Have you ever started something that lasted a lifetime? Charles Messier found a
whitish smudge near Zeta (ζ) Tauri on Aug. 28, 1758, while following a comet he
had discovered two weeks earlier. But this smudge didn’t look like any comet
he had ever observed, so he noted its location on a chart. And thus, without
fanfare, the French observer began his catalog of non-cometary objects.
But Messier was not the first to observe M1 (also cataloged as NGC 1952).
John Bevis is credited with first observing this supernova remnant in 1731.
William Parsons, Earl of Rosse, named the Crab Nebula based on his inter-
pretation of the shape from his observation in 1842. It isn’t the first deep-sky
object whose name might be considered questionable.
In 1928, Edwin Hubble proposed a connection between the Crab Nebula
and reports of a bright star that had appeared in Taurus in A.D. 1054. That
supernova — estimated to have popped off 6,500 light-years away — was
bright enough to see during the day for three weeks and remained in the
night sky for two years. Observations by Korean, Japanese, Chinese, and
90 Crab Nebula
Arab observers recorded a star brighter than Venus. Astronomers
now estimate the star blazed between magnitude –4 and –7.
The Crab Nebula is a source of energy across the electromagnetic
spectrum. Known as Taurus A, it’s the brightest radio source in that con-
stellation. Its central rapidly rotating neutron star — called a pulsar, the
remnant of the star that exploded — is the most persistent and brightest
gamma-ray source in the heavens. Don’t worry, though — observing it
won’t damage your eyes. Our atmosphere absorbs the radiation.
While the nebula is magnitude 8.4, its pulsar is magnitude 16.2
— bright enough for today’s larger telescopes to pick up. A chart is
essential for distinguishing it from other faint stars scattered in front
of the nebula.
A generous 6' by 4' across, M1 is expanding at 0.5 percent the
speed of light. It can be seen in binoculars or a spotting scope under
dark skies, and is bright enough to see in suburban skies, especially
with a filter. It’s a fun object to show your friends or guests at a star
party as you explain the nebula’s history. — A.G.