Radar images of the asteroid 2003 SD220, taken in the period 15-17 December. (Supplied: NASA)
The narrow approach of the asteroid on Earth to this Christmas revealed that it is similar in the form of a "hypopotamus that flies in a river," according to NASA.
The facility, dubbed 2003 SD220, is now closest to Earth for 400 years, NASA said.
They safely passed from the planet last Saturday to 2.9 million kilometers – about seven and a half times the distance from Earth to the Moon.
Next he will return to Earth in 2070, in a little closer.
Three spatial communication facilities gathered new data on the asteroid for three days from December 15, revealing its shape and surface, and giving astronomers a better understanding of their orbit, NASA says.
The images are 20 times more detailed than the previous asteroid readings.
"Hypno" is 1.6 kilometers long and has an "extremely slow rotation" of about 12 days, the space agency has reported.
"It also does what seems to be a complex rotation that is something analogous to badly thrown football," the NASA statement said.
Radar images of the asteroid, made using an antenna for transmission, and another to receive, are in detail comparable to the flight of space shuttles, such as NASA OSIRIS-REx photographed earlier this month from the asteroid Bennu, the agency said.
The asteroid Bennu was visited earlier this month. (NASA / Goddard / University of Arizona through AP)
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