StarDate: May 1, 2009

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An astronomical discovery takes time. It begins with "Eureka!" -- the moment when the astronomer sees something new. But it isn't official until the astronomer can say "aaahhh" -- a note of satisfaction after the discovery is confirmed.

For Gerard Kuiper, one of the Eureka moments came 60 years ago tonight. Kuiper was photographing the planet Neptune with the 82-inch telescope at McDonald Observatory. One of his plates showed a tiny dot of light near the planet -- a possible moon.

Kuiper was director of both McDonald and the Yerkes Observatory in Wisconsin. He also chaired the University of Chicago astronomy department, which operated both observatories. His administrative work pulled him back to Chicago, so he couldn't stay in Texas to confirm the discovery.

So another astronomer photographed Neptune two more times over the following two months. The tiny dot appeared close to Neptune in these pictures, too, moving around the planet. The discovery was confirmed: Neptune had its second known moon. It was time to say "aaahhh." Kuiper did so in a paper announcing the discovery, in which he proposed naming the moon Nereid after mythological sea nymphs who attended Neptune.

Nereid is only a couple of hundred miles wide. Its elongated orbit suggests that it was an asteroid that was captured by the giant planet. And because it's so small and far away, we don't have a good view of it. But these things take time -- just like the discovery of Nereid.

Script by Damond Benningfield, Copyright 2009

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