Edwin Hubble (1889-1953) guides the exposure of a photographic plate at the Newtonian focus of the 100-inch telescope in 1923. With this telescope, Hubble measured the distances and velocities of galaxies, work which led to today's concept of an expanding Universe. According to this profound idea, the Universe began ten to twenty billion years ago with a Big Bang. The receding galaxies that Hubble observed trace the expansion of space from that dense beginning. The telescope is a mechanical masterpiece and was dedicated as an International Historical Mechanical Engineering Landmark on June 20, 1981, by the American Society of Mechanical Engineers, only the fourth such award granted in the United States.
For more information about Edwin Hubble and his system of galaxy classification click here, then use the back arrow at the top of your browser to return here.
This page last updated December 12, 1997
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Rotating Spiral Galaxy animation by Josh Kennedy
Look at the rotating galaxy and then at the Hubble Tuning Fork Diagram next to it. Edwin Hubble would have classified this galaxy as type Sa. Notice its well defined center and spiral arms.
On the next page, you will have a chance to classify some unidentified galaxies, and use your mouse to place the galaxy images on the Hubble Tuning Fork Diagram. To move the galaxy pictures onto the Hubble Tuning Fork Diagram you will:
When you release the mouse button, the galaxy image will move to the spot you have selected. If you wish to move it again, you can follow the same directions. When you have finished placing all the galaxy images on the diagram, check your work by clicking on the the Galaxy Guy.
Start Here: Classifying galaxies
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