We are not alone

Except in San Mateo County, sometimes it feels like Pacifica may be.

San Francisco Chronicle/Associated Press, Alicia Chang, Science writer, 1/7/13.  "Study:  Billions of Earth-size planets in Milky Way."

Only 17 billion Earth size planets in our own Milky Way galaxy

"Our Milky Way is home to at least 17 billion planets that are similar in size to Earth, a new estimate suggests.  ....  Just how many are located in the sweet spot where water could exist is "simply too early to call," said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics, who presented his work at an astronomy meeting Monday.

....  Despite the explosion of exoplanet discoveries in recent years, one find remains elusive: A planet that's not only the right size but also in the so-called Goldilocks zone where it's not too hot or too cold for water to be in liquid form on the surface.

....   Using a different method, a team from the University of California, Berkeley and University of Hawaii separately came up with a similar estimate. They calculated 17 percent of distant stars have planets that are the same size as Earth or slightly larger."   Read article.

Reference definition - Bright Hub - Science, Space, Astronomy.  "What are Exoplanets?"  "The exact definition of an exoplanet is just a planet, any planet, that is orbiting a star other than our own Sun, and is therefore not in our Solar System. That's it. Nothing fancy about it. “Exoplanet” is just sort of “extrasolar planet”, which would be self explanatory if astronomers hadn't saved some space by shortening the term by two syllables." 

Posted by Kathy Meeh