Persian astronomer abed al-Rahman al-Sufi is 900s studied Andromeda galaxy and mentioned it in his book as a “small cloud”. Simon Marius in 1612 gives a description of the Andromeda Galaxy object based on telescopic observation. In 1800s Andromeda galaxy was still thought to be a nebula and called as an “Andromeda Nebula”. Isaac Roberts took this first photograph of the Andromeda galaxy in 1887. At that time Andromeda Galaxy was still believed as a nebula within our own galaxy. Heber Curtis observed a nova within M31 in 1917. After that more than 11 nova were observed. In early 1900s, Ernst Öpik presented a very simple method to estimate the distance of M31. The result of the method suggested by Ernst Öpik proved that the Andromeda Nebula lies far outside our Galaxy at a distance of about 1,500,000 light years. Later on the observations of Edwin Hubble proved that Andromeda Nebula is actually a Galaxy.
Credit: Adam Evans
Before Edwin Hubble’s observations, the distance of stars was measured in thousands of light years, but after observation of Edwin Hubble, the universe became much bigger place and the figure thousand was replaced with million. M31 is an important galaxy, because it is the closest spiral galaxy; although not the nearest galaxy.
The Andromeda Galaxy is a beautiful spiral galaxy with two spiral arms that glows with massive newly born stars. The Andromeda Galaxy is very much like our galactic home (The Milky Way Galaxy). The Andromeda Galaxy is about 220,000 light years wide and it contains about trillion stars that makes it larger and bigger than our Galaxy. The Andromeda Galaxy is twice the size of our galaxy. Light that received Hubble telescope left the Andromeda galaxy far before than human exist on earth. During the travel of this light coming from the Andromeda Galaxy towards the earth, we came into being and after thousands of years we made telescopes and caught the light when it finally reached our home planet Earth.
At the Andromeda’s core we can see a black hole with one hundred million solar mass. The sharpest ever made a picture of the core of an external galaxy is the Andromeda’s core. There is a blue glow at the center of the Andromeda galaxy, which appears to be double nucleus. The origin of this blue light surrounding the super massive black hole has been revealed by astronomers using the Hubble Space Telescope. New spectroscopic observations have revealed that blue light consists of more than 400 stars. These stars are tightly packed in a disc which is only one light year across. This disc is nested inside in elliptical, older, cooler and redder stars. This gives the illusion of second nucleus.
The Andromeda Galaxy is very much like our Galaxy Milky Way, full of stars, Nebulae, lots of dust and faintly glowing gas. This gas and dust hide much of the center of galaxy from us. To see through this disk of dust and gas we need to use eyes that are very different from those of human beings and that is infrared. NASA’s spritzer telescope is specially built for this purpose. It blocks the visible light and looks deeper in the Galaxy. Roughly 3 billion years from now the Andromeda Galaxy will ultimately collide with the Milky Way. This will result in forming more massive galaxy. Black holes in the centers of both of Galaxies possibly will join forming more massive one. On earth from some 3 billion years now, our night sky will be filled with stars and all of them will be heading towards us. That will be the collision of two galaxies and the formation of new Milky Way.