For generations, scientists have known that the Milky Way contains billions of stars. In more recent years, they have learned that many of those stars have planets orbiting them.
But how many of those planets have the potential to have life? The answer may be more than you might think.
According to researchers with the University of Florida, there could potentially be hundreds of millions of planets in the Milky Way galaxy situated in a star's habitable zone. A star's habitable zone is an area where the planet is close enough to keep water from completely freezing, but not too close so that water doesn't boil away.
Dwarf stars are the most common type of star in our galaxy. In order for planets orbiting them to be in their habitable zone, they would need to be relatively close to each other.
University of Florida astronomy professor Sarah Ballard and doctoral student Sheila Sagear studied 150 dwarf planets in the Milky Way using NASA's Kepler telescope. What the researchers wanted to know was not just the average distance a planet has to its star, but the shape of the planet’s orbit.
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The researchers said an eccentric orbit causes temperature extremes that would make holding liquid water difficult. By studying how long it takes planets to move across the face of the star, they can get a better sense of just how habitable a planet can be.
"The distance is really the key piece of information we were missing before that allows us to do this analysis now," Sagear said.
The new research was published last week in the Proceedings of the National Academy of Science. Researchers say it gives other scientists a number of targets to look at for signs of life outside of our solar system.
"I think this result is really important for the next decade of exoplanet research, because eyes are shifting toward this population of stars," Sagear said. "These stars are excellent targets to look for small planets in an orbit where it's conceivable that water might be liquid and therefore the planet might be habitable."
