Asteroid 3200 Phaethon. What‘s all the fuss about?

Planet Earth, November 25, 2017 (by Grig Richters) – Every now and then an asteroid makes the News. On November 15, 2017 Astronomers from the Immanuel Kant Baltic Federal University released an animation which created quite a bit of buzz:
We have been getting dozens of emails, tweets etc. since then. Although the asteroid will fly-by relatively close in December 2017 at “6.2 million miles from Earth“, as Newsweek reported, there is no need for panic. Asteroids fly-by the Earth all the time (read this article by Asteroid Day Expert Eric Christensen, here) and 3200 Phaethon poses no threat to us in the next one hundred years. Asteroid Day co-founder Rusty Schweickart states: “Phaethon has a 0 (zero) probability of impact over the next 100 years.“
Even though asteroid 3200 Phaethon poses no threat to our Planet, it is a really fascinating asteroid. NASA says the following about 3200 Phaethon: “The Geminids are a unique meteor shower in that their identified parent body is not a comet, but what seems to be an asteroid! Of the meteor showers with known parent bodies studied by meteor scientists, the Geminids are the only shower to have an asteroidal parent body; all others have a cometary origin. 3200 Phaethon measures 5.10 km in diameter which increases the ‘unique’ factor; considering the amount of debris we see, we would expect Phaethon to be a much larger body!
Phaethon was discovered on October 11, 1983 using the Infrared Astronomical Satellite, and named after the Greek myth of Phaethon, son of the sun god Helios, due to its close approach to our Sun.
Phaethon is technically classified as an asteroid — the first to be discovered via satellite. But how could an asteroid produce meteoroids that cause the Geminids? One theory is that Phaethon broke apart from another object, ejecting meteoroids as a part of the breakup. This doesn’t agree with other things we know, however. Another theory is that a collision with another object thousands of years ago could have produced debris that Earth now travels through. This theory appears to be unlikely as well, based on other evidence. Another theory assumes Phaethon to be a dead comet (the spent nucleus of a comet whose ices had been sublimated away) that produced debris in the past that now intersects Earth’s orbit. But no evidence for mass loss from the object has ever been reported…. until recently. In 2009 the NASA spacecraft STEREO-A observed 3200 Phaethon to brighten by a factor of two, quite unexpectedly. This brightening at perihelion was likely due to a release of dust from the object, possibly due to heating and cracking of the surface rocks as Phaethon came close to the Sun. That brings us to the fourth theory, that Phaethon is a rock comet. The problem with this theory is that it doesn’t account for the amount of dust in the Geminid stream.
So what it comes down to is that the Geminid parent object is a mystery.“
UPDATE (Thanks to Ryan F. Mandelbaum and Gizmodo):
We spoke to Gareth Williams, astrophysicist from the Harvard Smithsonian Center for Astrophysics, for a little more detail. Determining whether a large meteor will strike is never an easy yes-or-no answer, he said. As soon as an asteroid is discovered, there’s a large, uncertain region where scientists think it will travel, a region that may or may not include Earth. After subsequent observations, that region will become smaller, and an impact is ruled out once Earth is outside of that region.
But scientists have already modeled this new meteor pretty well. “(3200) Phaethon is not an object we need to worry about at this time,” said Williams. “Over tens of thousands of years the orbits will be perturbed by giant planets and the Earth, so the orbit could come closer.”


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