Visual Astronomy

MESSIER 1
Messier 1
   
RA:
05h 34m 30s
DEC:
+22° 01' 00''
Type:
Supernova remnant
NGC:
5272
Magnitude:
8.40
Surface brightness :
12.2
Apparent dimensions :
8'x4'
Distance:
6,300 ly
   
 

The Crab Nebula (catalogue designations M 1, NGC 1952, Taurus A) is a supernova remnant in the constellation of Taurus. The nebula was first observed in 1731 by John Bevis. It is the remnant of a supernova that was recorded, as a star visible in daylight, by Chinese and Arab astronomers in 1054. Located at a distance of about 6,300 light years (2 kpc) from Earth, the nebula has a diameter of 11 ly (3.4 pc) and is expanding at a rate of about 1,500 kilometres per second.

The nebula contains a pulsar in its centre which rotates thirty times per second, emitting pulses of radiation, from gamma rays to radio waves. The nebula was the first astronomical object identified with a historical supernova explosion.

The nebula acts as a source of radiation for studying celestial bodies that occult it. In the 1950s and 1960s, the Sun's corona was mapped from observations of the Crab's radio waves passing through it, and more recently, the thickness of the atmosphere of Saturn's moon Titan was measured as it blocked out X-rays from the nebula.

In the early 20th century, the analysis of early photographs of the nebula taken several years apart revealed that it was expanding. Tracing the expansion back revealed that the nebula must have formed about 900 years ago. Historical records revealed that a new star bright enough to be seen in the daytime had been recorded in the same part of the sky by Chinese and Arab astronomers in 1054 Given its great distance, the daytime "guest star" observed by the Chinese and Arabs could only have been a supernova—a massive, exploding star, having exhausted its supply of energy from nuclear fusion and collapsed in on itself.

Recent analyses of historical records have found that the supernova that created the Crab Nebula probably occurred in April or early May, rising to its maximum brightness of between apparent magnitude −7 and −4.5 (brighter than everything in the night sky except the Moon) by July. The supernova was visible to the naked eye for about two years after its first observation. Thanks to the recorded observations of Far Eastern and Middle Eastern astronomers of 1054, Crab Nebula became the first astronomical object recognized as being connected to a supernova explosion.

 
Other sketches
           
  Messier 1        
 
Messier 1 (2005.)
       

 

VEDRAN VRHOVAC©

2006.-2007.