The Crab Nebula (M1, NGC1952)
The Crab Nebula (M1, NGC 1952) is a supernova remnant which is a rapidly expanding cloud of gas
created in the explosion of a star as a supernova. It is found in the constellation Taurus, the Bull. The
supernova was noted on July 4, 1054 AD by Chinese and Arab astronomers as a new star. When first
observed It was about four times brighter than Venus, or about magnitude -6. According to these records,
it was visible in daylight for 23 days, and 653 days to the naked eye in the night sky. Very few supernovae
have been observed in our Milky Way Galaxy. However, supernovae are so bright, that many have been
found in other galaxies millions of light years away!
In visible light the Crab Nebula consists of an oval-shaped mass of filaments, about 6 arcminutes long and
4 arcminutes wide. By comparison, the full moon is 30 arcminutes across. Compared to many nebula, M1
is quite small and a challenge to image. It is thought to be about 6,300 light years from Earth. The Crab
Nebula spans about 10 light-years and is still expanding at the very high velocity of about 1,800 km/sec. In
the nebula's very center lies a pulsar: a neutron star weighing as much as our Sun, but with a diameter of
20-30 km. This is what remains of the original star after the supernova explosion. The Crab Pulsar rotates
about 30 times each second.
The filaments seen in the images below are the remnants of the progenitor star's atmosphere, and consist
largely of ionized helium and hydrogen, along with carbon, oxygen, nitrogen, iron, neon and sulfur. The
filaments' temperature is typically between 11,000 and 18,000 degrees. The images shown below were
taken with filters which selectively image emission radiation from hydrogen-alpha, oxygen III and sulfur II.
The French astronomer Charles Messier found this supernova remnant in 1758, when he was looking for
comet Halley on its first predicted return to the solar system. He first thought it was a comet, but soon
recognized that it was not moving relative to its background stars and thus could not be a comet. It was the
discovery of this object which caused Messier to begin the compilation of his famous Messier catalog (now
M1 through M110) of objects that look like comets through small telescopes. It is called the Crab Nebula
because early drawings of it had the appearance of a crab.
As mentioned above, the images below are derived from narrow band images using filters for the emission
wavelengths for hydrogen-alpha, sulfur II and oxygen III. A total of 5 x 10 minute exposures were obtained
for each filter using a Celestron 9.25 telescope operating at f/5 and a ST10XME camera. The three narrow
band images were each assigned a primary color (RGB) and then digitally combined. The color image
shown below uses the so-called Hubble palette. Other primary color assignments can be made to yield a
variety of colored images. These are more "artistic" images than a representation of what the nebula would
actually look like, but the narrow band images do show more structure than images obtained using
standard RGB filters. Each of the three narrow band images shows a somewhat different structure. Click
on the images below for the full size.
created in the explosion of a star as a supernova. It is found in the constellation Taurus, the Bull. The
supernova was noted on July 4, 1054 AD by Chinese and Arab astronomers as a new star. When first
observed It was about four times brighter than Venus, or about magnitude -6. According to these records,
it was visible in daylight for 23 days, and 653 days to the naked eye in the night sky. Very few supernovae
have been observed in our Milky Way Galaxy. However, supernovae are so bright, that many have been
found in other galaxies millions of light years away!
In visible light the Crab Nebula consists of an oval-shaped mass of filaments, about 6 arcminutes long and
4 arcminutes wide. By comparison, the full moon is 30 arcminutes across. Compared to many nebula, M1
is quite small and a challenge to image. It is thought to be about 6,300 light years from Earth. The Crab
Nebula spans about 10 light-years and is still expanding at the very high velocity of about 1,800 km/sec. In
the nebula's very center lies a pulsar: a neutron star weighing as much as our Sun, but with a diameter of
20-30 km. This is what remains of the original star after the supernova explosion. The Crab Pulsar rotates
about 30 times each second.
The filaments seen in the images below are the remnants of the progenitor star's atmosphere, and consist
largely of ionized helium and hydrogen, along with carbon, oxygen, nitrogen, iron, neon and sulfur. The
filaments' temperature is typically between 11,000 and 18,000 degrees. The images shown below were
taken with filters which selectively image emission radiation from hydrogen-alpha, oxygen III and sulfur II.
The French astronomer Charles Messier found this supernova remnant in 1758, when he was looking for
comet Halley on its first predicted return to the solar system. He first thought it was a comet, but soon
recognized that it was not moving relative to its background stars and thus could not be a comet. It was the
discovery of this object which caused Messier to begin the compilation of his famous Messier catalog (now
M1 through M110) of objects that look like comets through small telescopes. It is called the Crab Nebula
because early drawings of it had the appearance of a crab.
As mentioned above, the images below are derived from narrow band images using filters for the emission
wavelengths for hydrogen-alpha, sulfur II and oxygen III. A total of 5 x 10 minute exposures were obtained
for each filter using a Celestron 9.25 telescope operating at f/5 and a ST10XME camera. The three narrow
band images were each assigned a primary color (RGB) and then digitally combined. The color image
shown below uses the so-called Hubble palette. Other primary color assignments can be made to yield a
variety of colored images. These are more "artistic" images than a representation of what the nebula would
actually look like, but the narrow band images do show more structure than images obtained using
standard RGB filters. Each of the three narrow band images shows a somewhat different structure. Click
on the images below for the full size.
| H-alpha image |
| Oxygen III Image |
| Sulfur II Image |
| Combined color Image (Hubble Palette) |
