This past week was an exciting one for astronomy fans. That's because two comets — 252P and P/2016 BA14 — were scheduled to make their closest approach to Earth, back-to-back. The icy celestial bodies did not disappoint.
252 aka LINEAR was the first to zip past Earth on Monday, March 21. At its closest, the comet which is the bigger of the two came within 3.5 million miles (5.6 kilometers) or about 14 times the distance from the Earth to the Moon. This made it the fifth closest comet encounter in recorded history. According to AccuWeather Meteorologist, Dave Samuhel, LINEAR was almost visible to the unaided eye in the Southern Hemisphere.
With a diameter of just over one kilometer, P/2016 BA14 aka PanSTARRS, which made its closest near-Earth flyby the following day (March 22) at 7:30 a.m. PDT (10:30 a.m. EDT), was about half the size of LINEAR. However, it came significantly closer — Zipping past just 2.2 million miles away or about nine times the distance from the Earth to the Moon. While this makes it the third closest comet encounter, it is the closest one in recent history, given that the previous two were recorded in the 1700's - Over two hundred years ago!
What's interesting is that astronomers did not even know that P/2016 BA14 existed until January 22 when it was spotted by University of Hawaii’s PanSTARRS telescope (after which it was named) that sits atop the dormant Haleakala volcano in Maui. It was initially believed to be an asteroid. But that changed when the University of Maryland and Lowell Observatory team noticed the tail, a feature that is characteristic of comets.
P/2016 BA14’s close approach enabled the scientists from NASA's Jet Propulsion Lab in Pasadena, CA to take detailed images. The scientists say that the odd-shaped comet, which is brick-like on one side and pear-shaped on the other, possesses some interesting topographical features that include ridges and valleys. They also learned it takes the comet anywhere from 35 to 40 hours to spin on its axis.
The fact that the two comets have such similar orbits has led astronomers to suspect that P/2016 BA14 may just be a part of LINEAR that broke off. Given that the comet was just recently discovered, that theory certainly seems plausible. Further studies will confirm if the researchers are right.
If you are like most people, you probably had no idea these comets were making an appearance. But do not fret. Scientists believe that the debris left behind by the comets as they zipped past Earth will result in a minor meteor shower from March 28 to March 30.
There is even better news for the residents of the Northern Hemisphere, who were shut out from the close encounter with LINEAR. Thanks to the comet's orbit, it will be visible to them starting Tuesday, March 29. LINEAR, which is much brighter than had originally been thought, can be best viewed about 90 minutes before sunrise. Astronomers recommend pointing binoculars or telescopes towards the southern part of the sky between the Sagittarius and Scorpius constellations. Sky and Telescope Senior Editor Kelly Beatty says that viewers should expect to see a circular greenish glow which will be larger than the moon, but thousands of times dimmer — So be sure to look carefully!