Alpha Centauri in Context

Centauri Dreams ^ | 06/04/07

[KevinDavis]

If we’re finding planets in places 1500 light years away, as the TrES project just did, why don’t we know more about planets in the Alpha Centauri system? One problem is that Centauri A and B are relatively close to each other, with a semimajor axis of 23.4 AU. Leaving Proxima Centauri out of the picture (at 12,000 AU, its short-term effects can be disregarded), it’s still true that radial velocity studies have to take the complicated and varying spectra that binaries produce into account.

In other words, getting a read on binaries like these in terms of the slight wobbles that signal a planetary presence can consume lots of telescope time. Nonetheless, we do have some data thanks to observations with the Anglo-Australian Telescope. And we’ve learned this: No planet around either Centauri A or B induces a velocity variation as high as 2 meters per second. The implication is that any planet orbiting either star individually (in what is known as an S-type orbit) has to have a mass less than that of Saturn. Or if it is larger, and this is still possible, it must orbit in a plane that is substantially inclined to the line of sight to the system.

[KevinDavis]

ALPHA CENTAURI HO!!!!!

[KevinDavis]

[cripplecreek]

Nappy headed Alpha Centauri ho.

[scrabblehack]

I thought she was from Orion.

[BenLurkin]

LOL!

[true_blue_texican]

She gets around.

[SunkenCiv]

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[jmcenanly]

There is a minor problem with a world attempting an earth-like orbit around either of the two stars in th Alpha Centauri system. If the worlds are close together, the planets will orbit them as if they were just one big star (Lucas came pretty close in his depiction of Tatooine in Star Wars). If the worlds are far apart, the planets will orbit either one or the other, and the other star will not have much gravitational influence on the planets. In the case of Alpha Centauri, the stars are about 23 astronomical units apart. They would tend to disrupt the orbits of each other's planets.