New research from astronomers shows that one in six stars in our very own Milky Way galaxy contains a planet about the size of Earth. In the three years the Kepler Space Telescope has been operating it has discovered thousands of candidate planets that are the size of Earth, orbiting around stars similar to the sun and may be located in what astronomers call the habitable zone.
So we are less alone in the universe than we thought. Astronomers determined there are at least a hundred billion stars in the Milky Way and that about 17 percent of those stars similar to the sun contain Earth-like planets.
Erik Petigura, a University of California Berkeley graduate student, and Andrew Howard, formerly a Berkeley postdoctoral fellow now at the University of Hawaii, analyzed three years of data from the planet-hunting Kepler spacecraft. According to the SF Gate, they discovered that there may be a staggering number of them within their stars’ “habitable zones,” where temperatures would be just right for water to exist. Their analysis included only planets roughly the size of Earth, and with orbits around their stars that are closer than the orbit of Mercury to our sun.
Exoplanet expert Geoffrey Marcy says, “This is an exciting moment in science history.”
We are discovering just how crowded it is out there in the Milky Way.
Francois Fressin of the Harvard-Smithsonian Center for Astrophysics led the team that took Petigura and Howard’s data and factored in the exoplanets Kepler has discovered to date to determine there are at least 17 billion exoplanets in the Milky Way.
Our galaxy is thought to be at least 100,000 light years across and have more than 100 billion stars.
The Milky Way is a spiral galaxy with a bulge at its center and a surrounding spiral disc of stars, gas and dust.
The entire galaxy rotates around a central axis. Since the dinosaurs died out about 65 million years ago, the sun is estimated to have traveled about a third the way around the Milky Way’s center.
With a recent announcement of 461 new exoplanets orbiting distant stars in the Milky Way, astronomers have discovered 2,740 new planets outside our solar system.
William Borucki, lead astronomer on the Kepler mission, says he is “delighted” by the fresh batch of results.
He says, “The most important thing is the statistics – not to find one Earth but to find 100 Earths. That’s what we’ll be seeing as the years go on with the Kepler mission, because it was designed to find many Earths.”