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💫Arcs Tell The Tale Of A Giant Eruption


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 indicate 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.

Credit:
X-ray (NASA/CXC/M. Karovska); Radio 21-cm image (NRAO/VLA/J.Van Gorkom/Schminovich), Radio continuum image (NRAO/VLA/J. Condon); Optical (Digitized Sky Survey U.K. Schmidt Image/STScI)


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💫Wide-field view of the Coma Galaxy Cluster

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Hubble's Advanced Camera for Surveys has observed a large portion of the Coma Cluster, stretching across several million light-years. The entire cluster is more than 20 million light-years in diameter, is nearly spherical in shape and contains thousands of galaxies. Also known as Abell 1656, the Coma Cluster is over 300 million light-years away. The cluster, named after its parent constellation Coma Berenices, is near the Milky Way's north pole. This places the Coma Cluster in an area that is not obscured by dust and gas from the plane of the Milky Way, and so is easily visible to observers here on Earth. Most of the galaxies that inhabit the central portion of the Coma Cluster are elliptical galaxies. These apparently featureless "fuzz-balls" are a pale golden brown in colour and contain populations of old stars. Both dwarf and giant ellipticals are found in abundance in the Coma Cluster. Farther out from the centre of the cluster there are several spiral galaxies. These galaxies contain clouds of cold gas that are giving birth to new stars. Spiral arms and dust lanes "accessorise" these bright bluish-white galaxies, which have a distinctive disc structure.


S0 (S-zero) galaxies form a morphological class of objects between the better known elliptical and spiral galaxies. They consist of older stars and show little evidence of recent star formation, but they do show some structure -- perhaps a bar or a ring that may eventually give rise to more disc-like features. This Hubble image consists of a section of the cluster that is roughly one-third of the way out from the centre of the whole cluster. One bright spiral galaxy is visible in the upper left of the image. It is distinctly brighter and bluer than the galaxies surrounding it. A series of dusty spiral arms appears reddish brown against the whiter disc of the galaxy, and suggests that this galaxy has been disturbed at some point in the past. The other galaxies in the image are either ellipticals, S0 galaxies or background galaxies that are far beyond the Coma Cluster sphere. A wide star field image of the region around the Coma Cluster (Abell 1656). The field-of-view is approximately 2.7 x 2.85 degrees.



Credit: NASA, ESA, and the Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble)


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💫Milky Way Monster Stars


This Chandra image of the supermassive black hole at our Galaxy's center, a.k.a. Sagittarius A* or Sgr A*, was made from the longest X-ray exposure of that region to date. In addition to Sgr A* more than two thousand other X-ray sources were detected in the region, making this one of the richest fields ever observed. During the two-week observation period, Sgr A* flared up in X-ray intensity half a dozen or more times. The cause of these outbursts is not understood, but the rapidity with which they rise and fall indicates that they are occurring near the event horizon, or point of no return, around the black hole. Even during the flares the intensity of the X-ray emission from the vicinity of the black hole is relatively weak. This suggests that Sgr A*, weighing in at 3 million times the mass of the Sun, is a starved black hole, possibly because explosive events in the past have cleared much of the gas from around it.

Evidence for such explosions was revealed in the image - huge lobes of 20 million-degree Centigrade gas (the red loops in the image at approximately the 2 o'clock and 7 o'clock positions) that extend over dozens of light years on either side of the black hole. They indicate that enormous explosions occurred several times over the last ten thousand years. Further analysis of the Sgr A* image is expected to give astronomers a much better understanding of how the supermassive black hole in the center of our galaxy grows and how it interacts with its environment. This knowledge will also help to understand the origin and evolution of even larger supermassive black holes found in the centers of other galaxies.

Credit:
NASA/CXC/MIT/F.K.Baganoff


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💫Area around star-forming region S 106

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This image shows a ground-based telescope image of the region around star forming region Sh 2-106, or S106 for short. S106 is a compact star-forming region in the constellation of Cygnus (the Swan). Despite the celestial colours of this picture, there is nothing peaceful about star forming region Sh 2-106, or S106 for short. A devilish young star, named S106 IR, lies in it and ejects material at high speed, which disrupts the gas and dust around it. The star has a mass about 15 times that of the Sun and is in the final stages of its formation. It will soon quieten down by entering the main sequence, the adult stage of stellar life. For now, S106 IR remains embedded in its parent cloud, but it is rebelling against it. The material spewing off the star not only gives the cloud its hourglass shape but also makes the hydrogen gas in it very hot and turbulent. The resulting intricate patterns are clearly visible in this Hubble image. The young star also heats up the surrounding gas, making it reach temperatures of 10 000 degrees Celsius. The star’s radiation ionises the hydrogen lobes, making them glow. The light from this glowing gas is coloured blue in this image.


Separating these regions of glowing gas is a cooler, thick lane of dust, appearing red in the image. This dark material almost completely hides the ionising star from view, but the young object can still be seen peeking through the widest part of the dust lane. S106 was the 106th object to be catalogued by the astronomer Stewart Sharpless in the 1950s. It is a few thousand light-years distant in the direction of Cygnus (The Swan). The cloud itself is relatively small by the standards of star-forming regions, around 2 light-years along its longest axis.


This is about half the distance between the Sun and Proxima Centauri, our nearest stellar neighbour. This composite picture was obtained with the Wide Field Camera 3 on the NASA/ESA Hubble Space Telescope. It results from the combination of two images taken in infrared light and one which is tuned to a specific wavelength of visible light emitted by excited hydrogen gas, known as H-alpha. This choice of wavelengths is ideal for targetting star-forming regions. The H-alpha filter isolates the light emitted from hydrogen in gas clouds while the infrared light can shine through the dust that often obscures these regions.


Credit: NASA, ESA, and the Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble)


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💫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 160,000 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.

Credit:
NASA/SAO/CXC


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💫The CANDELS

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The supernova, designated SN UDS10Wil, belongs to a special class of exploding stars known as Type Ia supernovae. These bright beacons are prized by astronomers because they can be used as a yardstick for measuring cosmic distances, thereby yielding clues to the nature of dark energy, the mysterious force accelerating the rate of expansion of the Universe. “This new distance record holder opens a window into the early Universe, offering important new insights into how these supernovae form,” said astronomer David O. Jones of The Johns Hopkins University in Baltimore, Md., lead author on the science paper detailing the discovery. “At that epoch, we can test theories about how reliable these detonations are for understanding the evolution of the Universe and its expansion.” One of the debates surrounding Type Ia supernovae is the nature of the fuse that ignites them. This latest discovery adds credence to one of two competing theories of how they explode. Although preliminary, the evidence favours the explosive merger of two burned out stars — small, dim, and dense stars known as white dwarfs, the final state for stars like our Sun. The discovery was part of a three-year Hubble program called the CANDELS+CLASH Supernova Project, begun in 2010. This program aimed to survey faraway Type Ia supernovae to determine their distances and see if their behaviour has changed over the 13.8 billion years since the Big Bang, using the sharpness and versatility of Hubble’s Wide Field Camera 3. So far, CANDELS+CLASH has uncovered more than 100 supernovae of all types that exploded from 2.4 to over 10 billion years ago. The team has identified eight of these discoveries as Type Ia supernovae that exploded more than 9 billion years ago — including this new record-breaker, which, although only four percent older than the previous record holder, pushes the record roughly 350 million years further back in time. The supernova team’s search technique involved taking multiple near-infrared images spaced roughly 50 days apart over the span of three years, looking for a supernova’s faint glow.




After spotting SN UDS10Wil in December 2010, the CANDELS team then used the spectrometer on Hubble’s Wide Field Camera 3, along with the European Southern Observatory’s Very Large Telescope, to verify the supernova’s distance and to decode its light, hoping to find the unique signature of a Type Ia supernova. Finding remote supernovae opens up the possibility to measure the Universe’s accelerating expansion due to dark energy. However, this is an area that is not fully understood — and nor are the origins of Type Ia supernovae. “This new result is a really exciting step forward in our study of supernovae and the distant Universe,” said team member Jens Hjorth of the Dark Cosmology Centre at the Niels Bohr Institute, University of Copenhagen. “We can begin to explore and understand the stars that cause these violent explosions.” The team’s preliminary evidence shows a sharp decline in the rate of Type Ia supernova blasts between roughly 7.5 billion years ago and more than 10 billion years ago. This, combined with the discovery of such Type Ia supernovae so early in the Universe, suggests that the explosion mechanism is a merger between two white dwarfs. In the single white dwarf scenario — a pathway in which a white dwarf gradually feeds off a partnering normal star and explodes when it accretes too much mass — the rate of supernovae can be relatively high in the early Universe, because some of these systems can reach the point of explosion very quickly. The steep drop-off favours the double white dwarf mechanism, because it predicts that most stars in the early Universe are too young to become Type Ia supernovae. Knowing what triggers Type Ia supernovae will also show how quickly the Universe enriched itself with heavier elements, such as iron. These exploding stars produce about half of the iron in the Universe, the raw material for building planets, and life.


Credit: NASA, ESA, A. Riess (STScI and JHU), D. Jones and S. Rodney (JHU), S. Faber (University of California, Santa Cruz), H. Ferguson (STScI), and the CANDELS team.


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