Planet from Another Galaxy?

I saw this on Fox News this morning. I was just wondering if anyone knew the reasoning used to claim that this star was "born" in another galaxy and then captured by our own.

▶ Reply to This

Replies to This Discussion

Permalink Reply by Brian Guiley on November 19, 2010 at 10:05am

I think it has something to do with the lack of heavy metals in the star itself. Will be trying to look at the information a little closer as the day goes on.

▶ Reply

Permalink Reply by Jim Rupp on November 19, 2010 at 4:42pm

Here's the Q/A on metals from the Max Plank Institute for Astromony (http://www.mpia.de/Public/menu_q2.php?Aktuelles/PR/2010/PR101118/PR...)

What is the significance of the lack of heavy elements?
In astronomical parlance, all elements heavier than hydrogen and helium are called "metals". HIP 13044 is extremely poor in metal – it contains less than 1% as many metals as the Sun. In the most widely accepted model of planet formation ("core accretion"), this is very unusual. The prediction of these models is: The higher the metal abundance in the system, the higher the probability to form a planet. This is evidence for alternative mechanisms of planet formation (e.g. those involving "gravitational instabilities"), which allow for the formation of planets around extremely metal-poor stars.

All that has been observed is a radial velocity wiggle on a metal poor star (per the press release). The astronomers assume that the wobble is caused by a large (25x Jupiter) planet. As a brown dwarf can form at 10x Jupiter's density, it could be a brown dwarf companion which we have not observed. In my opinion, the astronomers at Max Plank decided to get some media buzz and arbitrarily say it's a planet. Even more, they went for broke by saying it's extragalactic by throwing out the core accretion model and saying this wobble is "evidence" of an alternate planet formation mechanism. Note that the core accretion model doesn't deny planet formation on metal poor stars; it only says it's improbable for those planets to form. Talk about creating a mountain out of a molehill!

▶ Reply

Permalink Reply by Stefan Morin on November 19, 2010 at 6:56pm

Jim Rupp said:
"The astronomers assume that the wobble is caused by a large (25x Jupiter) planet. As a brown dwarf can form at 10x Jupiter's density, it could be a brown dwarf companion which we have not observed."

Actually, just wanted to point out that the article said the planet is supposed to be 25 percent larger than Jupiter, not 25 times. That'll make a difference in the discussion! ;)

▶ Reply

Permalink Reply by Jim Rupp on November 19, 2010 at 7:08pm

Oh yes, my bad! How did I miss the "1." before the 25? I retract the brown dwarf companion statement - it's definitely not a fusionable mass. But throwing out the accretion model in favor of extragalactic postulation is a valid quibble in my eyes, though. ;)