A pair of comets is due to make a close pass by the Earth on March 21 and 22. One of these passages will be the second-closest approach any comet has ever made to our planet since astronomers began records of the events.
The pair of comets due to pass by Earth are traveling along nearly-identical orbits in their paths around the sun. This discovery, revealed through observations taken at the Discovery Channel Telescope (DCT), suggests the two bodies may have once been parts of a larger object that broke apart.
"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," said Paul Chodas of Jet Propulsion Laboratory.
Comet Panstarrs (P/2-16 BA14) will miss the Earth by 2.1 million miles, roughly nine times the distance to the moon. This may sound like a significant distance, but no comet has come this close to our home planet in 246 years.
On July 1, 1770, Lexell's Comet brushed within 1.4 million miles of the Earth. Observers at that time were able to see the apparition, nearly as bright as Saturn, stretching out across the sky, four times as wide as a full moon. In 1983, Comet Iras-Araki-Alcock passed just 2.9 million miles from the Earth. This record for the second-closest approach of a comet to our home planet will be broken during the upcoming visit.
Unfortunately, despite how near the celestial body will be to Earth, Panstarrs 2016 BA14 will not be visible to the naked eye. A telescope will be required to view the extraterrestrial visitor, although amateur astronomers may be able to view the body with a backyard instrument. When the body was first found, astronomers believed it was an asteroid. Denis Denisenko, a Russian astronomer, noted the body followed the path of comet 252P/Linear, revealing the true nature of the newly-discovered body. That comet will not be seen without a sizable telescope, according to astronomers.
Complicating issues even further is the moon, which will be visible during the comets' closest approach, drowning out views of the frozen bodies. However, on March 24, our planetary companion will remain hidden until after twilight, allowing amateur astronomers an opportunity to glimpse the extraterrestrial visitors.
Astronomers will take spectrographs of the comets, in order to show, conclusively, if the bodies were once a single object.
The nearest approach for 252P/Linear will some on March 21 at 8:14 a.m. EDT, while P/2-16 BA14 will be closest to Earth at 10:30 a.m. EDT on the following day.
