Pulsar Planets

A decade ago astronomers found the first planets outside our solar system– in a seemingly impossible place — around the spinning corpse of an exploded star. Astronomers claim to have discovered planets around a pulsar. How could planets survive the supernova explosion that created the pulsar?

A supernova — or exploding star — U a super-dense neutron star at its core. Some neutron stars are later detected from Earth as rapidly spinning pulsars, which emit a regular signal like a lighthouse.

That’s why people were surprised when, in 1992, Alex Wolszczan and Dale Frail announced three planets orbiting pulsar PSR 1257+12. Pulsar planets might be possible if supernovae don’t explode in all directions with equal force. If distant planets orbited where the explosion was weak, they might’ve survived.

But the supernova would have blasted away most of its own mass — and thereby decreased the gravity of the plusar left behind. So even if planets survived the blast, they might’ve escaped into space. A second scenario suggests the pulsar planets formed after the supernova. Suppose the original star had a companion star. As the star exploded as a supernova and formed its pulsar, the force of the explosion might’ve set the pulsar on a collision course with the companion star.

The companion star might have been destroyed. But the mass it left behind might’ve later condensed — to form planets orbiting the pulsar.

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