APOD: M51: The Whirlpool Galaxy in Dust... (2013 Feb 24)

Comments and questions about the APOD on the main view screen.
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Anthony Barreiro
Turtles all the way down
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Re: APOD: M51: The Whirlpool Galaxy in Dust... (2013 Feb 24)

Post by Anthony Barreiro » Tue Feb 26, 2013 10:56 pm

ta152h0 wrote:I got a 33 foot long roll of vellum and placed the sun in one end and Pluto ( still a planet in my book ) on the other end , and filled in the planets according to scale. Then I took it to my wife's class and rolled the thing out. The kids were amazed and so was I Prox Centauri would be a really long walk away. Whirlpool galaxy.......I need an ice cold one.
Here's a link to Guy Ottewell's 1000 yard model of the solar system (or the 1 kilometer model, if you prefer). Start with a ball 8 inches (20 cm) in diameter for the Sun, put a few pins and nuts in your pocket, and start walking.
May all beings be happy, peaceful, and free.

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You'll wonder where the yellow went....

Post by neufer » Mon Mar 04, 2013 7:39 pm

http://astrobob.areavoices.com/2013/03/03/former-supergiant-star-in-whirlpool-galaxy-goes-missing/ wrote: Former supergiant star in Whirlpool Galaxy goes missing
Astrobob, March 3, 2013

<<On May 31, 2011 a supernova suddenly appeared in M51, a bright spiral galaxy near the end of the Big Dipper’s handle. Better known as the Whirlpool Galaxy, M51 is one of the most picturesque galaxies in the sky and the first in which spiral structure was seen. The Whirlpool is on every amateur astronomer’s “must see” list because it’s bright, close (23 million light years) and one of the few galaxies that shows a spiral shape in smaller telescopes.

The supernova, dubbed 2011dh, peaked in brightness several weeks later and then gradually faded from view. Astronomers determined it was a Type II explosion. Type II supernovae occur in supergiant stars at least 8 times more massive than the sun that burn through the nuclear fuel in their cores until it’s exhausted. When the burning stops, so does the heat pressure that counteracts the ever-present force of gravity. Result: the star collapses in upon itself, creating shock waves that blast it to bits in a titanic explosion. The enormous energy released makes the former supergiant suddenly brighten by millions of times.

Relative size of a supergiant down to a black hole. Exploding supergiant stars sometimes leave a remnant neutron star or black hole in their wake. The crushing forces of collapse push electrons into protons to create neutrons, hence the name. Often the core continues collapsing into a tiny, city-sized neutron star or takes the final plunge and squeezes itself into a black hole. This weekend a team of astronomers using the Hubble Space Telescope report that the yellow supergiant star that went supernova two years ago has vanished. Gone.

Seems obvious, so what makes it interesting? When a star becomes a supernova, one of the first things astronomers do is go back and look at old pictures of the galaxy in which the supernova occurred to identify the original star called the “progenitor”. Because stars in distant galaxies are extremely faint and difficult to separate from others in their neighborhood, they can be hard to identify.

Now that the suspected supergiant star has disappeared, we’ve clinched the identity of the star before the explosion. That key data point helps astronomers unravel the evolution of supernova 2011dh from a yellow, hydrogen-burning behemoth to its present state as an expanding shock wave riddled with the former star’s innards. It also throws a bit of a wrench into our understanding of how stars evolve. The progenitor star began its life with 13 times the sun’s mass and became 100,000 times more luminous than the sun by the time it blew. Yellow supergiants aren’t typical supernova candidates unlike the red supergiant class, whose most famous member is Betelgeuse in Orion. That means that once again astronomers will need to reexamine theories. As for remnants of 2011dh, if there are any, they’ve yet to be found.>>
Art Neuendorffer