OUR Milky Way galaxy is going to collide with another galaxy in a few billion years – here’s what you need to know.
In around 4.5 billion years, the Milky Way is predicted to merge with Andromeda – our galaxy’s closest neighbor.
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Andromeda is a barrelled spiral galaxy that is located about 2.5 million light-years away from Earth.
Currently, our neighbor is racing towards the Milky Way at a rate of around 70 miles (113 km) per second.
And a recent 2020 study published in the Astrophysical Journal confirmed that the collision between the two galaxies is already underway.
Using the Hubble Space Telescope, scientists were able to observe the Andromeda galaxy – which like our Milky Way and other galaxies, sits within a large envelope called a galactic halo.
What is a galactic halo?
Basically, halos are an extended, spherical component of a galaxy that goes beyond the main, visible component.
They are made of three distinct components: the stellar halo, the galactic corona (usually made of hot gas, or plasma), and the dark matter halo.
Galactic halos mainly consist of dust, gas, and stars, and are extremely faint.
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However, in the study, astronomers were able to measure the size of Andromeda’s halo and believe that it’s of similar shape and size to our own.
Based on these measurements, it is very likely that Andromeda’s halo and the Milky Way’s halo are touching – meaning, the collision between the two galaxies has already started.
What will the merger look like?
In 2012, Nasa shared artists’ concepts of what someone on Earth might see as the Andromeda galaxy races toward us.
The images (see below) were created using the Hubble Space Telescope’s measurements of the Andromeda galaxy via computer modeling.
In around 2 billion years, the disk of the Andromeda galaxy will look noticeably larger.
Meanwhile, in 3.85 billion years, the sky will show a new star formation.
Four billion years later, Andromeda will appear stretched as the Milky Way becomes warped.
And in 7 billion years, the merged galaxies will have formed a huge elliptical galaxy.
What will happen when the two galaxies merge?
Galaxies collide all across the universe.
In many ways, when a galactic merger occurs, the two galaxies are like two ships passing in the night.
“Stars in a galaxy are spaced so far apart – grains of sand separated by the length of a football field – that the Andromeda stars [will] simply pass by,” Nasa writes.
“But galaxies are more than just stars. They contain giant clouds of gas and dust, and when galaxies collide, these clouds smash into one another.”
“The clouds contain the raw materials needed to make new stars, and it is the collision between clouds that has triggered a starry baby boom!”
That said, the roughly trillion stars in the Andromeda galaxy will throw our 300 billion stars and planets into new orbits around the newly merged center.
What about Earth?
The real threat, however, is our Sun which will eventually become a red giant and consume the Earth.
If our Earth exists five billion years from, it’s unlikely that anything will happen to it during the collision, though it may be in a different orbit.
However, it’s possible that by then humans will be an interplanetary species and not even living on Earth.
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