ANDROMEDA FACTS

The approximated distance between the Milky Way and Andromeda galaxies is around 2.5 million light-years. In galactic terms, this is quite close but it is getting closer because it is thought that our Milky Way is slowly becoming absorbed by Andromeda.

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While Andromeda is slowly absorbing the Milky Way, it has already consumed several others over its lifetime.

Thanks to its luminous matter (the bits that make it visible), Andromeda can be seen from August to February if you are in the Northern Hemisphere. If you are in the Southern Hemisphere it can be seen on the northern horizon between October and December.

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Andromeda is so bright in the sky, and it is so big, it can be seen with the naked eye – if you know where to look.

The Andromeda galaxy is also referred to as Messier 31, named after the astronomer Charles Messier. The French astronomer catalogued the galaxy, among many other things in the skies over the Northern Hemisphere.

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Charles Messier had been searching for Halley's Comet, but the calculations he had been given for the search were wrong. What he ended up observing was a part of the sky where he eventually found Andromeda.

The constellation, where the galaxy gets its name, was named after the Greek mythical princess Andromeda – wife of Perseus. This constellation was catalogued by Ptolemy, a Greek astronomer, in the 2^nd century.

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It is thought that the galaxy is named for the constellation due to its prominence in the chain of stars around it.

Our very own Milky Way has somewhere between 200 – 400 billion stars within it, but Andromeda has us firmly beat with somewhere in the region of one trillion stars. The Hubble Space Telescope uncovered a rather rare, large and bright cluster of stars that contains a large number of these stars.

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Blue stars are usually young and hot, but the ones found in Andromeda are ageing. The sun-like stars have shed their outer ‘shell’ to expose their core.

Both of the nuclei of Andromeda contain several million stars, which the two are separated by just 5 light-years – give or take. They have names too, with the first nucleus named P1 and the second is P2.

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Some astronomers think P1 and P2 are just one group of stars, and not two, orbiting a supermassive black hole on a tilt.

The Andromeda galaxy once had 9 observed black holes, but in 2013 this number rose to 35. The increase of discovered black holes is the largest find of its kind, outside of the Milky Way.

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Most of the 26 newly discovered black holes have between 5 to 10 times the mass of our Sun.

A globular cluster is a densely packed group of ancient stars, and these clusters can contain millions of stars. It is these globular clusters that can help astronomers determine how old the Universe is. The Milky Way contains 200 clusters (that have been identified so far).

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Because the outermost reaches of Andromeda have not been fully researched, the actual number of globular clusters could much higher – as many as 2,800 if they are similar in size to those in the Milky Way.

The Milky Way and Andromeda galaxies are the two largest galaxies in our local group of galaxies and are the most dominant. The two galaxies are so large that they have their own galaxy satellites. 

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Andromeda has around 12 other galaxies in its orbit, and they contain enough mass to create billions of stars.

The estimated mass of the Andromeda galaxy is 1 trillion solar masses. What does this mean? Andromeda has the combined mass of our Sun times by 1 trillion. Black holes may something to do with this as they individually can have a mass 10s of times that of our Sun.

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Despite being much larger than the Milky Way, the Virial mass of Andromeda is approximately the same.