The Crab Nebula, low in the western sky this month, looks like a faint cloud in a telescope, but its vaporous appearance belies the amazing event that occurred here 963 years ago. In early July of 1054, Chinese astronomers and others witnessed a spectacular supernova explosion here.
The titanic blast may have even been recorded by an Anasazi Indian artist in a pictograph on a rock overhang in Chaco Canyon. I once hiked to the spot many years ago, one of my first astronomical pilgrimages. From there, the artist would have had a wide open view to the east, where the supernova first appeared at dawn and remained visible for about two years.
Astronomers calculate that a star 9 to 11 times more massive than the sun 6,500 light-years from Earth ran out of fuel. Without the pressure and heat in its core to resist the force of gravity, the stellar giant underwent a sudden collapse, imploding and then exploding in a powerful blast called a supernova. The detonation created an expanding, glowing cloud of debris (which we still see today as the nebula) and a tiny, super-compressed remnant of the original star’s core called a neutron star.
This city-sized object rotates 33 times a second, shooting out rotating lighthouse-like beams of radio waves and light that earn it the name “pulsar” (the bright dot at image center at top). The nebula’s intricate shape is caused by a complex interplay of the pulsar, a fast-moving wind of particles coming from the pulsar, and material originally ejected by the supernova explosion and by the star itself before the explosion.
The Crab Nebula from radio to X-rays. Click here for a full-screen video option.
There are clearly so many ways to “see” the Crab Nebula depending on what wavelength or color of light you choose. In the video, we get five different perspectives from radio waves up through X-rays. The Crab radiates in all of these “colors” of light and reveals a different face in each.
In visible light, we see the leggy tendrils that give the object its crabby appearance. Red-colored radio-light shows how the neutron star’s fierce “wind” of charged particles energize the nebula, causing it to emit the radio waves. The yellow-colored infrared image includes the glow of dust particles absorbing ultraviolet and visible light from the neutron star. The green-colored Hubble visible-light image highlights the hot filamentary structures of dust and gas that thread the nebula. The blue-colored ultraviolet image and the purple-colored X-ray image show the light released by energetic electrons driven by a rapidly rotating neutron star at the center of the nebula.