DiscoveringUniverse: Galaxies

Its really fascinating that once humans didn’t know what is beyond our galaxy. But a discovery by Edwin Powell Hubble changed everything.

The 100-inch telescope at Mount Wilson was the largest in the world in the early 1900s. At that time small patches of light in the sky were termed as Nebulae and were thought to be existing inside the Milky Way.

We know that when a star shows fluctuation in its brightness the reason may be a planet orbiting it. But there are some variable stars named Cepheid variables which show fluctuations in their brightness for some different reason.

When the star is relatively cool it contracts thus its core contracts and it generates more heat and then star begins to expand. Energy is released before and after the expansion thus the star cools and contracts. The process repeats and that’s how we see fluctuation in its brightness.

Our pole star, Polaris is also a Cepheid Variable.

Edwin Hubble also discovered a Cepheid Variable in a Nebula named Andromeda and thus using its fluctuations and luminosity he calculated its distance and thus the distance of Andromeda Nebula from Earth. It was 900,000 light years away. And American astronomer Harlow Shapley had determined that the Milky Way was only 100,000 light-year across. So it must be outside our galaxy.

And later many stars were found in the nebula and thus it was proved to be a galaxy.

(Later it was proved that the distance measured by Edwin Hubble was not correct, please read this post.)