Milky Way Could Contain Billions Of Earth-Sized Planets

The Milky Way galaxy could contain billions of Earth-sized planets orbiting stars much like our sun. Astronomers using data from NASA calculated that our galaxy holds at least 8.8 billion stars with planets much like ours.

The study was published on Monday in the journal Proceedings of the National Academy of Sciences and is the first time astronomers conducted such a study.

For perspective, NBC News notes that there are more Earth-like planets in our galaxy than there are people on Earth. Study author Geoff Marcy, a longtime planet hunter with the University of California at Berkeley, added that it also means there is a chance there is life out there, in our own galaxy.

While it was operational, NASA’s Kepler Space Telescope looked at 42,000 stars, a sliver of our galaxy, to see how many planets are like Earth. From there, the astronomers extrapolated that figure to the rest of the galaxy, which is home to hundreds of billions of stars.

They found that, in the Milky Way, about one in five stars are like our sun in size, color, and age and have planets roughly the size of Earth in their habitable zone, notes ABC News

Based on the one-in-five estimate, the closest Earth-sized planet in its sun-like star’s habitable zone is likely within 70 trillion miles of Earth. Also, the 8.8 billion figure is only a start, because scientists in the study only looked at sun-like stars, which aren’t the most common.

An earlier study also showed that 15 percent of red dwarf stars, which are more common, have Earth-sized planets that are close enough to be in the habitable, or Goldilocks, zone. Putting the figures together, Marcy says that there are probably about 40 billion right-size, right-place planets.

Kepler only identified 10 Earth-sized planets circling sun-like stars. However, there are probably hundreds of planets missed for every one the space telescope found. Now, scientists have the task of finding them, and observing them better.

[Image via ShutterStock]

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