The Hubble Space Telescope offers us an unprecedented close-up look at the many strange and wondrous objects occupying our solar system and even in some of the farthest reaches of observable space. Occasionally, Hubble detects objects that defy classification and scientists’ understanding. One such discovery was made this week, and astronomers aren't sure what to make of it.
The object is actually a pair of objects orbiting around one another in an asteroid belt located between Mars and Jupiter. Astronomers have named the pair 288P and are at a current loss to explain and classify them. The pair is the first known set of objects which are both locked into orbit around one another while also ejecting trails of water vapor into space behind them. That second characteristic is usually only found in comets, but the 288P objects are locked into the asteroid belt unlike comets.
Furthermore, the orbits of the objects are unique. They lie around 100 km (~62 miles) apart in an elongated orbit not usually seen in asteroid pairs. Jessica Agarwal, a researcher at the Max Planck Institute who discovered the odd hybrid comet/asteroids (cometoids? astromets?), says that the 288P objects might be the first-known asteroids to eject water as comets do:
If that is the case, it basically can change our understanding of how asteroids evolve, so how fast they disintegrate and change their sizes. And this in turn can also change our understanding of how they have evolved in the past and our models of the initial distribution of asteroids in the asteroid belt.
Until astronomers find more objets like 288P to study, this odd couple will remain a mysterious anomaly.