60-Second Space

Past-Prime Star May Still Produce Planets

The star TW Hydrae should be too old to still have planets forming around it, but its gas and dust indicate it still has planetary potential. John Matson reports

In planet formation, as in adolescence, you’ve got your late bloomers. Such is the case for a nearby star called TW Hydrae. At some three million to 10 million years of age, it’s relatively old for a young star. That is, TW Hydrae formed much more recently than our sun but is past the point at which most fledgling stars are still encircled by a massive disk of dust and gas—the stuff of planet formation.

But a new analysis shows that TW Hydrae retains a surprisingly hefty circumstellar disk, implying that the star could still be forming giant planets. The study appears in the journal Nature. [Edwin A. Bergin et al., An old disk still capable of forming a planetary system]

Researchers from the U.S., Germany and the Netherlands pointed the European Space Agency’s orbiting Herschel Space Observatory at TW Hydrae to investigate the star’s disk. They detected a heavy hydrogen molecule called hydrogen deuteride. From that measurement they were able to estimate the abundance of ordinary hydrogen, which makes up the bulk of the disk.

The result: TW Hydrae still has enough raw material left to make 60 Jupiters or so, despite its maturity. For aging stars, then, perhaps 10 million is the new 30.

—John Matson

[The above text is a transcript of this podcast.]

[Scientific American is part of Nature Publishing Group.]

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