Image Credit: ESO
RCW 88 is an emission nebula, a star-forming region of about nine light-years across, located some 10,000 light-years away from Earth in our Milky Way galaxy.
This H II region is the birthplace of new stars. Recently formed stars are actually surrounded by a cocoon of red glowing hydrogen gas. The new stars form from clouds of this hydrogen gas as they collapse under their own gravity. Some of the more developed stars, already shining brightly, can even be seen peering through the cloud.
These hot young stars are very energetic and emit large amounts of ultraviolet radiation, which strips the electrons from the hydrogen atoms in the cloud, leaving the positively charged nuclei — protons. As the electrons are recaptured by the protons, they can emit H-alpha light, which has a characteristic red glow.
Observing the sky through an H-alpha filter is the easiest way for astronomers to find these star-forming regions. A dedicated H-alpha filter was one of the four filters used to produce this image.
This image is taken with the EFOSC2 instrument on ESO’s New Technology Telescope, using four different color filters.