Potentially Habitable Planets Are Common, Study Says

Aalok Mehta in Boston, Massachusetts
National Geographic News
February 18, 2008

More than half of the sunlike stars in the galaxy could have terrestrial planets with the potential to harbor life, a new study suggests.

The research, announced yesterday at a meeting of the American Association for the Advancement of Science in Boston, Massachusetts, is just one of a set of recent findings that suggest the roster of potential life-harboring worlds is huge—even in our own solar system.

"Our observations suggest that between 20 percent and 60 percent of sunlike stars form rocky planets like our solar system's," said Michael Meyer, an astronomer at the University of Arizona, at a press briefing Sunday.

Meyer and his team used NASA's Spitzer Space Telescope to study heat from the dust around sunlike stars of various ages, much like looking at "the smoke you see rising from chimneys in Boston on a cold day."

Such hot dust implies that larger rocky bodies are forming and colliding in the "messy" business of planet formation, Meyer explained.

Planet-forming dust was found at one to five times the distance from the sun to Earth, Meyer said (see an interactive map of the solar system.)

The dust was also seen in young stars but was absent from most stars older than 300 million years—a perfect fit with current models of planetary formation, he added.

(Read related story: "Newborn Planet Found Orbiting Young Star" [January 3, 2008].)

The study will appear in an upcoming edition of the Astrophysical Journal Letters.

Earth-Size Refugees?

At the briefing, scientists also advanced the possibility that our solar system contains hundreds or even thousands more dwarf planets like Pluto, hidden from view in the distant region known as the Kuiper belt.

There is a growing body of evidence that the poorly understood region contains several Earth- or Mars-size planets and many tinier bodies, said NASA planetary scientist Alan Stern, adding that this could very well be a "new Copernican revolution" in our understanding of planets.

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