APOD: 2025 January 31 - The Variable Nebula NGC 2261

Good Red Friday morning, Rallypoint, and welcome to this edition of Astronomy Picture of the Day (APOD) for January 31, 2025.

You've probably heard of 'variable' stars before...Betelgeuse (in the constellation Orion) and Antares (in the constellation Scorpius) are two of the more familiar names. But a 'variable' nebula? We have one of those today.

First noticed by William Herschel in 1783 as a fan-shaped nebula, this image from the Hubble Space Telescope (HST) resembles a small comet. Astronomer Edwin Hubble began studying NGC 2261 (aka Hubble's Variable Nebula) in 1916. It lies 2,500 light years away in the constellation Monoceros (the Unicorn, between Orion and Canis Major). The star marking the 'coma' of the nebula is R Monoceros. Scientists suspect that clouds of dust periodically block illumination from the star, casting shadows into the surrounding interstellar media.