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ISON Q&A: October 14, 2013

14 Oct 2013, 10:00 UTC
ISON Q&A: October 14, 2013
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Today we answer some of the Comet ISON questions you've posed on Facebook, Twitter and Google+. What do you need to know about ISON? Tell us and we'll try to find out.

I saw your post on how the last Hubble image of Comet ISON was made. Why don’t we see those kind of weird streaks in other Hubble images?

The short answer is that we see them all the time. For instance, here’s one:

In the box at the lower right is an image of an asteroid that Hubble happened to capture while imaging the distant galaxy in the main picture. Basically, this is what happens when Hubble takes in a moving target, like an asteroid or, in ISON’s case, a comet, while focused steadily on the background galaxies.

People are rarely exposed to Hubble’s raw images, but their features help explain how Hubble functions. So let’s do what the picture tells us, and see that closeup. Hello, asteriod.

This is a stacked image of several exposures, which is how all of Hubble’s images are made.

Hubble always takes multiple exposures, because that’s how it creates a picture. The multiple exposures ...

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