When Pluto was discovered 80 years ago, it happened to be moving through Gemini, a part of the sky that had a lot of stars. Clyde Tombaugh did an amazing job finding it, since it was almost lost among those stars.
I wonder if he could’ve found it had he been looking earlier this year? "Amateur" astronomer Anthony Ayiomamitis sent me this image he took of Pluto as was in Sagittarius, the most densely-packed area of the sky!
[Click to undwarfplanetate.]
Hard to spot, isn’t it? Pluto is unresolved in the picture, so it looks like just another star. And there are a lot of stars here; this region of sky is actually a cluster called Messier 24 (or just M24, and it’s pronounced "MEZ-ee-ay", since Charles Messier was French); the two dark splotches are thick dust clouds called Barnard 92 and 93. Finding Pluto in this ain’t easy.
… or is it? When I first looked over the picture, I found Pluto almost immediately, and then laughed, because I know a secret. First, take a look… can you find it?
OK, here’s the secret: this is a color picture, which means Anthony had to take four images, one each through a red, green, and blue filter, and one unfiltered. The stars all look good because they don’t move, but by the time he took the red image Pluto had moved a bit compared to the stars’ positions. So when my eye happened to catch a bright red spot in the image, I knew right away I was seeing Pluto. The picture here has Pluto’s position marked; click it to see the full sized version.
In modern terms, Pluto is pretty bright; I’ve never seen it with my own eyes through a telescope, but using a small ‘scope equipped with a digital camera I’ve gotten decent images of it in under a minute! But Tombaugh didn’t have that, nor did he have a computer to tell him where it was. He had to take picture after picture, night after night, guiding the telescope, developing the glass plates, then comparing each picture one after another. That’s why it took him months to find Pluto!
And remember, he didn’t even know if it existed!
Astronomy is not for the faint of heart. But for those of us who love it, it truly is something we do from the heart.
Related posts featuring Anthony’s imagery: