You are here

Messy Giant

April 12, 2013

Big stars tend to be a bit messy. They blow strong “winds” into space, surrounding themselves with dense clouds of gas and dust. These expanding clouds can ram into the material between stars, piling it up to form denser clouds.

Consider Betelgeuse, the bright orange shoulder of Orion, the hunter. It’s well up in the western sky at nightfall, above Orion’s “belt” of three stars.

Betelgeuse is many times heavier than the Sun. That enormous mass squeezes the star’s core tightly, producing intense heat that revs up the nuclear reactions that power the star. Energy from these reactions pushes the surrounding layers of gas outward, causing the star to puff up. In fact, Betelgeuse is about a thousand times wider than the Sun.

The star’s surface gravity is tiny compared to the Sun's, so radiation and magnetic fields drive dense winds of particles from the surface out into space. In a million years, these winds carry enough material to make a star as big as the Sun.

Recent observations have shown that the winds cool and condense to form giant shells and arcs around Betelgeuse. One shell is squeezed in the direction of Betelgeuse’s path around the center of the galaxy. That forms a bow shock, like water piling up in front of a ship.

And the clouds close to Betelgeuse are lumpy, suggesting that the wind sometimes blows stronger and thicker from some parts of the star than others - enhancing the “messy” appearance of this giant star.


Script by Damond Benningfield, Copyright 2013

Get Premium Audio

Listen to today's episode of StarDate on the web the same day it airs in high-quality streaming audio without any extra ads or announcements. Choose a $8 one-month pass, or listen every day for a year for just $30.