For obvious reasons, it’s difficult to reconstruct the full history of the Solar System. We can study asteroids and other fragments of the protoplanetary disk from which the planets and other objects formed. However, we can also look for very young star systems; while these take millions of years to go from a nebula to a recognizable star with planets, maybe we can catch a few at crucial moments in their development. One such system is TW Hya, about 178 light-years away from Earth, which has a protoplanetary disk almost face-on to us. Astronomers identified the carbon monoxide snow line in this system: a dividing point between the region where according to theory large planets could form, and the domain of the comets and other icy objects like Pluto.

Chunhua Qi and colleagues observed a disk around a newborn star, a disk that appears similar to what we think the Solar System looked like about 5 billion years ago. It surrounds a newborn star similar to the young Sun. They looked for light emissions that only occur where carbon monoxide is frozen. The observations discovered a ring of ice where theory predicted, roughly at the same distance Neptune is from the Sun. In the Solar System, that distance marks where large planets no longer form and where the realm of the comets and Pluto-like objects begins. This is the first observation of its kind, so it should help astronomers refine planetary formation models and understand the origins of prebiotic molecules—essential chemicals for life. [Read more…]

For what it’s worth, I wrote this piece about frozen carbon monoxide — which freezes at a much lower temperature than water — on the hottest day of the year so far. It didn’t help.