The AP via NBC News took notice of a study published this week in the Proceedings of the National Academy of Sciences: apparently, Earth is one of 8.8 billion similar planets in the Milky Way that fall inside the "Goldilocks zone," the area around a sun where a planet's orbit is neither too hot nor too cold for life.
A NASA press release cites Kepler Telescope data as ushering in a new era of astronomy. Data from Kepler was used in the recent study; that data helped to conclude that 22 percent (+/- 8 percent) of the stars in the Milky Way have Earth-like planets.
Kepler examined only a fraction of our galaxy (42,000 stars), and the 8.8 billion figure is just an extrapolation, but the findings are revolutionary. If there are 8.8 billion stars in the Milky Way, then that means there are at least 8.8 billion Earth-like planets. Geoff Marcy, a University of California-Berkeley planet hunter and a co-author of the study, said "Just in our Milky Way galaxy alone, that's 8.8 billion throws of the biological dice."
William Borucki, an Ames/Kepler science principal investigator, said "The impact of the Kepler mission results on exoplanet research and stellar astrophysics is illustrated by the attendance of nearly 400 scientists from 30 different countries at the Kepler Science Conference... We gather to celebrate and expand our collective success at the opening of a new era of astronomy."
William Chaplin, professor of astrophysics for the University of Birmingham in the UK, said "Kepler has revolutionized asteroseismology by giving us observations of unprecedented quality, duration and continuity for thousands of stars. These are data we could only have dreamt of a few years ago."
The next step in the search for extraterrestrial civilizations involves atmospheric observations. Kepler's total count for "Goldilocks" worlds comes out to 3538, but most of those would not be capable of holding carbon-based life. Since hundreds of Earth-like worlds are missed for every one Kepler spots, the 22 percent figure is considered final and accurate. MIT astronomer Sara Seager concurred, saying "Everything they've done looks legitimate."[Image via NASA.gov]