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Sifting through photographs : The comet 17P/Holmes' orbit from images on the WWW

I watched this video a long long time ago, where Dr. David W. Hogg using images publicly available on the internet to do science. Case in point is this paper they published where they tried understanding the trajectory of the comet 17P/Holmes from astrophotographers' images online. They searched for images of the comet, after it brightened and public interest in it had gone up. They then tagged the images to know what part of the sky they were looking at using astrometry.net. They then did some math, which I will hopefully understand one day, to weigh different images depending on their authenticity and how their metadata of when the images were taken was compared with their predictions of when the comet was in the field of view of the picture. One day. They were, in fact, finally able to reconstruct the orbit of the comet, albeit a slight error.

The video mentioned above gives more examples of such, including one awesome example where they rediscover stellar tidal streams observed using dedicated telescopes and instruments by searching for and stacking properly (there's a bit of math there as well) images available on the internet. The interesting comparison they draw in the paper is that this is citizen science but the citizens aren't volunteering their manpower, in fact they might not even have this purpose in mind when they take the picture.

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