Monday, June 6, 2011

Supernova in the Whirlpool Galaxy

There lays Messier 15 and its companion NGC 5194 (irregular galaxy on top), both probably the most well known galaxy in the night sky, aside from the Milky Way and Andromeda Galaxy. Yet, something peculiar occurred over the past few days May 31, 2011 to be exact.


“For the second time in six years, a star has exploded in the iconic Whirlpool Galaxy (Messier 51)” wrote Kelly Beatty from SkyandTelescope. If you look at the picture on the right, you'll notice a prominent red star in the lower-left of the picture in one of the beautifully adorned arms. This is about where this explosion is; and we have great news! This supernova will be in view for backyard observers everywhere, everyone with some type of telescope that is.

May 31, 2011 gave the first hint of some explosion in the lower-left of Messier 51, by French amateur astronomer Amédée Riou noticed an absent magnitude fourteen star in CCD images of the galaxy. It had been previously there, but then it had 'vanished.' Riou recorded this event the following evening and the result was the same. It was identified and the word was sent out to several astronomers June 1 for further research and explanation. French observer Stéphane Lamotte Bailey, noticed it the night after on digital images taken through his 8-inch telescope, images of Messier 51, that is. 

The supernova is clearly not at magnitude 19.5 anymore, despite the fact that it’s still too early to tell whether the supernova will brighten or fade. But, based on further research and investigation, astronomers are confident that this supernova is a type II supernova: the explosion of a single massive star whose core has abruptly collapsed. The Keck I telescope tells us that this explosion is racing earthward as Bradley Cenko from the University of California, Berkeley, says: “The shock wave has material moving at a variety of different speeds (typically faster farther out). The hydrogen that we see moving toward us at 17,600 km per second is probably a pretty good proxy for the fastest material in the outflow.”

So, SN 2011dh, the designated supernova’s official title, was a likely supergiant at magnitude 21.8 (extremely faint; the human eye can perceive to magnitude 6 and even that’s faint!), and had the mass of approximately 18-24 Suns as formulized by UC Berekely’s Weidong Li and Alex Filippenko. Actually, this is the third supernova to occur in the same arm of Messier 51 in seventeen years; six years ago, in 2005, another Type II event occurred, along with, in 1994, a somewhat brighter event.
“Supernova 2005cs was discovered on June 28th by amateur supernova hunter Wolfgang Kloehr of Schweinfurt, Germany, in a CCD image that he took with an 8-inch reflector.” ~SkyandTelescope
For those of who would like to observe this supernova in action, to locate the Messier 15: Messier 15 is approximately 31 million light-years away in the constellation Canes Venatici, high in the evening sky. SN 2011dh's J2000 coordinates (in Canes Venatici) are right ascension 13h 30m 5.1s, declination +47° 10′ 11″. It is positioned 2.3 arcminutes to the east and 1.5 arcminutes to the south of the Messier 15’s center, halfway between two bright star fields. The supernova should remain visible for a few weeks. 
“The supernova will be quite tricky to spot visually and you may need a good sized...telescope to spot it, but it will be a easy target for those interested in astro imaging.” ~UniverseToday

TOP: Before the explosion, BOTTOM: after the explosion. Credit: Stéphane Lamotte Bailey
Other photos from our gallery:

Jerry Lodriguss

More images are ascessible here, at these following links.

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