Alpha Centauri Has an Earth-Sized Planet 152
The Bad Astronomer writes "Astronomers have announced that the nearest star system in the sky — Alpha Centauri — has an Earth-sized planet orbiting one of its stars. Alpha Cen is technically a three-star system: a binary composed of two stars very much like the Sun, orbited by a third, a red dwarf, much farther out. Using the Doppler technique (looking for very small changes in the velocities of the stars) astronomers detected a planet orbiting the smaller of the two stars in the binary, Alpha Centauri B. The planet has a mass only 1.13 times that of the Earth, making it one of the smallest yet detected.However, it orbits the star only 6 million kilometers out, so it's far too hot to be habitable. The signal from the planet is extremely weak but solidly detected (PDF), giving astronomers even greater hope of being able to find an Earth-like planet orbiting a star in its habitable zone."
Dear /S/cientists (Score:5, Interesting)
how do planets orbit binary star systems? I would think two stars would give the planets erratic orbits that would either send them into one of the suns or shoot them into space.
I'd leave well enough alone! (Score:2, Interesting)
Re:Dear /S/cientists (Score:5, Interesting)
What are the prospects for a single orbiting planet (let's exclude other objects) orbiting both stars in a figure 8 configuration, crossing the barycenter of the star's combined rotations?
(Eg, both stars orbit clockwise as seen from plane of rotation north, and orbit each other in an elipse. A planet orbits first one star, then the other, crossing the barycenter at the period of maximal approach of the two stars, moving from one star to the other like a dance partner in a ballroom routine.)
Assuming that the objects are free from outside gravitational purturbations, are exactly the right distance apart, and that the periodicity of the planet's orbits between the stars is exactly synchronized, would such a system be stable?
Understatement of the Year (Score:5, Interesting)
"it's far too hot to be habitable."
That's an understatement. From the ArsTechnica article on the alpha Centauri planet [arstechnica.com]:
"But don't start building the colony ship just yet. With a 3.3 day orbit, the planet is only 0.04 Astronomical Units (1 AU is the typical distance from the Earth to the Sun). That makes this planet blazingly hot, at about 1,500 Kelvin."
And us space bloggers feel like chumps (Score:5, Interesting)
Space bloggers (like me) who are signed up with the ESO news feed got word of this overnight. But the story was under embargo. You do not break the story until the embargo lifts or the ESO and Nature magazine gets very angry at you.
But some loud-mouth in Croatia violated the embargo. We were patiently waiting for the embargo to lift, biting our collective tongues, when mouthy jumped the gun.
We got an email from the ESO about an hour ago that said:
"I just spoke to the Head of Press at Nature, Ruth Francis, and we have agreed to LIFT THE EMBARGO on the Alpha Cen story IMMEDIATELY due to an unfortunate leak. You may run your stories."
Nature and ESO lift exoplanet embargo early following coverage by Croatian news outlet [wordpress.com]
Re:Temperature = 1500K (Score:5, Interesting)
What makes this a big deal, is that prior to this it was an open question whether the Alpha Centauri system could support planets orbiting the individual stars or not. Now that it has been shown that planets can orbit the individual stars in this system, as opposed to orbiting outside both stars around the common center of gravity as is the case for most planets in binary systems, the probability of their being more planets including possible ones in the habitable zones of the stars just got a whole lot bigger.