Rocky exoplanet milestone in hunt for Earth-like worlds (BBC)

[eppur_se_muova]

By Jason Palmer

Science and technology reporter, BBC News, Seattle

Astronomers have discovered the smallest planet outside our solar system, and the first that is undoubtedly rocky like Earth.

Measurements of unprecedented precision have shown that the planet, Kepler 10b,has a diameter 1.4 times that of Earth, and a mass 4.6 times higher.

However, because it orbits its host star so closely, the planet could not harbour life.

The discovery has been hailed as "among the most profound in human history".

The result was announced at the 217th annual meeting of the American Astronomical Society in Seattle, US, by Nasa's Kepler team.
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more: http://www.bbc.co.uk/news/science-environment-12158028

[nadinbrzezinski]

1. It is not that much larger than earth

though not in the lifezone. Yes it is significant.

[txlibdem]

2. What would the gravity at its surface be? Much higher than Earth I'll bet

With a mass 4.6 times that of Earth and a diameter only 1.4 times Earth's that implies a much denser core, but how much difference in the gravitational pull at the surface would there be? It isn't a 1:1 ratio of diameter vs mass is it, so we can't just assume that it would be 1.4:4.6 as simple math would seem to imply.

Does anyone have an idea?

[laconicsax]

3. The ratio is mass over radius squared.

Gravity propagates according the inverse square law, so for this planet, the ratio is 4.6/(1.4^2), resulting in surface gravity 2.3 times that of Earth.

Of course, since its orbit is at .017 AU from a star .89 times the mass of our sun (about 1.05 times the radius), that means the gravitational pull from the planet's star at the orbit of this exoplanet is about half the planet's own surface gravity. If I'm not mistaken, that means that the gravity felt on this exoplanet varies greatly with where you are on the surface--side facing its sun being a lot less than the side facing away.