The “Andromeda Galaxy” is the closest cluster of constellations near the “Milky Way” and can be seen with clear eyes in the sky. This galaxy is also named “M 31” or “NGC 224”.

The first description of the “Andromeda Galaxy” was given by the astronomer from the Persian origin “Rahman al-Sufi” and he has described the details of the tuft of stars in his textbook “The book of fixed stars”. From the ancient period, the “Andromeda Galaxy” has been described as the “Small cloud” or the “Nebulous Smear”. Different astronomers have described the shape and size of the “Andromeda Galaxy” based on the view from telescopes. The “Andromeda Galaxy” is the nearest large constellation of the “Milky Way”. Roughly almost 10 billion years ago it was formed from the clash of the space bodies or the collaboration of the relatively smaller “Protogalaxies”. The “Andromeda Galaxy” is also known as the “Messier 31” or “NGC 224”.  


The estimated mass of “Andromeda Galaxy”

Before the year 2018, the halo of the “Andromeda Galaxy” including the “dark matters” was about 1.5810^12 solar mass where the mass of the “milky way” is approximately 8*10^11 solar mass. Various contradictions were there about the measurement of the actual mass of the “Andromeda Galaxy”, and in 2018, it has been established that the mass of the “Andromeda Galaxy” is about 8*10^11 solar mass which is equal to the “milky way”. Other than that the “Interstellar medium” of the galaxy has been estimated to contain a solar mass of about 7.2*10^9. The massive cluster of heated gas is surrounding the galaxy and that is almost covering the half mass of the stars that belong amidst the “Andromeda Galaxy”. The halo of the gaseous medium consists of specific elements that are heavier than helium and hydrogen gas. The compact mass of gases that are surrounding the cluster of stars is formed from the “Supernovae”.

Naming and meaning of the name 

According to Greek mythology, the name of this galaxy has been originated from the name of the daughter of the ruler of “Aethiopia”, “Cepheus” and his better half“Cassiopeia”. “Cassiopeia” perceived herself to be pretty than “Nereus’s” daughters and this made “Poseidon” angry who was the god of the sea. In order to punish the mother, “Andromeda” was chained to the rock to sacrifice to a monster of the sea, “Cetus”. Later she was saved by “Perseus” and was proposed to be his wife.

The name “Andromeda” has been generated from the Greek name “Andromede” which means the “Ruler of Men”.

Major stars in “Andromeda Galaxy”

  • “Alpheratz-⍺ Andromedae”- this is considered to be the brightest star of the “Andromeda Galaxy”.  The other name of “Alpheratz” is “Sirrah”. This star is discovered almost 97 light-years away from the Earth.
  • “Mirach-β Andromedae”- this star almost holds the similar magnitude as the “Alpheratz” and can be categorised as a “Semi-regular variable”.This star is bright and cool and brighter than the Sun almost 1900 times. “Mirach” is almost 3 to 4 times bigger than our own Sun. The distance of “Mirach” from the Sun is almost 200 light-years. 
  • “Almach-γ Andromedae”- this can be considered to be the 3rd brightest star in the cluster. The name “Almach” is derived from the Arabic name “Al-anaq-al-ard” which signified the meaning of “The desert lynx”.
  • “ẟ Andromedae”- this is a conjoined or double star of which the approx magnitude is 3.28. From the solar system, it is about 101 light-years in length. This is considered to be a “K-type” giant star.

Structure of “Andromeda Galaxy”

According to the visualisation in the “Spitzer Space Telescope” Andromeda can be called a “Barred Spiral galaxy” similar to the “Milky Way”. From the “Disc major axis” the “bar major axis” of Andromeda” is at 55° orientation in an anti-clockwise way. According to the vision of the “Keck telescopes”, numerous stars are sprinkled outwards from the cloud-like galaxy.

The nucleus of “Andromeda Galaxy”

The compact, dense and heavy clusters of stars are situated in the centre of the “Andromeda Galaxy”.  The “Hubble Space Telescopes” was used in the year 1991 to watch the centre of the nucleus of the “Andromeda Galaxy”. It has been thought the “black hole” is situated at the very centre of the galaxy and the measurement of the mass is 3-5*10^7 solar mass.

Collision with the “milky way”

It has been seen that the “Andromeda Galaxy” is coming towards the “Milky way” with a speed of 110 kilometres/ second. A possibility is there that after the collision the galaxies can combine into a massive “Elliptical galaxy”. The fate of the whole solar system along with our own planet earth still cannot be assessed by scientists.


From the above discussion, it can be concluded that the “Andromeda Galaxy” is the nearest galaxy to our “Milky way”. Scientists consider the other names of the “Andromeda Galaxy” as “M 31” and “NGC 224”. The name of “Andromeda Galaxy” has been derived from the character of the daughter of “Cassiopeia” and “Cepheus”. The cluster of constellations consists of different large and small stars of which the most important stars are “Almach-γ Andromedae”, “Alpheratz-⍺ Andromedae”, “ẟ Andromedae” and “Mirach-β Andromedae”. The nucleus of the “Andromeda Galaxy” is made up of a thick collection of stars and often can be considered as the “Blackhole”.


Frequently asked questions

Get answers to the most common queries related to the SSC Examination Preparation.

What is the nearest galaxy to the “Andromeda Galaxy”?

Ans. The nearest galaxy of “Andromeda Galaxy” is the “Milky way”.

What are the other names of the “Andromeda Galaxy”?

Ans. The other names of the “Andromeda Galaxy” are “NGC 224” and “M 31” or “Messier 31”.

What are the most important stars in the “Andromeda Galaxy”?

Ans. The names of the important stars are “Almach-γ Andromedae”, “Alpheratz-α Andromedae”, “ẟ Andromedae” and “Mirach-β Andromed...Read full

What is the structure of “Andromeda Galaxy”?

Ans. The structure of “Andromeda Galaxy” can be considered as a “Barred Spiral galaxy”.