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2012 February 27
Twenty five years ago, the brightest supernova of modern times was sighted. Over time, astronomers have watched and waited for the expanding debris from this tremendous stellar explosion to crash into previously expelled material. A clear result of such a collision is demonstrated in the above time lapse video of images recorded by the Hubble Space Telescope between 1994 and 2009. The movie depicts the collision of an outward moving blast wave with the pre-existing, light-year wide ring. The collision occurred at speeds near 60 million kilometers per hour and shock-heats the ring material causing it to glow. Astronomers continue to study the collision as it illuminates the interesting past of SN 1987A, and provides clues to the origin of the mysterious rings.
2012 January 27
About 40,000 light-years across, pretty, irregular galaxy NGC 3239 lies near the center of this lovely field of galaxies in the galaxy rich constellation Leo. At a distance of only 25 million light-years it dominates the frame, sporting a peculiar arrangement of structures, young blue star clusters and star forming regions, suggesting that NGC 3239 (aka Arp 263) is the result of a galaxy merger. Appearing nearly on top of the pretty galaxy is a bright, spiky, foreground star, a nearby member of our own Milky Way galaxy almost directly along our line-of-sight to NGC 3239. Still, NGC 3239 is notable for hosting this year's first confirmed supernova, designated SN 2012A. It was discovered early this month by supernova hunters Bob Moore, Jack Newton, and Tim Puckett. Indicated in a cropped version of the wider image, SN 2012A is just below and right of the bright foreground star. Of course, based on the light-travel time to NGC 3239, the supernova explosion itself occurred 25 million years ago, triggered by the core collapse of a massive star.
2011 August 26
A nearby star has exploded and telescopes all over the world are turning to monitor it. The supernova, dubbed PTF 11kly, was discovered by computer only two days ago as part of the Palomar Transient Factory (PTF) sky survey utilizing the wide angle 1.2-meter Samuel Oschin Telescope in California. Its rapid recovery makes it one of the supernovas caught most soon after ignition. PTF 11kly occurred in the photogenic Pinwheel galaxy (M101), which, being only about 21 million light years away, makes it one of the closest supernovas seen in decades. Rapid follow up observations have already given a clear indication that PTF 11kly is a Type Ia supernova, a type of white dwarf detonation that usually progresses in such a standard manner than it has helped to calibrate the expansion history of the entire universe. Studying such a close and young Type Ia event, however, may yield new and unique clues. If early indications are correct, PTF 11kly should brighten to about visual magnitude 10 in the coming weeks, making it possible to monitor with even moderately sized telescopes.
2011 June 11
Where do spiral galaxies keep their supernovae? Near their massive star forming regions, of course, and those regions tend to lie along sweeping blue spiral arms. Because massive stars are very short-lived, they don't have a chance to wander far from their birth place. Remarkably, in the last 6 years two Type II supernovae, representing the death explosions of massive stars, have been detected in nearby spiral M51. Along with a third supernova seen in 1994, that amounts to a supernova bonanza for a single galaxy. As demonstrated in these comparison images, SN2005cs, the supernova discovered in 2005, and more recently SN2011dh, the exceptionally bright supernova first recorded just last month, both lie along M51's grand spiral arms. Perhaps the original spiral nebula, M51 is also known as the Whirlpool Galaxy.
2011 June 5
One of the brightest supernovas in recent years has just been recorded in the nearby Whirlpool galaxy (M51). Surprisingly, a seemingly similar supernova was recorded in M51 during 2005, following yet another one that occurred in 1994. Three supernovas in 17 years is a lot for single galaxy, and reasons for the supernova surge in M51 are being debated. Pictured above are two images of M51 taken with a small telescope: one taken on May 30 that does not show the supernova, and one taken on June 2 which does. The June 2 image is one of the first images reported to contain the supernova. The images are blinked to show the location of the exploded star. Although most supernovas follow classic brightness patterns, the precise brightening and dimming pattern of this or any supernova is hard to predict in advance and can tell astronomers much about what is happening. Currently, the M51 supernova, designated SN 2011dh, is still bright enough to follow with a small telescope. Therefore, sky enthusiasts are encouraged to image the Whirlpool galaxy as often as possible to fill in time gaps left by intermittent observations made by the world's most powerful telescopes. Views of the developing supernova are being uploaded here
2009 May 8
This colorful telescopic skyscape is filled with galaxies that lie nearly 250 million light-years away, the galaxies of the Perseus cluster. Their extended and sometimes surprising shapes are seen beyond a veil of foreground stars in our own Milky Way. Ultimately consisting of over a thousand galaxies, the cluster is filled with yellowish elliptical and lenticular galaxies, like those scattered throughout this view of the cluster's central region. Notably, the large galaxy at the left is the massive and bizarre-looking NGC 1275. A prodigious source of high-energy emission, active galaxy NGC 1275 dominates the Perseus cluster, accreting matter as entire galaxies fall into it and feed the supermassive black hole at the galaxy's core. Of course, spiral galaxies also inhabit the Perseus cluster, including the small, face-on spiral NGC 1268, right of picture center. The bluish spot on the outskirts of NGC 1268 is supernova SN 2008fg. At the estimated distance of the Perseus galaxy cluster, this field spans about 1.5 million light-years.
2008 January 18
The stellar explosions known as supernovae are among the most powerful events in the universe. Triggered by the collapsing core of a massive star or the nuclear demise of a white dwarf, supernovae occur in average spiral galaxies only about once every century. But the remarkable spiral galaxy NGC 2770 has lately produced more than its fair share. Two still bright supernovae and the location of a third, originally spotted in 1999 but now faded from view, are indicated in this image of the edge-on spiral. All three supernovae are now thought to be of the core-collapse variety, but the most recent of the trio, SN2008D, was first detected by the Swift satellite at more extreme energies as an X-ray flash (XRF) or possibly a low-energy version of a gamma-ray burst on January 9th. Located a mere 90 million light-years away in the northern constellation Lynx, NGC 2770 is now the closest galaxy known to host such a powerful supernova event.
2007 October 16
What could cause a bang this big? This supernova explosion was so inherently bright that it could be seen nearly 5 billion light years away (a redshift of 0.28) even with a small telescope. Specific colors emitted during SN 2005ap indicate that it was a Type II supernova, a breed of stellar explosion that results when a high mass star begins fusing heavy elements in or near its core. Type II supernovas may be more powerful than their Type Ia cousins, but they are not currently more useful cosmologically because astronomers don't understand how to accurately recover their intrinsic brightnesses. It is therefore dimmer Type Ia supernovas that are used by astronomers to calibrate the distance scale of the nearby universe. Were Type II supernova better understood, astronomers might be able to probe distances further into the universe, and so probe the stability of the strange dark energy that dominates the present universe. Pictured above in a digitally compressed image, the bright supernova SN 2005ap is visible on the right where no exploding star had been seen on the left less than three months before.
2007 May 10
The stellar explosion cataloged as supernova SN 2006gy shines in this wide-field image (left) of its host galaxy, NGC 1260, and expanded view (upper right panel) of the region surrounding the galaxy's core. In fact, given its estimated distance of 240 million light-years, SN 2006gy was brighter than, and has stayed brighter longer than, any previously seen supernova. The Chandra observations in the lower right panel establish the supernova's x-ray brightness and lend strong evidence to the theory that SN 2006gy was the death explosion of a star well over 100 times as massive as the Sun. In such an exceptionally massive star, astronomers suspect an instability producing matter-antimatter pairs led to the cosmic blast and obliterated the stellar core. Thus, unlike in other massive star supernovae, neither neutron star, or even black hole, would remain. Intriguingly, analogs in our own galaxy for SN 2006gy's progenitor may include the well-known, extremely massive star Eta Carinae.
2006 March 7
One of the nearer supernovas of recent years was discovered last month in the bright nearby galaxy M100. The supernova, dubbed SN 2006X, is still near its maximum brightness and visible with a telescope toward the constellation of Berenice's Hair (Coma Berenices) The supernova, pictured above, has been identified as Type Ia indicating that a white dwarf star in the picturesque spiral galaxy has gone near its Chandrasekhar limit and exploded. Although hundreds of supernovas are now discovered each year by automated searches, nearby supernova are rare and important because they frequently become bright enough to be studied by many telescopes and are near enough for their immediate surroundings to be spatially resolved. Supernova 2006X's host galaxy M100 resides in the Virgo Cluster of Galaxies located about 50 million light years from Earth.
2006 January 25
Can you find supernova 1987A? It isn't hard -- it occurred at the center of the expanding bullseye pattern. Although this stellar detonation was first seen almost two decades ago, light from it continues to bounce off clumps of interstellar dust and be reflected to us today. These expanding light echoes have been recorded in the above time-lapse movie recorded over four years from the Blanco 4-meter telescope in Chile. The first image is an image of the SN 1987A region, while the next four images were created by subtracting consecutive images, taken a year apart, and leaving only the difference between the images. Light echoes can be seen moving out from the position of the supernova. The SuperMACHO team who recorded the above light echoes around supernova 1987A has also found faint and previously unnoticed light echoes from two other LMC supernovas. Study of these light echoes has enabled more accurate determinations of the location and date of these two supernova explosions that were first visible hundreds of years ago.
2004 September 7
The closest and brightest supernova in over a decade was recorded just over a month ago in the outskirts of nearby galaxy NGC 2403. Officially tagged SN 2004dj, the Type IIP explosion likely annihilated most of a blue supergiant star as central fusion could no longer hold it up. The supernova can be seen as the bright object in the above image in the direction of the arrow. The home galaxy to the supernova, spiral galaxy NGC 2403, is located only 11 million light years away and is visible with binoculars toward the northern constellation of Camelopardalis (the Giraffe). The supernova is fading but still visible with a telescope, once peaking at just brighter than magnitude 12. Supernovas of this type change brightness in a predictable way and may be searched for in the distant universe as distance indicators.
2004 February 12
Beginning with a full view of beautiful spiral galaxy M81, follow the insets (left, bottom, then right) to zoom in on a real survivor. Seen at the center of the final field on the right is a star recently identified as the survivor of a cosmic cataclysm -- the supernova explosion of its companion star. Light from the cosmic blast, likely triggered by the core collapse of a star initially more than 10 times as massive as the Sun, first reached Earth over 10 years ago and was cataloged as supernova SN 1993J. Though the supernova itself is no longer visible, light-echoes from dust in the region can still be seen near the companion, the first known survivor of a supernova in a binary star system. Astronomers believe that a substantial transfer of material to the surviving companion star during the last few hundred years before the stellar explosion can explain peculiarities seen in this supernova. After supernova SN 1987A in the Large Magellanic Cloud, SN 1993J in nearby M81 is the brightest supernova seen in modern times.
2003 April 14
New evidence has emerged that a mysterious type of explosion known as a gamma ray burst is indeed connected to a supernova of the type visible in the above image. Two weeks ago, the orbiting HETE satellite detected gamma-ray burst GRB030329. The extremely bright burst was found hours later to have an extremely bright afterglow in visible light, and soon set the record for the closest measured distance at redshift 0.17. The afterglow brightness allows unprecedented coverage of its evolution. Just this week, as many astronomers suspected would happen, the afterglow began to appear as a fading Type II Supernova. Type II Supernovas might not appear coincident with gamma-ray bursts, however, when the gamma-ray beam goes in another direction. The above spiral galaxy, NGC 3184, was home to a Type II Supernova in 1999 at the position of the arrow. Astronomers are currently pressing hard to find the host galaxy for GRB030329.
October 24, 1997
Yesterday's image highlighted reflective rings of light emitted by a supernova explosion. Today's pictures, taken over a year apart, highlight how these echoes are seen to move over time. Visible on the left of each picture is part of a reflective ring, an existing dust cloud momentarily illuminated by the light of Supernova 1987A. Note how the nebulosity reflecting the most light occurs farther to the left in the lower photograph. If you look closely, you can see the actual location of SN 1987A itself on the right of each photograph: it appears in the center of a small yellowish ring. The apparent motion and brightness of these echoes help astronomers understand the abundance and distribution of interstellar nebulae in the LMC galaxy, where the stellar explosion occurred.
October 23, 1997
Can you find Supernova 1987a? It's not hard - it occurred in the center of the bulls-eye pattern. Although this stellar detonation was seen more than a decade ago, light from it continues to bounce off nearby interstellar dust and be reflected to us. These two rings are thus echoes of the powerful supernova. As time goes on, these echoes appear to expand outward from the center. The above image was created by subtracting a picture taken before 1987, from a picture taken after.