The Shattered Remains of a Star
Sh2-240 is a supernova remnant that exploded approximately 40,000 years ago. What remains is a rapidly expanding shell of gas that has been shredded into incredibly fine, long filaments by its interaction with the interstellar medium. At the heart of this chaotic web lies a rapidly spinning neutron star—a pulsar (PSR J0538+2817)—which is all that is left of the original star's core. The nebula is so faint that it was not discovered until 1952 using a 25-inch telescope in Crimea.
Imaging Challenges
- • Extreme Faintness: This is one of the dimmest targets in the Sharpless catalog. You will need very long total integration time to rise above the sensor noise.
- • Processing Noise: Because you have to stretch the data so hard to see the filaments, managing grain and noise without blurring the fine 'threads' is a delicate balance.
- • Framing: Even with a wide-field scope, Sh2-240 is huge. You must center it perfectly, or consider a 2-panel mosaic to capture the faint outer reaches.
The shell of Sh2-240 is still expanding at a rate of nearly 1,000 kilometers per second.