|Hubble's Variable Nebula NGC 2261||Gregg1956||4/11/12 12:29 PM|
Comet!? No- this object was put into the correct category as a diffuse nebula. The bright star at the tip of the cloud of gas is called R Monocerotis. It is a variable star that is actually in the background of the this cloud of gas. The gas cloud is around 1 light year in extent and due to the variability of R Mon- the entire nebula changes in its brightness. However, R Mon is mysterious because the mechanism of its variations is uncertain. The most accepted explanation is that there exist clouds of gas and dust very close to R Mon; and these clouds eclipse R Mon (as they orbit about it) casting shadows onto the foreground nebula.
Optics Info & more at above link.
Astrophotography by Adam Block in the kmz.
Image Credit: Carole Westphal/Adam Block/NOAO/ AURA/NSF