APOD: M13: The Great Globular Cluster in... (2012 Jun 14)

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Expand view Topic review: APOD: M13: The Great Globular Cluster in... (2012 Jun 14)

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Skytreker » Sat Jun 16, 2012 8:16 am

Great movie! Too bad that it isn't in slightly better quality so that single stars doesn't show like square pixels, but nevertheless this is an awesome simmulation of the star movement inside a globular cluster. And yes the quote in the beginning of the file is exactly what came to my mind, when I saw the picture of M13 :)

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Chris Peterson » Sat Jun 16, 2012 5:08 am

Guest wrote:Well, "turbulent motion" is not spinning;
Actually, it is. When you have turbulent motion in a nebula, you have local regions where the net angular momentum is non-zero. That's spinning, and it's what determines the spin of anything that condenses from that region.
and with all those stars and density, the M13 cluster does not show spinning as a galaxy does, if a galaxy is spinning, as all do not seem to do as some do.
All galaxies have some spin. So do all globular clusters. In the case of globulars, however, the spin velocity is slow with respect to the random orbital motions of the member stars.
Spin is still a mystery to me, and seems absurd in the case of spin rates into hundreds per second. I still don't think that spin is explained by talk about angular momentum, I think it could be a separate form of energy, deserving to be studied more. For instance, is being flat a result or a cause of galaxy rotation, and how do globular clusters show that.
In classical mechanics (which is what we're dealing with here), spin is essentially synonymous with angular momentum. It is extremely well understood, and there's really no possibility of it being something exotic like a new form of energy. There's nothing absurd about bodies with extremely high rotation rates- they are easily explained by basic physics and the conservation of angular momentum.

Spiral galaxies, which are flat, have a significant net angular momentum because their formation mechanism left much of their material in orbits with similar angular momentums. Globular clusters (and elliptical galaxies) have low net angular momentum because their formation mechanisms left much of their material in orbits with random angular momentums. It's as simple as that.

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Guest » Sat Jun 16, 2012 1:47 am

At http://asterisk.apod.com/viewtopic.php?f=9&t=25290 I had asked about spinning, and Chris L Peterson replied, closing with "Everything is spinning. In some cases you have groups of things that are held together by other forces, and that prevents them from spinning independently of each other, that's all. Nebulas are spinning as well, although generally too slowly to notice many effects caused by it. Inside a nebula, you have all sorts of turbulent motion and spinning- it is precisely the spinning of local regions that results in the formation of stars."

Well, "turbulent motion" is not spinning; and with all those stars and density, the M13 cluster does not show spinning as a galaxy does, if a galaxy is spinning, as all do not seem to do as some do. Spin is still a mystery to me, and seems absurd in the case of spin rates into hundreds per second. I still don't think that spin is explained by talk about angular momentum, I think it could be a separate form of energy, deserving to be studied more. For instance, is being flat a result or a cause of galaxy rotation, and how do globular clusters show that.

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Chris Peterson » Fri Jun 15, 2012 5:20 pm

neufer wrote:With it's pixel size resolution of 0.13 arcsec Hubble is probably capable of transit monitoring a few tens of thousands of M13 central core stars for planets.

However, I doubt that it could do a very adequate "Keplerian" job for over 145,000 central core stars.

You can observe many apparently isolated stars but not the more numerous fainter ones that are hidden behind the overexposed Airy disks of their brighter neighbors.
But they aren't. Do the math. I assumed the core is about 50 ly across, and contains 250,000 stars. Change the numbers a bit if you want, but I think these are pretty close. Flatten this to a 2D projection. The odds of two stars having significantly overlapping Airy disks (assuming an optical resolution better than 1 arcsec) is low. Almost all the stars are resolvable, even to a small telescope.

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by neufer » Fri Jun 15, 2012 4:40 pm

geckzilla wrote:
Chris Peterson wrote:
neufer wrote:
Even Hubble doesn't have the resolving power to clearly distinguish most core stars from one another.
I don't think that's true. At the core, the typical separation of the stars is around 0.9 arcsec; resolving that requires only a 150mm objective. It also requires very good seeing, or better, a space telescope. Hubble has imaged the core of M13, and easily resolves the individual stars.
And if you take a look at the FITS data, they are even easier to distinguish without the processing which was done for aesthetically pleasing contrast.
With it's pixel size resolution of 0.13 arcsec Hubble is probably capable of transit monitoring a few tens of thousands of M13 central core stars for planets.

However, I doubt that it could do a very adequate "Keplerian" job for over 145,000 central core stars.

You can observe many apparently isolated stars but not the more numerous fainter ones that are hidden behind the overexposed Airy disks of their brighter neighbors. :arrow:
http://en.wikipedia.org/wiki/Kepler_%28spacecraft%29 wrote:
Kepler's only instrument is a photometer that continually monitors the brightness of over 145,000 main sequence stars in a fixed field of view.

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Ann » Fri Jun 15, 2012 6:20 am

Martin Pugh's image is a very fine one. Do compare it, however, with the ESA/HEIC Hubble Picture of the Week | 2012 Jun 11, showing the Compact Blue Dwarf galaxy UGC 5497. The galaxy and the globular look extremely similar, but thanks to Martin Pugh's excellent color data we can tell that the object in his image is a globular. The brightest stars in his picture are red giants, and the very brightest and most orange of them are so called Asymptotic Giant Branch stars, which have just reached their greatest luminosity before expelling their outer atmospheres and turning into white dwarfs. There is a large number of obviously blue stars, which are fainter than the red giants but brighter than an even larger population of neutral-colored stars. The blue stars are blue horizontal branch stars, which represents an intermediate stage between "normal" red giants and Asymptotic Branch Giants in metal-poor stellar populations. The neutral-colored stars are hydrogen-fusing dwarfs at about the same temperature as the Sun.

The color information of the UGC 5497 image is poor, however, since the picture was produced from exposures through only two filters, an optical or clear one centered at 606 nm, and an infrared one centered at 814 one.
http://www.spacetelescope.org/static/ar ... w1224a.jpg wrote:

The object is a compact blue dwarf galaxy that is infused with newly formed clusters of stars. The bright, blue stars that arise in these clusters help to give the galaxy an overall bluish appearance that lasts for several million years until these fast-burning stars explode as supernovae.
If you look at a better-resolved version of the ESA/HEIC image of UGC 5497, you can see that there really appears to be a brightish population of marginally orange stars in this dwarf galaxy as well as a number of faint blue stars. Personally I can't spot any bright blue stars at all in this object, however, and no clusters, either. I can see a few small, faint, extended, neutral-colored objects in or or next to UGC 5497 which may be emission nebulae, since they ought to be redder in color if they were background galaxies. Actually, though, I'm not sure they aren't galaxies.

We can clearly see how unfavorable the use of one clear optical filter and one infrared filter is, if you want to extract color information from a nearby, relatively dust-free object.

For another comparison, take a look at this ESA/HEIC picture of globular cluster M53. This image, too, is made from exposures through the clear filter at 606 nm and the infrared one at 814 nm. You can see how hard it is to extract good color information from this image. There really are a number of bright orange objects in M53, but nothing in this picture looks more orange than anything in the Hubble picture of UGC 5497. If anything, the most orange stars in UGC 5497 look more orange than anything in M53, while the blue stars in M53 look every bit as blue the blue population of UGC 5497, even though the latter object is certainly bluer overall. Not that you can tell.

Thank you so much, Martin Pugh, for producing pictures with such great color information! :D

(By the way, don't miss Martin's picture of the heart of M13, showing a greenish star at about 2 o'clock!)

Ann

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by geckzilla » Thu Jun 14, 2012 11:15 pm

Chris Peterson wrote:
neufer wrote:Even Hubble doesn't have the resolving power to clearly distinguish most core stars from one another.
I don't think that's true. At the core, the typical separation of the stars is around 0.9 arcsec; resolving that requires only a 150mm objective. It also requires very good seeing, or better, a space telescope. Hubble has imaged the core of M13, and easily resolves the individual stars.
And if you take a look at the FITS data, they are even easier to distinguish without the processing which was done for aesthetically pleasing contrast.

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by saturno2 » Thu Jun 14, 2012 10:25 pm

M 13 is a Globular Cluster very compact.
As the center of an atom

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by henrystar » Thu Jun 14, 2012 10:10 pm

How I miss Arthur C. Clarke and Isaac Asimov! Those were the days, my friend, we thought they'd never end, those were the days!

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Chris Peterson » Thu Jun 14, 2012 9:10 pm

Mactavish wrote:I wonder. . . Perhaps it could be globular clusters of dead stars emitting no light that might be the evasive “dark matter” that can’t be seen.
The stars would have to be just the right size... much smaller than the Sun, and they'd not have time to stop buring; much larger and they'd have exploded. Any sort of stellar remnant besides a black hole would still be glowing in infrared, and an entire globular cluster of IR emitters would show up to our instruments.

For the most part, ordinary matter has been eliminated as a dark matter candidate because in nearly any form people can come up with, it would glow in the IR- something we don't see.

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Mactavish » Thu Jun 14, 2012 8:54 pm

Chris Peterson wrote:
neufer wrote:Even Hubble doesn't have the resolving power to clearly distinguish most core stars from one another.
I don't think that's true. At the core, the typical separation of the stars is around 0.9 arcsec; resolving that requires only a 150mm objective. It also requires very good seeing, or better, a space telescope. Hubble has imaged the core of M13, and easily resolves the individual stars.

Of course, this is just an optical problem. In reality, M13 is essentially empty space. Looking at just the core, in projection (as we see it), the area of empty space is about one trillion (1012) times greater than the area of the stars. You could zip back and forth throughout the cluster billions of times before you ever hit a star. But optically, diffraction makes the stars appear huge. If they weren't emitting light, we'd never know that M13 was there- it wouldn't block enough light from the background to be detectable, even against something like a glowing gas cloud.
I wonder. . . Perhaps it could be globular clusters of dead stars emitting no light that might be the evasive “dark matter” that can’t be seen.

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by orin stepanek » Thu Jun 14, 2012 8:50 pm

Globular clusters just don't do it for me! I mean they're interesting; but I like open clusters better! Like the Sisters; also galaxies; nebulae; comets and planets. 8-)

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by owlice » Thu Jun 14, 2012 8:47 pm

Field trip to Boomer's house! Who's with me?

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Boomer12k » Thu Jun 14, 2012 8:21 pm

One of my favs to look at with my 10" Meade LX200 GPS....and my Deep Sky Imager 2....hope to get out soon as the weather permits. Been nice, but cloudy. Right now, it is clear, and hopefully night is the night!!!!

One thing I have done is hook up my DSI to my laptop, and use the VGA output to my Epson 705 HD projector, and have objects projected to a 72" screen....awesome!!!!! But there can't be any WIND!!!!! Blows over the screen.

That is Jupiter the size of my CAR DOOR!!!

PEOPLE STOPPED AND WERE AWESTRUCK!!!
Screen and Z...
Screen and Z...
Screen, laptop and Z...
Screen, laptop and Z...
Star map on garage...door is open on right, and you can see roof line and roses on the left side....
Star map on garage...door is open on right, and you can see roof line and roses on the left side....

:---[===] *

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Chris Peterson » Thu Jun 14, 2012 5:32 pm

neufer wrote:Even Hubble doesn't have the resolving power to clearly distinguish most core stars from one another.
I don't think that's true. At the core, the typical separation of the stars is around 0.9 arcsec; resolving that requires only a 150mm objective. It also requires very good seeing, or better, a space telescope. Hubble has imaged the core of M13, and easily resolves the individual stars.

Of course, this is just an optical problem. In reality, M13 is essentially empty space. Looking at just the core, in projection (as we see it), the area of empty space is about one trillion (1012) times greater than the area of the stars. You could zip back and forth throughout the cluster billions of times before you ever hit a star. But optically, diffraction makes the stars appear huge. If they weren't emitting light, we'd never know that M13 was there- it wouldn't block enough light from the background to be detectable, even against something like a glowing gas cloud.

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Case » Thu Jun 14, 2012 4:32 pm

dlw wrote:There's an interesting looking galaxy in the lower right corner of the image. Looks like 2 galaxies merging and there's a significant halo around it/them. Is this particular object being studied?
"Nearby, about 40 arc minutes north-east of M13, is the faint (mag 11) galaxy NGC 6207, visible in many large- and medium-size-field photographs of M13, e.g., in the DSSM image. This galaxy has recently produced a type II supernova (SN 2004A)."

The HST did have a look at it: image 1, image 2

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by dlw » Thu Jun 14, 2012 4:22 pm

There's an interesting looking galaxy in the lower right corner of the image. Looks like 2 galaxies merging and there's a significant halo around it/them. Is this particular object being studied?

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by rstevenson » Thu Jun 14, 2012 2:25 pm

neufer wrote:
rstevenson wrote:
Art, what does "Sucker Bait" have to do with "Nightfall"?
It is an Asimov story specifically about the Messier 13 globular cluster.
Ah! Got it.

Rob

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by neufer » Thu Jun 14, 2012 2:22 pm

rstevenson wrote:
Art, what does "Sucker Bait" have to do with "Nightfall"?
It is an Asimov story specifically about the Messier 13 globular cluster.

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by rstevenson » Thu Jun 14, 2012 2:19 pm

Art, what does "Sucker Bait" have to do with "Nightfall"?

Rob

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by neufer » Thu Jun 14, 2012 2:12 pm

Lordcat Darkstar wrote:
Ernest wrote:
Does the density of the cluster make it impossible for Kepler to detect any planets orbiting the core stars?
I would think kepler is sensitive enough to detect planets orbiting the core stars. The problem is that current models predict that globular clusters are far to chaotic for planets to form in stable orbits around their host stars. That's why kepler isn't pointed at a globular cluster
Even Hubble doesn't have the resolving power to clearly distinguish most core stars from one another.

A five meter mirror using 100x the magnification of Kepler might work though.

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by BillLee » Thu Jun 14, 2012 1:43 pm

What would the night sky look like on a planet around a sun within a cluster like that? Would there even BE a "night sky"?

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by neufer » Thu Jun 14, 2012 1:38 pm

Skytreker wrote:
This reminds me of the great story by Isaac Asimov - Nightfall. A Planet with 7 suns inside a globular cluster. When night falls, there were 30 000 bright stars shining across the sky. 10 times as much as one can see under dark skies on Earth. What a glorious sight to behold!!
http://en.wikipedia.org/wiki/Sucker_Bait wrote:
<<Asimov was approached in 1953 by Twayne Press editor Fletcher Pratt with a story proposal: a scientist would create a world, and then he, Poul Anderson and Virginia Kidd would write novellas set in that world. The three novellas would then be published as a book, together with an essay by the scientist who created the scenario. This formula, which Pratt called a Twayne Triplet, had already resulted in the 1952 book The Petrified Planet.

The scenario created was that of a binary star system in the Messier 13 globular cluster with an Earthlike planet called Troas (or more informally, Junior) located at one of the system's Lagrangian points. An earlier expedition to Troas had suffered some mysterious disaster, and a second expedition was being mounted to determine if the planet was suitable for colonization, and to find out what happened to the first expedition.

Asimov finished his story, and Anderson finished a story called "Question and Answer", but Kidd never completed the third story, and the proposed book never saw print. Asimov, anticipating just such an eventuality, confirmed that he held first serial rights on the story, and sold Sucker Bait to Astounding (where it appeared a few months before "Question and Answer").

The story concerns the starship George G. Grundy, or Triple G., which has been chartered by the Confederacy of Worlds to investigate Junior. The only nonscientist among the Triple G.'s passengers is 20-year-old Mark Annuncio of the Mnemonic Service, who has been trained from the age of five to memorize and correlate vast amounts of information.

Over a century earlier, an attempt to colonize Junior had failed; after nearly two years on the planet, all 1,337 colonists had died for reasons unknown. The Triple G.'s scientists and Annuncio have to find out what killed them. For the first two weeks after landing, everyone remains aboard while the scientists take readings. After Rodriguez, the expedition's microbiologist, declares the local life forms noninfectious, a handful of scientists, plus Annuncio, travel to the original colony site.

Relations between the scientists and Annuncio deteriorate rapidly. Mnemonics are loners by nature, and their training makes them even more so. The scientists, on the other hand, as specialists, tend to be contemptuous of a professional generalist like Annuncio. When Annuncio asks Rodriguez to explain how he came to a conclusion, the microbiologist regards the request as an affront to his professional reputation, and refuses to answer. The other scientists manage to offend Annuncio in various ways.

When Annuncio finally realizes that the abnormally high concentration of beryllium in Junior's crust was what killed the colonists, and that they all have to leave immediately, he does not trust the scientists to deal with it. He returns to the ship and persuades the crew to mutiny and take the ship off the planet. The captain is barely able to convince the crew to stop at the colony site to pick up the scientists. When Annuncio is put on trial for fomenting the mutiny, he explains his actions, is acquitted, and the ship returns to Earth to seek treatment.>>

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by owlice » Thu Jun 14, 2012 1:24 pm

I love this; it's my favorite glob!

Re: APOD: M13: The Great Globular Cluster in... (2012 Jun 14

by Lordcat Darkstar » Thu Jun 14, 2012 1:15 pm

Ernest wrote:Does the density of the cluster make it impossible for Kepler to detect any planets orbiting the core stars? What would they look like, showered with radiation?
I would think kepler is sensitive enough to detect planets orbiting the core stars. The problem is that current models predict that globular clusters are far to chaotic for planets to form in stable orbits around their host stars. That's why kepler isn't pointed at a globular cluster

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