Fasten Your Seat Belts! The Milky Way Is About To Collide With Another Galaxy!

Smart folks from over at the Space Telescope Science Institute (STScI) in Baltimore have some disturbing piece of information coming your way. According to a document released by NASA, our Galaxy, the Milky Way is on a collision course with another Galaxy – our giant neighbor, the Andromeda Galaxy. Also known as M31, the Andromeda Galaxy is bigger than our own Galaxy – which itself is among the bigger galaxies we know of. What is even more worrisome is the fact that this titanic collision is now expected to happen much earlier than what astronomers had predicted in their previous studies. Also joining the collision party would be hitherto unexpected guest, a small irregular Galaxy known as the Triangulum (M33).

Needless to say, this massive collision would ensure that all the galaxies involved in it would receive a complete makeover. It is predicted that our solar system, including the Sun, all its planets, asteroids and comets would be yanked away to a new region of our Galaxy. Currently, our solar system is located about 27,000 light years from the center of our the Milky Way. It is likely that we would be flung to an even more distant corner of the new galaxy that would form after this extreme makeover.

“After nearly a century of speculation about the future destiny of Andromeda and our Milky Way, we at last have a clear picture of how events will unfold over the coming billions of years,” says Sangmo Tony Sohn of the Space Telescope Science Institute (STScI) in Baltimore.

“Our findings are statistically consistent with a head-on collision between the Andromeda galaxy and our Milky Way galaxy,” added Roeland van der Marel of the STScI.

The question now is, do we need to worry about this and start making preparations for the inevitable? The answer is a resounding no. Here’s are reasons why you do not need to worry about the collision between the Milky Way and the Andromeda Galaxy – articulated in a QnA format.

1. Why are the two Galaxies colliding? Aren’t they happier staying apart?

The collision is inevitable even if both these giant galaxies prefer their individuality. This is because the sheer size of the two galaxies results in a strong gravitational pull between each other that has resulted in the two “falling” in to each other.

2. How do we know these two galaxies would collide?

Scientists and astronomers from NASA and other global agencies have painstakingly studied the measurements of the motion of the Andromeda Galaxy for years now. NASA’s Hubble Space Telescope played an important role in this study with accurate measurements of the movement. Over the years, they have deduced that the Andromeda is “falling” on to the Milky Way and that a collision is inevitable.

3. How fast is the Andromeda Galaxy “falling” towards the Milky Way and how far is it from us?

Current estimates show that the Andromeda Galaxy is a cool 2.5 million light years away from us. That is a crazy distance. A beam of light that set off from the Andromeda Galaxy would take 2.5 million years to reach us. This in spite of the fact that light beams travel 186,000 miles a second. This also means that the image you see of the Andromeda Galaxy is how it looked 2.5 million years ago! But then, the Andromeda Galaxy is also falling towards us at an amazing speed. Current estimates say that it is traveling toward the Milky Way at about 250,000 miles per hour. Fast enough to travel from here to the moon in one hour.

This illustration shows the collision paths of our Milky Way galaxy and the Andromeda galaxy. The galaxies are moving toward each other under the inexorable pull of gravity between them. Also shown is a smaller galaxy, Triangulum, which may be part of the smashup.

4. OK. We’re doomed then. How catastrophic would the collision be? Will stars and objects within the two galaxies collide with each other?

The collision would be an awe inspiring scene for a person who is watching it all unfold from a different Galaxy, far far away from us. For most objects inside the two galaxies however, it would be life as usual. Here’s why. The Milky Way is estimated to contain around 300 billion stars and the Andromeda, about 1 trillion. Even though those are some amazing numbers, most of the area in the two galaxies is vast, empty space. Even with the huge number of objects these two galaxies together hold, it is unlikely that any of them would collide with each other because there is enough empty space for all of them to “pass through.” Scientist Gurtina Besla of Columbia University in New York, NY explains,

“In the worst-case-scenario simulation, M31 slams into the Milky Way head-on and the stars are all scattered into different orbits. The stellar populations of both galaxies are jostled, and the Milky Way loses its flattened pancake shape with most of the stars on nearly circular orbits. The galaxies’ cores merge, and the stars settle into randomized orbits to create an elliptical-shaped galaxy.”

5. When is this happening? What precautions do I take?

No precautions are needed. Make sure you live your life on this planet properly. This is because it is unlikely that anyone of us – or even the human species on the whole would be around to see this collision. Newer estimates say that it would take Andromeda a further 4 billion years before it strikes the Milky Way. To put things into perspective, the earth itself is only about 4.5 billion years old – same is the case with the sun. The sun is expected to last another 4.5 billion years before its hydrogen reserves run out and it turns into a red giant, probably consuming the earth. If humans do survive for that long, rest assured, we would be on another planet. Still, it is quite likely that we as a species would have ceased to exist by the time this collision initiates.

This series of photo illustrations shows the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy.
First Row, Left: Present day.
First Row, Right: In 2 billion years the disk of the approaching Andromeda galaxy is noticeably larger.
Second Row, Left: In 3.75 billion years Andromeda fills the field of view.
Second Row, Right: In 3.85 billion years the sky is ablaze with new star formation.
Third Row, Left: In 3.9 billion years, star formation continues.
Third Row, Right: In 4 billion years Andromeda is tidally stretched and the Milky Way becomes warped.
Fourth Row, Left: In 5.1 billion years the cores of the Milky Way and Andromeda appear as a pair of bright lobes.
Fourth Row, Right: In 7 billion years the merged galaxies form a huge elliptical galaxy, its bright core dominating the nighttime sky.

6. Damn. Anyway, what happens after the collision?

Before we talk about the after effects of the collision, we should add that the collision itself would last around four billion years! It would take another two billion years for the entire sequence to be completed. At the end of it, the Milky Way and the Andromeda Galaxy – both spiral shaped galaxies — would merge to form a massive elliptical galaxy. There would be a new galactic center as well. There is still no clarity as to how the inclusion of the Triangulum galaxy (M33) would affect the collision. It is generally thought that the M33 is too small to cause any significant impact. It is also likely that the M33 would collide with the Milky Way before Andromeda collides with our galaxy.

Here is a video that shows the entire timescale of the collision and how it would look to an observer from a vantage point. This is of course if the observer has a 7 plus billion year life span! The first frame is the present day; the last frame is 7 billion years from now.

Once again, the huge time scale involved in this huge inter galactic phenomenon yanks us back to reality and once again reminds us how insignificant we all are in the grand scheme of things.

Do you wish to be around when this collision between the Milky Way and the Andromeda Galaxy unfolds?

[Images via NASA]

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