2I/Borisov

2I/Borisov, originally designated C/2019 Q4 (Borisov), is the first observed rogue comet and the second observed interstellar interloper, after ʻOumuamua. It was discovered by the amateur astronomer and telescope maker Gennadiy Borisov on 29 August 2019 UTC (30 August local time) in MARGO Observatory. 2I/Borisov has a heliocentric orbital eccentricity of 3.36 and is not bound to the Sun. The comet passed through the ecliptic of the Solar System at the end of October 2019, and made its closest approach to the Sun at just over 2 AU on 8 December 2019. The comet passed closest to Earth on 28 December 2019. In November 2019, astronomers from Yale University said that the comet's tail was 14 times the size of Earth, and stated, "It's humbling to realize how small Earth is next to this visitor from another solar system."