Astronomers Still Puzzled by Blue Asteroid Causing the Geminid Meteor Showers

Thursday, 25 October 2018 - 12:26PM
Astronomy
Space
Solar System
Thursday, 25 October 2018 - 12:26PM
Astronomers Still Puzzled by Blue Asteroid Causing the Geminid Meteor Showers
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Composite adapted from Pixabay
When we're not narrowly avoiding collisions with them or planning to blow them up with nuclear weapons, scientists are busy studying the thousands of asteroids zipping around our solar system. Most of them are boring, grey, and potato-shaped, but one of the significant exceptions is 3200 Phaethon, a rare blue asteroid that acts like a comet. In the words of Teddy Kareta, the lead researcher on a new study focusing on Phaethon: "It's a weird blue asteroid that created the Geminids and gets so hot that metals on the surface turn to goo."

That plain-English description is appreciated, but it leaves a lot of questions: aren't meteor showers like the Geminids created by comets? Why does the surface of Phaethon turn to goo? Where did it come from?

The new research by Kareta and his team have shed some light on those mysteries. Let's start with the goo. According to the study, Phaethon's eccentric orbit takes it extremely close to the Sun, heating the surface to a temperature of around 1,500 degrees Fahrenheit, which is hot enough to melt the asteroid's surface metals. That process may also create a faint trail of dust when Phaethon moves away from the Sun, creating the raw material for the Geminid meteor shower. Meteor showers are generally caused by the Earth passing through a comet's dust trail, which contains tiny particles that rain down to Earth as meteors.

Scientists have had Phaethon pegged as the 'parent body' for the Geminids for decades due to the asteroid's orbit syncing up so closely to the showers, but that wasn't the case when it was first discovered. According to Kareta: "At the time, the assumption was that Phaethon probably was a dead, burnt-out comet, but comets are typically red in color, and not blue. So, even though Phaeton's highly eccentric orbit should scream 'dead comet,' it's hard to say whether Phaethon is more like an asteroid or more like a dead comet."

Only a few other asteroids in our solar system share Phaethon's blue color, and one of them is 2 Pallas, which is much larger. It's thought that Phaethon may be a chunk of Pallas that broke free, but discovering its origins will take another round of research.
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