科学美国人60秒:Past-Prime Star May Still Produce Planets

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

[Scientific American is part of Nature Publishing Group.]