Other sunlike stars could be more hospitable to life

Posted by Kate Taylor

Most stars in the Milky Way that resemble our sun are more likely to host planets that support life than our own.

The interiors of any terrestrial planets in these systems are likely  up to 25 percent warmer than Earth, making them more geologically active and more likely to retain plenty of liquid water.

Ohio State University geologists and astronomers studied eight 'solar twins' of our sun — stars that very closely match the sun in size, age, and overall composition — and measured the amounts of radioactive elements they contain.

They looked for elements such as thorium and uranium, which are essential to Earth’s plate tectonics because they warm our planet’s interior.  Plate tectonics helps maintain water on the surface of the Earth, improving the chances of life.

Of the eight solar twins they’ve studied so far, seven appear to contain much more thorium than our sun — which suggests that any planets probably contain more thorium, too. That, in turn, means that the interior of the planets are probably warmer than ours.

One, for example, contains 2.5 times more thorium than our sun, so that terrestrial planets that formed around that star probably generate 25 percent more internal heat than Earth does. This allows plate tectonics to persist longer through a planet’s history, giving more time for life to arise.

"If it turns out that these planets are warmer than we previously thought, then we can effectively increase the size of the habitable zone around these stars by pushing the habitable zone farther from the host star, and consider more of those planets hospitable to microbial life," says doctoral student Cayman Unterborn.

"With only nine samples including the sun, we can’t say much about the full extent of that variation throughout the galaxy. But from what we know about planet formation, we do know that the planets around those stars probably exhibit the same variation, which has implications for the possibility of life."