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Earth-mass satellite found around a brown dwarf!
http://sfrpg-discussion.net/viewtopic.php?f=41&t=3021
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Author:  EDG [ Wed Nov 04, 2015 8:15 pm ]
Post subject:  Earth-mass satellite found around a brown dwarf!

http://www.smithsonianmag.com/science-n ... com&no-ist

This is very interesting - an earth-mass satellite has been found around a brown dwarf! (the actual abstract says it's "Venus mass", which is close as dammit to "Earth mass", and it doesn't actually "say that it's "venus-like" which would imply that it's a roasting hellhole of a world).

So at least the idea of planets around BDs has been confirmed, though they'd most likely be frozen iceballs unless the BD was really young.

Author:  Cyborg IM1 [ Thu Nov 05, 2015 3:57 pm ]
Post subject:  Re: Earth-mass satellite found around a brown dwarf!

Interesting - I seem to remember something you wrote a while ago about the upper limit of moon mass around a Gas Giant world. You mentioned that based on what we could see in our system, an Earth-massed world would require a Brown Dwarf's mass to let it form. Uranus is the exception as Triton is obviously a captured moon from the Kuiper Belt (lots of other things wrong with the Uranian system that supports something BAD happened there a while ago).

I believe the number you used was 0.001% of the mass of the primary???

Author:  EDG [ Thu Nov 05, 2015 4:02 pm ]
Post subject:  Re: Earth-mass satellite found around a brown dwarf!

Triton orbits Neptune, but yes. Uranus has a relatively normal system of 5 mid-sized moons and lots of smaller ones, albeit they orbit in Uranus' tipped orbital plane.
And it looks like this BD satellite follow the same mass limit I described earlier (from the Canup and Ward paper) as Jupiter, Saturn and Uranus' system do.

Author:  Matt Wilson [ Thu Nov 05, 2015 6:41 pm ]
Post subject:  Re: Earth-mass satellite found around a brown dwarf!

If only that BD were in the life zone of a G or K star...

Author:  EDG [ Thu Nov 05, 2015 9:16 pm ]
Post subject:  Re: Earth-mass satellite found around a brown dwarf!

I don't think they're usually found around G or K stars much. M V stars can have them as companions, but they're rarer around more massive stars (probably because the formation conditions are different? BDs forming as "failed stars" around other stars is one thing, but it might not be possible for that to happen above a certain mass ratio?).

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