2011 06 27 – M51/NGC 5194, NGC 5195/H 1.186, Supernova 2011dh

Last night, I observed a supernova in the Whirlpool galaxy. A supernova is the explosion of a star. Simply put, at the end of its life, a large star collapses in on itself and its inert core exceeds its critical mass (1.44 solar masses). At that point, a shock wave is formed that causes a massive explosion.  A type II supernova marks the death of the star.  Depending on the star’s mass, either a neutron star or a black hole is formed as a result. So much energy is released in a supernova that it is possible to visually observe it even in a galaxy millions of light years away.

The ejected matter (that is left over after a supernova) forms what is known as a supernova remnant, which is a rapidly expanding shell of hot gas. Probably the most famous supernova remnant is the Crab Nebula in the constellation Taurus. The Crab Nebula was formed when a star ~6500 light years away (in our own galaxy) went supernova. Chinese astronomers in the year 1054 A.D. recorded a “guest star” (supernova) that was so bright that it was visible during daylight hours for more than three weeks and they were able to observe it for ~2 years before the supernova faded away. This supernova formed the crab nebula, which is still expanding.  (2011 03 03, M1/NGC 1952 report)

click on thumbnail for inverted view


The supernova in M51 is a type II supernova. A star with a mass of 9-50 times that of our Sun is required for a type II supernova to occur. Also known as: Arp 85 and UGC 8493.

So how do we determine solar mass of other suns (stars)? We compare it to our own Sun’s mass:

   (or 1:332,946 ratio of Sun:Earth)

This is the second time in 6 years (first was in 2005) that a type II supernova occurred in M51. A third supernova occurred in 1994. You can see the supernova in my sketch from last night, marked to the left of the M51’s spiral arms. For comparison, I’ve included an image of M51 that Paul took prior to the explosion with the ED 80 and a DSI III Pro.

Credit: Paul Rix, M51 taken with Orion ED 80, DSI III Pro

For more information regarding the supernova 2011dh in M51 and supernovae in general, please visit the following links:

”The first hint of the eruption came on May 31st, when French amateur Amédée Riou noticed a previously absent 14th-magnitude star in CCD images of the galaxy. Riou recorded it again the following evening. Independently, it was identified on June 1st by Thomas Griga in Schwerte, Germany. The next night it got picked up by Tom Reiland in Glenshaw, Pennsylvania, and by French observer Stéphane Lamotte Bailey who noticed it on digital images taken through his 8-inch telescope.”

The Whirlpool Galaxy (otherwise known as M51 and NGC 5194) is a face-on spiral and is just south of its companion galaxy NGC 5195. The stellar core of NGC 5195 was brighter than that of the M51, although M51’s core seemed larger. They are located in Canes Venatici. M51 is ~35 million light years distant from us, magnitude 8.4v, and is ~ 08.2’ x 6.9’ in size.


~ by Erika Rix on June 27, 2011.

One Response to “2011 06 27 – M51/NGC 5194, NGC 5195/H 1.186, Supernova 2011dh”

  1. […] related posts regarding supernovae can be found here: 2011 03 03, M1/NGC 1952 2011 06 27 – M51/NGC 5194, NGC 5195/H 1.186, Supernova 2011dh Share this:FacebookTwitterEmailDiggStumbleUponRedditLike this:LikeBe the first to like […]

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