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C/2017 U1 (PANSTARRS). An interstellar comet?

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nickjames's picture
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C/2017 U1 (PANSTARRS). An interstellar comet?

I mentioned this object at the meeting in London today.

PANSTARRS discovered an object on October 18 which is now designated C/2017 U1. This object made a relatively close approach to the earth on October 14 and astrometry over a 6-day arc indicates that it has a strongly hyperbolic orbit (e=1.19). If the orbit is extrapolated backwards it appears that this is an object which arrived from outside the Solar System with a significant velocity (approx 25 km/s). The object is small (approx 150m diameter) and it is now fading rapidly as it moves away from us. As of this morning it was around magnitude 21. Hopefully large telescopes will get further astrometry over the next few days since this will allow us to tie down the direction of arrival. At present it appears to have come from a direction corresponding to the constellation of Lyra although it could have been moving through the galaxy for billions of years so it is unlikely to be associated with any nearby stellar system.

If confirmed this will be the first detected interstellar object known to passed through our Solar System. Quite an exciting find.

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Comet C/2017 ( Panstarrs)

By a  remarkable coincidence  Space Weather.com is this evening is commenting on the orbit and  make up of Comet 96P/Machholz1  and making a link to Comet Yanaka ( (1988;1988Y1) both  being suspects  as Interstellar Objects.

Nothing is  quite brand new  it appears

nickjames's picture
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There is indirect and rather

There is indirect and rather weak evidence that some other objects may have interstellar origins but A/2017 U1 (now demoted from cometary status) has direct evidence from its strongly hyperbolic orbit. We've never seen anything with this kind of orbit before.

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This object has been

This object has been redesignated 1I/ʻOumuamua in MPEC 2017-V17. The "1I" is a new designation and it signifies that this is the first confirmed interstellar object to be detected transiting our Solar System. The pronunciation of the name is (ō'u-mu'-a-mu'-ă) and, according to the MPEC, the name is of "Hawaiian origin and reflects the way this object is like a scout or messenger sent from the distant past to reach out to us". This is probably the first of many interstellar objects that will be discovered over the coming decades given the sensitivity of modern sky surveys.

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Large aspect ratio

Apparently, the light curve (if a uniform albedo is assumed) implies a length to width ratio of 6:1 or more which is pretty phenomenal. Theres also a spectral response similar to a Jovian Trojan but dissimilar to a  KBO. How does that form?

Its name is something or other in Hawaiian. Cannot understand how an interstellar interloper plunging through the solar system and boasting a large aspect ratio has not ended up being called Rama - as fans of AC Clarke would know.

Fascinating object. Shame it was at mag 23. But there are, allegedly, lots more around.

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Ha ha! when I saw the various

Ha ha! when I saw the various graphics for it Rendevous with Rama was the very first thing I thought of!

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Rama

Yes, Rama would have been a very appropriate name, particularly because, in the book, it was the very odd lightcurve that was the first thing that drew attention to the object. A long, thin object in a strongly hyperbolic orbit. There is no indication that this isn't a natural object but the parallels with the Clarke's novel are quite interesting. It's definitely worth a read if you haven't read it already. There was also a very good Radio 4 adaptation which must be available somewhere.