Kepler And The Goldilocks Planets

NASA called a big press conference today to announce the latest findings from their planet-hunting Kepler satellite. The news concerned two planetary systems with rocky worlds in the "Goldilocks zone" where liquid water might exist. The more interesting is the Kepler 62 system, 1200 light years away:

* Star Kepler-62 is not Sun-like: just 2/3 the size of the Sun, cooler, older, and only 1/5 as bright.

* Planet Kepler-62f, 40% larger than Earth, the smallest known habitable zone exoplanet, orbits every 267 days.
* Planet Kepler-62e, about 60% larger than Earth, orbits every 122 days in the the habitable zone's inner edge.
* Kepler-62b, Kepler-62c and Kepler-62d, orbit every 5, 12, and 18 days, respectively, making them very hot and inhospitable for life as we know it. Two are larger than Earth and one is about the size of Mars.

Notice that the "habitable zone" is a vague concept, and our Sun's stretches from Venus to well beyond Mars. Whether a planet actually has liquid water depends on the details of its atmosphere and so on. But planets, it seems, are everywhere, and given how many stars there are, there must be many more or less like the earth.

Source: dark-shadowy-line.blogspot.com