Clyde Tombaugh (February 4, 1906 - January 17, 1997)

Like a UFO, Clyde Tombaugh visited me the other night, while I was shooting target galaxies at 9 hours of Right Ascension. No, not Tombaugh the man. But rather the asteroid (1604) Tombaugh. While looking at my telescope's position on the sky in Cartes du Ciel as it settled in on the galaxy trio NGC 2911, 2914, and 2919, I recognized Tombaugh's name in the periphery. Hmm. I've never taken a picture of (1604) Tombaugh, and here it is at around 15th magnitude. It'll be easy!

Perhaps you've heard the story of young Clyde Tombaugh, son of a Kansas farmer, getting hired by Lowell Observatory in 1929, where he picked up the torch from Percival Lowell to discover the 9th major planet in our solar system. His discovery of Pluto in 1930 was one of 800 minor planets he came across in his many years of searching for the 9th planet. It was the first major planet to be discovered photographically, and also the first major planet to be discovered by an American.

The method Tombaugh used to make his discovery was sheer genius. In those days, photographers used glass plates instead of emulsion film negatives to take their pictures. After processing, the glass plates were like slide transparencies. You could use them to make prints on photographic paper or put them on a light table to view them directly. Tombaugh used a "blink comparator" (invented in 1904 by Carl Pulfrich) that was like a modified light table. He would insert two photographic plates of the same star field taken a day or two apart, and then turn a knob to rapidly alternate the view of each plate separately. Objects in the plates that moved by a few arcminutes would appear to hop back and forth, allowing Tombaugh to easily spot them.

Nowadays, of course, we don't use photographic plates to take our images. We use digital cameras. But the blinking technique remains the same. We align two images taken hours apart and create an animated GIF image. The animation essentially blinks the two images, and moving objects like asteroids and comets will appear to hop back and forth, like my GIF image at the top of this page.

Using the blinking technique, Tombaugh found Pluto within a few degrees of where Percival Lowell had predicted it would be. That alone gave Tombaugh confidence that he had found the 9th major planet in our solar system. That and the fact that an analysis of Pluto's orbit showed that it was a trans-Neptune object. However, its small size caused much doubt amongst many other professional astronomers that it could be a major planet. 

In 2006, the final nail in Pluto's coffin was hammered, when astronomers redefined what constitutes a planet, and Pluto didn't make the cut. Clyde had passed away nine years earlier, so he didn't have to suffer the grave disappointment of his one claim-to-fame being canceled. 

In 1980, on the 50th anniversary of Pluto's discovery, the good people of Lowell Observatory honored Clyde by having one of his 15 asteroid discoveries officially named for him. That certainly sets Tombaugh apart from other asteroid discoverers, who are not usually allowed to have their discoveries named after them.

I think it's great! Clyde Tombaugh certainly earned his place in history and is well-deserving of this unique honor that broke the rules. And I am happy to share this GIF of (1604) Tombaugh, taken almost exactly 119 years since his birth (and nearly 94 years since he discovered it), in recognition of his many accomplishments. 

Here's lookin' at you, kid!