jan 1, 1923 - Hubble discovers extragalactic objects
Description:
Using the fluctuations of light from variable stars in Andromeda, Hubble was able to determine the Andromeda galaxy exists outside the realms of the Milky Way at what he estimated was 900,000 light years away while in reality it exists at almost 2.5 million light years away (Messier 31) & (Biography.com).Added to timeline:
Date:
jan 1, 1923
Now
~ 102 years ago