Snow Lines and Protoplanetary Disks, Or, Where’d All The Water Go?
Planet formation theory predicts a water-rich Earth. On a comparative basis, the Earth is water-poor. This paper aims to reconcile theory and observation.
A Cosmic Vanishing Act
The authors report on a young, Sun-like star with a debris disk of dust and larger rocks that has had the dust particles mysteriously vanish from the disk in a span of less than two years.
How to Build a Low-Density Super-Earth
Many Super-Earths appear to be less dense than the Earth. How do such planets form? Could a rocky Super-Earth accrete a hydrogen-helium atmosphere in-situ?
Finding dust grains (and planetesimals?) in a circumstellar disk
AU Mic is a low mass star that undergoes unpredictable brightening events, called flares. It’s located just 10pc and has a circumstellar disk. In this paper, Wilner et al. report on observations of the disk at millimeter wavelengths and find evidence for a planetesimal ring.
In the Shadow of a Circumstellar Disk
We know other stars have planets. We know that certain stars have circumstellar disks. We know that before there are planets, there must be a protoplanetary disk; we also know that these two states must be connected through a evolutionary path which includes planet formation.
What if–if we were just so lucky–we found a protoplanetary system that had a disk, that was aligned so perfectly, and that was bright enough, and ….
Did our Earth have 2 Moons?
Astronomers think one impact may not have been enough to see the Moon as we do today. If two moons formed out of the massive collision first hypothesized, they could have merged which would explain the terrain dichotomy we see on the near and far sides of our Moon.