M1, the crab nebula, is an ultra young planetary nebula in the Taurus constellation.  It’s very challenging to nail down a date when M1 was first observed.  Technically speaking - the supernova behind M1 was visible to the naked eye and recorded in China in the year 1054 AD.  Come 1056 AD, M1 was no longer visible and it vanished from recorded history until the discovery of its remnants as early as 1921 but only decisively so in 1942.  While by no means the first to discover it, Charles Messier observed and incorrectly assumed it was a comet.  Upon learning of his mistake, M1 became the first object on Charles Messier’s list of things that were of interest but weren’t comets. 

Aside from being historically interesting, M1 is also scientifically intriguing as it presents numerous phenomena that bridge the gap between the human and astronomical timescales.  Being such a young supernova remnant, the outwards expansion of M1 can be observed on the scale of years - instead of millennia.  Likely the best example of this is by Adam Block, https://www.astrobin.com/users/CWTauri/,  in his recent work comparing a 2021 observation with one done in 2012 on identical instrumentation, https://www.astrobin.com/3o83se/.  The radial expansion of the outer envelope of gasses is evident but - the changes observable in the interior of the remnant are more subtle.  The rapid motion of the pulsar found at the center of M1 leads to perturbations in the interior gasses that propagate outwards as waves.  This is best observed in the Hubble work viewable via the below link.


https://www.nasa.gov/feature/goddard/2017/messier-1-the-crab-nebula

Processing this target was an interesting one as I have never seen such a unique result after combining the S, H, and O frames.  The discretely coloured filaments observable in narrowband images of M1 point towards highly local distributions of ionized gasses.  While this is arguably common on all supernova remnants, I find that it’s rare to see more colors than the usual ionized oxygen and hydrogen.  What a spectacular target and what a good example of the resolving power of our CDK 17!