APOD: 3D Homunculus Nebula (2014 Jul 17)

Comments and questions about the APOD on the main view screen.
therodly1
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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by therodly1 » Sat Jul 26, 2014 2:52 am

Chris Peterson wrote:
therodly1 wrote:I suspect that this will turn out to be nothing but two stars that have collided.
While there's no particular reason to make that assumption, the reality is that stars colliding is a vanishingly rare event, so an observation would be scientifically valuable.
It is my opinion, arrived at after considerable thought since testing is out of the question, that there must be several collisions visible and in various states of completion that are being misinterpreted as other phenomena. When two stars collide, at onset of the collision, all motion is two directly opposite directions. Inertia would play a part in reversing the motion of some of the mass and ejecting it from the body, but mostly in the direction from whence it came.

By virtue of gravity's constancy, all the mass will be subject to motions as defined by the rules of gravity(after all, it is what brought the stars together). Since most of the mass is in the single star resulting from the collision, that star will control any escaping material.

Years down the road, the expanding cones from Eta Carina will become flute shaped because the material will be still being affected by the mass of the single star. The process has already started. In my opinion.

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Chris Peterson
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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by Chris Peterson » Sat Jul 26, 2014 3:51 am

therodly1 wrote:
Chris Peterson wrote:
therodly1 wrote:I suspect that this will turn out to be nothing but two stars that have collided.
While there's no particular reason to make that assumption, the reality is that stars colliding is a vanishingly rare event, so an observation would be scientifically valuable.
It is my opinion, arrived at after considerable thought since testing is out of the question, that there must be several collisions visible and in various states of completion that are being misinterpreted as other phenomena. When two stars collide, at onset of the collision, all motion is two directly opposite directions. Inertia would play a part in reversing the motion of some of the mass and ejecting it from the body, but mostly in the direction from whence it came.

By virtue of gravity's constancy, all the mass will be subject to motions as defined by the rules of gravity(after all, it is what brought the stars together). Since most of the mass is in the single star resulting from the collision, that star will control any escaping material.

Years down the road, the expanding cones from Eta Carina will become flute shaped because the material will be still being affected by the mass of the single star. The process has already started. In my opinion.
I fear you're straying into crackpot country.
Chris

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geckzilla
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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by geckzilla » Sat Jul 26, 2014 5:02 am

Everyone has their own theories sometimes but no matter how strongly convicted you feel about your opinion, it's nothing without the immense body of knowledge that the mainstream provides. Please check out the rules, therodly. http://asterisk.apod.com/viewtopic.php?f=28&t=26696
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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by therodly1 » Mon Jul 28, 2014 6:25 am

I fear you're straying into crackpot country.
Said the Abominable Snowman, Chris Peterson.

I quite likely am, apparently.
But really, what would a collision between two stars look like? Do astronomers have a particular set of features to look for when searching through the images that would indicate a collision? Can't call it crackpot country if there's no set of features for those lucky folks that get to peruse the data first!
geckzilla wrote:Everyone has their own theories sometimes but no matter how strongly convicted you feel about your opinion, it's nothing without the immense body of knowledge that the mainstream provides. Please check out the rules, therodly. http://asterisk.apod.com/viewtopic.php?f=28&t=26696
Unfortunately, mainstream doesn't supply much about star collisions and if I suspect that mainstream is overlooking something isn't it best to bring it up in a thread about findings that might lead to a possible explanation of a Eta Carina?
It is more appropriate than seeking a couch to crash on. Again, my opinion only!

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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by geckzilla » Mon Jul 28, 2014 11:17 am

You need to have more than just an opinion about it to back it up. Otherwise all you are doing is appealing to ignorance.
Just call me "geck" because "zilla" is like a last name.

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Chris Peterson
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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by Chris Peterson » Mon Jul 28, 2014 2:18 pm

therodly1 wrote:But really, what would a collision between two stars look like? Do astronomers have a particular set of features to look for when searching through the images that would indicate a collision?
Well, stars don't really collide, so that's not a scenario people look at very hard. There's no mechanism to cause a direct collision, except for pure chance, with the probability so low as to be ignored. What can happen is that binary stars can merge, which is a kind of gentle collision (and still very rare). And that's something that has theory behind it, and which has been modeled. Such a merger itself isn't a particularly violent process. You get a new star, and it behaves pretty much like a star with the combined mass ought to behave. Certainly, the mass could be high enough that you could get a core collapse supernova.
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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by geckzilla » Mon Jul 28, 2014 4:19 pm

Chris Peterson wrote:What can happen is that binary stars can merge, which is a kind of gentle collision (and still very rare). And that's something that has theory behind it, and which has been modeled. Such a merger itself isn't a particularly violent process.
How gentle do you mean? Say, if there was a planet in orbit around the binary pair (I know this is unlikely, too, but just for the sake of example...) would it be destroyed? If you say not particularly violent, does that just mean it wouldn't make much of a blip? I haven't heard of anyone detecting anything like this. There are all-sky surveys constantly on the lookout for novas and supernovas. I guess they wouldn't turn up on those if they did happen, unless of course they went supernova like you mentioned...
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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by Chris Peterson » Mon Jul 28, 2014 4:31 pm

geckzilla wrote:
Chris Peterson wrote:What can happen is that binary stars can merge, which is a kind of gentle collision (and still very rare). And that's something that has theory behind it, and which has been modeled. Such a merger itself isn't a particularly violent process.
How gentle do you mean? Say, if there was a planet in orbit around the binary pair (I know this is unlikely, too, but just for the sake of example...) would it be destroyed? If you say not particularly violent, does that just mean it wouldn't make much of a blip? I haven't heard of anyone detecting anything like this. There are all-sky surveys constantly on the lookout for novas and supernovas. I guess they wouldn't turn up on those if they did happen, unless of course they went supernova like you mentioned...
You wouldn't want to be around it! By "gentle" I just mean compared with big explosive processes like supernovas, or even planetary nebula formation. Obviously, there are large energies involved.
Chris

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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by therodly1 » Tue Jul 29, 2014 4:58 am

Well, you bring up a good point about stars merging rather than colliding, and I'm sure that happens as well. In regards to how often stars collide, which might mean combine, there is the following from the New York Times:
http://partners.nytimes.com/library/nat ... sions.html
With most of the universe being empty space, astronomers once thought the chance of stars colliding was roughly once in an eternity.

But in recent years, astronomers have realized that collisions are not uncommon within dense clusters of stars.

"We believe there are several hundred every hour somewhere in the universe," said Dr. Michael Shara, curator of the astrophysics department at the American Museum of Natural History, in a symposium at the museum two weeks ago.

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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by geckzilla » Tue Jul 29, 2014 5:10 am

You'll note, however, that eta Carinae is not in a dense star cluster.
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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by Chris Peterson » Tue Jul 29, 2014 2:16 pm

geckzilla wrote:You'll note, however, that eta Carinae is not in a dense star cluster.
Not only that, but even in dense clusters collisions are rare. The recognition that they sometimes occur is based on dynamic modeling. None has ever been observed.
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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by therodly1 » Thu Jul 31, 2014 5:43 am

While none have been observed, where would one find out what they expect to see when they do observe one? And I grant that just because I would expect to see something like Eta Carina doesn't mean that others would, but what is it that they expect to see? I expect it just because of how I understand the laws of motion, theory already developed and accepted.

'That which is in motion tends to stay in motion....' etc.

Is there anything that rules out a collision in this case?

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Re: APOD: 3D Homunculus Nebula (2014 Jul 17)

Post by geckzilla » Thu Jul 31, 2014 5:51 am

If you wanted to begin searching you could look for them in the densest parts of the globular clusters we have nearby for study. If you think that the aftermath should look like the Homunculus nebula, you might expect to see that somewhere in one of them. Globular clusters are weird things, though. There are only a handful of nebulas allegedly within them (Pease 1, for example) and they are all planetary nebulas.
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