Edits/updates at the end of the despription!
Normally when I've captured a series of light frames, I blink through them after they have been registered (aligned), to look for anything moving. A few times I've seen asteroids and minor planets.
This one is a little different. The moving object is a star! It has a boring name (usnoa2-1125-01255816) and that's about the only information I've been able to find.
It is found at 03h45m50s +24deg11'41", in the middle of M45. The characteristic blue and red stars close by should lead you the way.
It's apparent magnitude is somewhere between 18 and 19, but I can't find that anywhere, so it's based on a visual estimate comparing it with known stars (using skymap.org). In the CI image, which has better colour fidelity, the star looks orange or red.
The images are from DSS taken by the Palomar 48-inch Schmidt telescope, and my Crowd Image of M45. The DSS image was taken between Nov. 5, 1986 and Sept. 11, 1996. The images used in the Crowd Image was taken primarily the last couple of years.
The motion is somewhere around 6" in 27 years, based on the green channel of the DSS image, which was shot first (1986) and the CI image shot in2013 (estimated average). That's quite a lot, but nothing compared to Barnard's Star, which moves 10" pr year. On the other hand: Barnard's Star is a mag 9.5 red dwarf, so it's a lot closer to earth than usnoa2-1125-01255816 at mag 18-19. Therefore the movement of usnoa2-1125-01255816 is quite significant, and maybe even larger than Barnard's Star.
EDIT: I've tried to do a simple calculation of the motion of usnoa2-1125-01255816. Assuming that it is a red dwarf similar to Barnard's Star, a rule of thumb is to add 5 to apparent magnitude for every 10 times increase of distance. Barnard's Star (am9) is 6 ly away, so that put's usnoa2-1125-01255816 at 100 times that distance or 600 ly. If usnoa2-1125-01255816 isn't a red dwarf it put's it even further away. That means that the motion of usnoa2-1125-01255816 should also be multiplied by at least 100 (or more), to be comparable to Barnard's Star. Therefore the motion of usnoa2-1125-01255816 at the same distance as Barnard's Star is perhaps up to 22" pr. year. That is twice that of Barnard's Star! Might be have a new known record here?
2nd EDIT: The star is already known to have high proper motion, according to Simbad.http://simbad.u-strasbg.fr/simbad/sim-id?Ident=NLTT+11761
3rd EDIT: This is actually pretty interesting. First: From hereon I'll use the name NLTT11761 instead. It's "easier"
The star has a Bmag of 19,7 and a Rmag of 15.6 (red and blue mag), indicating that it is indeed red. An average of the two magnitudes is about 17.5. That means that the star is more than 10 times further away than Barnard's Star giving it a very large proper motion. On the other hand it could be a lot closer. High proper motion is normally an indicator of nearby stars (if a star is close the movement in arc sec pr year will appear larger, than if it's further away).
4th EDIT: My calculations are still very loose, but I'm beginning to belive that NLTT11761 is a so called Hyper Velosity Star, based on estimates of it's space velocity. The star is a type K-M spectral class, making it (probably) an orange dwarf. Lot's of ifs here, but it's pretty interesting to study. I'm learning a lot, that might come in handy
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