The Milky Way Isn’t the Only Galaxy

The Milky Way Isn’t the Only Galaxy

“On this day in 1924, American astronomer Edwin Hubble announced the existence of galaxies outside of the Milky Way, profoundly changing our understanding of the universe.

Born in 1889 to John Powell Hubble, an insurance executive, and Virginia Lee James, in Marshfield, Missouri, and raised near Chicago, Hubble was more athletically than intellectually inclined in his youth. He often placed in high school track and field and in 1906, set a state record for the high jump in Illinois. He was also an amateur boxer and went on to play basketball for the University of Chicago. There, he studied math, astronomy, and philosophy, then won a Rhodes scholarship and studied law at Oxford. He earned a Ph.D. in astronomy, practiced law, served in World War I, and finally returned to astronomy.

At the time, the scientific community believed the Milky Way galaxy comprised our entire universe. Around 1919 in Mount Wilson, California, Hubble began using the newly completed Hooker Telescope, then the world’s largest, to study spiral nebulae, fuzzy patches of light in the sky presumed to be clouds of gas or dust within our galaxy. With the Hooker Telescope, he identified Cepheid variable stars, a new kind of star, in several spiral nebulae, including Andromeda Nebula and Triangulum. Using a formula discovered by Harvard astronomer Henrietta Leavitt, he calculated the distance of these new stars. Andromeda, he found, was approximately 860,000 light years away, more than eight times the distance to the farthest stars in the Milky Way. That astonishing computation proved the stars were much too far to be a part of the Milky Way and were, in fact, entire galaxies outside of our own. Hubble presented his findings in a paper at the meeting of the American Astronomical Society to considerable awe. His discovery had fundamentally changed our view of the universe.

Hubble went on to discover dozens more galaxies. He died in 1953. NASA honoured his contribution to astronomy by naming its space telescope after him.”

Credit: NASA Images
Caption: By calculating the distance of the Andromeda Nebula (shown), Edwin Hubble proved there were galaxies outside the Milky Way.