Extended Data Fig. 1: Mass-radius diagram for V1298 Tau c (left) and d (right) at the system’s age of 23 Myr.
From: A young progenitor for the most common planetary systems in the Galaxy
The gray shaded region marks the boundary of parameter space accessible by standard, high-entropy formation models (initial Kelvin-Helmholtz cooling timescale τKH ≲ 10 Myr), with the 1-σ and 2-σ uncertainty on its location shown in dark and light gray. Illustrative model tracks are shown for comparison: the green and orange lines demonstrate that high-entropy models fail to simultaneously match the measured mass and radius, while the blue line shows a successful low-entropy model (τKH ~ 300 Myr) consistent with the data. The positions of planets c and d firmly in the lower-right region provide direct evidence that their formation required a low-entropy initial state, such as that produced by a ‘boil-off’ phase.
