Astronomers working with the Kepler spacecraft have announced new evidence suggesting that there are far more potentially habitable planets in our galaxy than we had believed. And just as surprisingly, these planets emerged much longer ago than expected — a revelation that could have profound implications in the search for extraterrestrial intelligence.
What does it mean? We talked to the head of SETI, who explained why this news changes everything.
The researchers came to this conclusion by studying the way that planets are formed. Conventional thinking suggests that no planets can form until the requisite raw materials are present — something that can't happen until stars pour considerable amounts of silicon and oxygen into the Universe. These elements form the basic building blocks of rocks, which in turn are the stuff that planets are made out of.
But researchers at the Harvard-Smithsonian Center for Astrophysics discovered that the base elements required to form rocky planets formed very quickly after the formation of the Universe. Moreover, they discovered that Earthlike planets can still take shape with a limited variety of elements available, including systems with only one-quarter of the Sun's metal content. What this suggests is that rocky planets can form almost anywhere in the galaxy — and they have been doing so for billions of years.
To conduct their research, the Kepler team examined more than 150 stars known to have planets. They measured each stars' metal-producing qualities, and contrasted that to the sizes of their planets. The researchers noticed that large planets tended to orbit stars with high solar metallicities, and that smaller worlds could be found in both metal-rich and metal-poor stars.
Their discovery indicates that giant planets prefer metal-rich stars, but little ones don't care.
Given the insight that the galaxy is strewn with small, rocky planets, it's quite possible that life is far more ubiquitous than we think. This realization will have serious implications to SETI, the search for extraterrestrial intelligence. To get a sense of what this recent discovery means to SETI, we contacted Seth Shostak, the SETI Institute's Senior Astronomer, to get his reaction.
Shostak tells io9 the discovery could certainly speed up the search for ET as there are simply more targets out there. "The message we've been getting from the planet hunting community is loud and clear," said Shostak, "and that message is that all stars have planets." And not only that, he added — "Most of them might have small planets, too, and not just gas giants."
He admitted that the announcement from the CfA will require a change in thinking, and that change could impact on the way SETI conducts its search. In particular, Shostak would like to spend more time looking at the center of the Galaxy. "There's more energy and more stuff in there." he said. Moreover, now that we know that potentially habitable planets can form around virtually any kind of star, it's important to focus our attention on star-rich areas, "And the deeper you look into the galaxy," said Shostak, "the more chance you have of detecting targets."
At the same time, however, Shostak admitted that, by virtue of a galaxy filled with Earthlike planets, it actually doesn't matter where we look. The important thing to know is that life is potentially everywhere.
Shostak also admitted that the discovery reaffirms the idea that life could have emerged in the Galaxy a long time ago. "It's been possible to have worlds with life for quite some time now," he said, "there could be life out there that's billions of years old."
The complete study has been published in the journal, Nature.
Top image via Harvard-Smithsonian Center for Astrophysics. Inset images via SETI and Simthsonian Institute