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Author Topic: What are rogue planets?  (Read 1190 times)

Offline oatman

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What are rogue planets?
« on: 19/11/2012 12:41:53 »
I understand these to be planets not orbiting a star....though I thought this was one of the very features that defined a planet? Can anyone shed light on what makes a planet and a rogue planet, and what orbit it would take, if not part of a solar system?

Thanks!


 

Offline Phractality

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Re: What are rogue planets?
« Reply #1 on: 19/11/2012 18:13:09 »
Most planetary systems begin in utter chaos. They remain chaotic until they find a stable configuration. In a chaotic system, planets often swap orbits, collide or break up when passing a larger planet; or a planet may be ejected from the system into interstellar space. Each time such an event occurs, the system becomes either more stable or less stable. This may continue for hundreds of millions of years. When the system becomes highly stable, it may remains that way for billions of years, which is why most planetary systems appear to be stable.
So most rouge planets are believed to have formed around stars and been ejected due to close encounters with other planets. The distance between stars is so great that a rogue planet may drift for billions of years before finding another star to orbit. To enter orbit, it must exchange momentum and energy with another planet already orbiting that star. Adding a planet to a stable system will most likely put the system back into a chaotic state for hundreds of millions of years.
« Last Edit: 19/11/2012 18:15:03 by Phractality »
 

Offline CliffordK

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Re: What are rogue planets?
« Reply #2 on: 19/11/2012 23:03:26 »
Could a rogue planet form as part of a supernova?  Either clumps of matter ejected from the star, or as a planet getting displaced from its orbit?
 

Offline evan_au

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Re: What are rogue planets?
« Reply #3 on: 22/11/2012 11:00:30 »
I think a supernova would tend to scatter hot gas and dust in all directions, making it unlikely to coalesce into a planet until it cooled and slowed as part of a dust cloud.

Even then, I think it would take the frictional effects of an accretion disk to dissipate the different velocities of different gas and dust particles into a sufficiently dense cloud which is pretty much in the same location, heading in pretty much the same direction, at pretty much the same speed, at a sufficiently low temperature, which could then coalesce into a planetoid. 

I agree that any pre-existing planets which survived the supernova without being shattered could well be cast adrift in interstellar space, with signs of a severe scorching.
« Last Edit: 22/11/2012 19:30:55 by evan_au »
 

The Naked Scientists Forum

Re: What are rogue planets?
« Reply #3 on: 22/11/2012 11:00:30 »

 

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