A ROCK COMET APPROACHES EARTH: On Dec. 16, 2017, an unusual space rock named "3200 Phaethon" will fly past Earth only 10.3 million km away. It's the closest approach in 40 years for this large object. Measuring 5 km across, 3200 Phaethon is half the size of the asteroid that wiped out the dinosaurs 65 million years ago. ...
What is 3200 Phaethon?... When 3200 Phaethon was discovered in 1983 by NASA's IRAS satellite, astronomers quickly realized that they had found the source of the annual Geminid meteor shower. The orbit of 3200 Phaethon was such a close match to that of the Geminid debris stream, no other conclusion was possible. Yet here was a puzzler: Meteor showers are usually caused by comets. Everything about 3200 Phaethon suggests it is an asteroid.
In fact, 3200 Phaethon resembles main belt asteroid Pallas so much, it could well be a 5-kilometer chip off that 544 km block. If 3200 Phaethon broke apart from asteroid Pallas long ago, as some researchers believe, then Geminid meteoroids might be debris from the breakup ...
This year's close approach of 3200 Phaethon to Earth happens only days away from the peak of the Geminid meteor shower on Dec. 13th and 14th. ... Meteoroids leaving 3200 Phaethon need time to drift over to the orbit of our planet. "It would take at least another revolution around the sun before material from this flyby could encounter Earth - probably longer," explains Bill Cooke of NASA's Meteoroid Environment Center. ...
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