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The asteroid 3200 Phaethon is the type of object that doesn’t usually get a lot of attention. It’s a boulder about three miles across that orbits the Sun once every year and a half. It passes so close to the Sun that any ice it might have had has long since vaporized, leaving only bare rock.
Yet Phaethon is of special interest because it’s the parent of the Geminid meteor shower, which is at its best the next few nights. Moonlight will overpower most of this year’s fireworks, but a few bright meteors should shine through.
Over the last few years, as Phaethon passed closest to the Sun, it behaved much more like a comet than an asteroid — it grew much brighter, and it sprouted a tail.
Comets have lots of frozen water and gases. When they get close to the Sun, some of the ice vaporizes, releasing gas and dust into space. This material surrounds the comet, making it much brighter. Sunlight and the solar wind blow some of it away from the comet, forming the tail.
Phaethon has long since lost any ice, though. Instead, the intense heat probably cracks its rocky surface, releasing grains of dust into space. This outburst briefly surrounds Phaeton, making it appear brighter. The Sun pushes the dust away, forming a tail. Most of the dust is quickly blown out into space. But some of the larger bits join the cloud of debris that causes the Geminid meteor shower — providing fresh material for a celestial lightshow. More tomorrow.
Script by Damond Benningfield, Copyright 2013