A pair of comets are set to whiz by Earth this week, one of which will make the closest pass of any comet in 246 years.

The first one, named 252P/LINEAR, passed our planet at a distance of 3.3 million miles Monday morning, according to Smithsonian. Astronomers have followed this comet for years, but they can't say the same about the other one, which will fly even closer to our planet on Tuesday.

The comet P/2016 BA14 is expected to come as close as 2.1 million miles– about nine times further from the Earth than our Moon– at noon EDT on Tuesday, according to Sky and Telescope. It'll be the closest a comet has come to our planet since Lexell's Comet on July 1, 1770, which is the closest known brush with Earth at just 1.4 million miles, the report added.

"Comet P/2016 BA14 is possibly a fragment of 252P/LINEAR. The two could be related because their orbits are so remarkably similar," Paul Chodas from NASA's Center of NEO Studies (CNEOS) told Astronomy Magazine. "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."

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252P/LINEAR has been followed by astronomers since 2000, but P/2016 BA14 was just spotted in January, Science Alert said. At first, they believed it was an asteroid that may have been aiming for Earth, but when they found a tail, they knew it was less of a threat to the planet.

At this point, 252P/LINEAR is burning brighter than astronomers anticipated, but it's only visible in the Southern Hemisphere, Science Alert added. If it stays bright for the next couple of weeks, it may be visible to the naked eye in both hemispheres, so keep an eye out for a green glow in the nighttime sky.

As for P/2016 BA14, although it's going to travel closer to Earth, it's not as big and will probably only be visible if you have a high-powered telescope, Astronomy Magazine said.

If you're unable to see either comet as it passes Earth, The Virtual Telescope will broadcast live on Monday and Tuesday. It might be worth watching online because neither comet will be back around in the near future.

"March 22 will be the closest comet P/2016 BA14 gets to us for at least the next 150 years," Chodas told Astronomy Magazine. "Comet P/2016 BA14 is not a threat. Instead, it is an excellent opportunity for scientific advancement on the study of comets."

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