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Galaxy – Ten Things You Don’t Know About Hubble


Galaxy – Ten Things You Don’t Know About Hubble

Galaxy, You can look at all the images it has ever taken, as long as they’re over a year old. Since its launch in 1990, Hubble has orbited the Earth over 100,000 times and taken something like a half million separate observations. Those figures alone are a bit staggering.

But did you know that you (potentially) have access to those images? Well, most of them, anyway. All the data taken by Hubble that is more than one year old is stored in an archive that the public can query. Want to know what Hubble was observing on your birthday two years ago, or at the moment your kid was born?

Just ask the database! In many cases, when you search the database, you can also get a preview of the image; the above shot is of the spiral galaxy M51, also called the Whirlpool Galaxy. The preview shows the raw data right off the ‘scope; it’s not always particularly pretty. To beautify it you need to process it, which means subtracting a dark frame, a bias frame, dividing by the flat field, flagging bad pixels, combining multiple exposures to get rid of cosmic rays, performing a geometric correction… and if you want color, you have to do that for the other filters used in the observation, and then combining those using Photoshop or some other software.

Obviously, not everyone can do that (it’s a lot harder even than it sounds). So not everyone is allowed to actually retrieve the data; that would strain the archive servers. To do that you have to justify the need and get an account. I used to have one, but I lost my password a long time ago. Probably all for the best; I’d just download gigabytes of cool images and get everyone at the archive ticked off at me.

Oh, about that “… as long as they’re over a year old” thing: data is proprietary to the person who took it for the period of one year, so the scientists involved have time to look it over. It does take some time to process the data, and a lot more time to analyze it; if everyone had instant access to all the data, someone more experienced than you could scoop you on your own observations! However, it’s also not fair to let people have the data forever. The compromise is the one year proprietary period; that gives scientists time to look things over, but still motivates them to get things done. I think this is a fine idea, and it even works in practice in the real world, amazingly. If a scientist wants, they can release the data early, too, so everyone wins.

In fact, I used old data quite a bit back in the day. If we found something interesting in our own data, we could go look for older observations to see if it had been seen before, or if there were related observations. And many times, even if the older data were still proprietary, the scientists involved were interested in collaborating. Funny thing about scientists: in lots of cases they are open, friendly, and interested in seeing what everyone else is doing. There were exceptions, of course, but that’s what I found for the most part.

Maybe that’s the thing that’ll surprise you most in this article. But it’s true.

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