Clyde Tombaugh Discovers Pluto

*click* ….. *click* …. *click* …. *click*

On this day in 1930, a 24-year-old man named Clyde Tombaugh was squinting into the Lowell Observatory’s Zeiss Blink microscope. The unique device, also known as a blink comparator, held two photographic plates that each contained the image of a star field taken the previous month–the images showing the same section of sky, taken a few days apart. Tombaugh could rapidly switch between the two images by rotating a dial, allowing him to quickly compare the images and watch for any variations between the two that would indicate a body moving more rapidly than the background stars (eg. planets, asteroids, etc.).

*click* ….. *click*

Late into that February afternoon, a subtle difference between the two images caught his eye.

Animation comparing Tombaugh's star fields.

Can you spot Pluto?  Click on the image to see a version with Pluto identified.   Image Credit: National Air & Space Museum

 

*click* … *click* … *click* .. *click* . *click* *click*

He spent 45 minutes comparing the two images. Convinced of his findings, he contacted his supervisors. Over the next couple of weeks, the observatory focused its attention to the object before confirming Tombaugh’s discovery. On May 1st, 1930, a new planet was introduced to the world: Pluto.

And of course, in 2015, we got to see Pluto in a way that Mr. Tombaugh himself could only have imagined.

NASA’s New Horizons spacecraft captured this high-resolution enhanced color view of Pluto on July 14, 2015.

NASA’s New Horizons spacecraft captured this high-resolution enhanced color view of Pluto on July 14, 2015.        Source: NASA

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