Extrasolar planets

[bigdamnhero]

Re: Extrasolar planets

 

it won't get here for about 1.5 million years...

Wow. Really puts the "How To Have Long Combats" thread in perspective!

[Old Man]

Re: Extrasolar planets

 

One wonders at the power of entities who can re-direct the courses of stars' date=' and what sinister purpose they have.[/quote']

 

"Duuude, where's my red dwarf?"

 

"Check it out dude, I got a tattoo!"

 

"Sweet!"

[Nyrath]

Re: Extrasolar planets

 

Wow. Really makes the "How To Have Long Combats" thread in perspective!

Actually, that star or one just like it was featured in the SF novel Eternal Light by Paul J. McAuley

[Cancer]

Re: Extrasolar planets

 

Another new paper in Astrophysical Journal Letters nominates 18 Scorpii and HD 98618 as the two best candidates as "solar twins", stars with overall properties most resembling the Sun, and hence worth looking at carefully in hopes of seeing planetary systems like ours. (Both are already in the list Nyrath links a few posts up.) They both seem to be younger than the Sun by about 1 Gyr.

[Cancer]

Re: Extrasolar planets

 

Necromancy ... does thread conservation justify it?

 

Pollux, the first-magnitude K0III ("red giant") star in Gemini, is confirmed to have a planet. 590 day period, orbital size 1.69 AU, orbital eccentricity 0.06 +/- 0.04, m sin i (that is, lower limit on planetary mass) 2.9 +/- 0.1 Jupiter masses (assuming a stellar mass of 1.86 solar masses).

[Old Man]

Re: Extrasolar planets

 

I'm jaded enough at this point that extrasolar planets need to be either Earth-sized or else directly imaged for it to really impress me. It's clear now that the galaxy is completely infested with planets. I never had much doubt, though I know many other people probably did.

[Cancer]

Re: Extrasolar planets

 

Planets around red giants ... in particular, one as well-studied as Pollux ... interest me, because the fact they're still there puts some interesting (well, interesting to me, but stellar evolution is my thing) constraints on what happens on the giant branch. Pollux is now a nice helium-burning clump star, but to get to that state it was once much larger (in radius), and in all likelihood shed some mass on the way. That it still has a planet puts limits on how large it could have got, and how much mass it could have lost.

 

(Lose too much mass, and the planet orbits become unbound. If the star gets too large, then it engulfs the planets whose orbits it touches.)

 

Also, at current mass about 1.7 solar masses, it's more massive than any of the stars we've found planets around. As a main sequence star, it probably was around the A/F spectral type boundary. (The stars being examined for planets are selected for being old and stable, because instabilities make the radial velocity changes induced by planets hard to separate from the junk the star is doing, and cool, because for the warmer ones the spectral lines are fewer (and broader) making the velocity again harder to measure.) So, those more massive stars have planets too. There are some versions of planetary formation theory that get ruled out by that observation (though you need a more massive star to really test them ... 1.7 solar masses isn't quite high enough).

[Hunter]

Re: Extrasolar planets

 

I'm jaded enough at this point that extrasolar planets need to be either Earth-sized or else directly imaged for it to really impress me. It's clear now that the galaxy is completely infested with planets. I never had much doubt' date=' though I know many other people probably did.[/quote']

 

Current techniques to detect extrasolar planets (with the exception of the transit method) are pretty much limited to Neptune sized planets. Although a planet of 5 Earth masses was detected by the micro-lensing technique.

 

At the moment, 209 extrasolar planets have been confirmed.