Spun in the sun

摘要

Two asteroids have been observed gradually spinning faster and faster, and the hot tip is that sunlight is the cause. If so, this could give us a handle on the dynamics and evolution of the asteroid belt in general. "Captain, something is spinning up these asteroids, and there's no way we can stop it!" What might sound like an excerpt from a long-lost episode of Star Trek is, in fact, a pretty precise description of a genuine scientific mystery. On page 420 of this issue, Kaasalainen et al. show that asteroid (1862) Apollo, a 1,400-metre-diameter near-Earth asteroid (one whose orbit intersects that of Earth), has noticeably increased its rate of rotation over 25 years of observation.