Credit: KPNO/NOIRLab/NSF/AURA/Carole Westphal/Adam Block

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 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. This image was taken as part of Advanced Observing Program (AOP) program at Kitt Peak Visitor Center during 2014.

Provider: NOIRLab

Image Source: https://noirlab.edu/public/images/noao-n2261westphal/

Curator: NSF's NOIRLab, Tucson, AZ, USA

Image Use Policy: Creative Commons Attribution 4.0 International License