How Common are Terrestrial, Habitable Planets?

[frigidmagi]

universe today

[quote]Once again news from the Kepler mission is making the rounds, this time with a research paper outlining a theory that Earth-like planets may be more common around class F, G and K stars than originally expected.

In the standard stellar classification scheme, these type of stars are similar or somewhat similar to our own Sun (which is a Class G star); Class F stars are hotter and brighter and Class K stars are cooler and dimmer. Given this range of stars, the habitable zones vary with different stars. Some habitable planets could orbit their host star at twice the distance Earth orbits our Sun or in the case of a dim star, less than Mercury’s orbit.

How does this recent research show that small, rocky, worlds may be more common that originally thought?

Dr. Wesley Traub, Chief Scientist with NASA’s Exoplanet Exploration Program outlines his theory in a recent paper submitted to the Astrophysical Journal.

Based on Traub’s calculations in his paper, he formulates that roughly one-third of class F, G, and K stars should have at least one terrestrial, habitable-zone planet. Traub bases his assertions on data from the first 136 days of Kepler’s mission.

Initially starting with 1,235 exoplanet candidates, Traub narrowed the list down to 159 exoplanets orbiting F class stars, 475 orbiting G class stars, and 325 orbiting K class stars – giving a total of 959 exoplanets in his model. For the purposes of Traub’s model, he defines terrestrial planets as those with a radius of between half and twice that of Earth. The mass ranges specified in the model work out to between one-tenth Earth’s mass and ten times Earth’s mass – basically objects ranging from Mars-sized to the theoretical super-Earth class.

The paper specifies three different ranges for the habitable zone: A “wideâ€

[The Minx]

How common are F, G and K class stars? I think I remember seeing somewhere that G class stars (the same as our sun) are about 14% of all the stars in the galaxy, and that single stars are about 40% of all stars, so single G-class stars should be about 5.6%. I don't remember the figure for the F and K class stars, though.

The single star bit is important because they have an easier time having stable planetary orbits around them (a binary star with a planet was found recently, but that may be an exception).

If the K and F class stars are similar in number to the G class stars, the total number of stars in our galaxy with planets in the [habitable zone] would be over 5% of the total - over 10 billion.


EDIT: fixed goof.

[The Cleric]

I saw this on io9 today. The art is hokey, but the article was interesting.

[Comrade Tortoise]

Well, the art is not that hokey. Afterall, Earth looked like that before plants invaded the land.