Dark comets sit in one of the stranger corners of solar-system science. They look like asteroids, without bright tails or fuzzy comas, yet their motion suggests a gentle extra push like the outgassing seen in comets. NASA-backed researchers now say the known group is large enough to separate into two families.
Objects that reveal themselves by moving wrong
The first clues came from bodies whose orbits did not quite match the pull of gravity alone. That kind of drift usually points to material venting from a comet, but these objects looked visually quiet.
The new classification suggests one population has larger, outer-solar-system-style orbits, while another consists of smaller bodies closer in. The distinction could help explain where they formed, what they contain and how common comet-like behavior may be among objects that appear rocky.
Why labels matter
Astronomy depends on categories, but nature keeps blurring them. Dark comets challenge the tidy split between asteroid and comet, and they may help scientists interpret future small-body discoveries with more care.
