The Sciences

Why, King Triton, how nice to see you!

Bad AstronomyBy Phil PlaitMar 13, 2009 6:31 PM


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It figures: I spend hours and hours putting together my Ten Things post about Pluto, and the New Horizons team releases a way cool image too late for me to include it! But it is way cool. Check this out:

This image shows Neptune and its large moon Triton. That's a remarkable shot, given that the planet and moon were nearly four billion kilometers away when it was taken! As I mentioned in the Pluto post, Neptune and Pluto never get really close together, so New Horizons isn't exactly dropping by on its way to Pluto. This image was taken as a test of the equipment, and has some scientific value as Emily points out. And as the press release says:

Triton is only slightly larger than Pluto (1,700 miles [2,700 kilometers] in diameter compared to Pluto’s 1,500 miles [2,400 kilometers]). Both objects have atmospheres primarily composed of nitrogen gas with a surface pressure only 1/70,000th of Earth’s, and comparably cold surface temperatures (-390° F on Triton and -370° F on Pluto). Triton is widely believed to have once been a member of the Kuiper Belt (as Pluto still is) that was captured into orbit around Neptune, probably during a collision early in the solar system’s history.

New Horizons will start taking images of Pluto while it's still a long way off from the tiny world, so this observations shows the probe is up to the task. In case you're curious, the image itself is interesting. Neptune was overexposed, causing that column of light called blooming. This kind of detector "sees" light by converting incoming photons into electrons, and then counting the electrons. But if an object is too bright, too many electrons are created which overflow the pixels, something like rain overflowing a bucket. Due to the structure of the detector, the electrons flow more easily in one direction than another, and you get blooming. Worse, this effect can suppress the number of electrons seen per pixel along that column, which is why there is a dark streak above Neptune as well. This kind of thing is just something you have to deal with when using electronic detectors of this type. It takes a while to get used to it, and can lead to all sorts of problems (there could be a faint interesting source near your target that gets obliterated by this effect). It also leads to pseudoscience, as I pointed out in my Planet X debunking a while back. In science you have to understand your camera just as well as your astronomical target. Clearly, the astronomers involved with New Horizons did for their detector, since you'll note that Triton is off to the side, away from the blooming issue.

And for those wondering about the post title... it's from The Little Mermaid. Ursula said it, and I used to imitate her to crack up The Little Astronomer when she was very little. It still makes me laugh.

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