Planets:
huge and hot

Ultra-Hot Transiting Planets

KELT-9 b KELT-20 b Other Ultra-Hot Jupiters

Directly-Imaged Exoplanets

HR 8799 c HR 7672 B Other Imaged Exoplanets

Featured: directly imaged planets formed early

How and when do giant planets far from their stars form? The atmospheres of directly imaged planets are often enriched in metals compared with their host stars, a sign that they accreted solid material as they formed. In Wang (2025, ApJ 981, 138), I analyzed seven directly imaged planets with measured stellar and planetary chemical abundances: 51 Eri b, β Pic b, HIP 65426 b, HR 8799 c and e, AF Lep b, and YSES 1 c.
Violin plot of the accreted solid mass for seven directly imaged exoplanets
Each violin shows the inferred mass of solids accreted by one planet. White points mark the medians, thick bars the 25–75% range, and the dotted line the average of 53.5 Earth masses.
These planets accreted large amounts of solids, on average about 50 Earth masses each and between 23 and 223 Earth masses for individual planets, whether they formed by core accretion or by disk instability. Such large amounts of solids were only available early on, in young and massive protoplanetary disks, which implies that these planets formed early, within about 2 million years. The work was featured by OSU News.