Spaghetti Nebula (Simeis 147/Sh2-240)
Astrophotography
The "Spaghetti Nebula", located 3000 light years away, is an expanding debris field of a massive star that underwent a core-collapse explosion approximately 40,000 years ago.The visual "strands" are density enhancements formed where the expanding supernova shockwave encounters inhomogeneities in the surrounding Interstellar Medium. As the shock front sweeps up interstellar gas, it heats and compresses it. The nebula is predominantly visible in the H-alpha (Hα) spectrum (656.3 nm). As the shock-heated gas cools, electrons recombine with protons, cascading down energy levels and emitting photons. The distinct, thread-like appearance suggests an "old" remnant where the shock velocity has slowed sufficiently to allow significant radiative cooling behind the shock front. Angular Extent: It is visually massive. The nebula covers a circular area roughly six times the diameter of the full Moon. At its estimated distance, this translates to a physical diameter of roughly 150 light-years. Despite its immense physical size, Simeis 147 is notoriously difficult to observe visually. The energy of the explosion is spread over a vast volume, making the photon flux per unit area very low. It is generally invisible to the naked eye even in large telescopes, requiring deep-exposure astrophotography with narrowband filters to resolve the contrast between the filaments and the background sky.