The Andromeda galaxy is our closest neighbour located at a distance of 2.5 million light-years from our own Milky Way galaxy. Andromeda galaxy is a spiral galaxy and the largest galaxy in the galaxy cluster known as the Local Group. The Local Group cluster contains 54 galaxies including Milky Way and Triangulum. The Andromeda galaxy can be seen with the naked eye from Earth from August to February, and in the Southern Hemisphere can be seen low on the northern horizon from October to December. Continue reading to know 10 Fascinating Facts About our interesting neighbour Andromeda Galaxy.
1.It Is Larger Than The Milky Way:
The Andromeda Galaxy is the largest member of the Local Group in terms of extension. While the Milky Way measures about 100,000 light-years or 30 kiloparsecs across, the Andromeda Galaxy has a diameter of about 220,000 light-years. The galaxy is 2.5 million light-years away from Earth and could’ve appeared larger than the Moon if it were brighter. While the Moon is only 384,400 kilometres away. Although it is difficult to estimate the exact mass of any of these galaxies, it is estimated that the Andromeda has a mass of 400 billion solar masses. In the past, Andromeda Galaxy was suggested to be more massive than the Milky Way, recent studies suggest that the Milky Way has the most mass because of more dark matter in it.
2. Andromeda Has A Double Nucleus:
The Andromeda galaxy contains a double nucleus. M31 is known to harbour a dense and compact star cluster at its heart. The first nucleus is known as P1 and the second is known as the P2 separated by about five light-years and both of them contains a few million densely packed stars. While P1 is the brighter concentration offset from the centre of the galaxy, P2 is the dimmer concentration containing a black hole at the true centre of the galaxy and also a compact disk of hot, spectral-class A stars.
3. Named After The Andromeda Constellation:
Persian astronomer Abd al-Rahman al-Sufi was the first to describe the Andromeda Galaxy around the year of 964. The Andromeda galaxy is also identified as Messier 31 or M31, named after the French astronomer who catalogued the large galaxy, Charles Messier. But it was named Andromeda as it appears in the area of Andromeda constellation. The constellation, however, was named after mythical Greek princess. The constellation Andromeda can be seen between Cassiopeia’s “W” asterism and the Great Square of Pegasus in the northern night sky.
4. Globular clusters:
The Andromeda Galaxy has roughly 460 globular clusters orbiting in and around it. Some of these globular clusters are among the most densely populated globulars ever seen. The most massive of these clusters, identified as Mayall II containing several million stars. This globular is about twice the size of Omega Centauri which is the brightest known globular cluster in the Milky Way. The Andromeda Galaxy’s globular clusters have a much diverse range of ages, some of them being as old as the galaxy itself.
5. It Has Many Blackholes:
Not only the Andromeda Galaxy has a supermassive black hole with a mass of 100 million Suns at its centre but also likely two other black holes orbiting as a binary that has a mass around 140 million times of our Sun. The black hole at its centre has a large central bulge much bigger than the one at the core of our own galaxy which allows it to form more black holes. In 2013, scientists recorded 35 black holes in the galaxy and two more were added in 2017. And most of these black holes have a mass of 5-10 times greater than the mass of our Sun.
6. The Bully:
The Andromeda Galaxy has satellite galaxies, consisting of 14 known dwarf galaxies and among them, M32 and M110 are the most well-known galaxies. The Andromeda galaxy is known as the galactic bully because it often encounters with its satellites and M32 and M110 are the worst sufferers of those encounters. Andromeda once ripped off a stream of stars away from M110 and also a large chunk of M32’s stellar disk. The Andromeda Galaxy has at least two spiral arms, plus a ring of dust that may have come from the smaller galaxy M32. Those spiral arms are also being distorted by gravitational interactions with two companion galaxies, M32 and M110. It is suggested that M32 may once have been a larger galaxy and had a close encounter with the Andromeda Galaxy.
7. One Trillion Stars:
The Andromeda Galaxy is estimated to have one trillion stars or roughly twice the number estimated for the Milky Way. Our own Milky Way galaxy has anywhere from 100 billion to 400 billion stars. A large and rare population of hot, bright stars were uncovered as a part of those one trillion by the Hubble Space Telescope.
8. It’s Magnitude:
The Andromeda Galaxy has an apparent magnitude of 3.4 which is among the brightest of the Messier objects. As a result, when viewed from areas with even moderate light pollution on dark nights it may appear more than six times wider than the Moon through a large telescope. It can also be seen with the naked eye from Earth but only the brighter central region will be visible.
9. Thought To Be A Nebula At First:
Astronomer Abd al-Rahman al-Sufi who first described the Andromeda Galaxy referred to it as a “nebulous smear” in his Book of Fixed Stars. Nebulas are massive clouds of gas, dust, hydrogen, helium, and plasma. This is where stars are born. Before astronomer Edwin Hubble announced that Andromeda was actually a galaxy, it was thought to be a spiral nebula.
10. It Will Clash With The Milky Way:
The Andromeda Galaxy is believed to have been formed about 10 billion years ago. It was born through the collision and subsequent merger of smaller protogalaxies. For now, the Andromeda Galaxy is progressing towards the Milky Way at about 110 kilometres per second. It is expected to collide directly with the Milky Way in roughly 4 billion years resulting in a formation of a giant elliptical galaxy. The collision could also form a large disc galaxy. There is another possibility that before the collision, the Solar System could be ejected from the Milky Way or join the Andromeda Galaxy.
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