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It’s hot out there

Asteroid 6478, discovered in 1988 by the Shoemaker’s at Palomar Observatory (yes, the comet is named after them), was just imaged by the Hubble Space Telescope. A6478 is named “Gault”, after Donald Gault, a scientist who studied impact cratering processes.

This is one of the few “active” asteroids that have been found. It is spinning so fast that it is flinging off bits of itself, forming two long tails of debris. Unlike a comet, which has tails of ice, Gault’s trail is formed of particles that have been sorted by solar pressure — the smallest and lightest are further away because they are accelerated faster than the heavy particles. Just for the record, “fast” is a relative term here. Gault is spinning about once every two hours.

The Sun is also responsible for setting it to spinning in the first place, indirectly, through the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect. Solar radiation heats the asteroid, which then re-radiates in the infrared. If the material of the asteroid is non-homogenous, causing higher re-radiation on one side, the offset forces will cause it to spin.

Comparing the featured image (from a ground-based telescope in Siding Spring, Australia) to the following goes to show how valuable the Hubble Space Telescope still is:

Asteroid Gault

When we get a human presence going in the Asteroid Belt, there’s going to be some interesting fog to watch out for.

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