Researchers recently determined that there are potentially tens of billions of planets in the Milky Way galaxy where alien life could exist.
Scientists from University of California, Berkeley, and University of Hawaii, Manoa used data from NASA’s Kepler space telescope and the W. M. Keck Observatory to statistically determine that one in five Sun-like stars in our galaxy have Earth-sized planets that could host life. Erik Petigura, a UC Berkeley graduate student who led the study’s data analysis, explains in a press release issued by the W. M. Keck Observatory, “What this means is, when you look up at the thousands of stars in the night sky, the nearest sun-like star with an Earth-size planet in its habitable zone is probably only twelve light years away and can be seen with the naked eye. That is amazing.”
Andrew Howard, an astronomer with the Institute for Astronomy at the University of Hawaii, adds, “For NASA, this number – that every fifth star has a planet somewhat like Earth – is really important, because successor missions to Kepler will try to take an actual picture of a planet, and the size of the telescope they have to build depends on how close the nearest Earth-size planets are.”
The research team included UC Berkeley professor of astronomy Geoffrey Marcy who explained on the program PBS Newshour:
Of course, the properties of a planet that make it suitable for life is — the basics have to be water, because our own human bodies are made of water. All life-forms on the Earth depend on water. And so we assume — perhaps incorrectly — that life out there among the stars would also depend on liquid water.
But Marcy also cautions that not all these planets are necessarily hospitable to life. He explains, “Some may have thick atmospheres, making it so hot at the surface that DNA-like molecules would not survive. Others may have rocky surfaces that could harbor liquid water suitable for living organisms . . . We don’t know what range of planet types and their environments are suitable for life.”
The team’s research was published on November 4 in the journal Proceedings of the National Academy of Sciences.