When Galaxies Collide

The Andromeda Galaxy is heading for us, and will collide with the Milky Way galaxy to create a much larger galaxy called Milkdromeda. Andromeda is larger than our galaxy at 152,000 light years across. Compared to the Milky Way at around 100,000 light years in diameter. It’s a barred spiral galaxy that has an estimated mass of 1 trillion suns. It is heading toward us at 70 miles per second.

Andromeda Courtesy: Peter Forister

It can be seen with the naked eye on a clear night. It’s best viewed in October in the northern hemisphere when it will be high overhead on a dark night. It looks like a large fuzzy star. It is the most distant object you can see with the naked eye and it’s only going to get larger in the sky. The best way to find Andromeda or any other celestial body is to use an app of course. I use Sky map on my android devices. SkyView is a decent alternative on your Apple device.

Galaxy Collisions

The image below was taken by the Gemini North Telescope in Hawaii. It’s of the two galaxies, NGC 4568 and NGC 4567. They are in the process of colliding with each other to form one galaxy. It’s an ominous picture of what is to be the fate of our galaxy one day. Luckily, galaxies are made up of mostly empty space so the number of stars colliding with each other will be minimal. However it wont be uncommon for planets to change orbits or to be hurled from their host stars when other stars come near them.

Galactic Collison of NGC 4568 and NGC 4567


As Andromeda approaches our galaxy, the two will pass by each other several times. Like a final dance of sorts before they become one galaxy. The supermassive blackholes of each galaxy will eventually merge into one. The resulting galaxy, “Milkdromeda” will be an elliptical galaxy. We are apart of a cluster of galaxies known as the Virgo Supercluster. This is our local group. It is thought that in over 100 billion years, Milkdromeda will collide with other surrounding galaxies to form a massive super galaxy. It will be a sight to see if anyone is still around to see it.

Don’t Hold your breathe

Even at 70 miles per second, it will take approximately 5 billion years for Andromeda to reach us. At around the same time our sun is expected to start running out of fuel and will start expanding into a red giant. It will grow so large that it will most probably envelop the earth. Scorching everything on the surface subsequently rendering it uninhabitable. By then we will have hopefully found a new home elsewhere in the stars. Andromeda will however, continue to become larger and larger in the sky. It should make for a gorgeous view 1 billion years from now.

Studying Messier 31

Also known as Messier 31, Andromeda is close enough that the new JWST can see it’s individual stars and study them. There are approximately 229 Red Giant stars within Andromedas spiral arms. Star formation is crucial in galaxy building, with Andromeda being so similar to the Milky Way galaxy, it will help us better understand how our galaxy was formed. Studying Red Giants, which are older stars, allows us to know their true age. Using spectroscopy, scientists are able to split the light of the star up into bands, this reveals the elements present in the star.

The first generation of stars only burned hydrogen and helium. Over time stars started producing heavier elements. So knowing this they are able to know the true age of stars. I discuss this in more depth my star stuff article.

Spectroscopy is used a ton in astronomy now. Scientists can tell the chemical makeup of some exoplanets also, by viewing the atmosphere as the planet transits its host star. This topic is discussed in more depth on my exoplanet post. It’s a good read if you’ve got a minute.

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