Andromeda Galaxy

The Universe is made up of many Galaxies, Stars and other things. Do you have any idea that which is the nearest galaxy our own milky way? It is the Andromeda Galaxy.

It is around 2.5 million light years away from earth.  Yes it’s the big spiral known as ANDROMEDA GALAXY also known as MESSIER it is the galaxy nearest to our MIKYWAY. Andromeda is the largest galaxy of the Local Group, which consists of the Andromeda Galaxy, the Milky Way, the Triangulum Galaxy, and about 30 other smaller galaxies. Although the largest, Andromeda may not be the most massive, as recent findings suggest that the Milky Way contains more dark matter and may be the most massive in the grouping.

Andromeda is estimated to be 7.1×1011 solar masses. In comparison a 2009 study estimated that the Milky Way and Andromeda are about equal in mass, while a 2006 study put the mass of the Milky Way at ~80% of the mass of Andromeda. The Andromeda Galaxy and the Milky Way are expected to collide in perhaps 4.5 billion years. Andromeda plays an important role in galactic studies, since it is the nearest spiral galaxy (although not the nearest galaxy). In 1943, Walter Baade was the first person to resolve stars in the central region of the Andromeda Galaxy. Based on his observations of this galaxy, he was able to discern two distinct populations of stars based on their metallicity, naming the young, high velocity stars in the disk Type I and the older, red stars in the bulge Type II. This nomenclature was subsequently adopted for stars within theMilky  way and elsewhere.

Like the Milky Way, the Andromeda Galaxy has satellite galaxies, consisting of 14 known dwarf galaxies. The best known and most readily observed satellite galaxies are M32 and M110. Based on current evidence, it appears that M32 underwent a close encounter with M31 (Andromeda) in the past. M32 may once have been a larger galaxy that had its stellar disk removed by M31, and underwent a sharp increase of star formation in the core region, which lasted until the relatively recent past.M110 also appears to be interacting with M31, and astronomers have found a stream of metal-rich stars in the halo of M31 that appears to have been stripped from these satellite galaxies. M110 does contain a dusty lane, which may indicate recent or ongoing star formation. In 2006 it was discovered that nine of these galaxies lay along a plane that intersects the core of the Andromeda Galaxy, rather than being randomly arranged as would be expected from independent interactions. This may indicate a common tidal origin for the satellites.

What makes the talk more interesting is the future prediction regarding collision of MILKY WAY and ANDROMEDA. Andromeda Galaxy is approaching the Milky Way at about 100 to 140 kilometres per second (62 to 87 mi/s) (400 lightyears every million years), making it one of the few blueshifted galaxies. The Andromeda Galaxy and the Milky Way are thus expected to collide in about 4.5 billion years, although the details are uncertain since Andromeda's tangential velocity with respect to the Milky Way is only known to within about a factor of two. A likely outcome of the collision is that the galaxies will merge to form a giant elliptical galaxy. Such events are frequent among the galaxies in galaxy groups. The fate of the Earth and the Solar System in the event of a collision are currently unknown. If the galaxies do not merge, there is a small chance that the Solar System could be ejected from the Milky Way or join Andromeda.

Let's look four billion years into the future:

 A group of our descendents stands with their teacher and looks up at a night sky ablaze with thousands of dazzling white stars. All of these new stars are being born, their teacher tells them, because of an immense cosmic event. Our galaxy, the Milky Way, has collided with another galaxy, called Andromeda. Although the two galaxies are passing through each other at a million miles an hour, the whole process will take many millions of years to complete. And when everything settles down, the two galaxies will have merged into one.

The students fear that this may be the end of life, as they know it. But, their teacher reassures her class that there is very little chance of stars from the Andromeda galaxy hitting the Sun or the Earth. Even though the galaxies pass clear through each other, she says, stars in a galaxy are spaced very far apart. They are like grains of sand separated by the length of a football field. The Andromeda stars simply pass by. 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. It is the collision between clouds that has triggered a starry baby boom!

Finally concluding, although my story describes an event that is far distant in future but galaxy collisions are real but still hope that our descendants will see earth as the same planet teeming with life.  Sun will still be shining but, what will they see in the night sky?