The NASA Kepler space telescope has identified at least 300 million planets in the galaxy that are potentially habitable.
In a new article updated on the NASA website, the agency’s study revealed that a number of these habitable planets — referred to as exoplanets — could be our “interstellar” neighbors. There are at least four exoplanets that could be within 30 light-years of our Sun, and the closest might be at 20 light-years.
NASA considered a number of factors for a planet to be deemed potentially habitable, including the ability to support liquid water, a radius that is 0.5 and 1.5 times of the Earth’s, how rocky the planet is, the similarity of the Earth’s Sun to the planet’s star in terms of age and temperature and, finally, the amount of light given off by the star and how much the planet can absorb.
“We always knew defining habitability simply in terms of a planet’s physical distance from a star, so that it’s not too hot or cold, left us making a lot of assumptions,” Ravi Kopparapu, an author on the paper and a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said. “Not every star is alike, and neither is every planet.”
The Kepler space telescope was retired after nine years in 2018 when it ran out of fuel. Its mission, which was to find how many exoplanets exist, also revealed that there are billions of planets in our galaxy, and that there are more planets than stars. “Kepler already told us there were billions of planets, but now we know a good chunk of those planets might be rocky and habitable,” lead author Steve Bryson, a researcher at NASA’s Ames Research Center in California’s Silicon Valley, added. “Though this result is far from a final value, and water on a planet’s surface is only one of many factors to support life, it’s extremely exciting that we calculated these worlds are this common with such high confidence and precision.”
He continued, “To me, this result is an example of how much we’ve been able to discover just with that small glimpse beyond our solar system. What we see is that our galaxy is a fascinating one, with fascinating worlds, and some that may not be too different from our own.”
In related news, Christie’s will auction off a collection of rare NASA photographs.