Spotted from afar: comet coming in from the cold
Lead researcher Dr David Jewitt, from the University of California at Los Angeles, said: “K2 is so far from the sun and so cold, we know for sure that the activity – all the fuzzy stuff making it look like a comet – is not produced, as in other comets, by the evaporation of water ice.
“Instead, we think the activity is due to the sublimation (a solid changing directly into a gas) of supervolatiles as K2 makes its maiden entry into the solar system’s planetary zone.
“That’s why it’s special. This comet is so far away and so incredibly cold that water ice there is frozen like a rock.”
The Hubble observations suggest that sunlight is heating frozen gases such as oxygen, nitrogen, carbon dioxide, and carbon monoxide that coat the comet’s frigid surface.
As the icy volatiles lift off the comet they release dust, forming the coma.
“Most comets are discovered much closer to the sun, near Jupiter’s orbit, so by the time we see them, these surface volatiles have already been baked off. That’s why I think K2 is the most primitive comet we’ve seen,” added Dr Jewitt.