This animation was assembled from radar images of near-Earth asteroid 3200 Phaethon taken by astronomers at the National Science Foundation’s Arecibo Observatory last week. Observations of Phaethon were conducted at Arecibo from 15 to 19 December, 2017. At time of closest approach at about 11:00 UTC on the 16th, the asteroid was about 1.8 million km away (about 4.6 times the distance from Earth to the Moon). That should be the Earth’s closest encounter with the asteroid until 2093.
The Arecibo radar images show that Phaethon has a diameter of about 6 km. That’s about a km larger than previous estimates. Given it’s size and near-Earth orbit, Phaethon is the second largest near-Earth asteroid classified as “Potentially Hazardous.”
Other Phaethon facts: It was the first asteroid discovered by a spacecraft—The Infrared Astronomical Satellite in 1983. It’s the parent body of the Geminids meteor shower. It has a highly elliptical orbit which brings it closer to the Sun than any other named asteroid. The orbit extends from beyond Mars’ to inside Mercury’s.
Image Credit: Arecibo Observatory / NSF / NASA