Life on other planets? A recent study by UNLV astrophysicist Jason Steffen is shedding new light on this persistently challenging question.
In our galaxy, there may be billions of planetary systems where more than one planet is habitable. NASA’s Kepler spacecraft has found planet pairs on very similar orbits — with orbital distances differing by as little as 10 percent. If such a planet pairing occurred in the right place, then both planets could sustain life — and even help each other along.
Steffen and research partner Gongjie Li from the Harvard Smithsonian Center for Astrophysics studied some of the ramifications for life in these multihabitable systems.
“It’s pretty intriguing to imagine a system where you have two Earth-like planets orbiting right next to each other,” said Steffen. “If some of these systems we’ve seen with Kepler were scaled up to the size of the Earth’s orbit, then the two planets would only be one-tenth of one (astronomical unit) apart at their closest approach. That’s only 40 times the distance to the Moon.”
Mars, at best, is 200 times the lunar distance, he noted.
With planets so close together, a number of interesting processes become important. For one, the seasons on the Earth, and the Earth’s climate in general, depend upon its “obliquity,” or the 23.5-degree tilt of the Earth’s axis relative to its orbit. A change of only a few degrees could cause a permanent ice age. If two planets on neighboring orbits caused large changes in each other’s obliquities, then their climates would not be stable. … (University of Nevada)