Some Fascinating Facts About Galaxies

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A galaxy is a massive collection of millions to trillions of stars, nebulae (clouds), gas and dust, dark matter and black holes, all held together with gravitational force. There are an infinite number of galaxies in the universe. The universe, discovered till date, is believed to contain 170 billion galaxies. Our galaxy, Milky Way, contains about 100 billion stars and the sun is only one of them. All galaxies have different shapes, sizes and ages. Galaxies, having about 10 million stars are called dwarfs and the ones with a hundred trillion stars are called giants. All the stars orbit around the galaxy’s center of mass.

           Here are some fascinating facts about galaxies:

  • There are, mainly, three types of galaxies – spiral galaxies, elliptical galaxies and irregular galaxies. Spiral galaxies have a flat disk and a convex or popping out center with surrounding spiral arms. The flat disk of the galaxy contains stars, planets, dust and gas, all rotating around the center of the galaxy in a regular way. Our Milky Way is also a spiral galaxy.
  • Elliptical galaxies are almost spherical or highly elongated. They have an elliptical shape from any angle they are viewed. These types of galaxies can extend to very big sizes. These galaxies are believed to be the result of interaction of galaxies.
  • The irregular galaxies are those which have neither the shape of spiral galaxies nor the shape of elliptical galaxies. These galaxies are deprived of any distinct form because they are having the gravitational force of other galaxies nearby.
  • Galaxies were formed about 10 billion to 20 billion years ago after the Big Bang took place in the universe. Scientists believe that shortly, after the cosmic Big Bang, there were clouds of gases which started merging, folding and compressing under gravitational force to give birth to the building blocks of galaxies.
  • The shapes of the galaxies are often the result of collision. Our galaxy, Milky Way was also formed after collision with its closest neighbor, the Andromeda galaxy. The stars in Andromeda galaxy are much younger than those in the Milky Way. This proves that the Andromeda galaxy has already collided with one or more galaxies and is, therefore, younger than Milky Way.
  • Edwin Hubble, an American astronomer, was the first to prove the existence of other galaxies than the Milky Way. He used a very powerful 100-inch telescope at Mount Wilson Observatory in California, in year 1924, to discover the Andromeda galaxy. He also discovered many other spiral-shaped galaxies. The fact that galaxies rotate about their center was proved by Dutch astronomer, Jan Oort in year 1927.
  • The reserve of cold gas in the form of giant molecular clouds gives birth to stars in the galaxy. Sometimes, stars are born as a result of this activity at an exceptional fast speed which is called a starburst. The starburst activity continues for a period of about 10 million years. Though, these galaxies were more often during the early history of the universe, they still contribute about 15% to the total star production rate.
  • Our solar system is found about 27000 light years from the galactic center of the Milky Way, within the disk of the galaxy.
  • Elliptical galaxies have a collection of stars emitting out bright light in the center. The light from them is so bright that if Earth were found inside it, there would have been daylight everywhere all the time.
  • One can see four galaxies from our planet with a naked eye: the Milky Way, the Andromeda, and the small and large Magellanic Clouds.
  • The galaxy which emits far more energy than a normal galaxy is called active galaxy. Our Milky Way is stable and quiet as compared to an active galaxy. Active galaxies are also known as Quasars and emit a hundred times more energy than a normal galaxy and are 10 trillion times brighter than sun.

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