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Object data: M1, the Crab Nebula (NGC 1952) in the constellation of Taurus, is perhaps the most famous supernova remnant in the skies. Its position corresponds to a very bright supernova recorded by Chinese and Arab astronomers in 1054 - at the time it was so bright that it was visible even in daylight for several weeks. A supernova is a massive star which has exploded, having exhausted its supply of energy from nuclear fusion and collapsed in on itself. What we see now is the shattered remains of this giant explosion - a tangled web of filaments glowing by the light of ionized hydrogen gas woven amongst a bluish reflection glow from the debris of dust and gases. At the centre of this cloud is the remains of the original (progenitor) star - now a neutron star of massive density and magnetic flux spinning at 30 times a second, creating intense beams of electromagnetic radiation which appear to blink on and off as the beams pass the direction of the Earth (roll your mouse over the above image to identify the neutron star). These pulsations, first detected in 1967 by British astronomy graduate Jocelyn Bell, were so extraordinary that her team held on to the results for some months, quite unsure of the cause - could they even be of alien origin? Professor Fred Holye was one of the first to suggest the real cause as a supernova. These extraordinary stars became known as "pulsars" (pulsating stars). This was the first discovery of a pulsar and contributed greatly to our understanding of stars and supernovae in particular, which became an important standard candle for measuring astronomical distances. Jocelyn Bell's story can be read here.
The Crab Nebula is estimated to be approximately 6,500 light-years from Earth, with a diameter of 11 light-years. It is expanding at a rate of about 1,500 kilometres per second. It was first observed in 1731 by English astronomer John Bevis, and independently observed in 1758 by Charles Messier who catalogued it as the first entry in his famous Messier catalogue. See more about the crab nebula in this NASA video. The radiation from the Crab Nebula is especially powerful but weaker Supernovae are quite common, being the final stage in the lifecycle of giant stars (mass more than 8 times the mass of our Sun). Some other well known examples are: IC 443 (Jellyfish Nebula), Simeis 147, and the Veil Nebula.
Date: 24/11/09
Location: Southern France
Conditions: Calm, Transparency=8, Seeing=7
Optics: RCOS 12.5" Ritchey-Chretien with custom field flattener working at f/9.5
Mount: AP 900 GTO on Portable Pier
Camera: SBIG STL-11K, SBIG LRGBC filter set, -25°C
Guiding: Integral STL-11K autoguider
Exposure: LRGB Seq: 9x 20 minutes; 2x 20 : 13 : 20 minutes (binned 2x2).
Processing: Image acquisition and initial processing using Maxim DL, subsequent processing in RegiStar and Photoshop.
Notes: I would greatly have preferred more sub-frames, both Luminance and RGB, but time was out - this was the very last night in France. Seeing was projected to be pretty good - in fact it was so, but only during a window between about 23:00 and 4:00 - outside of those times it was quite poor. Fortunately that was enough time to capture 9 reasonable luminance frames.
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