Planetary Picture? Criteria for planethood cloud object's identity | Science News



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Planetary Picture? Criteria for planethood cloud object's identity

10:16am, May 4, 2005

When is a Jupiterlike object a planet and when is it just a blob of gas? That's the question that astronomers are debating this week after two teams independently confirmed that a distant speck of light recorded a year ago is the first image of a planetary-size body beyond the solar system.

Two to five times as massive as Jupiter, the body would seem to automatically qualify as a giant planet. But the object almost certainly doesn't meet what many astronomers consider to be an equally important criterion for planethood: formation from a swirling disk of gas and dust that surrounds a young star.

The distant object orbits a brown dwarf rather than an actual star. Although brown dwarfs form as stars do, from the collapse of a cloud of gas and dust, they're not massive enough t

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