The Crab Nebula (Messier 1) is a supernova remnant about 6,500 light years away in the constellation Taurus. It is the first astronomical object connected to a supernova (SN 1054).
Though the supernova has long since faded, you can still observe the remnants (magnitude 8.4) in a telescope.
Description
History
John Bevis, an English astronomer, discovered the nebula in 1731, while Charles Messier independently discovered it in 1758. He cataloged it as the first object in his now-famous catalog of comet-like objects.
Almost a century later in 1840, William Parsons sketched Messier 1 as he observed it in a telescope. His drawing looked vaguely like a crab, resulting in its current name.
However, the Crab Nebula’s history goes all the way back to 1054, when Chinese astronomers first recorded a “guest star” that was visible even during the day. 13th century Japanese and Islamic records of the supernova also exist.
The Crab Pulsar
The Crab Nebula supernova remnant is the result of the violent explosion of a massive star (10-29 solar masses) when it runs out of fuel. When nuclear fusion shut down, the star collapsed under its own gravity and formed a neutron star. The resulting neutron star has more mass than our sun squeezed into a volume only 10-20km across. That is a density equivalent to atomic nuclei – truly exotic stuff!
In the case of the Crab Nebula, the neutron star emits beams of electromagnetic radiation and spins at 30 times a second. This kind of neutron star is known as a pulsar and we see the radiation it emits when the beams point toward Earth. The Crab Pulsar is one of the brightest sources of X-ray and gamma rays in the skies. Furthermore, this year (2019), scientists observed the Crab Nebula emitting gamma rays at energies of over 100TeV, the first identified source at these energy levels.
The Crab Pulsar is also one of very few pulsars that can be identified optically. I believe I captured it in the image as annotated below.
The Supernova Remnant
When the progenitor star went supernova, it expelled most of its material at at up to 10% the speed of light (about 30,000 km/s). This results in a shock wave in the interstellar medium ahead of the ejecta and creates temperatures of millions of Kelvin. The shock wave continues traveling and decelerating over centuries as it moves through the ambient interstellar medium.
The Crab nebula is roughly oval in shape and contains many intricate filaments. We can see just a hint of that intricacy in the captured image.
Scientists and amateurs have observed the Crab Nebula over the years and have seen changes over time. I hope to come back to it over the next decade or so to capture that change for myself!
Acquisition and Image Processing
Unfortunately, the optimal time of the year for imaging the Crab Nebula coincides with the monsoon season. I waited for several weeks before conditions were acceptable for imaging. Even then, the periods of clear skies were brief. Apart from that, acquisition was smooth and unremarkable.
The Pixinsight imaging processing workflow I used was as follows:
Narrowband Data:
- Dynamic Background Extraction (DBE)
- Noise reduction (TGV, ACDNR, etc)
- Masked stretch
- Combination into LRGB image
Luminance Data (synthetic combination of narrowband data after DBE):
- Deconvolution
- Noise reduction
- Masked stretch
- Combination into LRGB image
I tweaked the LRGB image for color and stretched it to produce the final image.
Reflections
[T]hen the Lord God formed the man of dust from the ground and breathed into his nostrils the breath of life, and the man became a living creature.
…
[F]or you are dust, and to dust you shall return.
Gen 2:7, 3:19 (ESV)
Observing this supernova remnant reminded me of the passages from Genesis, which are often quoted at funeral services.
Why so? Well, scientists believe that the death of giant stars in supernovas spread elements like carbon, oxygen, and iron throughout the cosmos – elements that are essential to life. In a way, we are made of, eat, live, and breathe the remains of stars.
The author of Genesis reveals where we came from, and where we (at least our currently earthly bodies) will return to. Thanks be to God that in Him and His victory over death, our story does not end in eventual oblivion, but in life everlasting!