Tales of the Crab

In June or July 1054, a dazzling new star erupted in the eastern morning sky. To ancient Chinese observers, it was brighter than any other celestial object except the sun and moon; it far outshone the next most brilliant object, Venus. It remained visible by day for 23 days. By August that position in the sky, which we know as the constellation Taurus, had rotated so that the area was in the predawn; later, it was in the nighttime sky. The new star continued glowing there.

“During the third month in the first year of the Chia-yu reign period the Director of the Astronomical Bureau said, ‘The Guest Star has become invisible, which is an omen of the departure of the guest,'” wrote Te-hsiang, an official of China’s Sung Dynasty. (The month was from March 19 to April 17, 1056, according to Robert Burnham Jr., in Vol. 3 of Burnham’s Celestial Handbook. He is quoting a translation by J.J. Duyvendak, published in 1942.)

When it first erupted, it seemed to be guarding a nearby star called T’ien-Kuan, today’s Zeta Tauri. “It was visible in the day like Venus, with pointed rays in all four directions. The color was reddish-white,” Te-hsiang added. Some experts think the supernova may have been recorded in pictographs by Anasazi Indians of the Southwest.

The “Guest Star” was a ferocious supernova, the explosive detonation of a star 6,300 light-years away. When it exploded, material blasted into space while the core collapsed into a neutron star, the densest material known. (We don’t know what’s inside a black hole.) The neutron star has as much mass as our sun but is the size of small town. It spins on its axis 30 times a second, sending out a beam of energy.

The remains of the material blown off the star look like gas clouds and strands of filamentous material. They make up an expanding nebula. This was noticed by an English amateur astronomer, Dr. John Bevis, in 1731, Burnham writes. Its more famous notice came when the French comet-seeker Charles Messier rediscovered the nebula on Sept. 12, 1758, close to Zeta Tauri. He was looking for Halley’s Comet, which was predicted to return that year. It did return and Messier observed it in January 1759.

His stumbling across the supernova remnant was the genesis of the famous Messier Catalog, the most useful guide to deep-space objects a beginner could use. Fixated on discovering comets, Messier decided to list every fuzzy, comet-like thing his telescope picked up that did not move in the heavens – that is, every deep-space object that wasn’t a comet, planet, star or moon. Then he and other comet-seekers wouldn’t waste time trying to track them.

As he was watching the supernova remnant at the time, he called it Messier 1, shortened to M1. The list goes through most of the closest galaxies, novas and star clusters, including such glorious sights as M31, the Great Galaxy in Andromeda; M22, the spectacular star cluster in Sagittarius — all the way to M104, the Sombrero Galaxy in Virgo. Later, others added to the list, bringing the number to 110.

The Messier Catalog became outdated as telescopes improved and thousands of other galaxies, cluster, nebulas and other objects were discovered. Much longer lists were compiled, like the New General Catalog (NGC) and the Index Catalog (IC). But the Messier list is treasured by many as showing some of the easiest and brightest astronomical targets.

In 1844 William Parsons, the Third Earl of Rosse, Ireland, observed the debris cloud using a 36-inch-diameter reflector (his famous “Leviathan of Parsonstown,” 72 inches in diameter and weighing nearly 4 tons, would not be completed until 1845). Parsons’ sketch of M1 looked something like a crab, and ever since then M1 has been known as the Crab Nebula.

Debris from the 1054 blast has continued to expand at varying rates, now about 600 miles per second. Today it is an estimated 10 light-years across, according to NASA’s Astronomy Picture of the Day site on the Internet, LOCATED HERE.

NASA’s Chandra X-Ray Telescope, an orbiting observatory, took a series of close-up views of the Crab’s inner vortex. Put together as a movie, the images shows violent whirling motion as material spews out of the neutron star and charged fragments churn away at nearly the speed of light.

I had my first look at the Crab around 3:30 a.m., Oct. 18, while making astrophotos in southern Utah. My friend Don Colton pointed out that M1 should be at a high altitude at the time, best for photography, and it was. My telescope and camera were cranky and I didn’t get a good image with the green filter, so I could not make a nice color photo.

[View I took of the Crab Nebula, morning of Oct. 18]

But the picture I assembled from images through the other filters — clear, red and blue — was chilling to me. Not only are we witnessing a violent event, but the view gives us a scary sense of scale. Here are the remains of a star whose explosion was witnessed in 1054, still flying apart at 50 million miles per day, and yet the Crab Nebula is a comparatively small blob among the stars.

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