An Etymological Dictionary of Astronomy and Astrophysics

A new → interstellar object of → cometary nature.

Orbital and morphological properties of this body show that this is the first certain case of an interstellar comet, and the second-known interstellar minor body identified in the → Solar System (after → 1I/‘Oumuamua).

2I/Borisov’s motion shows significant systematic deviation from what is expected for a → parabolic orbit and is consistent with an enormous orbital → eccentricity of 3.14 ± 0.14. Images show an extended → coma and a faint, broad → tail. The → color index of 0.63 ± 0.03 is essentially the same as measured for the native Solar System → long-period comets.

2I/Borisov will reach its → perihelion on 7 December 2019, when it will be 2 → astronomical units (AU) from the Sun and also 2 AU from Earth. By January 2020 it will be at its brightest in the southern sky. It will then begin its outbound journey, eventually leaving the Solar System forever

(Guzik et al., 2019, Nature Astronomy, 14 October).

See also: Named after the amateur astronomer Gennady Borisov, from MARGO observatory, Crimea, who on 30 August 2019 discovered an object with a comet-like appearance.