APOD: 21st Century M101 (2012 Jul 13)

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APOD: 21st Century M101 (2012 Jul 13)

Post by APOD Robot » Fri Jul 13, 2012 4:05 am

Image 21st Century M101

Explanation: One of the last entries in Charles Messier's famous catalog, big, beautiful spiral galaxy M101 is definitely not one of the least. About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way Galaxy. M101 was also one of the original spiral nebulae observed with Lord Rosse's large 19th century telescope, the Leviathan of Parsontown. In contrast, this mulitwavelength view of the large island universe is a composite of images recorded by space-based telescopes in the 21st century. Color coded from X-rays to infrared wavelengths (high to low energies), the image data was taken from the Chandra X-ray Observatory (purple), the Galaxy Evolution Explorer (blue), Hubble Space Telescope (yellow), and the Spitzer Space Telescope (red). While the X-ray data trace the location of multimillion degree gas around M101's exploded stars and neutron star and black hole binary star systems, the lower energy data follow the stars and dust that define M101's grand spiral arms. Also known as the Pinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major, about 25 million light-years away.

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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by bystander » Fri Jul 13, 2012 4:10 am

Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by Beyond » Fri Jul 13, 2012 4:18 am

Big, colorful, AWEsome. That's it, I'm out of words!
To find the Truth, you must go Beyond.

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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by Ann » Fri Jul 13, 2012 6:08 am

Today's APOD is informative, and it is very colorful and fun to look at.

To me, the blue-star fanatic, there is an even bigger story to be told about M101, a story that I don't think is being very clearly revealed in today's APOD. It is that M101 is unique in the nearby universe in that it is so big and so blue.

Over time, galaxies in the universe will become ever yellower. First of all, much of the gas supply of the universe is continually being turned into stars, so that there is less and less "raw material" available for the universe to make hot massive blue stars in the first place.
Image
Second, every time the universe makes massive blue stars, it makes a larger number of less massive and non-blue stars at the same. This false-color Hubble image of a star formation region in the Small Magellanic Cloud clearly shows that the large, hot, newborn blue stars are surrounded by a "retinue" of smaller stars. These smaller stars are non-blue, although you can't see that in this picture.

Third, the hot, bright, blue, massive and luminous stars will "burn out" and die quite quickly, while the smaller, less blue stars will hang on. In fact, the smaller and redder a star is, the longer it will live! So over time, more and more yellow and red stars will be created, and these stars will simply not go away.
This SDSS image of galaxy M90 demonstrates what time can do to spiral galaxies. M90 has a bright yellow bulge and large "intermediate" arms without dust lanes and without star formation. M90 has already converted almost all its available star forming material into stars, and now its stars are aging. This means that the blue stars are dying, but the yellow ones are hanging on. M90 is gradually becoming more and more yellow.


Practically all large galaxies in the nearby universe have large yellow populations of stars. This means that even those large spiral galaxies that form a lot of young blue stars, such as M99, nevertheless have their blue color "diluted" by the massive underlying population of old yellow and red stars. The B-V color index, which compares the light from blue stars with the light from yellow stars, is +0.57 for M99. That is really blue for a large galaxy.

But for M101, the B-V index is as low and as blue as +0.45. To my knowledge, that is absolutely unique for a large galaxy. It is absolutely remarkable.

Why is the color index of M101 so blue? It has to mean that the underlying yellow population is comparatively faint, while the young blue population is absolutely incredibly widespread and bright. In my opinion, M101 must have undergone a fantastic, massive, global star formation event quite recently. Before that, the galaxy must have been rather "quiet", yellow, faint and small. It must have been surrounded by a lot of gas just waiting for a reason to turn itself into stars.

What set off the fantastic star formation? Well, if you check out this image by Fabian Neyer, you can see a small bluish galaxy, NGC 5474, to the left of large M101. Look more closely at NGC 5474, and you can see that it appears to have a central bulge with a thick "arc" to the left of it! The bulge of the galaxy is displaced relative to the galaxy's disk!

I believe that NGC 5474 has a lot to do with all the action in M101. I believe that these two galaxies are interacting, and this interaction has "sloshed the gas of M101 around" and created incredibly widespread star formation. As you can see from Fabian Neyer's image, an even smaller but also more nearby galaxy, NGC 5477 (a small blue galaxy above M101 in Fabian Neyer's image) is also a part of the action. You can see that the spiral arms of M101 appear to "reach out" for NGC 5477, as if the arms wanted to embrace this small galaxy.

In any case, brilliantly blue and star-sparkling M101 is a unique galaxy in the nearby universe.

Ann
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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by Moonlady » Fri Jul 13, 2012 6:18 am

Wow that's a great link: Astrophysics Picture of the WEEK! :clap: :thumb_up:
Thanks, I didn't know it!

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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by bystander » Fri Jul 13, 2012 7:49 am

Moonlady wrote:Wow that's a great link: Astrophysics Picture of the WEEK! :clap: :thumb_up:
Thanks, I didn't know it!
High Energy Astrophysics Picture of the Week!
I post them every week in Communications.
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by orin stepanek » Fri Jul 13, 2012 12:31 pm

Wow! So many wavelengths; so many colors; so much contrast! 170,000 light years across; makes this a huge galaxy indeed! 8-)
Orin

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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by rmollise » Fri Jul 13, 2012 1:31 pm

"Catherine Wheel." The common name "Pinwheel Galaxy" was taken--by M33. ;-)

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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by neufer » Fri Jul 13, 2012 1:59 pm

Ann wrote:

graydawn wrote:
Near top left corner of Big Dipper mosaic is M101. Enlarge the picture. At about 8 o'clock from M101, 2 inches away from M101, is what appears to be a transparent sphere, looking carefully, another object can barely be seen at about 1 o'clock within the sphere.
What is this object?
That is NGC 5474, one of M101's satellite galaxies. :arrow:

NGC 5474 by Adam Block. The object that seems to be inside this galaxy is actually the galaxy's bulge. The disk has been displaced to one side, probably due to interaction with M101.
Ann wrote:
Well, if you check out this image by Fabian Neyer, you can see a small bluish galaxy, NGC 5474, to the left of large M101. Look more closely at NGC 5474, and you can see that it appears to have a central bulge with a thick "arc" to the left of it! The bulge of the galaxy is displaced relative to the galaxy's disk! I believe that NGC 5474 has a lot to do with all the action in M101. I believe that these two galaxies are interacting, and this interaction has "sloshed the gas of M101 around" and created incredibly widespread star formation. As you can see from Fabian Neyer's image, an even smaller but also more nearby galaxy, NGC 5477 (a small blue galaxy above M101 in Fabian Neyer's image) is also a part of the action. You can see that the spiral arms of M101 appear to "reach out" for NGC 5477, as if the arms wanted to embrace this small galaxy.
slosh v.tr. [Perhaps blend of slop and slush.]
  • 1. To spill or splash (a liquid) copiously or clumsily: slosh paint on the floor.
    2. To agitate in a liquid: slosh clothes in a solution of bleach and detergent.
http://www.noao.edu/outreach/aop/observers/n5474.html wrote:

<<NGC 5474 is an asymmetric spiral galaxy and it it is being dramatically disturbed by its much larger neighbor M101. With respect to this image, M101 is several fields away towards the upper left direction. At first glance, it might appear that M101 is somehow gravitationally dragging the nucleus right out of NGC 5474. However, astronomers that model these kinds of galactic interactions on a computer find a slightly different story. When using tens (if not hundreds) of thousands of point masses for stars, astronomers found that the asymmetry displayed in NGC 5474 is probably relatively short lived. We just happen to be looking at this galaxy in a state of "sloshed" agitation. As NGC 5474 orbits M101, the amount of asymmetry depends of the relationship between the direction of orbital revolution about M101 and the sense of rotation for NGC 5474's disk. If the revolution is opposite that of disk rotation, as it is in the case of NGC 5474, then the lopsided state can survive for many galactic rotations after an initial (strong) tidal perturbation.

Note that the seemingly grainy appearence of this galaxy is due to partially resolving some of the brighter stars in the disk (v=20-21). A healthy sprinkling of pink starforming regions, and blue (young) stellar associations can also be seen along the spiral structure of the galaxy. >>
Art Neuendorffer

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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by neufer » Fri Jul 13, 2012 2:08 pm

rmollise wrote:
"Catherine Wheel." The common name "Pinwheel Galaxy" was taken--by M33. ;-)
Art Neuendorffer

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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by dlw » Fri Jul 13, 2012 5:05 pm

I wonder about the apparent great asymmetry. The almost detached straightened arms in the upper left; the differently straightened arm center left; the multiple arms on the right as compared with the left, etc.

Could this be the result of several close encounters and/or merger with smaller galaxies?

Maybe it's just my misinterpretation of the image...

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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by neufer » Fri Jul 13, 2012 5:40 pm

Click to play embedded YouTube video.
dlw wrote:
I wonder about the apparent great asymmetry. The almost detached straightened arms in the upper left; the differently straightened arm center left; the multiple arms on the right as compared with the left, etc.

Could this be the result of several close encounters and/or merger with smaller galaxies?
Indubitably.

Dancing with dwarf galaxies stretches one's arms out. :arrow:
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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by Boomer12k » Sat Jul 14, 2012 2:52 am

In some pictures it looks like a net being splayed out. In some others it looks like a Nautilus Shell...Awesome Galaxy either way...

Will try to get a pic of it tonight...

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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by ta152h0 » Sat Jul 14, 2012 6:06 pm

Has there been any studies made regarding the distribution of the axis of rotation of these monsters and find some kind of order, or are these truly helter skelter vectors ?
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Re: APOD: 21st Century M101 (2012 Jul 13)

Post by neufer » Sat Jul 14, 2012 7:50 pm

ta152h0 wrote:
Has there been any studies made regarding the distribution of the axis of rotation of these monsters and find some kind of order, or are these truly helter skelter vectors ?
Helter skelter globally... but probably not locally:
http://iopscience.iop.org/1538-4357/640/2/L111/fulltext/20344.text.html wrote:
Detection of the Effect of Cosmological Large-Scale Structure on the Orientation of Galaxies
Ignacio Trujillo ,1,2 Conrado Carretero ,3 and Santiago G. Patiri 3
The Astrophysical Journal, 640:L111-L114, 2006 April 1
© 2006. The American Astronomical Society.

ABSTRACT: <<Galaxies are not distributed randomly throughout space but are instead arranged in an intricate "cosmic web" of filaments and walls surrounding bubble-like voids. There is still no compelling observational evidence of a link between the structure of the cosmic web and how galaxies form within it. However, such a connection is expected on the basis of our understanding of the origin of galaxy angular momentum: disk galaxies should be highly inclined relative to the plane defined by the large-scale structure surrounding them. Using the two largest galaxy redshift surveys currently in existence (2dFGRS and SDSS), we show at the 99.7% confidence level that these alignments do indeed exist: spiral galaxies located on the shells of the largest cosmic voids have rotation axes that lie preferentially on the void surface.>>
http://arxiv.org/abs/astro-ph/0609629 wrote:
The orientation of galaxy dark matter haloes around cosmic voids
Riccardo Brunino, Ignacio Trujillo, Frazer R. Pearce, Peter A. Thomas
(Submitted on 22 Sep 2006 (v1), last revised 10 Nov 2006 (this version, v2))

<<Using the Millennium N-body simulation we explore how the shape and angular momentum of galaxy dark matter haloes surrounding the largest cosmological voids are oriented. We find that the major and intermediate axes of the haloes tend to lie parallel to the surface of the voids, whereas the minor axis points preferentially in the radial direction. We have quantified the strength of these alignments at different radial distances from the void centres. The effect of these orientations is still detected at distances as large as 2.2 R_void from the void centre. Taking a subsample of haloes expected to contain disc-dominated galaxies at their centres we detect, at the 99.9% confidence level, a signal that the angular momentum of those haloes tends to lie parallel to the surface of the voids. Contrary to the alignments of the inertia axes, this signal is only detected in shells at the void surface (1<R<1.07 R_void) and disappears at larger distances. This signal, together with the similar alignment observed using real spiral galaxies (Trujillo, Carretero & Patiri 2006), strongly supports the prediction of the Tidal Torque theory that both dark matter haloes and baryonic matter have acquired, conjointly, their angular momentum before the moment of turnaround.>>
Art Neuendorffer