SAN FRANCISCO, CALIFORNIA—As asteroids go, Phaethon is a weird one. The enigmatic space rock, about 5 kilometers wide, is one of only a handful known to eject dust from its surface. Now, cameras aboard the Sun-grazing Parker Solar Probe have imaged a 20-million-kilometer-long trail of dust shed by Phaethon. This trail, spotted for the first time (seen above as the faint track between the two red arrows), is part of a longer stream that’s responsible for the Geminid meteor shower, an annual light show that peaks today and tomorrow in both hemispheres.
Previous attempts to image debris from Phaethon (named for the son of Helios, the Sun god in Greek mythology)—even using the sensitive Hubble Space Telescope—were unsuccessful. The asteroid’s trajectory takes it within the orbit of Mercury, and scientists have hypothesized that the Sun’s extreme heat causes the rock’s surface to fracture and release dust. But the amount of dust that Parker Solar Probe spotted is less than what’s expected for the Geminid meteor shower. That means the dust trail is only one part of a longer stream shed by Phaethon, researchers reported here this week at the annual meeting of the American Geophysical Union.