This phenomenon is thought to be the cause of the comet-like tail associated with Elst Pizarro, an asteroid discovered in 1996, said Marsden. This could also be the cause of 3200 Phaethon's debris tail. "Although it is difficult to see how the rock-like dust could persist to yield Geminids annually, with records from centuries ago," he said. "So that brings us back to the comet idea."
Recent studies on the orbits of the Geminid meteors indicate that they were produced when 3200 Phaethon passed closest to the sun, which is comet-like behavior.
"I actually believe that 3200 Phaethon is a comet, albeit an inactive one. [But] because it doesn't look like a comet, we have classified it as an asteroid," said Marsden.
Cooke holds to his theory that 3200 Phaethon is an object that cannot be defined with current astronomical terms.
"Phaethon may well be a 'Twilight Zone' object, intermediate between asteroids and comets. In which case, both sides of the debate would be part right and part wrong," Cooke said. "This is my current opinion."
Regardless of whether 3200 Phaethon is indeed an asteroid or a comet, it is classified as a potentially hazardous asteroid. Its orbit brings the body close enough to Earth that scientists believe it has a chance of actually making impact.
To be classified as a potentially hazardous asteroid, a body must pass within 4.6 million miles (7.5 million kilometers) of Earth. There are currently 480 known potentially hazardous asteroids, according to NASA.
Every year in mid-December when the Geminid meteor shower is active, Earth is less than 2 million miles (3.2 million kilometers) from Phaethon's orbit.
The closest upcoming approach for 3200 Phaethon is to 1,812,640 miles (2,917,162 kilometers) on December 14, 2093, said Marsden, making contact in the foreseeable future unlikely. The distant future, however, is less certain.
"I don't know that anyone has specifically made long-term calculations for Phaethon, but over a million years the chance of a hit would be rather good, judging by what we know about similar bodies," he said.
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