Another Interstellar Visitor?

C/2019 Q4 Borisov, candidate interstellar cometOn August 30th, 2019, Gennady Borisov, an optician and astronomer at the Crimean Astrophysical Observatory, using equipment he built himself, discovered a dim (18th magnitude) object moving with respect to the distant stars.  Further observations indicated it was cometary in appearance, with a coma around its brightest spot and apparent short tail.  Orbital computations from the limited number of observations indicate that it was discovered at a distance of around 3 astronomical units (AU) (the mean radius of the Earth’s orbit) from the Sun, inbound toward a perihelion on December 10th near 2 AU.

As with ’Oumuamua (1I/2017 U1) in 2017, attempts to fit a typical elliptical or parabolic orbit to the observations failed, and the best fit was found to be a hyperbolic orbit with an eccentricity in excess of 3.  Such an object is not gravitationally bound to the solar system and must be of interstellar origin; after rounding the Sun, it will depart into interstellar space never to be seen again.  This is only the second such object to be observed.  From observations so far (and with less than two weeks of data, these figures will be revised as further observations are made), its inbound velocity to the solar system before it began to be accelerated by the Sun’s gravity was around 30 km/sec, which rules out a hyperbolic orbit due to interactions with solar system objects, as such perturbations cannot create a velocity greater than 3 km/sec.  Here is the Minor Planet Center Circular, MPEC 2019-R106, announcing the discovery, its apparent interstellar nature, and preliminary orbital elements based on the news that’s come to Harvard.... [Read More]

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