They signal to us across thousands of light-years, pulsing through the cosmic static like a vinyl record that’s reached the end of its songs....like the furious rhythm of a tom-tom....or like the whine of an electric motor....
These are the calls of pulsars — the remnants of once-mighty stars that emit beams of energy like cosmic lighthouses.
A pulsar is born when the core of a massive star stops producing energy. It collapses, forming a neutron star. Such a stellar remnant is more massive than the Sun, but only a few miles in diameter. A chunk of its matter the size of a thimble would weigh billions of tons.
As the core collapses, it spins faster, like an ice skater who pulls in her arms — up to dozens of revolutions every second. It also generates a powerful magnetic field. As the newborn neutron star spins, particles trapped in the magnetic field emit beams of energy from the magnetic poles — often in the form of radio waves. If Earth lies in the path of one of the beams, telescopes detect rapid pulses of energy — hence the name “pulsar” — short for “pulsating star.”
Over time, pulsars lose energy, so they spin slower. But if they have a companion star, they can spin up again by stealing some of its gas — a process that can make the pulsar spin hundreds of times a second.
The rate at which a pulsar spins can be changed by the pull of companions — including planets. More about that tomorrow.
Script by Damond Benningfield, Copyright 2011
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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