Two comets will fly past Earth on Monday 21 and Tuesday 22 March in the third closest comet flyby in recorded history.
NASA says the comets, 252P/LINEAR and P/2016 BA14, may be twins of sorts and will zip past Earth at a range of about 3.3 million miles and 2.2 million miles respectively.
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Comet P/2016 BA14 was discovered by the University of Hawaii's PanSTARRS telescope on January 22 and was initially thought to be an asteroid, but follow-up observations by a University of Maryland and Lowell Observatory team with the Discovery Channel Telescope showed a faint tail revealing that it was a comet.
It follows an unusually similar orbit to that of comet 252P/LINEAR, which was discovered by the Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research (LINEAR) survey on April 7 2000.
P/2016 BA14 is roughly half the size of comet 252P/LINEAR and might be a fragment that calved off sometime in the larger comet's past.
Paul Chodas, manager of NASA's Center of NEO Studies (CNEOS), said: "Comet P/2016 BA14 is possibly a fragment of 252P/LINEAR. The two could be related because their orbits are so remarkably similar."
It will be the third closest flyby of a comet in recorded history next to comet D/1770 L1 (Lexell) in 1770 and comet C/1983 H1 (IRAS-Araki-Alcock) in 1983.
The time of closest approach for comet 252P/LINEAR on March 21 will be around 5:14 am PDT. The time of closest approach for P/2016 BA14 on March 22 will be around 7:30 am PDT.
NASA says that While both comets will safely fly past at relatively close distances, anyone hoping to see them will need powerful, professional-grade telescopes due to their relatively small size.