sff_corgi_lj | And now for something different: back to space science

electroweak shared this in the notes for today's installment of his webcomic, A Miracle of Science -- from National Geographic:

Solar System With Neptune-Like Planets Discovered

Anne Minard
for National Geographic News

May 17, 2006

Another Earth? Not yet.
But astronomers say they're getting ever closer to finding planets more like Earth around sunlike stars.

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Christophe Lovis of Switzerland's Observatory of Geneva and colleaguesannounced that they have found a solar system containing three rocky,medium-size planets—the smallest so-called extrasolar planets that haveever been observed.
The rocky, Neptune-size planets are orbiting a star called HD 69830,barely visible with the naked eye near the southern constellationPuppis.
One of the planets is in the star's "habitable zone," where liquid water could exist on its surface, the researchers said.
The astronomers report their discovery in tomorrow's issue of the journal Nature.
Scientists have discovered almost 200 extrasolar planets so far. Thefirst one was found in 1995 by Michel Mayor, an astronomer at theUniversity of Geneva who is also an author of the new study.
Mayor said one of the most exciting aspects of the new discovery isthat the planets are the smallest yet found, proving that astronomers'techniques are getting sharp enough to someday detect distant planetsthe size of Earth.
"These objects are still not Earth twins, but the amazingprogress … suggests that the dream to detect real 'Earths' could bepossible," Mayor said.
Star Signal
NASA's Spitzer Space Telescope recently spotted HD 69830, about 41light-years away, as part of a wider survey. The telescope found thatthe star had an unusually strong infrared signal.
Astronomers said last month that they think the signal is caused by abelt of asteroids that's about as far from the star as Earth is fromthe sun.
Astronomer David Charbonneau of Harvard University in Cambridge,Massachusetts, points out that HD 69830 is the only known star that iscomparable in mass and age to the sun that also has an asteroid belt.

"It's a really neat system," said Charbonneau, who wrote a commentary accompanying the Nature study.
"It's the first one to have both planets and asteroid belt. There are alot of similarities to our own solar system and a lot of differences,too."
The European researchers first discovered the three planets in October 2003.
Between then and January of this year, the scientists made 74 more observations.
They concluded that the planets are made mostly of rockfragments that had collided and fused to form solid cores. According tothis model of planet formation, gases would have then collected aroundeach core to form an atmosphere.
Planet Has Water?
The innermost planet appears to orbit HD 69830 once every nine days and is about ten times as massive as Earth.
The second planet orbits about once a month and has a mass around 12 times that of Earth.
The outermost planet is about 18 times the mass of Earth and orbits HD69830 once every 197 days. The researchers say this planet is near theinner edge of the star's habitable zone.
Lead study author Lovis said the outermost planet probably isenveloped by hydrogen, which makes it look more like Uranus and Neptunethan Earth.
"Nonetheless," he said, "this discovery opens the way to the detection of even smaller planets in the near future."
Mayor called it the discovery "a small step in the direction of the research for possible life in other parts of the universe."
"As we believe that rocky planets are the most suitable placefor the development of life, the detection of this exciting system hasalso to be considered in that frame," he said.
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