May 2, 2011

Comet Bops Past Neptune Cleanly

Comet Hale-Bopp has been spotted beyond the orbit of Neptune, far enough from the sun to be without its dirty tail. John Matson reports

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If the solar system were a Peanuts cartoon, the role of Pigpen would be played by a comet. Comets are messy creatures: they surround themselves in a cloud of gas and dust and often carry a long tail of debris.

But even these celestial dirtballs clean up their act now and then. When a comet is far from the sun, it freezes and stops shedding material. In the case of Hale–Bopp, the Great Comet of 1997, that freeze-out has taken a while—astronomers have spotted Hale–Bopp out past the orbit of Neptune, where it’s finally chilling out. That’s according to research that’ll be published in the journal Astronomy & Astrophysics [Gyula Szabó, K. Sárneczky, and L. L. Kiss, "Frozen to death? -- Detection of comet Hale-Bopp at 30.7 AU"]

Hale-Bopp has far less sunlight-reflecting material surrounding it now than it did in 2007. So the comet's slovenly behavior has either tapered off to a low level, or it’s gone dormant and is no longer shedding material at all.

Either way, Hale–Bopp managed to travel billions of kilometers before giving up its messy ways, farther than any comet astronomers have ever seen. Even Pigpen couldn’t compete with that dedication to debris.

—John Matson

[The above text is an exact transcript of this podcast.]

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