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View from Mars Hill: After 45 years, important Pluto plates are reunited

View from Mars Hill: After 45 years, important Pluto plates are reunited

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Archivist Lauren Amundson and researcher Brian Skiff hold up the reunited Pluto plates.

It’s a story told before, of siblings separated for decades by some circumstance but eventually reunited. Forty-five years ago, the eldest of the two nearly identical twins ended up across the country in Washington, DC.; a star, of sorts, that saw millions of visitors every year. Meanwhile, the younger one remained in Flagstaff, sheltered from the hustle and bustle of the world and, in fact, rarely seeing the light of day. And while they could stand alone as individuals, they packed a lot more punch when they were together.

This long separation finally ended earlier this week, when they were brought back together at Lowell Observatory.

The story of these siblings goes back more than 90 years. From the start, they looked for all intents identical. They were so alike, in fact, that even scientists could not tell them apart. Until one day, that is, when a relative neophyte in his field observed a modest disparity, a perturbation so slight that even the most seasoned expert would have missed it. Yet the impact of this visually unexceptional stone in a pond, as it were, rippled far wider than the discoverer could ever have imagined, and it vaulted him into a career that saw him reach legendary status.

So who were the siblings, and why were they separated? Well, to start with, the question isn’t who, but what.

The main characters here aren’t people, but glass photographic plates of the sky that Clyde Tombaugh of Lowell Observatory took in January 1930. He was carrying out the search for a ninth planet commenced 25 years earlier by Percival Lowell and continued sporadically through the years.

The plates revealed images of a specific area of the sky taken a few days apart. Most of the hundreds of thousands of miniscule dots on each plate represented a star, and over a few days’ time would appear in the same relative position, as captured on the plates.

Tombaugh wasn’t so much interested in these, but rather in the potential needle in a haystack — a dot that changed position over those few days. Such movement would indicate an object much closer to us, like a planet. Tombaugh took the first plate on January 23 and the second one on the 29th. While examining the plates on February 18, he noticed just such a dot, which turned out to be Pluto. In the blink of an eye, the discovery plates were transformed into important scientific artifacts.

Jump ahead to 1977, when the Air & Space Museum in Washington, D.C., wanted several artifacts from Lowell to put on display. One of these items was the January 23 discovery plate. An agreement between the two institutions was signed by the directors of the two organizations at the time — Art Hoag of Lowell and the Air & Space’s Michael Collins — the same Michael Collins who rode with Neil Armstrong and Buzz Aldrin to the moon on Apollo 11.

The plate soon took up residence in the same building that houses the Wright Flyer, Charles Lindbergh’s Spirit of St. Louis, and the Columbia command module used on the Apollo 11 mission that first saw human land on the Moon. This Flagstaff heritage stayed on display there for the next 4½ decades, visible for the hundreds of millions of visitors who explored the museum during that time.

Last year, leaders at the Air & Space Museum decided to renovate the exhibit space, replacing many of the existing displays — including the Pluto plate — with new ones with new ones. They thus returned the plate to Lowell. Archivist Lauren Amundson ordered a special box to store the two plates, and this past Wednesday — the sixth anniversary of the New Horizons flyby of Pluto — observatory staff reunited the two plates that made that very mission possible.

And after 45 years apart, it’s unlikely the will be separated again anytime soon.

Get an astronaut’s view of auroras, stars, and the Milky Way surrounding our beautiful planet. 12,500 images taken by European Space Agency astronaut Alexander Gerst were combined to create the incredible timelapses of Earth from the International Space Station.


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