View Full Version : Loose Gas Giants

2009-Feb-17, 05:27 PM
Awhile back, I read an article about Gas Giants in the Orion Nebula, which do not orbit any of the stars, there. I can't remember if I read it in the one issue of ASTRONOMY MAGAZINE, which I can't find; or if I read it in the Smithsonian magazine or in the Nat'l Geographic magazine. Anyway, it was an article in a reputable magazine.

What I'm wondering, is the Nebula gravity enough to keep the loose gas giants in the Orion Nebula? Or, could these things from time to time escape the Orion Nebula and float into interstellar space?

If the latter were possible or probable, at what velocity (ball park figure, I know there's a lot of variables but don't have the math) would such a planet travel, in interstellar space?

I have a story idea, is why I'm asking.


2009-Feb-17, 08:01 PM
You can be pretty certain that there are 'loose' planets and brown dwarfs throughout interstellar space that have been ejected from nebulae and clusters during the formation process. Those planets that have been detected in the Orion Nebula will almost certainly move away from that region; just as the stars that have recently been formed in that region will eventually move apart from each other, and the nebula and associated clusters will disappear.

See this wiki page about rogue planets
They are also sometimes called planetars and planemos, depending on size and context.

2009-Feb-18, 04:55 AM
Thank you, for your reply and for the link, which made interesting reading. However, no mention of estimated velocity was made.

Can you make a more educated guess, than I'm capable of? Hmmm, considering the Orion Nebula as the originating source of the rouge planet I'm interested in, then could the Nebula's orbital speed around the center of our galaxy be considered? Do you have any idea of the rotational velocity of our galaxy?

I think I could use that.

Any help will be appreciated.

2009-Feb-18, 08:49 PM
Well, the Orion Nebula isn't realy moving at any significant speed with respect to the rest of the Orion Arm as far as I know, so any unusual velocity these rogue planets might have would probably be due to the speed they acquired while being ejected from the nebula.

If they were ejected from a protoplanetary cloud they would have at least the escape velocity from that cloud, which could be several tens of kilometers per second, or more.

2009-Feb-23, 12:31 AM
Thanks, that's what I needed.

I guess after that, any further acceleration would accrue from sling-shotting around any stars they passed. Nevertheless, tens of kilometers per second remains a respectable velocity.

I appreciate your help.