The Telegraph
Since 1st March, 1999
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Bigger, hotter cosmic cousin for Earth

Washington, June 14 (Reuters): Earth’s bigger, hotter planetary cousin may have been detected orbiting a star in our cosmic neighbourhood, astronomers said yesterday.

The most Earth-like of all 155 so-called extrasolar planets found orbiting stars besides our sun, the newly unveiled planet is probably rocky like Earth, rather than big and gassy like Jupiter and most other extrasolar planets discovered in the past decade, the scientists said at a briefing.

“It took 150 observations of this star to glean the existence of this Earth-like planet,” said planet hunter Geoffrey Marcy of the University of California, Berkeley. “This will definitely be one of our favourite stars from now on.”

“It’s a very unearthly world,” said Jack Lissauer of Nasa’s Ames Research Center. “It’s likely to be the first rocky planet orbiting a star like our sun.” “It’s like Earth’s bigger cousin,” Paul Butler of the Carnegie Institution of Washington said in a statement accompanying the announcement. Butler is a member of the team that found the planet.

The new planet is the smallest extrasolar planet ever detected, with about 7.5 times the Earth’s mass. Before this, the smallest planets found orbiting stars besides the sun were at least 15 times Earth’s mass, making them more like distant, icy Neptune.

By contrast, this planet’s surface is far too hot ' ranging from 204 to 371 Celsius ' to support life as it is known on Earth.

While Earth orbits the sun at a distance of about 150 million km, this extrasolar planet almost hugs its star, orbiting 3.2 million km from the star Gliese 876 in the constellation Aquarius, just 15 light-years from Earth. A light-year is about 10 trillion km, the distance light travels in a year. In astronomical terms, 15 light-years is right around the corner.

The new planet races around its star once every two Earth days or so, and has a radius about twice the size of Earth, the astronomers said. The star it orbits is about one-third the sun’s mass.

Like dozens of other extrasolar planets detected over the past 10 years, this one was first discovered by the distinctive wobble its gravity exerts on the star it orbits. As it happened, this is the third planet circling that particular little star. The two others are gas giants like Jupiter and orbit much farther out.

Astronomers have no direct proof the new planet is a space rock like Earth, but its low mass means it probably is not a giant gas planet like Jupiter, the scientists said.

Planet hunters have detected three other rocky planets outside our solar system, but all three orbit a pulsar ' the remnant of an exploded star ' so this is the only planet orbiting a normal star.

A team of scientists has known about the new planet for three years but wanted to confirm its theory it was a terrestrial planet before going public, Marcy said.

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