Overview
- An international team measured the masses of all four planets in the V1298 Tau system using transit timing variations after nearly ten years of ground- and space-based monitoring.
- The worlds measure roughly 5–10 Earth radii yet only about 5–15 Earth masses, implying ultra‑low densities comparable to polystyrene foam.
- The host star is about 20 million years old, and the planets are actively losing gas under strong stellar heating.
- A lucky ground-based recovery of a previously missed outer-planet transit pinned down its orbital period, enabling the full TTV analysis.
- Researchers report the first direct evidence that many planets begin inflated and later contract into super‑Earths and sub‑Neptunes, with the findings published January 7 in Nature.