for National Geographic News
A newly formed planet orbiting a young star offers the first observational evidence for the long-held theory that planets form early, within the first ten million years of a parent star's life, according to a new study.
Until recently all of the 250-plus planets outside our solar system have been found around much older stars—a hundred million years of age or more.
Now a research team led by Johny Setiawan of the Max Planck Institute for Astronomy in Heidelberg, Germany, has found a newborn extrasolar planet—or exoplanet—around a star that's between eight million and ten million years old.
The exoplanet, which is ten times more massive than Jupiter, is still linked to the dusty disk of material surrounding its parent star.
With this new find, Setiawan said, so-called protoplanetary disks have at last earned their name.
"It is very exciting to know that things we called 'protoplanetary' disks are indeed protoplanetary—they form planets!"
Setiawan and colleagues describe the findings in this weeks' issue of the journal Nature.
The new planet's star, known as TW Hydrae, sits about 180 light-years from Earth in the constellation Hydra.
Although TW Hydrae is our galactic neighbor, the young planet it hosts is too small and distant to be seen with modern instruments.
Instead astronomers spotted the exoplanet using an indirect technique called radial velocity.
This method measures the effect of the gravitational tug of a planet on its host star's movement.
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