Did you know that it is possible to see other galaxies in this universe?
Considering the vastness of the universe, we can easily give a call that Andromeda Galaxy lies in the neighborhoods of the Milky Way.
But, then there are many more galaxies in between then why Andromeda is so important to us!
For Milky Way, Andromeda is the closest spiral galaxy – only 2.5 million light years away from us! Astonishingly, Andromeda is even bigger than our own Milky Way in this universe!
Do you know that the universe that we can see is much larger than we can think of by any estimates? By a rough estimate, the universe is made of over 2,000 billion galaxies. Many of them are tens and hundreds and thousands of million light-years away from the Milky Way!
Our ordinary telescopes cannot view such distant galaxies in this cosmos and for that purpose extremely powerful telescope such as Hubble Space is doing its job in outer space to snap much sharper images of the celestial objects that include galaxies. And, images received from Hubble Space Telescope reveal that the universe is extremely vast than anticipated earlier, only a few decades back!
In this vastness of the universe, the Andromeda galaxy is truly our neighbor by any standards. Andromeda is so vast that light takes almost 200,000 years to map it from one end to the other end of the galaxy and surprisingly, we can see or image the entire galaxy as one complete celestial object!
Andromeda also called M31 in the scientific language falls under a local group of galaxies that also include our Milky Way and around 50 other galaxies in our neighborhoods. Almost 1,000 billion stars constitute Andromeda galaxy, which is two times higher than the numbers of stars believed to be in Milky Way!
Andromeda Galaxy possesses two spiral arms and at least 450 globular clusters orbit around the galaxy. Many of them are said to be the most densely populated clusters.
But, what is so special about spiral galaxies?
A bulge at the center with a flattened disk and spiral arms are the main features of spiral galaxies. Bulge is made of redder and older stars. While yellow stars such as our Sun can be seen across disk and arms. The entire disk rotates like a whirlpool or a hurricane!
In contrast, Elliptical galaxy does not have any disk or arms. An oval-shaped or ball-kind appearance is the cornerstone of elliptical galaxy and stars do not revolve around any center!
You may be surprised to know that in a pitch dark sky we can see Andromeda even by our naked eyes! But it appears so faint that we need special efforts if we want to view it by naked eyes!
That is why a clear sky – free of air and light pollution with extreme dark– is necessary when you attempt to find Andromeda through naked eyes. Always remember that Andromeda is at least 6-7 times as large as the full moon that we see regularly.
But the question remains which part of the sky to search for to see Andromeda?
For this, you have to locate a huge W like figure in Cassiopeia constellation in the sky!
Draw an imaginary line between the lowest point in W and the left lower corner of the famous square of Pegasus. You will find Andromeda in and around the top one-third portion of this imaginary line. Firstly, try to locate it through binoculars and then use 4″ or 6″ telescope to see a sharper version of it.
You can then clearly view the spherical structure of Andromeda!
Ideally, you should not use a telescope with aperture size more than 4-6 inch as it will restrict your field of view.
In the center of Andromeda, you will find a concentrated pouch of matter with arms stretched in spirals full of stars, gas, and dust.
Can you guess how many stars constitute Andromeda Galaxy, roughly?
Overall, Andromeda is said to have contained over a billion stars that counts almost four times as much as found in the Milky Way.
Yet you will be surprised to know that our Milky Way is more massive than Andromeda?
How can it be so?
That is because Milky Way contains much more Dark Matter than that is contained in Andromeda!
But, by the way, do you know anything about the Dark Matter?
Dark Matter and Dark Energy are two mystical substances found in this cosmos, and they are invisible by any means, tools, equipment or sensors available at our disposal so far!
You may be surprised to know that all visible matter including all stars, nebulas, planets, etc. constitute only 5% of the total matter; remaining all is either Dark Matter or Dark Energy!!
The scientists define Dark Matter as a dense cloud of Weakly Interacting Massive Particles (WIMPS). While they do not interact with normal matter, they exert a gravitational force and are the source of gamma rays radiation in our universe.
Scientists have noticed the strong signals of gamma-rays emitting from the center of Andromeda. Similar signals come from the innermost regions of the Milky Way too. These signals provide a clue to the presence of Dark Matter in these galaxies.
Due to the presence of Dark Matter, Andromeda and Milky Way are moving closer and closer.
Images from Hubble Telescope reveal that Andromeda is moving toward the Milky Way at the speed of about 6000 kilometers per minute.
Astrophysicists estimate that these two galaxies will merge in 4.0 to 4.5 billion years from now.
Dark Energy is the antigravity force evenly distributed throughout the universe causing faraway galaxies to move apart on a continued basis.
Unlike Dark Energy, Dark Matter is not evenly spread throughout the galaxy or universe, but it is believed to have accumulated in the centers of the galaxies whether Andromeda or Milky Way.
That is why powerful gamma-ray signals continue to emit from the center of Andromeda and Milky Way all times!
The merger of Andromeda with Milky Way will not occur at once but will take at least 2 billion years before both the galaxies merge completely!
No surprise that during the time of merging our Sun will get displaced from its current location keeping all its planets intact!
It is a different thing that by that time our Earth might not remain habitable for several other reasons!