Radar Zings Comet BA14 During its Close Flyby, Reveals New Details

On March 22, Comet P/2016 BA14 (Pan-STARRS) flew just 2.2 million miles (3.5 million...

BA14 Gianluca March 24

BA14 radar pix
These radar images of comet P/2016 BA14 were taken on March 23, 2016, by scientists using an antenna of NASA's Deep Space Network at Goldstone, California. At the time, the comet was about 2.2 million miles (3.5 million kilometers) from Earth. Credit: NASA/JPL-Caltech/GSSR

On March 22,  Comet P/2016 BA14 (Pan-STARRS) flew just 2.2 million miles (3.5 million kilometers) from Earth, making it the third closest comet ever recorded. The last time one flew this close was in 1770, when Lexell's Comet came out of nowhere and slid by Earth at half that distance. In ordinary telescopes, even big ones, BA14 looks just like a star. Deep photos reveal a soul patch of a tail.

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Watch the comet spin in these radar images While normal telescopes show few details, NASA's  Goldstone Solar System Radar in California's Mojave Desert pinged P/2016 BA14 with radar over three nights during closest approach and created a series of crisp, detailed images from the returning echoes. They show a bigger comet than expected — about 3,000 feet (one kilometer) across —  and resolve features as small as 26 feet (8 meters) across.


BA14 Gianluca March 24
Comet P/2016 BA14 looks like a star with a short tail in this photo taken on March 24, 2016. Credit: Gianluca Masi

"The radar images show that the comet has an irregular shape: looks like a brick on one side and a pear on the other," said Shantanu Naidu, a researcher at NASA's Jet Propulsion Laboratory. "We can see quite a few signatures related to topographic features such as large flat regions, small concavities and ridges on the surface of the nucleus."

Comet albedo charcoal comparison
Comets are as dark as charcoal but appear light only because the sun illuminates them against the blackness of outer space. I shined a flashlight on a charcoal briquette (left) to simulate comet lighting. The same charcoal, when viewed in normal light, appears black. Credit: Bob King

Radar also shows that the comet is rotating on its axis once every 35 to 40 hours. While radar eyes focused on BA14,  Vishnu Reddy , of the Planetary Science Institute, Tucson, Arizona, used the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii to examine the comet in infrared light. He discovered its dark surface reflects less than 3% of the sunlight that falls on it. The infrared data is expected to yield clues of the comet's composition as well.

Comets are exceptionally dark objects but compared to the ultra-black of outer space they look bright. Comet 67P/Churyumov-Gerasimenko, still the apple of the orbiter Rosetta's eye, is similarly dark, reflecting about 4% of sunlight. That's about the same amount of light reflected by fresh asphalt.

P/2016 BA14 is headed away from Earth but will return in another 5.25 years when it swings around the sun again. It's a periodic comet, the reason for the "P" in front of its name, so it orbits the sun once every 5.25 years or a little more than twice the time it takes Mars to do the same.

Because it's period and orbit are very similar to another comet, 252P/LINEAR, it's thought that BA14 may be related, possibly having broken away from 252P sometime in the past. While BA14 is faint, its relation is much brighter, having recently reached naked eye brightness. For more information and finder maps please click HERE .

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