Edwin Hubble

The Hubble Space Telescope was named after Edwin Hubble, one of the foremost astronomers of the 20th century. His discovery in the 1920s that countless galaxies exist beyond our own Milky Way galaxy revolutionized our understanding of the universe and our place within it.

Most astronomers of Hubble’s day thought that all of the fuzzy objects called spiral nebulae were contained within the Milky Way galaxy. Our galaxy, it was thought, was the universe. However, in 1923 Hubble aimed the Mount Wilson Observatory’s 100inch Hooker telescope at a hazy patch of sky called the Andromeda Nebula. He found that it contained stars just like the ones in our galaxy, only dimmer. One star he saw was a Cepheid variable, a type of star that can be used to measure distances. From this, Hubble deduced that the Andromeda Nebula was not a nearby star cluster but rather an entire other galaxy, now called the Andromeda galaxy.

In the following years, he made similar discoveries with other nebulae. And by the end of the 1920s, most astronomers became convinced that our Milky Way galaxy was but one of millions in the universe. This shift in thought was as profound as our understanding that the world was round and that it revolved around the sun.

But the most astonishing discovery Hubble made resulted from his study of the spectra of 46 galaxies and, in particular, the Doppler velocities of those galaxies relative to our own Milky Way. What Hubble found was that the farther apart galaxies are from each other, the faster they move away from each other. Based on this observation, Hubble concluded that the universe expands uniformly.

Celebrate the 25th anniversary of the Hubble Space Telescope at Carnegie Science Center on Saturday. Hubblerelated activities and demonstrations will be hosted throughout the building. A panel of professional scientists will also discuss the impact of the space telescope.