Explanation: If not perfect, then this spiral galaxy is at least one of the most photogenic. An island universe of about 100 billion stars, 32 million light-years away toward the constellation Pisces, M74 presents a gorgeous face-on view. Classified as an Sc galaxy, the grand design of M74's graceful spiral arms are traced by bright blue star clusters and dark cosmic dust lanes. Constructed from image data recorded in 2003 and 2005, this sharp composite is from the Hubble Space Telescope's Advanced Camera for Surveys. Spanning about 30,000 light-years across the face of M74, it includes exposures recording emission from hydrogen atoms, highlighting the reddish glow of the galaxy's large star-forming regions. Recently, many astronomers are tracking a bright supernova that has been seen in M74.
I'm always glad to see a spiral galaxy as the Astronomy Picture of the Day, and M74 is a particularly good choice, since there is right now a bright supernova in this galaxy.
Obviously I can't help thinking that it would have been fun if today's APOD had shown the general vicinity of the current supernova, SN 2013ej. But since today's APOD only shows the inner part of M74, the progenitor star is outside the field of view here.
Astronomers are very interested in identifying the progenitor stars that later explode as supernovae. A very few such stars have been identified. The most famous one is Sanduleak -69° 202, a blue supergiant that exploded to become supernova 1987A in the Large Magellanic Cloud in 1987. Another progenitor that has been identified is the star that exploded in M81 as supernova 1993J. You can read about the progenitors of both SN 1987A and SN 1993J here.
I look forward to better pictures of the star that blew up before it blew up. Maybe, when such a picture exists, M74 can be the Astronomy Picture of the Day once again!
Ann
Re: APOD: M74: The Perfect Spiral (2013 Aug 11)
Posted: Sun Aug 11, 2013 7:19 am
by geckzilla
If you really want, you could try to find the 2013EJ supernova progenitor in Hubble archive data. It's definitely there and in multiple filters but it isn't included in this picture for aesthetic reasons. http://hla.stsci.edu/hlaview.html#Image ... 2CGHRS&ds=
Re: APOD: M74: The Perfect Spiral (2013 Aug 11)
Posted: Sun Aug 11, 2013 12:52 pm
by Boomer12k
Looks like a Nautilus Shell. I wonder if the Fibonacci Numbers come into play when creating a Spiral Galaxy...
Someone...."up there"....with a Banker's Visor, and a Slide Rule....
:---[===] *
Re: APOD: M74: The Perfect Spiral (2013 Aug 11)
Posted: Sun Aug 11, 2013 1:14 pm
by neufer
Click to play embedded YouTube video.
Boomer12k wrote:
Looks like a Nautilus Shell. I wonder if the Fibonacci Numbers come into play when creating a Spiral Galaxy...
Most spirals in nature are pretty much dimensionless
which more or less forces them to be logarithmic spirals
(though not necessarily related to the golden ratio or Fibonacci Numbers).
This is a lovely image of M74 to be sure, but it left me wanting to see more. After all, if this galaxy is called “The Perfect Spiral” one would like to see more of its spiral structure. A search for images of M74 led me to this APOD from 4/6/11: http://apod.nasa.gov/apod/ap110406.html
Another observation in general about the descriptions of spiral galaxies, a very common phrase seems to be that they contain “about 100 billion stars” as is said about this galaxy too. I don’t mean this as a criticism, for even just approximating the stars in a distant galaxy with all the uncertainty involved (size, distance, 3D shape, etc.) would make a more precise accounting quite difficult.
I do wonder though if this could in fact be understating reality as to star counts to a large degree. Our galaxy was said to have “about 100 billion stars” too, although I’ve also read that some more recent estimates peg the Milky Way’s star count at over 1 trillion.
This nice round number of 100 billion comes up a lot in science. Number of stars in a galaxy, number of galaxies in the observable universe, number of neurons in the human brain. It’s a polite, scientific way of saying ‘we don’t really know how many, but it’s a humongous ___ load.’
Re: APOD: M74: The Perfect Spiral (2013 Aug 11)
Posted: Sun Aug 11, 2013 2:26 pm
by neufer
Click to play embedded YouTube video.
BDanielMayfield wrote:
Another observation in general about the descriptions of spiral galaxies, a very common phrase seems to be that they contain “about 100 billion stars” as is said about this galaxy too.
I do wonder though if this could in fact be understating reality as to star counts to a large degree. Our galaxy was said to have “about 100 billion stars” too, although I’ve also read that some more recent estimates peg the Milky Way’s star count at over 1 trillion.
This nice round number of 100 billion comes up a lot in science. Number of stars in a galaxy, number of galaxies in the observable universe, number of neurons in the human brain. It’s a polite, scientific way of saying ‘we don’t really know how many, but it’s a humongous ___ load.’
Re: APOD: M74: The Perfect Spiral (2013 Aug 11)
Posted: Sun Aug 11, 2013 3:06 pm
by BDanielMayfield
Boomer12k wrote:Someone...."up there"....with a Banker's Visor, and a Slide Rule....
Yes, but without the visor, slide rule, or chalk board, nor any material objects, since there was nothing to have made such things from yet. "Someone" would have had to have done the math in his head. But He had a long, long, LONG time to work it all out, since time had no beginning.
Re: APOD: M74: The Perfect Spiral (2013 Aug 11)
Posted: Sun Aug 11, 2013 3:22 pm
by FloridaMike
OR, it's all just a simulation running on a fantastically complex machine you could loosely define as a computer where a simulation of someone like me is typing on a simulation of a computer.
Re: APOD: M74: The Perfect Spiral (2013 Aug 11)
Posted: Mon Aug 12, 2013 1:14 pm
by Monkeys = Believers
BDanielMayfield wrote:
Boomer12k wrote:Someone...."up there"....with a Banker's Visor, and a Slide Rule....
Yes, but without the visor, slide rule, or chalk board, nor any material objects, since there was nothing to have made such things from yet. "Someone" would have had to have done the math in his head. But He had a long, long, LONG time to work it all out, since time had no beginning.
With a mind like his it could easily have been intuition .. but he could have counted them all, plus all the alls in the to be universe (s?) in the twinkling of an eye.
M74: The Perfect Spiral
