1 December 2020
The imposing Andromeda Galaxy (M31) is the largest galaxy of the Local Group of Galaxies, to which our galaxy, the Milky Way also belongs. Together with the smaller Triangle Galaxy (M33), that spiral galaxies dominate the group, which contains more than thirty minor galaxies. Andromeda is believed to be slightly larger than the Milky Way, having 140 000 in diameter. Very close can be seen two satellite galaxies, M32 at the left of the center and M110 just below.
M31 is maybe the most studied galaxy besides the Milky Way. In 1920, Edwin Hubble was able to estimate its distance using Cepheid Variable Stars, demonstrating that it was indeed an extragalactic object, far away from the Milky Way.
Recent studies of the halo (envelope of gas surrounding the galaxy) of the Andromeda Galaxy shows that it extends as far as 1.3 million light-years from the galaxy, meaning that halos of Andromeda and the Milky Way are already interacting. This halo is a reservoir of gas for future stellar formation within the galaxy.
Taken from the Observatorio del Teide, Tenerife by Jorge A. Pérez Prieto and Pedro A. González Morales. Instrument: 10cm refractor and Canon 6D full spectrum. Exposure: 44 x 5min (3h40m).