"Mystery of the Wispy Clouds"

Trisha Borgman - March 26, 1996

    Well, it's another gorgeously clear night at Kitt Peak, and we're in the middle of a 45-minute sequence of exposures. I haven't been outside to see the comet since just past sunset--I'll go take a look soon.

Actually, the comet is a small source of frustration for us here--we will have to scrap a few of our planned observations because they're so close to the comet! It's not at all a serious problem, though.

How do we know which of our target stars will be near the comet, and when? Luckily, we have a printout of the comet's ephemeris-- a list of all kinds of statistics about the comet. The ephemeris lists its position, magnitude, and speed for every 15 minutes or so of time...for every day. Since we also have the position of our target stars, we have been very careful to check for proximity to the comet.

Hmmm...here's something interesting. Two of those long exposures are finished now, and on the right side of the image is something that looks like wispy clouds. They're not clouds, though. In fact, I don't know what they are! I suppose it could be part of a nebula--and what a pretty nebula!!--but we just checked another sky-survey image of this region and there's nothing there! A mystery!!! We're still waiting for the other 2 images of this region to finish, so perhaps those images can help us figure out what's going on! Another possibility, unfortunately, is that there could be something wrong with our CCD chip. Let's hope that's not the problem... After all, it's also possible that we just discovered a new nebula!

Our third image of that region is coming out now... Yep, it's still there. One interesting observation is that these cloudlike features are considerably brighter in our R-band images (red) than in the V-band (visible--a greenish filter). I don't know yet why that is, but I'll do my best to figure it out!

...It's just past midnight now. We haven't had much time to investigate our little mystery any further; these cloudlike features are not in any of our other images, so it's difficult to understand where they're coming from. However, the fact that all of our other images are clean allows us to rule out the possibility that something was wrong with the CCD itself. Phew!

We took about half an hour to try to get a few images of the comet. We used the ephemeris I talked about earlier as a guide to its position. We were actually a little early in using the listed coordinates, so we took a series of 5-second exposures. It turns out that the comet moved almost perfectly through each of our frames! So, we now have a sequence of 14 frames in which we can literally see the comet moving diagonally from one corner to the opposite corner. They're beautiful! Wow!

Well, our next exposure is coming up, so I'd better get back to work. I still have a long night ahead of me!!

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