Astronomers Crack Open The Crab Nebula And Feast On Its Light

This composite image of the Crab Nebula, the remnant of the supernova explosion in the constellation Taurus in the year 1054, was assembled by combining photos from five telescopes spanning nearly the entire breadth of the electromagnetic spectrum: the Very Large Array (radio), the Spitzer Space Telescope (infrared), the Hubble Space Telescope (visible light), the XMM-Newton Observatory (X-rays), and the Chandra X-ray Observatory. Credits: NASA, ESA, NRAO/AUI/NSF and G. Dubner (University of Buenos Aires)

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.

This 11th century pictograph at Chaco Canyon may depict the supernova of 1054. The supernova and crescent moon were in this configuration when the supernova was near its brightest. An imprint of a hand at the top signifies that this is a sacred place. Credit: Alex Marentes

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.

Using Stellarium, I recreated the scene a skywatcher would see facing east at dawn on July 5, 1054. The crescent moon and supernova make a good match to the pictograph. The supernova was about as bright as Venus.

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.

The Crab Nebula is best viewed during the winter months when it’s high in the sky at nightfall. In May, it’s sinking in the western sky at dusk. Created with Stellarium

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.

2 Responses

  1. allison

    Hi AstroBob

    I was reading your article at S&T about the new supernova ‘AT 2017eaw’ – could you please explain the naming scheme employed for this object? What does the ‘AT’ stand for? Is the IAU no longer issuing names for supernovae in the old SN YYYY# format (e.g. ‘SN 2008S’)? I am aware that the number of supernova discoveries has multiplied immensely in recent years, perhaps rendering old nomemclature systems obsolete. Thanks, I intend to attempt a visual observation of AT 2017eaw tonight if i can drag myself out of bed.

    1. astrobob

      Hi Allison,

      That name was originally passed along to me from one of the people who confirmed it (or maybe that was the original name on D. Bishop’s SN website – I can’t remember which), but in any case, it shouldn’t have been. It’s now 2017eaw. I deleted the “AT” reference in the S&T article. Thanks for pointing that out! You’re right about the exponential increase in the number of SN discoveries in recent years. That’s the reason for the three-letter combos. I remember the old days — not long ago! — when supernovae never went past double-letters! I hope you get good weather to view it. I was able to observe it last night at ~12.6 mag.

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