New observations and analysis of the recently-discovered comet C/2019 Q4 have confirmed its hyperbolic orbit and interstellar origin. Experts from the Minor Planet Center at the International Astronomical Union (IAU) have therefore assigned the permanent interstellar designation 2I to it, and members of the IAU Working Group for Small Body Nomenclature have decided to retain the name Borisov for the permanent designation.
This composite image, obtained by the Gemini North Multi-Object Spectrograph on the 8.2-m Gemini North telescope, shows 2I/Borisov. Image credit: Gemini Observatory / NSF / AURA / Travis Rector.
2I/Borisov was detected on August 30, 2019 by Gennady Borisov, an astronomer at the Crimean Astrophysical Observatory in Nauchnij, Ukraine. Borisov made this discovery with a 0.65-m telescope he built himself.
On September 12, the 10.4-m Gran Telescopio Canarias — one of the largest telescopes in the world — obtained a spectrum of 2I/Borisov and found it to resemble those of typical cometary nuclei.
Astronomers from the IAU Minor Planet Center then computed its preliminary orbit, which suggested this object was indeed interstellar.
“Of the thousands of comets discovered so far, none has an orbit as hyperbolic as that of 2I/Borisov,” they said.
“This conclusion is independently supported by the Solar System Dynamics Group at NASA’s Jet Propulsion Laboratory.”
According to the IAU astronomers, 2I/Borisov is between 1.2 and 10 miles (2-16 km) across. It has a condensed coma and a broad, short tail.
The comet will make its closest approach to the Sun — reach its perihelion — on December 7, 2019, when it will be 2 AU from the Sun and also 2 AU from Earth.
By December 2019 and January 2020 it is expected that it will be at its brightest in the southern sky.
It will then begin its outbound journey, eventually leaving the Solar System forever.
“Coming just two years after the discovery of the first interstellar object 1I/‘Oumuamua, this new finding suggests that such objects may be sufficiently numerous to provide a new way of investigating processes in planetary systems beyond our own,” the IAU astronomers said.
The IAU announcement was published on September 13, 2019 in the Minor Planet Electronic Circular (MPEC).
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G. Masi et al. 2I/Borisov = C/2019 Q4 (Borisov). Minor Planet Electronic Circular # 2019-S72
