due to the energetic flow of radiation and particles from the rapidly spinning neutron star. During the supernova event, the core of a massive star collapsed to form a neutron star that is highly magnetized and creates an enormous electric field as it rotates. The electric field accelerates particles near the neutron star and produces jets blasting away from the poles, and as a disk of matter and anti-matter flowing away from the equator at high speeds. As the equatorial flow rams into the particles and magnetic fields in the nebula, a shock wave forms. The shock wave boosts the particles to extremely high energies causing them to glow in X-rays and produce a bright ring. The particles stream outward from the ring and the jets to supply the extended nebula, which spans approximately 6 light years. The features observed in SNR G54.1 are very similar to other "pulsar wind nebulas" found by Chandra in the Crab Nebula, the Vela supernova remnant, and PSR 1509-58. By analyzing the similarities and differences between these objects, scientists hope to better understand the fascinating process of transforming the rotational energy of the neutron star into high-energy particles with very little frictional heat loss. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (Credit: NASA/CXC/UMass/F. Lu et al.)
Artist's concept of the neutron star 1E 1207.4-5209. This artist's conception illustrates 1E 1207.4-5209, a neutron star with a polar hot spot and a strong magnetic field (purple lines). The neutron star is about 7,000 light years from Earth. The graph in the box to the right of the star shows the expected (dashed blue line) and the observed (solid green line) spectra of the X-radiation from the hot spot. The dips in the observed spectrum are absorption features due to gas in the atmosphere of the neutron star. According to the team of scientists that made the Chandra observation of 1E 1207, the most likely explanation for the dips in the spectrum is absorption by helium ions in a magnetic field about a hundred trillion times more intense than the Earth's magnetic field. This interpretation implies that the strong gravity of the neutron star has reduced the energy of the photons by 17 percent. The reduction of photon energy, known as the gravitational redshift, enables astronomers to relate the mass to the radius of the star. This information can then be used to help determine whether the collapsed star is composed mostly of neutrons, or contains large amounts of sub-nuclear particles called pions, kaons, or free quarks. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (CXC/M.Weiss)
Chandra image of the elliptical galaxy NGC 4697 Chandra's image of the elliptical galaxy NGC 4697 reveals diffuse hot gas dotted with many point-like sources. As in the elliptical galaxies, NGC 4649 and NGC 1553, the point-like sources are due to black holes and neutron stars in binary star systems. Material pulled off a normal star is heated and emits X-radiation as it falls toward its black hole or neutron star companion. Black holes and neutron stars are the end state of the brightest and most massive stars. Chandra's detection of numerous neutron stars and black holes in this and other elliptical galaxies shows that these galaxies once contained many very bright, massive stars, in marked contrast to the present population of low-mass faint stars that now dominate elliptical galaxies. An unusually large number of the binary star X-ray sources in NGC 4697 are in "globular star clusters," round balls of stars in the galaxy that contain about one million stars in a volume where typically only one would be found. This suggests that the extraordinarily dense environment of globular clusters may be a good place for black holes or neutron stars to capture a companion star. The origin of the hot gas cloud enveloping the galaxy is not known. One possibility is that the gas lost by evaporation from normal stars- so-called stellar winds - is heated by these winds and by supernova explosions. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (NASA/CXC/UVa/C.Sarazin et al.)
Chandra X-ray Observatory image of the NGC 1553 Galaxy Chandra's image of the lenticular -- an elliptical-type galaxy with a disk of old stars -- galaxy NGC 1553 reveals diffuse hot gas dotted with many point-like sources. As in the elliptical galaxies, NGC 4649 and NGC 4697, the point-like sources are due to black holes and neutron stars in binary star systems where material pulled off a normal star is heated and emits X-radiation as it falls toward its black hole or neutron star companion. Black holes and neutron stars are the end state of the brightest and most massive stars. Chandra's detection of numerous neutron stars and black holes in this and other elliptical galaxies shows that these galaxies once contained many very bright, massive stars, in marked contrast to the present population of low-mass faint stars that now dominate elliptical galaxies. The bright central source in NGC 1553 is probably due to a supermassive black hole in the nucleus of the galaxy. The nature of the spiral feature curling out from either side of this source is not known. It could be caused by shock waves from a pair of bubbles of high energy particles that were ejected from the vicinity of the supermassive black hole. (NASA/CXC/UVa/E.Blanton et al.)
Chandra X-ray Observatory image of the elliptical galaxy NGC 4649 Chandra's image of the elliptical galaxy NGC 4649 reveals a large, bright cloud of hot gas and 165 point-like sources. As in the elliptical galaxies, NGC 4697 and NGC 1553, most of the point-like sources are due to black holes and neutron stars in binary star systems. Black holes and neutron stars are the end state of the brightest and most massive stars. Chandra's detection of numerous neutron stars and black holes in this and other elliptical galaxies shows that these galaxies once contained many very bright, massive stars, in marked contrast to the present population of low-mass faint stars that now dominate elliptical galaxies. Many of the X-ray binaries are in "globular star clusters," round balls of stars that contain about one million stars in a volume where typically only one would be found. This suggests that the extraordinarily dense environment of globular clusters may be a good place for black holes or neutron stars to capture a companion star. The hot gas cloud filling the galaxy has a temperature of about 10 million degrees Celsius. In the bright central region there appear to be bright fingers of X-ray emission which could be due to rising cells of hot gas. (NASA/CXC/UVa/S.Randall et al.)
Every 64 hours, NASA's Chandra X-ray Observatory follows a path that dodges darkness, stretches one-third of the way to the Moon, and has a more elliptical shape than most orbiting satellites. Chandra's unique orbit was selected by, from left, Russell Stone, Steve Evans and Larry Mullins, all of NASA's Marshall Space Flight Center in Huntsville, Ala. (NASA/MSFC/Emmett Given)
N132D: Glowing Remnant from a Star-Shattering Explosion This "true color" Chandra image of N132D shows the beautiful, complex remnant of an explosion of a massive star in the Large Magellanic Cloud, a nearby galaxy about 180,000 light years from Earth. The colors represent different ranges of X-rays, with red, green, and blue representing, low, medium, and higher X-ray energies respectively. Supernova remnants comprise debris of a stellar explosion and any matter in the vicinity that is affected by the expanding debris. In the case of N132D, the horseshoe shape of the remnant is thought to be due to shock waves from the collision of the supernova ejecta with cool giant gas clouds. As the shock waves move through the gas they heat it to millions of degrees, producing the glowing X-ray shell. NASA's Marshall Space Flight Center in Huntsville, ala., manages the Chandra program for NASA. Credit: NASA/SAO/CXC
Chandra X-ray Observatory image of Arp 270: Merging galaxies and cosmic collisions
Chandra X-ray Observatory image of the Tarantula Nebula The Chandra image of the Tarantula Nebula gives scientists a close-up view of the drama of star formation and evolution. The Tarantula, also known as 30 Doradus, is in one of the most active star-forming regions in our local group of galaxies. Massive stars are producing intense radiation and searing winds of multimillion-degree gas that carve out gigantic super-bubbles in the surrounding gas. Other massive stars have raced through their evolution and exploded catastrophically as supernovas, leaving behind pulsars and expanding remnants that trigger the collapse of giant clouds of dust and gas to form new generations of stars. 30 Doradus is located about 160,000 light years from Earth in the Large Magellanic Cloud, a satellite galaxy of our Milky Way Galaxy. It allows astronomers to study the details of starbursts - episodes of extremely prolific star formation that play an important role in the evolution of galaxies. At least 11 extremely massive stars with ages of about 2 million years are detected in the bright star cluster in the center of the image. This crowded region contains many more stars whose X-ray emission is unresolved. The brightest source in this region known as Melnick 34, a 130 solar-mass star located slightly to the lower right of center. On the lower right of this panel is the supernova remnant N157B, with its central pulsar. In the image, lower energy X-rays appear red, medium energy green and high energy are blue. The Marshall Center manages the Chandra program. (NASA/CXC/Penn State/L. Townsley et al.)
Chandra image of the galaxy Arp 220 The Chandra observations of the peculiar galaxy Arp 220 gives new insight into what happens when two galaxies the size of the Milky Way collide. The image shows a bright central region at the waist of a glowing hour-glass-shaped cloud of multimillion degree gas that is rushing out of the galaxy at hundreds of thousands of miles per hour. This "superwind" is thought to be due to explosive activity generated by the formation of hundreds of millions of new stars. Further out, spanning a distance of 75,000 light years, are giant lobes of hot gas. These could be galactic remnants that have been flung into intergalactic space by the early impact of the collision. Whether the lobes will continue to expand into space or fall back into Arp 220 is unknown. In the central region of Arp 220, the Chandra observations allowed astronomers to pinpoint an X-ray source at the exact location of the nucleus of one of the pre-merger galaxies. Another fainter X-ray source nearby may coincide with the nucleus of the other galaxy remnant. These sources could be due to supermassive black holes at the centers of the merging galaxies. In a few hundred million years the two supermassive black holes could merge to produce a larger, supermassive black hole in the center of the conglomerate galaxy. Arp 220, at a relatively nearby distance of about 250 million light years from Earth, is a prototype for understanding what conditions were like in the early universe when massive galaxies and supermassive black holes may have been formed by numerous galaxy collisions. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (NASA/SAO/CXC/J. McDowell et al.)
3C58: Cosmic X-rays May Reveal New Form of Matter Chandra observations of RXJ1856.5-3754 and the pulsar in 3C58 suggest that the matter in these collapsed stars is even denser than nuclear matter, the most dense matter found on Earth. This raises the possibility that these stars are composed of free quarks or crystals of sub-nuclear particles, rather than neutrons. By combining Chandra and Hubble Space Telescope data, astronomers found that RXJ1856 radiates like a solid body with a temperature of 700,000 degrees Celsius and has a diameter of about 7 miles. This size is too small to reconcile with the standard models of neutron stars. One exciting possibility, predicted by some theories, is that the neutrons in the star have dissolved at very high density into a soup of "up," "down" and "strange" quarks to form a "strange quark star," which would explain the smaller radius. Observations of 3C58, the remnant of a supernova noted on Earth in AD 1181, reveal that the pulsar in the core has a temperature much lower than expected. This suggests that an exotic, denser state of matter might exist inside this star as well. These observations demonstrate that the universe can be used as a laboratory to explore physics under conditions that are not accessible on Earth. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (NASA/SAO/CXC/P.Slane et al.)
RXJ1856.5-3754: Cosmic X-rays May Reveal New Form of Matter Chandra observations of RXJ1856.5-3754 and the pulsar in 3C58 suggest that the matter in these collapsed stars is even denser than nuclear matter, the most dense matter found on Earth. This raises the possibility that these stars are composed of free quarks or crystals of sub-nuclear particles, rather than neutrons. By combining Chandra and Hubble Space Telescope data, astronomers found that RXJ1856 radiates like a solid body with a temperature of 700,000 degrees Celsius and has a diameter of about 7 miles. This size is too small to reconcile with the standard models of neutron stars. One exciting possibility, predicted by some theories, is that the neutrons in the star have dissolved at very high density into a soup of "up," "down" and "strange" quarks to form a "strange quark star," which would explain the smaller radius. Observations of 3C58, the remnant of a supernova noted on Earth in AD 1181, reveal that the pulsar in the core has a temperature much lower than expected. This suggests that an exotic, denser state of matter might exist inside this star as well. These observations demonstrate that the universe can be used as a laboratory to explore physics under conditions that are not accessible on Earth. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (NASA/SAO/CXC/J. Drake et al.)
Chandra image of three most distant quasars These three quasars, recently discovered at optical wavelengths by the Sloan Digital Sky Survey, are 13 billion light years from Earth, making them the most distant known quasars. The X-rays Chandra detected were emitted when the universe was only a billion years old, about 7 percent of the present age of the universe. A surprising result was that the power output and other properties of these quasars are similar to less distant quasars. This indicates that the conditions around these quasars' central supermassive black holes must also be similar, contrary to some theoretical expectations. As astronomer Smita Mathur of Ohio State, who was involved in the research said, "Perhaps the most remarkable thing about them is that they are so absolutely unremarkable." By various estimates, the supermassive black holes in these quasars weighed in at somewhere between one and 10 billion times the mass of the Sun. The implication is that the black holes put on a lot of weight soon after the galaxies formed. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program. (NASA/CXC/PSU/N. Brandt et al.)
Chandra X-ray Observatory image of the twin quasar Q2345+007 The Chandra image of the twin quasar Q2345+007 A, B shows that they are not identical twins. This means that it is unlikely that they are an optical illusion, rather, they were probably created by merging galaxies. When galaxies collide, the flow of gas onto the central supermassive black holes of each of the galaxies can be enhanced, resulting in two quasars. The light from the quasar pair started its journey toward Earth 11 billion years ago. Galaxies were about three times closer together then than they are now, so collisions were much more likely. Quasar pairs that are seen close to one another on the sky and are at the same distance from Earth often turn out to be an illusion as part of a gravitationally lensed system. In these cases, the image of a single quasar has been split into two or more images as its light has been bent and focused on its way to Earth by the gravity of an intervening massive object like a galaxy, or a cluster of galaxies. The quasar pair Q2345+007 A, B was thought to be such an illusion because of the remarkably similar patterns of the light, or spectra, from the pair at both optical and ultraviolet wavelengths. However no intervening galaxy or cluster has been found for this pair, leading to the speculation that the gravitational light-bending might be caused by a new type of cluster that contains hot gas and dark matter, but no stars. Such a "dark cluster" would be invisible to optical and ultraviolet telescopes, but would be detectable in X-rays. The Chandra X-ray images showed no evidence for a massive dark cluster. Further, the X-ray spectra of the two quasars were distinctly different, supporting the idea that they are distinct objects, rather than a mirage. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA. (NASA/SAO/CXC/P.Green et al.)
Chandra reveals bow-shaped shock wave in galaxy cluster Chandra's image of the extremely hot galaxy cluster 1E0657-56 reveals a bow-shaped shock wave toward the right side of the cluster. This feature, thought to be the result of the merger of a smaller group or sub-cluster of galaxies with 1E0657-56, gives astronomers a rare opportunity to study how clusters grow. The shock wave appears to have been formed as 70 million degree Celsius gas in the sub-cluster plowed through 100 million degree gas in the main cluster at a speed of about 6 million miles per hour. This motion created a wind that stripped the cooler gas from the sub-cluster, similar to leaves from a tree being blown off in a storm. The speed, appearance and shape of the sub-cluster indicates that it would have passed through the core of the larger cluster about 150 million years ago. By the time the gravity of the cluster stops the motion of the sub-cluster, it is likely that the cooler gas will have been totally stripped. 1E0657-56 is of great interest because it is one of the hottest known clusters. Astronomers hope to use this and future observations to determine if the high temperature of the cluster gas is due to shocks waves produced by the merger of many sub-clusters. (NASA/CXC/SAO/M. Markevitch et al.)
Chandra X-ray Observatory scores a double bonus with a distant quasar The X-ray image of the quasar PKS 1127-145, a highly luminous source of X-rays and visible light about 10 billion light years from Earth, shows an enormous X-ray jet that extends at least a million light years from the quasar. The jet is likely due to the collision of a beam of high-energy electrons with microwave photons. The high-energy beam is thought to have been produced by explosive activity related to gas swirling around a supermassive black hole. The length of the jet and the observed bright knots of X-ray emission suggest that the explosive activity is long-lived but intermittent. On their way to Earth, the X-rays from the quasar pass through a galaxy located 4 billion light years away. Atoms of various elements in this galaxy absorb some of the X-rays, and produce a dimming of the quasar's X-rays, or an X-ray shadow. In a similar way, when our body is X-rayed, our bones produce an X-ray shadow. By measuring the amount of absorption astronomers were able to estimate that 4 billion years ago, the gas in the absorbing galaxy contained a much lower concentration of oxygen relative to hydrogen gas than does our galaxy - about five times lower. These observations will give astronomers insight into how the oxygen supply of galaxies is built up over the eons. The Marshall Center manages the Chandra program. (NASA/CXC/A. Siemiginowska (CfA) & J. Bechtold (U. Arizona))
Chandra image of the Centaurus galaxy The Chandra image of the Centaurus galaxy cluster shows a long plume-like feature resembling a twisted sheet. The plume is some 70,000 light years in length and has a temperature of about 10 million degrees Celsius. It is several million degrees cooler than the hot gas around it, as seen in this temperature-coded image in which the sequence red, yellow, green, blue indicates increasing gas temperatures. The plume contains a mass comparable to 1 billion suns. It may have formed by gas cooling from the cluster onto the moving target of the central galaxy, as seen by Chandra in the Abell 1795 cluster. Other possibilities are that the plume consists of debris stripped from a galaxy that fell into the cluster, or that it is gas pushed out of the center of the cluster by explosive activity in the central galaxy. A problem with these ideas is that the plume has the same concentration of heavy elements such as oxygen, silicon, and iron as the surrounding hot gas. (NASA/IOTA/J. Sanders and A. Fabian)
X-ray mosaic of galactic center This 400 by 900 light-year mosaic of several Chandra images of the central region of our Milky Way galaxy reveals hundreds of white dwarf stars, neutron stars, and black holes bathed in an incandescent fog of multimillion-degree gas. The supermassive black hole at the center of the galaxy is located inside the bright white patch in the center of the image. The colors indicate X-ray energy bands - red (low), green (medium), and blue (high). (NASA/UMass/D. Wang et al.)
Chandra Image of Abell 2597 This X-ray image of the galaxy cluster Abell 2597, taken by NASA's Chandra X-ray Observatory, shows a vast bright cloud of hot gas with two cavities on the upper left and lower right, about 100,000 light years from the center of the cluster. These so-called ghost cavities are thought to be 100-million-year old relics of an ancient eruption that originated around a supermassive black hole in the core of a centrally located galaxy. (NASA/CXC/Ohio U./B. McNamara et al. photo) |
