Coupled with the long-heldtheories that gas giants are necessary for the formation of smaller Earth-likeplanets, the discovery raises intriguing possibilities about the searchfor other planets that might harbor life."The new findings strengthenthe likelihood that a larger fraction of stars form solar systems likeour own, and that some stars near the Sun are still forming giant planets,"said Jack Lissauer, a researcher at NASA's Ames Research Center who wasnot involved in the study.
Enough hydrogen for sixJupiters
The three stars in the studyare relatively young -- between 8 million and 30 million years old (ourSun formed nearly 5 billion years ago). Each is less than 260 light-yearsaway (our Milky Way Galaxy is roughly 100,000 light-years across).
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Each of the stars was knownto be encircled by a flat disk of dust. These so-called protoplanetarydisks, the leftovers of star birth, are the stuff of which planetsare made. But previous studies had concluded the disks contained very littlehydrogen gas. Researchers assumed that hydrogen does not hang around ina dust disk for more than about 5 million years. (The interplanetary spacein our own solar system is now mostly hydrogen-free.)
The new study, reported inthe Jan. 4 issue of the journal Nature, found enough hydrogen gasaround one of the stars to form six Jupiters. Each of the other two diskshad a fraction of the hydrogen needed to make one Jupiter, but still morethan expected.
Many of the stars in ourneighborhood of the Milky Way are at least 10 million to 30 million yearsold. Until now, researchers assumed these stars could no longer form giantplanets,because their disks would be depleted of hydrogen gas.
According to theories ofsolar system formation, giant planets are key to allowing the developmentof smaller planets in potentially habitable orbits -- not too hot, nottoo cold. Gas giants, as the theory goes, also help set up livable conditionsas they use their gravity to sweep the inner solar system relatively freeof life-threatening asteroids and comets.
The researchers involvedwith the study said their work is "good news, though indirectly, in thesearch for extraterrestrial life," because life as we know it needs a planetin one of these so-called "Goldilocks" orbits.
Clues to our own solarsystem
The findings also representanother step toward fathoming the range of ways in which solar systems,including our own, come into being and evolve.
"If indeed planet formationis still going on in these [nearby] systems, they are among the closetto the Earth," said Geoffrey Blake, a Caltech researcher who participatedin the study. "They may therefore provide unique windows into how planetarysystems are assembled."
Classic explanations of giant-planetformation say that a core of rock roughly 10 times the mass of Earth forms,and then the gravity of this "protoplanet" attracts gas until it becomesthe size of Jupiter. But computer models have shown this would take severalmillion years -- longer than hydrogen gas was expected to be available.
"Our new findings are importantbecause they lengthen the time that it is possible to form Jupiter-likeplanets," Blake told SPACE.com.
Next Page: Missing matter?
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