When a star explodes as a supernova, it’s bad news for any planets that orbit it. The shockwave and radiation rip the planets apart, leaving nothing more than puffs of debris. As things settle down, though, some of that debris may coalesce to make new planets - desolate chunks of rock orbiting the supernova’s dead core, known as a neutron star.
In fact, astronomers have discovered planets orbiting two neutron stars. The stars spin rapidly, emitting bursts of energy with each spin, so they’re also known as pulsars. The time between pulses of energy is like the tick of an ultra-precise clock. But the gravitational pull of an orbiting planet changes the length of each tick by a tiny amount, revealing the planet’s presence.
The first pulsar planets were discovered more than two decades ago - the first planets discovered around any star other than the Sun. All three planets in the system are no bigger than Earth. A second pulsar system consists of a planet orbiting the pulsar and a companion star.
Another small object has been discovered around a third pulsar. Although it’s sometimes described as a planet, it was born as a star. But the supernova and the extreme radiation from the pulsar have eroded all but its carbon core. Today, it’s basically a chunk of solid diamond orbiting its violent companion.
Astronomers study these systems with radio telescopes. And they’re getting ready to dedicate a giant new radio telescope in Chile. More about that tomorrow.
Script by Damond Benningfield, Copyright 2013
For more skywatching tips, astronomy news, and much more, read StarDate magazine.