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| Space on Dec 01, 2010

Geminid meteor storm from 3200 Phaethon in 2093?

3200 Phaethon is the source of the Geminid meteor shower, which peaks every year around December 13. Most meteor showers stem from comets – but Phaethon doesn’t appear to be an active comet anymore.

Lew of New York wrote, “The object called 3200 Phaethon will pass somewhat close to Earth in December, 2093. Could that produce a meteor storm?”

The answer is … probably not. 3200 Phaethon is known to be the source of the Geminid meteor shower, which peaks every year around this time. Most meteor showers stem from comets – but Phaethon doesn’t appear to be an active comet anymore. It probably ejected the debris needed to lay down the Geminid meteor stream long ago.

There’s a remote possibility that Phaethon is just dormant. There could be fresh ice below its surface crust. If a hole opened, sunlight might reach these ices, which might begin to boil off the nucleus, replenishing the Geminid meteor stream.

But even that doesn’t mean there’d be a storm of meteors seen on Earth. There are many complex factors affecting the structure of a meteor stream, and that’s why the connection between a comet’s passage and the intensity of a meteor shower isn’t a sure thing.

Meteor showers originate in comets orbiting the sun. A comet nucleus, or core, is a loose agglomeration of ices and dust particles – a deep-frozen specimen of the primeval solar system. As a comet’s orbit brings it near the sun, the ices in its nucleus sublimate in sunlight and spew off into space from one or more geysers springing from the comet’s fragile surface crust. This process leaves behind a trail of debris that follows the outline of the comet’s orbit.

Meteor storms can occur when the Earth passes through a meteor stream recently replenished with fresh material from a comet. When Earth crosses the path of a dense knot in the meteor stream, the night sky can come alive, for a brief time, with hundreds or even thousands of meteors per hour. That’s why the close passage of Phaethon – the object thought to spawn the Geminid meteor shower – prompted this question. It’s logical to assume that Phaethon’s close passage in 2093 could indeed spawn a meteor storm.

Here are some of the things astronomers know about Phaethon: its size (5.1 kilometers in diameter), its albedo, or how much light it reflects (9.8%), its rotation period (3.604 hours), its spectral type (F, which could make it an asteorid or a comet). Astronomers also know the orbit of this object very well.

The possibility that Phaethon is dormant rather than extinct is not so remote. Astronomers really think that it is very difficult for a comet to boil away all its ices and survive as an intact nucleus, so Phaethon may have some ices still in it.

On the other hand, Phaethon comes rather close to the sun with each orbit. So it’s difficult to believe that it has not been heated throughout. Another factor is that Phaethon’s rotation period is relatively fast, which argues that it is not a low-density object – though the real density of a cometary nucleus is unknown.

Phaethon’s close approach is on Dec. 14, 2093 at 10:52 UT, or 4:52 a.m. CST. The distance will be 1.84 million miles.

Our thanks to:

Daniel Green
Harvard-Smithsonian Center for Astrophysics

Paul Weissman
Jet Propulsion Laboratory