Nebulae
Read More
Cosmic Storm
Astrophotographers often go to great lengths to produce the most realistic and aesthetically pleasing images of distant objects, free from any distracting artefacts.
Yet, beauty lurks even on the scrap heap of astronomical image data.
Visible here in this 41 hour exposure of a particularly colourful region in Orion, centered on the bright reflection nebula NGC 1999, are thousands of tiny bright streaks in all shapes and forms.
These are signatures of high energy particles colliding with the CCD and interacting with the atoms in the thin silicon substrate itself. The high energy particles originate from both cosmic rays emitted by exotic objects such as black holes and supernovae, and from more earthly events like the natural decay of radioactive elements present in the environment near the CCD camera.
The long and short straight tracks are left behind by of muons; the decay products of collisions of cosmic rays with particles in the upper parts of Earth's atmosphere.
Muons travel nearly at the speed of light, usually continuing in the direction of the original cosmic ray, and can penetrate hundreds of metres into the Earth. But muons are very short-lived and only reach all the way to the surface thanks to the effects of Special Relativity. This is because in the Earth's reference frame a muon appears to have a longer half-life due to time dilation, whereas from the muon's perspective it is the Lorentz Contraction which allows it to survive the apparent shortened distance from the upper atmosphere to the ground.
The curved wandering tracks, a.k.a. worms, are caused by recoil electrons from Compton scattering of γ rays in the natural environment.
These γ rays originate from the decay of Potassium-40 to Argon-40 as well as the Uranium and Thorium decay chains.
Astronomical image processing involves performing statistical analysis on large amounts of data, in order to discard anomalous signals such as these and produce a clean and accurate image of the target subject matter. A cleaned version of this nebula can be seen here: NGC 1999 and HH1/HH2 in Orion
Image data:
Date: 19 nights, Nov 2016 - Feb 2017
Exposure: LHaRGB: 1175:692:215:205:195 mins, total 41 hours 22 mins @ -25C
Telescope: Homebuilt 12.5" f/4 Serrurier Truss Newtonian
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from my observatory in Auckland, New Zealand
