One of the comets will zoom by Earth closer than any other since 1983.
Today and tomorrow (March 21 to March 22), two comets will fly past Earth, with one of them coming closer to our planet than any other comet since 1983.
The larger but more distant comet, called Comet 252P/LINEAR, was first spotted in the year 2000, and it has continued to be monitored ever since. It will become so bright that scientists believe, at its closest point, it might be visible in the night sky with the naked eye.
On the other hand, the smaller comet, P/2016 BA14, was only spotted in January of this year, and at first, astronomers thought it was a potentially dangerous asteroid hurtling towards Earth. But with further investigation, it was determined that P/2016 BA14 actually has a tail — meaning it is a mixture of dust and rock frozen into a solid mass. In other words, a comet!
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Unfortunately, this closer comet will not be as easy to see. However, it will pass Earth at a distance of just 3.5 million kilometers (2.2 million miles), making it the third closest flyby of a comet in recorded history.
But there is nothing to worry about — it is still more than nine times further away than the moon, so there is no chance that the comet will impact Earth.
“Comet P/2016 BA14 is not a threat,” Paul Chodas, manager of NASA's centre of Near Earth Object (NEO) Studies, in a explained in a press release. “Instead, it is an excellent opportunity for scientific advancement on the study of comets.”
Having two comets passing Earth within a day of each other is extremely rare, and astronomers hope that they will learn a lot more about how comets work.
“There are many more asteroids in near-Earth space than comets, which are significantly more rare,” Michael Kelley, an astronomer at the University of Maryland, told The LA Times. “When a comet does come this close to Earth it is something to get excited about, and take advantage of to learn whatever we can.”
There may be something special about these two comets too — they could be related. Although the orbits of the two comets are not identical, as you can see in the image below, they are similar enough to suggest that they are somehow linked. One of the leading hypotheses is that comet P/2016 BA14 is a fragment that broke away from the larger comet at some point.
Photo credit: NASA/Jpl-Caltech
People are most excited about comet 252P/LINEAR because it is already 100 times brighter than expected, according to The Conversation. Although it will not be passing as close as P/2016 BA14, it will still pass at a distance of 5.2 million kilometers (3.3 million miles) — making it the fifth closest comet in recorded history. Even more, 252P/LINEAR is also a very pretty shade of green because of the release of diatomic carbon (C2), a gas that glows green when its molecules become ionised.
Unfortunately, unless you are in the Southern Hemisphere, you won’t be able to see comet 252P/LINEAR at its closest point. However, if the comet stays bright for the next couple of weeks, people in both hemispheres will have the opportunity to see it.
However, if you would rather watch the comets in the comfort of your own home, the Virtual Telescope Project will be hosting live broadcasts showing the flyby of both comets on March 21 and 22. Comet 252P/LINEAR will make its closest approach at 9:14 am EDT today (March 21) and Comet P/2014 BA14 will make its closest approach around 11:30 am EDT on March 22.
There's also the possibility that a weak meteor shower will follow on March 28 as Earth crosses the dust trail of comet's orbits.
Below is an animation of the how close the comets will get to Earth.