APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

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Expand view Topic review: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by Ann » Thu Apr 02, 2020 4:55 am

TheOtherBruce wrote: ↑Wed Apr 01, 2020 11:52 pm
Ann wrote: ↑Fri Mar 20, 2020 6:14 pm
Click to play embedded YouTube video.

I thought I had already posted this video, but apparently not. I like seeing how stars move inside a cluster and how the stars evolve over time.
Interesting. Any guesses what the simulation did about 30 seconds in, when a bright giant and a smaller star went <p'ting> <zoom> off in opposite directions? Maybe a very close encounter that gave them both a gravity assist?
Exactly. In a crowded environment, stars may meet each other in just such a way that gives each of them a mighty boost in opposite directions.
















Bob King of Sky & Telescope wrote:

So what caused the three to abruptly pick up and leave the scene? A supernova explosion might have sent the stars reeling in opposite directions, but recently discovered evidence points to gravitational interactions within a compact star cluster. It's thought that Mu Col and AE Aur once shared company as a binary system that collided or strayed too close to another binary pair. Complicated gravitational interactions ensued, breaking the binary's bond and flinging the stars into space as "runaways" while leaving the other binary intact, still lurking near the scene of the crime.

If you've ever observed the beautiful, 3rd-magnitude triple star Iota Orionis located just south of the Orion Nebula, you've caught the culprit red-handed. Besides its telescopic partners, Iota also possesses a massive, spectroscopic companion that revolves around the primary star in a highly eccentric orbit with the same velocity as runaways Mu Col and AE Aur. This and its location are important clues that tie Iota Ori to its distant cousins.
Ann

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by TheOtherBruce » Wed Apr 01, 2020 11:52 pm

Ann wrote: ↑Fri Mar 20, 2020 6:14 pm
Click to play embedded YouTube video.

I thought I had already posted this video, but apparently not. I like seeing how stars move inside a cluster and how the stars evolve over time.
Interesting. Any guesses what the simulation did about 30 seconds in, when a bright giant and a smaller star went <p'ting> <zoom> off in opposite directions? Maybe a very close encounter that gave them both a gravity assist?

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by felix_wegerer » Wed Apr 01, 2020 9:31 am

Lovely object for apochromatic refractors! So many stars :0

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by CuriousChimp » Thu Mar 26, 2020 2:29 pm

Ann wrote: ↑Fri Mar 20, 2020 6:14 pm
CuriousChimp wrote: ↑Fri Mar 20, 2020 2:24 am
Chris Peterson wrote: ↑Fri Mar 20, 2020 12:54 am

They are all in orbit. They don't coalesce for the same reason our solar system doesn't.
Though, like elliptical galaxies and utterly unlike the Solar System, a Galactic Cluster's components seem to move more like a bee swarm than a sensible planetary system. Stars orbit in 3D, sometimes in exceedingly thin, long ellipses and in chaotic ones heavily influenced by all of the millions of other stars whirling nearby.

Clusters are complicated dances of tiny, bright diamonds around a theoretical centre that may never be occupied by anything for very long. They are examples of the Many Body Problem written very, very large.

They are fun.
<snipped>

I thought I had already posted this video, but apparently not. I like seeing how stars move inside a cluster and how the stars evolve over time.

Ann
Thank you, that's pretty. :)

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by CuriousChimp » Thu Mar 26, 2020 2:27 pm

MarkBour wrote: ↑Fri Mar 20, 2020 4:52 pm

Got a planetarium nearby?
Nope. Sorry.
You realize that you're just purposely making yourself feel bad, don't you? Actually, based on your last statement, I'm thinking you understood this already.
An interesting take on it. Maybe true, too.

I'm not sure I can explain myself, but what I feel I've come to realize lately is a paradox. There are lots of things in this universe that are inutterably sad. And I mean sad in reality, truly tragic. But then, after a longer reflection, it turns into a matter of perspective. Perhaps the greatest gift given to mankind is the ability to change our perspective, at will, with just a bit of effort. (Take the coronavirus COVID-19, for example. It's pure, pure badness, right?)
SARS mark 2 is not bad, evil or even judgemental, it's just a chemical reaction like a fire. What it does is sad, hurting people, but the bug itself is entirely neutral.

Lots of other things are like this, too. It is us that give meaning to them and only when they affect us.

But you're right, I'm feeling sentimental and maudlin and I need a hug. Sorry.

You explained yourself well. :)

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by MarkBour » Wed Mar 25, 2020 5:16 pm

Ann wrote: ↑Fri Mar 20, 2020 6:14 pm youtube -- https://www.youtube.com/watch?v=VF6J7P2cpn8

I thought I had already posted this video, but apparently not. I like seeing how stars move inside a cluster and how the stars evolve over time.

Ann
Thanks, a delightful simulation! It said "Rendered as you would see it with the Hubble Space Telescope, if it would snap a picture every 31250 year, that is!"

It's so nice to get to see things no human can ever actually watch.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by MarkBour » Wed Mar 25, 2020 4:58 pm

Chris Peterson wrote: ↑Fri Mar 20, 2020 5:20 pm Of course, humans might be the best thing that every happened to the virus. Whether we look at numbers or at mass, it seems clear that the Universe (or our little corner of it) was created for single-celled organisms and viruses. Everything more complex simply exists to serve them in some way.
Loved this perspective. I wonder, will the viruses want us to carry them to the stars?

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by Ann » Fri Mar 20, 2020 6:14 pm

CuriousChimp wrote: ↑Fri Mar 20, 2020 2:24 am
Chris Peterson wrote: ↑Fri Mar 20, 2020 12:54 am
donaldbullock wrote: ↑Thu Mar 19, 2020 7:32 pm Can you explain;
Why with such a huge number of stars within very close proximity, has gravity not coalesced them into a super star.
Thanks
They are all in orbit. They don't coalesce for the same reason our solar system doesn't.
Though, like elliptical galaxies and utterly unlike the Solar System, a Galactic Cluster's components seem to move more like a bee swarm than a sensible planetary system. Stars orbit in 3D, sometimes in exceedingly thin, long ellipses and in chaotic ones heavily influenced by all of the millions of other stars whirling nearby.

Clusters are complicated dances of tiny, bright diamonds around a theoretical centre that may never be occupied by anything for very long. They are examples of the Many Body Problem written very, very large.

They are fun.
Click to play embedded YouTube video.

I thought I had already posted this video, but apparently not. I like seeing how stars move inside a cluster and how the stars evolve over time.

Ann

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by TheOtherBruce » Fri Mar 20, 2020 5:43 pm

MarkBour wrote: ↑Fri Mar 20, 2020 4:59 pm
TheOtherBruce wrote: ↑Fri Mar 20, 2020 12:49 am FWIW, "coalescing into a super star" generally isn't a thing colliding stars do. Instead, they tend to go boom. Very boom. All the boom.
Loved this description. :D Maybe it's a reference, too. It sounds familiar, but I don't recognize it.
I'm a big fan of both Babylon 5 (in particular the wit and wisdom of Susan Ivanova) and the webcomic Schlock Mercenary. The resulting mental car crash inspired me. :wink:

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by Chris Peterson » Fri Mar 20, 2020 5:20 pm

MarkBour wrote: ↑Fri Mar 20, 2020 5:17 pm
Chris Peterson wrote: ↑Fri Mar 20, 2020 4:58 pm ... the virus is actually SARS-CoV-2. COVID-19 is the disease caused by that virus.
Thanks, a helpful correction. And it can help clarify what I'm talking about.

... One can think about whether the virus itself is viewed as the bad thing or whether it is the disease or pandemic we're living through that is so bad. I guess most of us would not view the virus, in an isolated test-tube, as bad in and of itself. Maybe. On the other hand, I think that both the disease and the pandemic are very awful and tragic things to us.

The part I'm leaving out there, and probably not something to explore in this forum, is that from other perspectives, not everything we find as evil, hurtful, and sad, will be viewed with the same conclusion. But I couldn't help it, because I've been thinking about this idea a fair amount lately.
Of course, humans might be the best thing that every happened to the virus. Whether we look at numbers or at mass, it seems clear that the Universe (or our little corner of it) was created for single-celled organisms and viruses. Everything more complex simply exists to serve them in some way.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by MarkBour » Fri Mar 20, 2020 5:17 pm

Chris Peterson wrote: ↑Fri Mar 20, 2020 4:58 pm ... the virus is actually SARS-CoV-2. COVID-19 is the disease caused by that virus.
Thanks, a helpful correction. And it can help clarify what I'm talking about.

... One can think about whether the virus itself is viewed as the bad thing or whether it is the disease or pandemic we're living through that is so bad. I guess most of us would not view the virus, in an isolated test-tube, as bad in and of itself. Maybe. On the other hand, I think that both the disease and the pandemic are very awful and tragic things to us.

The part I'm leaving out there, and probably not something to explore in this forum, is that from other perspectives, not everything we find as evil, hurtful, and sad, will be viewed with the same conclusion. But I couldn't help it, because I've been thinking about this idea a fair amount lately.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by Chris Peterson » Fri Mar 20, 2020 5:04 pm

CuriousChimp wrote: ↑Fri Mar 20, 2020 2:24 am
Chris Peterson wrote: ↑Fri Mar 20, 2020 12:54 am
donaldbullock wrote: ↑Thu Mar 19, 2020 7:32 pm Can you explain;
Why with such a huge number of stars within very close proximity, has gravity not coalesced them into a super star.
Thanks
They are all in orbit. They don't coalesce for the same reason our solar system doesn't.
Though, like elliptical galaxies and utterly unlike the Solar System, a Galactic Cluster's components seem to move more like a bee swarm than a sensible planetary system. Stars orbit in 3D, sometimes in exceedingly thin, long ellipses and in chaotic ones heavily influenced by all of the millions of other stars whirling nearby.

Clusters are complicated dances of tiny, bright diamonds around a theoretical centre that may never be occupied by anything for very long. They are examples of the Many Body Problem written very, very large.

They are fun.
Yes, the orbits are highly perturbed. But even in the densest parts, the distance between the stars is huge compared with the diameter of the stars, which is why collisions are extremely rare.

I once did an analysis of a dense globular cluster by projecting lines with a stellar cross section through a model cluster. Less than one in a million ended up intersecting a star.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by MarkBour » Fri Mar 20, 2020 4:59 pm

TheOtherBruce wrote: ↑Fri Mar 20, 2020 12:49 am FWIW, "coalescing into a super star" generally isn't a thing colliding stars do. Instead, they tend to go boom. Very boom. All the boom.
Loved this description. :D Maybe it's a reference, too. It sounds familiar, but I don't recognize it.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by Chris Peterson » Fri Mar 20, 2020 4:58 pm

MarkBour wrote: ↑Fri Mar 20, 2020 4:52 pm
CuriousChimp wrote: ↑Fri Mar 20, 2020 2:32 am ...
When I was very much younger than I am now, I saw the beginning of Man's great adventure into the deep black between the stars and I dreamed of one day touching their worlds. It was a hard thing to learn that neither I nor Man himself ever will and that the dream has gone, forever.

In a way, APoD is a small hurty thing. It brings to us the little, tiny flicker of hope of seeing the beauties and wonders of our home, the cosmos, before the reality snatches away that flicker. SF movies, TV and books sometimes do similarly.

We can read Dr. Asimov's lovely "Nightfall" and we can dream but we'll never see.

We are blessed and cursed by wanderlust.
Got a planetarium nearby?

You realize that you're just purposely making yourself feel bad, don't you? Actually, based on your last statement, I'm thinking you understood this already.

I'm not sure I can explain myself, but what I feel I've come to realize lately is a paradox. There are lots of things in this universe that are inutterably sad. And I mean sad in reality, truly tragic. But then, after a longer reflection, it turns into a matter of perspective. Perhaps the greatest gift given to mankind is the ability to change our perspective, at will, with just a bit of effort. (Take the coronavirus COVID-19, for example. It's pure, pure badness, right?)
Quibble, utterly unrelated to your comment: the virus is actually SARS-CoV-2. COVID-19 is the disease caused by that virus.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by MarkBour » Fri Mar 20, 2020 4:52 pm

CuriousChimp wrote: ↑Fri Mar 20, 2020 2:32 am ...
When I was very much younger than I am now, I saw the beginning of Man's great adventure into the deep black between the stars and I dreamed of one day touching their worlds. It was a hard thing to learn that neither I nor Man himself ever will and that the dream has gone, forever.

In a way, APoD is a small hurty thing. It brings to us the little, tiny flicker of hope of seeing the beauties and wonders of our home, the cosmos, before the reality snatches away that flicker. SF movies, TV and books sometimes do similarly.

We can read Dr. Asimov's lovely "Nightfall" and we can dream but we'll never see.

We are blessed and cursed by wanderlust.
Got a planetarium nearby?

You realize that you're just purposely making yourself feel bad, don't you? Actually, based on your last statement, I'm thinking you understood this already.

I'm not sure I can explain myself, but what I feel I've come to realize lately is a paradox. There are lots of things in this universe that are inutterably sad. And I mean sad in reality, truly tragic. But then, after a longer reflection, it turns into a matter of perspective. Perhaps the greatest gift given to mankind is the ability to change our perspective, at will, with just a bit of effort. (Take the coronavirus COVID-19, for example. It's pure, pure badness, right?)

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by Chris Peterson » Fri Mar 20, 2020 1:49 pm

TheZuke! wrote: ↑Fri Mar 20, 2020 1:47 pm Sorry to get theological on you great folks...

But, I think, someday in Eternal Life, I may get to view, if not travel, this vast beautiful universe!

Okay, neufer, your turn to put me down! :)
Maybe it's all the Matrix. Get out, and you can inspect the code that is used to create globular clusters.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by TheZuke! » Fri Mar 20, 2020 1:47 pm

Sorry to get theological on you great folks...

But, I think, someday in Eternal Life, I may get to view, if not travel, this vast beautiful universe!

Okay, neufer, your turn to put me down! :)

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by TheOtherBruce » Fri Mar 20, 2020 3:21 am

CuriousChimp wrote: ↑Fri Mar 20, 2020 2:32 am We can read Dr. Asimov's lovely "Nightfall" and we can dream but we'll never see.
I just realised β€” the planet in Nightfall was in the middle of a big globular cluster. But the people there didn't know, because with (I think) six suns, it was never night. Until suddenly it was... :idea: :shock: :!:

Also going back to the classics, Poul Anderson had a short story, Starfog, about the problem of navigating through a large region of stars at ridiculously close distances. Can't remember whether the term "globular cluster" was actually used, but the description does fit very closely.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by CuriousChimp » Fri Mar 20, 2020 2:32 am

Ann wrote: ↑Thu Mar 19, 2020 7:45 pm
christianhoffmann wrote: ↑Thu Mar 19, 2020 10:22 am I am a mathematician and would like to estimate/compute the brightness in the interior/middle of a globular cluster, given eht number of 'normal' stars of teh entire cluster, e.g. M13.https://apod.nasa.gov/apod/image/2003/M ... mColes.jpg
I am very much a non-mathematician, so I can't help you, but at least I can post two interesting illustrations of what a view from a planet inside a globular cluster might look like. Judging from the presence of blue horizontal branch stars in the globular in the picture at right, we might guess that that globular might be either M13 or Omega Centauri.

Ann

Thank you, lady, those are pretty but also so sad.


When I was very much younger than I am now, I saw the beginning of Man's great adventure into the deep black between the stars and I dreamed of one day touching their worlds. It was a hard thing to learn that neither I nor Man himself ever will and that the dream has gone, forever.

In a way, APoD is a small hurty thing. It brings to us the little, tiny flicker of hope of seeing the beauties and wonders of our home, the cosmos, before the reality snatches away that flicker. SF movies, TV and books sometimes do similarly.

We can read Dr. Asimov's lovely "Nightfall" and we can dream but we'll never see.

We are blessed and cursed by wanderlust.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by CuriousChimp » Fri Mar 20, 2020 2:24 am

Chris Peterson wrote: ↑Fri Mar 20, 2020 12:54 am
donaldbullock wrote: ↑Thu Mar 19, 2020 7:32 pm Can you explain;
Why with such a huge number of stars within very close proximity, has gravity not coalesced them into a super star.
Thanks
They are all in orbit. They don't coalesce for the same reason our solar system doesn't.
Though, like elliptical galaxies and utterly unlike the Solar System, a Galactic Cluster's components seem to move more like a bee swarm than a sensible planetary system. Stars orbit in 3D, sometimes in exceedingly thin, long ellipses and in chaotic ones heavily influenced by all of the millions of other stars whirling nearby.

Clusters are complicated dances of tiny, bright diamonds around a theoretical centre that may never be occupied by anything for very long. They are examples of the Many Body Problem written very, very large.

They are fun.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by Chris Peterson » Fri Mar 20, 2020 12:54 am

donaldbullock wrote: ↑Thu Mar 19, 2020 7:32 pm Can you explain;
Why with such a huge number of stars within very close proximity, has gravity not coalesced them into a super star.
Thanks
They are all in orbit. They don't coalesce for the same reason our solar system doesn't.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by TheOtherBruce » Fri Mar 20, 2020 12:49 am

donaldbullock wrote: ↑Thu Mar 19, 2020 7:32 pm Can you explain;
Why with such a huge number of stars within very close proximity, has gravity not coalesced them into a super star.
Thanks
As a wise man* once said, β€œSpace is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.”

In comparison, stars β€” even the biggest super-giants β€” are very not-big. Even in the crowded conditions in the middle of a globular cluster, there's lots of room between them for any number of nearly-but-not-quite close passes. Collisions aren't impossible, they happen occasionally in a normal galaxy, but on a human timescale, they'll be few and far between.

FWIW, "coalescing into a super star" generally isn't a thing colliding stars do. Instead, they tend to go boom. Very boom. All the boom.

* I don't think I need to give a name, we've got some hoopy froods here.

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by sillyworm 2 » Thu Mar 19, 2020 8:30 pm

Thanks Chris & Ann.I do read up daily but I still miss some details.I did not know that a Red Giant could turn blue.I thought that stars ,toward their end time,expanded and turned red..then went supernova or collapsed.I'll have to do more reading.Chris..I know in all likelihood we will never teach other Galaxies.Time and radiation our enemies.I do believe we may someday figure out quick space travel....Is it not space radiation that will not allow this even if we do?

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by Ann » Thu Mar 19, 2020 8:05 pm

sillyworm 2 wrote: ↑Thu Mar 19, 2020 2:01 pm Thanks..I always confuse color with age.Color is eventually more a size element?
As Chris said, color means temperature. We are talking about the temperature of the photosphere, the outermost visible layer of a star.
The Herzsprung-Russell diagram of stars. When stars are on the main sequence, they fuse hydrogen to helium in their cores. The more massive the stars are, they faster they fuse their hydrogen, and the hotter and bluer they are. The more lightweight the stars are, the slower they fuse their hydrogen, and the cooler and redder they are. When stars have used up their core hydrogen, they swell into giants. Red supergiants like Betelgeuse become tremendously big, whereas blue, white and even yellow supergiants are somewhat smaller. Medium-mass stars like the Sun will eventually turn into red giants, but they will never be as big as Betelgeuse. In many globular clusters, red giants can shrink and become blue horizontal branch stars before swelling into red asymtotic branch giants. Illustration: Astronomy magazine.

Massive young stars are blue (Chris would say blue-white), because they fuse hydrogen to helium in their cores at a furious rate. Medium-mass stars like the Sun have never been blue, because they have never produced enough energy in their cores to look blue. They don't need that much energy to keep themselves from collapsing, unlike the stellar heavyweights. And small stars like Proxima Centauri need even less energy to "hold themselves up", and they are yellow-orange in color.

When massive stars have used up their supply of energy in their cores, they start expanding. At first it doesn't affect their color that much. An example of a star that has used up its core hydrogen and started expanding without losing its blue color is Alnilam, the middle star in Orion's Belt. But another star in Orion, Betelgeuse, started out as a hot blue star, and it has since expanded so mightily that its outer layers have cooled to a yellow-orange color. Note that the core of Betelgeuse is still very hot, but we can't see it.

In globular clusters the brightest stars are red giants. The outer layers of the red giants have expanded mightily (though not as much as Betelgeuse) and they have cooled to an orange-yellow color. But there are blue stars in many globular clusters, too. These stars are always fainter than the brightest red giants, but they are relatively bright anyway.

These blue stars, called horizontal branch stars, are former red giants which have "turned on" their helium fusion. As they did so, they shrunk a lot and turned blue precisely because they became relatively small. Their outer layers are relatively close to their hot interiors, and the outer layers are therefore hot enough to be blue.

Ann

Re: APOD: M13: The Great Globular Cluster in... (2020 Mar 19)

by Ann » Thu Mar 19, 2020 7:45 pm

christianhoffmann wrote: ↑Thu Mar 19, 2020 10:22 am I am a mathematician and would like to estimate/compute the brightness in the interior/middle of a globular cluster, given eht number of 'normal' stars of teh entire cluster, e.g. M13.https://apod.nasa.gov/apod/image/2003/M ... mColes.jpg




















I am very much a non-mathematician, so I can't help you, but at least I can post two interesting illustrations of what a view from a planet inside a globular cluster might look like. Judging from the presence of blue horizontal branch stars in the globular in the picture at right, we might guess that that globular might be either M13 or Omega Centauri.

Ann

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