"Majornewclass"ofmoreEarth-likeplanetsdiscovered

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"Long before it's in the papers"
June 20, 2005

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“Major new class” of more Earth-like planets discovered

Posted August 31, 2004
Special to World Science

Astronomers this morning announced the discovery of a major new class of planets, which are far more Earth-like than any discovered outside our Solar System before.

The Hobby-Eberly telescope in Texas, used in making some of the new planetary discoveries. (Images courtesy NASA and NASA AMES Research Center)

The new findings also suggest there may be 20 billion or more planetary systems in our galaxy alone, said the researchers.

Some of the newfound planets appear to be substantially more small and solid than the giant, gaseous planets discovered before, researchers said. This means these newer planets are more likely to be able to harbor life forms, although whether they do so is completely unknown.

Two newfound planets, not far from our galactic neighborhood, are only two to three times as wide as Earth and weigh 15 to 20 times as much, said Geoff Marcy of the University of California at Berkeley, one of the co-discoverers. Previous discoveries of planets outside the solar system involved objects some 50 times heavier than Earth.

"We're poised for the next step in planet discovery, namely finding truly Earth-mass planets," he said. NASA and the astronomers reported the discovery at a news conference on Tuesday.

Most of the planet detection techniques available to date have been suitable only for detecting the very largest planets outside our Solar System. Such planets are usually made entirely of gas, a fact that combined with their tremendous gravity would make life virtually impossible to sustain there. Astronomers have been racing to find smaller planets. With the next generation of telescopes, many speculate, it will be possible to detect Earth-sized planets. The current findings are seen as an intermediate step toward such a finding.

"This is a milestone. We've crossed a hurdle, finally," said Paul Butler of the Carnegie Institution of Washington. "We can't quite see the Earth-like planets yet, but we are seeing their big brothers."

One of the two planets, called Gliese 436, is orbiting a very common type of small star, called an M dwarf, Marcy added. This means that planetary systems may be much more common in the solar system than has been suspected to date, he added. There may be an estimated 20 billion of them or more, he said.

In addition, the planet is part of a system containing at least four planets, the researchers added. This would be the largest number planets found orbiting one star, with the exception of our solar system.

The two newfound planets are within 40 light years of Earth, considered a relatively small distance in space terms. They were discovered using the so-called wobble technique, in which a planet is detected based on the the wobble of the star it orbits. The wobble is due to the planet's gravity.

"We've just made a huge leap toward finding planets that look like our own," said Alan Boss of the Carnegie Institution of Washington, D.C., who wasn't involved in the research.

However, there may be some reason for skepticism that the newfound planets contain life. Some researchers have reported that the vast differences between our Solar System and other solar systems thus far discovered mean that Earth-like planets are more unlikely to be found than the others. (See World Science story of Aug. 3, 2004).

—EJL