6 Jan 2019

Our closest friend "The Andromeda "


Andromeda galaxy

At night when we look at sky we see the real beauty with trillions of stars, constellations, galaxies, shooting stars, planets. If we talk about galaxies, then milky-way is our native Galaxy and our neighbour and closest Galaxy is Andromeda. It is really bigger and larger than our milky way. It is really interesting to know about this giant Galaxy. So, let begin..................

History of discovery

Not from now, but from very long decades humans were very curious to know about mysterious and exciting things and among one of them is our sky. From very long time people have observed the night sky and found many interesting things about it. And when astrologers see the Andromeda galaxy many of them say different about it.

History of early observations on Andromeda

First image of Andromeda

Around the year 964, the Persian astronomer Abd-al-Rahman al-Sufi described the Andromeda Galaxy as little cloud. When Charles Messier labelled it as M31 in 1764, he incorrectly credited the discovery of what was then called a nebula to the German astronomer, Simon Marius, who provided the first telescopic observation of the object.

In 1850, William Parsons, saw and made the first drawing of Andromeda’s spiral structure. And the first photographs of Andromeda were taken in 1887, by Isaac Roberts.
Roberts mistook Andromeda and similar spiral nebulae as solar systems being formed.
In the 1920s, the Andromeda galaxy became part of the Great Debate between American astronomers Harlow Shapley and Heber Curtis.

At the time, astronomers thought the Milky Way composed the whole universe, and the strange patches known as nebulae lay inside of them. Curtis had spotted various novae in Andromeda, and argued instead that it was a separate galaxy.

In 1925, Edwin Hubble settled the debate by identifying Cepheid variable (a kind of star characterises to precise measurements of distance) for the first time on astronomical photos of Andromeda. Because Shapley had previously determined that the Milky Way was only 100,000 light-years across, but Hubble's calculations revealed that the fuzzy patch was too far away to lie within the Milky Way.

In the 1940s, calculated distance to Andromeda doubled  when Walter Baade was the first to observe individual stars in the central region of the galaxy, and found two different types of Cepheid variables. And the first radio maps of Andromeda was captured in the 1950s by John Baldwin.

Recent discoveries about Andromeda

Our understanding of the size of the Andromeda galaxy has grown bigger in recent years. In 2015, observations from the Hubble Space Telescope found that a halo of material surrounding Andromeda is six times larger and 1,000 times more massive than what was previously measured.

In 2015, scientists released the most detailed photo of Andromeda ever, using a mosaic of images from the Hubble Space Telescope. The image included 7,398 exposures taken over 411 pointing’s of the telescope. The image revealed more than 100 million stars within the galaxy, as well as dust structures and other features.

In late 2017, scientists unexpectedly found two supermassive black holes closely orbiting each other. At the time, the research team said these black holes were likely the "most tightly coupled" of any supermassive ones known.

Here we know all about the discoveries and observations did by the astrologers and their excitement about Andromeda galaxy.

But, now the question is about its formation. How does Andromeda formed? How much time taken in its formation?

Let’s try to answer these question......

Formation of Andromeda

Collision of galaxy

The Andromeda Galaxy was formed roughly 10 billion years ago from the collision and subsequent merger of smaller protogalaxies.
The violent collision formed most of the galaxy's (metal-rich), galactic halo and extended disk. During this epoch, its rate of star formation would have been very high, to the point of becoming a luminous infrared galaxy for roughly 100 million years.

Andromeda and the Triangulum Galaxy had a very close passage 2–4 billion years ago. This event produced high rates of star formation across the Andromeda Galaxy's disk—even some globular clusters—and disturbed M33's outer disk.

Over the past 2 billion years, star formation throughout Andromeda's disk is thought to have decreased to the point of near-inactivity. There have been interactions with satellite galaxies like M32, M110, or others that have already been absorbed by Andromeda Galaxy. These interactions have formed structures like Andromeda's Giant Stellar Stream.

A galactic merger roughly 100 million years ago is believed to be responsible for a counter-rotating disk of gas found in the centre of Andromeda as well as the presence there of a relatively young (100 million years old) stellar population.

Structure and future of Andromeda Galaxy

Collision of galaxy

If we talk about shape of Andromeda so, it is is actually a barred spiral galaxy, like the Milky Way. And the galaxy is inclined an estimated 77° relative to Earth (where an angle of 90° would be viewed directly from the side).
Analysis of the cross-sectional shape of the galaxy appears to demonstrate a pronounced, S-shaped warp, rather than just a flat disk. A possible cause of such a warp could be gravitational interaction with the satellite galaxies near the Andromeda Galaxy.

The Andromeda Galaxy is approaching the Milky Way at about 110 kilometres per second (68 miles per second). This makes the Andromeda Galaxy one of about 100 observable blueshifted galaxies and therefore it is expected to collide directly with the Milky Way in about 4 billion years.

1 comment:

  1. All your articles are well researched and presented beautifully.. continue the good work..Thank you Best wishes from Top 20 Universe facts