Scientists knew comet BA14 would make a relatively close pass by Earth last week, but the space rock did have a surprise: it was seven times larger than they expected.

The comet passed by Earth on March 22, only days after fellow comet 252P/LINEAR. Initially, BA14 was thought to be about half the size of 252P/LINEAR, which measured approximately 820 feet wide.

However, after days of observing this hurtling chunk of space rock, NASA’s Goldstone Solar System Radar in California’s Mojave Desert determined that this comet was larger than the one passing Earth days before -- much larger.

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Using an antenna of NASA’s Deep Space Network at Goldstone, California, radar images of comet BA14 were obtained during its close flyby.

(NASA/JPL-Caltech/GSSR)

BA14 was recorded to have spun one its axis every 35 to 40 hours,making the size somewhere around 3,000 feetin diameter, according to NASA Jet Propulsion Laboratory.

"We were able to obtain very detailed radar images of the comet nucleus over three nights around the time of closest approach," said Shantanu Naidu, a postdoctoral researcher at NASA’s Jet Propulsion Lab.

"The radar images show that the comet has an irregular shape: looks like a brick on one side and a pear on the other," Naidu explained. "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."

Astronomers have suggested that BA14 and 252P/LINEAR were once part of the same object.

"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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BA14 became the third closest flyby in recorded history, buzzing within 2.2 million miles of the blue marble of Earth. For reference, that’s a modestnine times the distance between the Earth and moon, according to Space.com.

The closest flyby on record was in July 1770, whenLexell’s comet soared 1.4 million miles from the Earth, according to a news release from the Planetary Science Institute.

As for the miscalculation of the comet’s size, that’s likely contributed to the lack of sunlight reflected off of the comet’s nucleus. Nuclei tend to be very dark, reflecting about 3 percent of the sunlight that strikes them. In comparison, fresh asphalt reflects about 4 percent of the sunlight that’s beamed onto it.

It wasn’t until the comet came close enough to measure with a radar that the true mass of the object was seen. Astronomers are hard at work to not only better understand this most recent flyby, but celestial objects that may roar by the Earth in the future.

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