Cousin Earth

As their search continues, astronomers are finding more and more planets orbiting nearby stars. This time, they’ve detected a solid planet that’s just 15 light-years from Earth.

This image shows an artist’s impression of what a newly detected planet that could be Earth’s closest cousin beyond the solar system might look like.

Trent Schindler, National Science Foundation

Many details about the planet remain unknown because the astronomers didn’t see it directly. Instead, they were able to detect how the planet’s gravity makes its star wobble a little bit.

Out of 156 planets discovered so far in other solar systems, the new extrasolar planet is the smallest one yet found. It’s about 7.5 times heavier than Earth.

Along with two, much bigger planets, the new world orbits a star called Gliese 876. The planet takes just 1.9 days to complete an orbit around Gliese 876. So, its year is much, much shorter than ours. It’s so close to its star that its surface is hot enough to roast a chicken.

Most extrasolar planets that have been found so far are big balls of gas, like Jupiter and Saturn. Because the planet’s mass is low, it probably couldn’t hold onto much gas. So, scientists suspect that it’s rocky.

“This could be the first [known] rocky planet around any normal star other than the sun,” says team member Jack Lissauer of NASA’s Ames Research Center in Mountain View, Calif.

Scientists are still trying to figure out how rocky planets might form so close to their stars.

Whatever the answer, the new discovery gives researchers confidence that they will one day find even closer cousins to Earth somewhere in the universe. And, on a planet resembling Earth, they might also discover traces of life as we know it.—E. Sohn

Going Deeper:

Cowen, Ron. 2005. Planet hunt strikes rock: Hot kin of Earth orbits nearby star. Science News 167(June 18):387. Available at http://www.sciencenews.org/articles/20050618/fob1.asp .

You can learn more about the discovery of the planet orbiting Gliese 876 at www.nsf.gov/news/news_summ.jsp?cntn_id=104243&org=NSF (National Science Foundation).

Sohn, Emily. 2004. A dusty birthplace. Science News for Kids (Oct. 13). Available at http://www.sciencenewsforkids.org/articles/20041013/Note2.asp .

______. 2004. A very distant planet says “cheese.” Science News for Kids (Sept. 22). Available at http://www.sciencenewsforkids.org/articles/20040922/Note2.asp .

______. 2004. Planet hunters nab three more. Science News for Kids (Sept. 8). Available at http://www.sciencenewsforkids.org/articles/20040908/Note2.asp .

______. 2003. A planet from the early universe. Science News for Kids (July 16). Available at http://www.sciencenewsforkids.org/articles/20030716/Note2.asp .

______. 2003. A planet’s slim-fast plan. Science News for Kids (March 19). Available at http://www.sciencenewsforkids.org/articles/20030319/Note2.asp .