What is the Andromeda Galaxy?

A 3D rendering of the Andromeda Galaxy.

If you happen to get a clear night and the sky is dark enough from where you’re located, you just might be able to see the Andromeda galaxy with your own two eyes. If the conditions align, you won’t need a telescope either. ‘Parked’ right next to the galaxy we live in, the Milky Way, Andromeda is the farthest object that can be observed from Earth with a naked eye.

Being a spiral galaxy, and one so close to our little blue planet at 2.5 million light-years (which is really close in space distances), it’s a fascinating research point for scientists who are eager to learn more about other spiral galaxies that might not be so easy to observe. Oh, and it’s on a collision course with our Milky Way, but we’ll get to that in a bit.

Why the Name Andromeda?

What appears to us as a blurry speckle of clustered stars was named after the Andromeda constellation where it is actually located. The name itself comes from the Greek Mythology according to which Andromeda was the daughter of Cassiopeia who boasted that her daughter was more beautiful than the Poseidon’s sea nymphs themselves. The Poseidon did not appreciate the comparison and decided to punish Andromeda - he had her chained to a rock and offering her to the sea monster but Perseus saves her from certain death.

And indeed, the galaxy is extraordinarily beautiful with an enormous halo that surrounds it. Although Andromeda contains substantially more stars than our own galaxy, the Milky Way is presumed to contain more dark matter which makes it heftier.

From Persians to the Hubble

The first ever record of Andromeda can be tracked all the way back to the Persians. In 964, in his ‘’Book of Fixed Stars’’ and astronomer Abd al-Rahman al-Sufi made the reference to a ‘’little cloud’’.

Almost 900 years later, in 1764, what we now know as Andromeda was then wrongly classed as a nebula and was given a designation of M31. The finding was attributed to Simon Marius who was the first man to observe it via telescope. In 1887, Issac Roberts took the very first photographs of Andromeda.

Some 30 years later, when the Milky Way was thought to encompass our entire universe, Harlow Shapley and Heber Curtis, American astronomers discussed the nebulae that were observed within the galaxy. However, Curtis asserted that Andromeda is not actually a nebula but a galaxy unrelated to our own.

The assertion was not taken as fact and the debate went on until Edwin Hubble found evidence of a star called Cepheid variable within the Andromeda. Since the star’s features allowed it to be used in calculating space distances, Hubble concluded that Andromeda cannot be located inside the Milky Way as it is too far away, therefore it is its own galaxy.

However, not long after, it was revealed that the distance from the Milky Way to the Andromeda galaxy is even larger than previously thought.

An Impending Crash?

The Milky Way once had an enormous sister galaxy that Andromeda engulfed at one point, billions of years ago. Will the Milky Way face the same fate?

In about 4 billion years, the two neighboring galaxies will be colliding and changing their respective structures for all future time. The merger of the Milky Way and Andromeda will take another 2 billion years, but by the time that happens all the planets inside them will be consumed by the Sun. The consequences of the collision would make the sun grown into an even bigger star, a red giant, and the planets will just be gone under the expansion.

A new galaxy will be born out of the monstrously huge collision and the stardust inflow is expected to encourage the formation of new stars, potentially expelling our current sun from its home.

This wouldn’t be the first time that either of the galaxies has collided with others before, and Andromeda actually has a rather interesting reminder of the crash. It is presumed that the massive dust ring inside the galaxy is a remnant from the collision.

How to See Andromeda

Although, it can be seen without a telescope or binoculars, having access to any will help to appreciate this massive spiral galaxy.

When using the telescope, it is clear that the Andromeda is more than six times the width of our full Moon.

Andromeda is easily seen from mid to northern latitudes during the entire year for at least a part of the night. During autumn, it is most visible until dawn, starting when the night sets, as Andromeda sits high in the sky.

It is possible that you end up catching it in your eyeline, if you get away from the city bustle in late summer, autumn or winter - just look for a blurry spot in the sky.

Recent Discoveries

With the advancement in technology up until today, it doesn’t come as a surprise that we have learned so much more about Andromeda than we ever thought possible.

We now know that the size of Andromeda’s halo is substantially larger than we were previously able to measure. It was even speculated that both Andromeda and the Milky Way both have a halo and that they’re already beginning their merger.

The Hubble Space Telescope was used in 2015 to produce the most accurate photo of the spiral galaxy than ever before. Comprised of over 7,398 exposures, the final image unveiled hundreds of millions of stars along with other attributes and formations. The data is used to not only learn about Andromeda but to also extrapolate about other galaxies that aren’t able to be seen from our planet.

There are many more discoveries made about Andromeda galaxy, including a couple of supermassive black holes orbiting one another, 26 black hole candidates and a fast spinning dead star - a pulsar. In 2017 we gamma-ray radiation has also been detected which would indicate the existence of dark matter.


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