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Monday, April 25, 2005
The Hubble Space Telescope was deployed fifteen years ago today. Two weeks ago the incoming NASA Administrator, Mike Griffin, said that he would reconsider a shuttle repair mission for Hubble, which previous Administrator Sean O'Keefe had decided against.
One of these days -- soon, I hope -- I'll get around to writing a post on why we still need Hubble. A lot of people seem to think that new space telescopes and new technology for ground-based telescopes have rendered Hubble unnecessary, but this is not true.
In the meantime, STScI has released two new Hubble pictures for the anniversary. I'm sorry to say that I'm not really very impressed. One is the familiar Whirlpool Galaxy, which is very nice, but I've seen pictures of it before, including Hubble pictures.
Somewhat more interesting is a new image of one of the pillars in the Eagle Nebula. Now, this is obviously not anything like the famous image of the nebula, so I figured it must be (at least partly) an infrared image. (One of the frustrating things about the way the Hubble images are presented is that it's damned hard to find real information about them. That's especially true when you have to poke around and the site is very slow because ten gazillion people are trying to get to it.)
For example, this copy says that the blue is oxygen and the red is hydrogen. Well, that's helpful. What lines of oxygen and hydrogen? They say that the emission arises from UV radiation, the oxygen is probably [OIII] (5007 A), which in true color would be green) rather than the other likely oxygen line, [OI] (6300 A, red). But what the heck is the hydrogen? I couldn't see any way they could take an H alpha image (which would be the logical hydrogen line to observe) and come up with this new picture.
Well, it turns out that this new image is not of the familiar pillars, but a pillar in a slightly different part of the nebula. This lovely picture shows the region of the latest pillar in the upper left-hand corner. The Hubble image has obviously been rotated about 90 degrees counter-clockwise to the orientation in this ground-based image.
Mmmm, check out that guy's whole site. Beautiful.
(Ah, here, finally, are the Fast Facts, which give the filters used and the correct orientation and scale. I was right, [OIII] and H alpha. Click on the image, and it even shows you what filters were used for what colors. Still don't see where it shows you the position within the nebula. Gee, this information could be less well-hidden.)