This comet, gb00234, is currently on the PCCP. The best-fit orbit by Bill Gray has it with an eccentricity in excess of 3. If confirmed this will be the first certain example of an interstellar comet. Observations and astrometry should be a priority. It is currently around mag 18. An image by Borisov is here.
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gb00234, a bright interstellar comet?
Wed, 2019-09-11 08:37
#1
gb00234, a bright interstellar comet?
Now designated C/2019 Q4 (Borisov) in the MPEC here.
There is a preprint in arXiv this morning about this object at https://arxiv.org/abs/1909.05851
The comet moved away from a mag 13.4 star and I managed to get a set of frames before the sky started brightening noticeably. The sky was excellent though and I saw Sirius rising! Taken through a Baader V filter.
David. Thanks for this image. It may not look that impressive but it is extraordinary that we are now able to discover and track objects like this which have come from interstellar space. I'm sure that the pros will be doing everything they can to get a spectrum of this object in the near future. I've not been around to image this yet but will try as soon as I get the opportunity. It is not often that you get the opportunity to image a chunk of ice from another star system with an amateur telescope.
I tried having a look for it visually in my 60 cm scope in the early hours of Monday (5am - 5.30am) but the skies were very humid and claggy, only SQM 20.95 overhead and mag 5 N/E so was no chance really at 20 degrees altitude but always worth having a go. Maybe another window tomorrow morning but again humidity forecast for 96% here in Norfolk. Andrew
It is in Crater now, isn't it. I can only imagine how difficult it must be now to see visually. If there's a clear spell tomorrow morning, I might get up before the streetlight switch on at 0500 and try to capture an image.
Yes. I think I read somewhere that if the comet interceptor mission had already been deployed, this would have been one helluva target.
Nice idea but the perihelion distance is around 2 au so comet interceptor wouldn't have been able to get close. I managed to get it this morning despite the annoyingly bright Moon.
Good image. I suspected there would be significant constraints but didn't know the detail - the idea was probably put forward by that comet Hergenrother journalist!
Interestingly someone at ESA implies that this would have been possible in this Twitter thread but I don't think it is. As I understand it the best case delta-V of comet interceptor from L2 is around 3 km/s. If that was all used as a prograde, in-plane impulse it wouldn't be enough to raise the aphelion to 2au (the Earth's velocity around the Sun is around 30 km/s).
Is it possible that objects like Borisov, asteroids, comets, even free floating planets permeate the vast regions of interstellar space. So objects like Borisov and Oumuamua are like nomads of the Galaxy having chance encounters with other Solar systems. If this is the case wouldn't it be difficult to pin down the home star of these objects. Would more of them have a tendency to enter the Solar system from the direction of the Solar apex, the 19.5Km/sec motion of the Sun through space.
Peter
I'd expect more to come from the hemisphere around the solar apex but we're going to be in the small number statistics regime for a long time yet. Even if interstellar objects are found annually it will be a few decades before the statistics are good enough to make a definitive statement.
I see very little chance of determining their original star. Unless they were ejected very recently from a very close neighbour the perturbations from other stars will make the trajectory very curvy. It takes a long time to travel anywhere at only 30km/s (chosen because it make the arithmetic easier --- it is 0.0001c). At that speed it takes over 3 million years to travel 100 parsecs --- close by in galactic terms.
Nice image from Gemini https://www.gemini.edu/node/21240 something for Pete, Nick and Denis to aim for :-)
Owen
I imagine a C14 was rather cheaper than the Gemini though....
IAU CBET 4672 announced that this comet has now received the 2I prefix, marking it as the second interstellar object butt he first to show definite cometary features. There are plenty of images of it in the section archive here.
Nick James writes in the December 2019 Journal that Borisov is the first confirmed interstellar comet.
I think I have read somewhere that the 1956 comet Arend-Roland came from (and went back to) interstellar space? Maybe that was just a guess?
Before 2I all of the comets that we know with very slightly hyperbolic orbits acquired the extra velocity through planetary perturbations when they were in the inner Solar System. We would expect comets falling in from the Oort cloud to be in parabolic orbits, i.e. have a velocity of zero at infinity. The largest eccentricity known prior to 2I was 1.057 for C/1980 E1 (Bowell). This large excess velocity (around 3.8 km/s) was acquired from a Jupiter encounter in 1980 December. Comet C/1956 R1 (Arend-Roland) had an exit eccentricity of 1.0002. The pre-perihelion eccentricity was indistinguishable from parabolic. The ultimate end for our comets is to either fall into the Sun or be ejected from our Solar System and become an interstellar comet for some one else.
I obtained this image using the T30 500 mm telescope at Siding Spring Observatory . It is the average of three 600 s exposures with a luminance filter.