The universe abounds with Earth-sized planets. That hopeful notion has been reinforced by individual planets finds like possible Goldilocks planet Gliese 581g, by the hordes of planet candidates discovered by the Kepler mission, and now, by a census of a small space in the sky that tells us one in four sun-like stars should possess worlds that are close to the size of Earth. Take a moment to think about that: One in four. In Science, exoplanet hunters Geoffrey Marcy and Andrew Howard published their team's census of 166 nearby stars like ours, of which they picked 22 at random to investigate for planets. They watched the stars' doppler shifts to hunt for planets over the last five years, and used the results to extrapolate how common terrestrial planets must be far beyond just this set of stars.
In total, the astronomers detected 33 planets orbiting 22 stars, and the distribution of the planets showed they became more plentiful the lower their mass.... They estimate that 23% of sun-like stars are circled by an Earth-like planet, 12% are orbited by more massive "super-Earths" and around 1.6% are circled by planets similar to the gas giant, Jupiter. [The Guardian]
