Many Earths A Maybe

A recent study suggests from 20 to 60 percent of the sun-like stars in the disk of our galaxy might have planets similar to Earth orbiting them. Scientists using NASA's Spitzer Telescope, a cousin of Hubble, took the temperature of dust orbiting some 300 stars at distances roughly equivalent to between Earth's and Jupiter's orbits, and found warmer dust around many of them. Higher temperatures are taken to mean bodies in those dust rings are colliding regularly, which is precisely the process theory says leads to the formation of planets, especially rocky planets like Earth.

The 250 exoplanets so far discovered are all much larger than Earth, but that is due to the limitation of our technology. As technology and techniques have improved over the past fifteen years, smaller worlds, though still larger than Earth, have been found. Over the next twenty years, with space-based instruments dedicated to the task planned, many astronomers expect to find the first sibling Earths in what may well be a large, extended family.