Protoplanetary Disks Are Smaller Than Expected

Summary

In astronomy, the first thing you see may be the least typical. A case in point: ‘Hot Jupiters.’ A few prescient souls, among them Buzz Aldrin and John Barnes in their novel Encounter with Tiber, speculated about gas giants that survived incredibly tight orbits around their star, and when asked about this in the 1990s, Greg Matloff ran the numbers and confirmed to his surprise that there was a theoretical case for their existence. Let me quote Matloff on this: Although I was initially very skeptical since then-standard models of solar system formation seemed to rule out such a possibility, I searched through the literature and located the appropriate equation (Jastrow and Rasool, 1965)….To my amazement, Buzz was correct. The planet’s atmosphere is stable for billions of years. Since I was at the time working as a consultant and adjunct professor, I did not challenge the existing physical paradigm by submitting my results to a mainstream journal. Since “Hot Jupiters” were discovered shortly before the novel was published, I am now credited with predicting the existence of such worlds. 51 Pegasi b made the case for ‘hot Jupiters’ convincingly in 1995, and we also know that the reason we began finding these planets was that our best methods for detecting exoplanets in the mid-1990s involved radial velocity and transit measurements, both of which are most effective when dealing with large planets in close orbits. As best I can determine, current estimates find a scant ~0.5–1% of these planets around F-, G-, or K-class stars. The rarity of hot Jupiters like TOI-4201b underlines how rare these objects are around M-dwarfs. Observational bias can be a tricky thing. So is something of the same phenomenon occurring in our study of how planets form? Protoplanetary disks are extensively studied, some of them showing what appear to be planets in their early stages of formation. As I’ve read studies about disks like those at TW Hydrae and HL Tauri, I’ve always assumed that they w...