Picture of the month

This image shows a nebula named after Edwin Hubble, recorded by the observatory that bears his name. Hubble’s Variable Nebula was discovered more than 200 years ago and later studied in detail by Hubble in the 20th century. This object is peculiar because its appearance is known to change within a matter of weeks. This so-called reflection nebula consists of gas and fine dust fanning out from the star R Monocerotis. The faint nebula is about one light-year across and lies about 2500 light-years away towards the Unicorn constellation. One of the explanations for the fast variability of such a large object is that dense clouds of opaque dust move around the star, which is seen in the top left of the image. As the clouds move between the star and the nebula they cast shadows on the reflective gasses, causing different parts of the nebula to light up at different times.

About the author

Compiled by Merlin Kole, Department of Particle Physics, University of Geneva.