By: Astroathens On: February 12, 2017 In: Astronomy Comments: 0
  • What is a galaxy!?
  • A MASSIVE SPINNING cluster of stars, celestial objects, solar systems, gas and dust clouds (like nebulae); all held together by a strong force called GRAVITY.
  • *mic drop*
  • Theorized to have formed from huge clouds of gas billions of years ago.
  • Areas began to collapse where there was more gravity and the gas clouds began to spin.
  • Over time creating a shape that is either…
  • Theorized to all rotate around something called a black hole.
  • Since black holes are believed to have a very strong gravitational pull, we theorize that they may be this super strong source of gravity that holds together this massively spinning masterpiece.
  • In 1612, Simon Marius made the first observation of Andromeda through a telescope, however claimed it was a nebula.
  • In 1764, Charles Messier labeled it as the Andromeda Nebula-M31.
  • However the GREAT DEBATE happened between two astronomers in 1920.
  • Harlow Shapley and Heber Curtis debated over whether Andromeda was a spiral nebula or a totally separate galaxy.
  • But then in 1923 Edwin P. Hubble measured flickering stars known as cepheid variables (stars that pulsate) and found that this flickers was caused by both nearby dust and gas.
  • By using the Hooker telescope with its 100-inch mirror, on top of Mount Wilson in California.
  • By measuring the change in brightness of these stars Hubble was able to calculate just how far away these stars were.
  • This then found that these stars were MUCH further away than what we measured the size of our Milky Way galaxy to be.
  • This showed that these stars were then part of an entirely SEPARATE galaxy.
  • Hubble published this discovery in 1929.
  • We then knew that our universe wasn’t just our Milky Way Galaxy.

Courtesy Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF

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