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[Chicago Astronomer - Astro Joe]

New Planet Discovered

Jun 13, 2005 2:15 pm US/Central
WASHINGTON (AP) A planet that may be Earth-like—but too hot for life as we know it—has been discovered orbiting a nearby star.

The discovery of the planet, with an estimated radius about twice that of Earth, was announced Monday at the National Science Foundation.

“This is the smallest extrasolar planet yet detected and the first of a new class of rocky terrestrial planets,” Paul Butler of the Carnegie Institution in Washington said in a statement. “It’s like Earth’s bigger cousin.”

Geoffrey Marcy, professor of astronomy at the University of California, Berkeley, added: “Over 2,000 years ago, the Greek philosophers Aristotle and Epicurus argued about whether there were other Earth-like planets. Now, for the first time, we have evidence for a rocky planet around a normal star.”

Though the researchers have no direct proof that the new planet is rocky, its mass means it is not a giant gas planet like Jupiter, they said. They estimated the planet’s mass as 5.9 to 7.5 times that of Earth.

It is orbiting a star called Gliese 876, 15 light years from Earth, with an orbit time of just 1.94 Earth days. They estimated the surface temperature on the new planet at between 400 degrees and 750 degrees Fahrenheit.

Gliese 876 is a small, red star with about one-third the mass of the sun. The researchers said this is the smallest star around which planets have been discovered. In addition to the newly found planet the star has two large gas planets around it.

Butler said the researchers think that the most probable composition of the planet is similar to inner planets of this solar system—a nickel/iron rock.

Gregory Laughlin of the Lick Observatory at the University of California, Santa Cruz, said a planet of this mass could have enough gravity to hold onto an atmosphere. “It would still be considered a rocky planet, probably with an iron core and a silicon mantle. It could even have a dense steamy water layer.”

Three other extrasolar planets believed to be of rocky composition have been reported, but they orbit a pulsar—the flashing corpse of an exploded star—rather than a normal type of star.
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The day will come when it will be common knowledge that planets orbit most stars, just like we talk of lands beyond our horizon now.

[Maddad]

I saw a different article about this somewhere else. That article was saying they didn't know what the composition of the planet might be, and listed ices among other things as a possible consituant. I remember being surprised because at that surface temperature there sure as the dickens would be no ice on the planet.

At 2 million miles from its star, it's 23 times closer than Mercury is from our sun. The mass though means that this star will be much less energetic than our Sun. I've forgotten what the formula is though, so I can't say right now how much less energetic. Those surface temps though are similar to what I remember for the sunny side of Mercury.

[Chicago Astronomer - Astro Joe]

Yes, it's more of a lava and brimstone planet, hoving around 600 degrees F. And where's one planet, there's bound to be more around the same star.

[Maddad]

Two more. Both gas giants. Could be more tiny ones of course. Don't remember what distance the gas giants orbit at. If they're out at say's Jupiter's range, 500 million miles, then there's plenty of room for planets too small for us to see yet.

[Chicago Astronomer - Astro Joe]

One day real soon, the technology to indentify Earth sized planets will come to be, and enable a virtual explosion of new data. It will appear as if all the stars in the sky will have planets orbiting them.

Look to the skies...We are not alone.