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Beta Cassiopeia

February 28, 2015

A bright star in Cassiopeia is in a short but impressive phase of life: it’s beginning to puff up like a giant balloon.

Beta Cassiopeia is in the northwest early this evening, at the bottom of a sideways letter W formed by some of the constellation’s brightest stars.

Beta Cass is probably less than half the age of the Sun. But it’s almost twice as massive as the Sun, so it burns through its nuclear fuel much more quickly. In fact, it’s probably already consumed the original hydrogen fuel in its core, converting it to helium. Gravity is causing the core to shrink and get hotter, which eventually will allow it to start burning the helium to make even heavier elements.

In reaction to the changes in the core, Beta Cass’s outer layers are starting to puff up. Right now, the star is roughly four times the diameter of the Sun. That’s big, but not nearly as big as the star will be. Over millions of years, it’ll puff up to dozens of times the Sun’s diameter. It’ll then shrink and cool a little as it goes through another series of changes, before puffing up to even bigger proportions.

At the end of that second cycle, Beta Cass will shed its outer layers into space, briefly surrounding itself with a glowing bubble of gas and dust. The bubble will quickly dissipate, though, leaving only the star’s now-dead core — a hot but tiny cosmic ember known as a white dwarf: a stellar corpse that will slowly cool and fade away into the long cosmic night.


Script by Damond Benningfield, Copyright 2014

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