You are here

Crab Nebula

December 14, 2015

A colorful crab scuttles across the sky on December nights. It’s faint and far away. But almost a thousand years ago, it announced its birth in dramatic fashion — as a brilliant new star in the constellation Taurus. It was bright enough to see in daylight for several weeks.

The Crab Nebula is a cloud of glowing gas that spans about a dozen light-years. It’s called the crab because its tendrils of gas resemble a crab.

The nebula was born when a heavy star exploded as a supernova, blasting its outer layers into space. The gas is racing outward at millions of miles per hour, so it’s spread out to form a big cloud.

At the center of the nebula is the star’s crushed core — a neutron star. It’s roughly twice as massive as the Sun, but only about as wide as a small city. At such extreme density, a teaspoon of its matter would weigh as much as 10 million African elephants.

The explosion that created the nebula also caused the neutron star to spin more than 30 times a second. And it created a magnetic field a trillion times stronger than Earth’s. As the star spins, the magnetic field causes it to beam energy into space. [audio: pulsar] Radio telescopes detect this beam as “pulses” of energy, so the neutron star is also known as a pulsar.

Taurus is low in the east at nightfall and climbs high across the south later on. The nebula is in its southern horn, and is visible through a small telescope — the glowing remains of an exploded star.

Script by Damond Benningfield, Copyright 2015

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.