Massive halos of dust are surrounding young planets for much longer than the laws of physics say they should.
April 23, 2026
Original Paper
Dust characterization of halos -- The extended emission in protoplanetary disks
arXiv · 2604.18332
The Takeaway
Protoplanetary disks are the birthplaces of solar systems, and their dust should rapidly spiral inward toward the central star. Observations of three specific disks show extended dust halos that persist long after they should have disappeared. Standard radial drift theory predicts that this dust should have grown into rocks or fallen into the star millions of years ago. These halos prove that there is a missing piece in our models of how planets form from tiny grains. If dust stays in the outer disk longer than expected, it could mean that giant planets like Neptune and Uranus form much more easily than we thought.
From the abstract
Extended, low surface brightness emission has been identified in a number of protoplanetary disks, in tension with predictions of radial drift theory. We aim to investigate the nature and origin of faint, extended dust emission in the outer regions of protoplanetary disks, which we define as the Halo, using multiwavelength (sub-)millimeter continuum observations of three systems: Elias 2-24, IM Lup, and DM Tau. We utilize Atacama Large Millimeter Array (ALMA) observations of our targets to perfo