Two comets set to whiz past Earth this week

Comet 252P/LINEAR will safely fly past Earth on March 21, 2016, at a range of about 3.3 million miles (5.2 million kilometers). The following day, comet P/2016 BA14 will safely fly by our planet at a distance of about 2.2 million miles. (NASA/JPL-Caltech)

Two comets that scientists have dubbed twins for their similar orbits are expected to safely fly past Earth this week, though they will be the closests any comes for the next 150 years.

Comet 252P/LINEAR, approximately 750 feet in size, zipped past Earth on Monday morning, at a range of about 3.3 million miles. On Tuesday, comet P/2016 BA14 will safely fly by our planet around 10:30 a.m. ET at a distance of about 2.2 million miles.

This 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.

"March 22 will be the closest comet P/2016 BA14 gets to us for at least the next 150 years," Paul Chodas, manager of NASA's Center of NEO Studies at the Jet Propulsion Laboratory in Pasadena, California said in a statement. "Comet P/2016 BA14 is not a threat. Instead, it is an excellent opportunity for scientific advancement on the study of comets."

Comet P/2016 BA14 was only discovered on Jan. 22 the University of Hawaii's Pan-STARRS telescope on Haleakala, on the island of Maui. Sixteen years ago, Comet 252P/LINEAR was spotted the Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research survey.

Initially, scientists thought Comet P/2016 BA14 was an asteroid until observations by a University of Maryland and Lowell Observatory team with the Discovery Channel Telescope spotted the tail. But that wasn’t the only surprise offered up by the comet.

It turned out to have a very similar orbit to Comet 252P/LINEAR, which has scientists suggesting they are similar in nature. P/2016 BA14 is roughly half the size of comet 252P/LINEAR, raising the possibility that it might be a fragment that calved off sometime in the larger comet's past.

"The two could be related because their orbits are so remarkably similar," Chodas said. "We know comets are relatively fragile things, as in 1993 when comet Shoemaker-Levy 9 was discovered and its pieces linked to a flyby of Jupiter. Perhaps during a previous pass through the inner solar system, or during a distant flyby of Jupiter, a chunk that we now know of as BA14 might have broken off of 252P."

Observations made by the Hubble Space Telescope of comet 252P/LINEAR, and by NASA's Infrared Telescope Facility of comet P/2016 BA14 will work to determine if they are twins.