Andromeda Galaxy
The Andromeda Galaxy (M31) is the nearest major galaxy to the Milky Way, located about 2.5 million light-years away. It is a spiral galaxy similar in structure to our own.
Source: science.nasa.gov
APODs including "Andromeda Galaxy"
Blue Arcs Toward Andromeda
04/08/2025
What are these gigantic blue arcs near the Andromeda Galaxy (M31)? Discovered in 2022 by amateur astronomers, the faint arcs -- dubbed SDSO 1 -- span nearly the same angular size as M31 itself. At first, their origin was a mystery: are they actually near the Andromeda Galaxy, or alternatively near to our Sun? Now, over 550 hours of combined exposure and a collaboration between amateur and professional astronomers has revealed strong evidence for their true nature: SDSO 1 is not intergalactic, but a new class of planetary nebula within our galaxy. Dubbed a Ghost Planetary Nebula (GPN), SDSO 1 is the first recognized member of a new subclass of faded planetary nebulas, along with seven others also recently identified. Shown in blue are extremely faint oxygen emission from the shock waves, while the surrounding red is a hydrogen-emitting trail that indicates the GPN's age.