A dying star gives birth to planets

Astronomers have long known that planets form in dusty disks around newborn stars. Now, researchers suspect that planets also can develop in debris disks surrounding exploded stars.

By Richard Talcott

Published: May 26, 2009

Dying star.

Photo by NASA/JPL-Caltech/R. Hurt (SSC)

No one expected that the first planets discovered outside the solar system would be circling a stellar corpse. Yet that's exactly what radio astronomers Aleksander Wolszczan and Dale Frail found in 1991 when they detected planets circling a pulsar designated PSR B1257+12. This pulsar — a neutron star that spins once every 6.22 milliseconds — formed when a star at least 8 times the Sun's mass exploded. The crushed remnant contains about 1.5 solar masses and measures about 10 miles (16 kilometers) across.

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	Sun	Sun	Moon
RISE	—		—	PHASE	—
SET	—		—	DISK	—

	Mercury	Mercury	Venus	Venus
RISE	—		—
SET	—		—
		—		—