Huge Hot Stars Create Planetary "Danger Zones"

April 19, 2007

Massive stars create "planetary danger zones"—regions of space where extreme solar winds and radiation make planets less likely to form, according to a new study.

The zones extended 1.6 light-years—about 10 trillion miles (16 trillion kilometers)—around so-called O-type stars, which are roughly 20 times bigger than our sun and a million times brighter.

Using NASA's Spitzer Space Telescope, the study team mapped out the Rosette Nebula, a stellar nursery where many stars have formed close together.

The team searched the nebula for protoplanetary disks—the gas, dust, and rocks that swirl around some stars. With time, gravity can pull the clumps of matter together to form planets.

But if the younger stars are in a danger zone, solar wind and radiation from the nearby O-stars tend to blow away their orbiting disks, the study suggests.

(See related images of solar storms.)

The stars and their disks "look like comets … with a bright head and a tail," said study leader Zoltan Balog of the University of Arizona.

Dangerous Bubbles

The new study mapped out hundreds of stars in the Rosette Nebula to find out how big planetary danger zones can get.

What they found is that beyond ten trillion miles from an O-star, about 45 percent of the neighboring stars had planet-forming disks.

But closer to the massive star, only 27 percent of the stars had disks, with fewer and fewer disks spotted around the small stars closest to the O-star.

If someone drew a ten-trillion-mile-wide bubble around one of these massive stars, outside of the bubble, planets would be as likely to form there as elsewhere.

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