Astronomers are searching the sky diligently for planets much like Earth on which they may be able to find signs of life similar to our own.  But astronomer Lisa Kaltenegger says we may be not be looking at the right type of planet and we may find life by expanding our search to worlds originally thought to be uninhabitable, according to the Washington Post.

Kaltenegger, director of the Carl Sagan Institute at Cornell University, and her colleague, Ramses Ramirez developed a model based on the premise that older stars, ones that are about at the end of their fuel source and are much larger than our own sun, could have planets surrounding them that are becoming more likely to sprout life.

The team explained as stars get older, they also become larger.  In four billion years from now, our sun, currently a yellow dwarf star, will exhaust it’s supply of hydrogen fuel at the core, and become a much larger red star, as much as 200 times its current size.  The planets in the habitable zone will be reduced to fiery cinders and planets much farther away from the sun will be warmed.

Possible life-supporting planets would not have a lot of time to develop life as we know it.  Those worlds in the new habitable zone around an aging star would only have about half a billion years before the zone shifted again.  Most scientists agree that it took almost a full billion years for life to develop on Earth.

But, says the team, if life began to develop beneath the frozen surfaces of these planets, with heat from the planet’s core, it may be jump-started into the development process, and could venture out onto the surface as the world warms from the heat of the dying star.

Kaltenegger and Ramirez say they have noted 23 stars within 100 light-years of our solar system that could fit into this scenario.  Currently, we don’t know what types of worlds are orbiting around these aging stars, much less if any of them may have conditions that may support some type of life.

Now that we have a list of possible targets, Kaltenegger said, “we can use our telescopes to take a look and tell us if they find something there. That will be fascinating to see.”  She adds, “We don’t know if there are planets there because nobody has ever looked. Nobody ever thought of it.”

The team’s findings were published in a paper in the Astrophysical Journal.