Home › Comets › 2I/Borisov

Fact file

Type

Interstellar visitor

Diameter of the nucleus

1 km

Orbit

open (hyperbola) – will never return

Closest point to the Sun

passed on 8 December 2019

Interesting facts about 2I/Borisov

• The second known visitor from another star – and the first that looked like a proper comet, with a coma and a tail.
• It was discovered in 2019 by the amateur astronomer Gennady Borisov in Crimea, with a telescope he had built himself.
• It contained an unusually large amount of carbon monoxide ice – it must have formed in a very cold region around another star.

Origin

A comet from another planetary system that was flung out at some point – perhaps by a giant planet.

Coma and tail

It showed a coma and a tail just like our own comets. Part of its nucleus broke off in 2020.

Exploration

Many telescopes, including the Hubble Space Telescope, observed it for months.

Connection with Earth

With an initial speed of 32 km/s, it was even faster than ʻOumuamua.

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