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Did We Miss an Interstellar Comet Four Years Ago? (arxiv.org)
Long-time Slashdot reader RockDoctor writes: A paper published on Arxiv last week reports on a project to redetermine the "orbits of long period comets... We recently attempted to check, whether the assumption of a parabolic orbit for hundreds of comets discovered after 1950 is fully justified in all cases." The full work by Królikowska & Dybczynski remains in preparation (which is perfectly normal), but this intriguing result deserved early attention.
During this research we found an interesting case of the comet C/2014 W10 PANSTARRS.
(that's the 10th reported comet in fortnight W of year 2014, source : the PANSTARRS team)
After discovery on 2014-11-25, fourteen observations were made over three days, giving a first-estimate orbit with an eccentricity of 0.6039453. So far, so boring — as the temporary designation suggests, these get found on most days. But that orbit is subject to uncertainty so some more measurements were made on 2014-12-22 from a different observatory. When all of the data is considered, it becomes impossible to clearly assign an orbit to this object (this is possible if, for example, there is a fragmentation of the object between observations), but many of the solutions which can be obtained have a hyperbolic orbit — that is, the object is extra-solar.
If correct, this "post-covery" would double the size of the catalogue of interstellar objects known.
Unfortunately, the quality of the original data remains poor — estimates of the orbital eccentricity vary between 1.22 and 1.65 — which is in contrast to the prompt recognition and intense observation campaign for 'Oumuamua. The report's main conclusion is that
Our main purpose is to show that similar cases should be treated in future with greater care by more reliable preliminary orbit determination and alerting observers about the importance of the object to initiate more follow-up observations.
Which is exactly what happened with 'Oumuamua.
During this research we found an interesting case of the comet C/2014 W10 PANSTARRS.
(that's the 10th reported comet in fortnight W of year 2014, source : the PANSTARRS team)
After discovery on 2014-11-25, fourteen observations were made over three days, giving a first-estimate orbit with an eccentricity of 0.6039453. So far, so boring — as the temporary designation suggests, these get found on most days. But that orbit is subject to uncertainty so some more measurements were made on 2014-12-22 from a different observatory. When all of the data is considered, it becomes impossible to clearly assign an orbit to this object (this is possible if, for example, there is a fragmentation of the object between observations), but many of the solutions which can be obtained have a hyperbolic orbit — that is, the object is extra-solar.
If correct, this "post-covery" would double the size of the catalogue of interstellar objects known.
Unfortunately, the quality of the original data remains poor — estimates of the orbital eccentricity vary between 1.22 and 1.65 — which is in contrast to the prompt recognition and intense observation campaign for 'Oumuamua. The report's main conclusion is that
Our main purpose is to show that similar cases should be treated in future with greater care by more reliable preliminary orbit determination and alerting observers about the importance of the object to initiate more follow-up observations.
Which is exactly what happened with 'Oumuamua.
It's been decades since I studied this, and most of the neurons I used to store the details have long since been recycled, but I do remember a little bit about orbital mechanics. If an object's velocity is lower than escape velocity, it's in an elliptical orbit, and if it's above, the orbit's hyperbolic. You only get a parabolic orbit if it's traveling exactly at escape velocity. OK, yes, I understand that there are limits to how precise our measurements are and that leads to a margin of error in the calculated orbit, but I can't help but think that there's something wrong when there are hundreds of comets discovered since 1950 with calculated orbits at exactly escape velocity, as close as we can calculate it. What I wonder is why it took astronomers this long to start checking their figures and finding all of these mistakes. Of course, they might just have been too busy to recheck all of those figures, but still, I'd like to find out.
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No wonder you're an AC. I'd be ashamed to put my name to such an admission of incompetence.
Birds are not dinosaur descendants;birds are dinosaurs, for all useful meanings of "birds", "are" and "dinosaurs"
Yes, I do recall a sort of emptiness and longing as it swooshed by.
It little behooves the best of us to comment on the rest of us.