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White Dwarf Quakes
As darkness falls this evening, some of the brightest stars in the night sky congregate in the west and southwest. Aldebaran, the “eye” of Taurus, is due west, not far from the planet Venus, the brilliant “evening star.” Sirius, the brightest true star in the night sky, is in the southwest, with Procyon high above it.
All of these stars share a common fate -- a fate also shared by the Sun and almost all of the other stars in the galaxy: They’ll end their lives as white dwarfs. A white dwarf is a stellar corpse -- a dense, hot ball that no longer produces energy, but that is simply whiling away the eons by slowly cooling.
As it cools, blobs of dense material near its surface move around. That creates “starquakes” that ripple through the white dwarf’s interior and back to the surface, creating “pulses” in the star’s light.
Astronomers at McDonald Observatory and elsewhere use the starquakes to probe a white dwarf’s interior, just as geologists use earthquakes to probe the interior of Earth.
The quakes have confirmed that white dwarfs are some of the simplest astronomical objects around. They’re made of carbon and oxygen, and most have a thin layer of helium at the surface, or a layer of helium with a layer of hydrogen atop it.
The carbon and oxygen in the oldest and coolest white dwarfs crystallize -- in essence, turning the white dwarf into a giant diamond in the sky.
We’ll have more about pulsating white dwarfs tomorrow.
Script by Damond Benningfield, Copyright 2012
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