Astrophysics

A decade of monitoring the HIP 41378's planetary system

S. Grouffal, A. Santerne, X. Dumusque, B. Akinsanmi, T. Guillot, N. C. Hara, A. Leleu, L. Malavolta, M. Saillenfest, D. J. Armstrong, S. C. C. Barros, D. Bayliss, A. S. Bonomo, D. J. A. Brown, A. Collier Cameron, M. Cretignier, I. J. M. Crossfield, F. Dai, M. Damasso, O. Demangeon, P. Figueira, P. Leonardi, A. F. Martinez Fiorenzano, M. Lopez-Morales, E. Molinari, A. Mortier, L. D. Nielsen, H. P. Osborn, E. Petigura, K. Rice, N. C. Santos, A. Sozzetti, S. Sulis, S. Udry, C. Watson

Featured June 28, 2026

Original Paper

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Simply

Scientists watched a distant star for ten years, using powerful telescopes to measure its tiny wobbles, and found that two of its planets orbit at 278 and 393 days, and one super-fluffy planet is twice as heavy as thought, confirming its extremely low density.

In depth

The study significantly advances the characterization of the HIP 41378 system by combining a decade of high-precision radial velocity data with photometric observations. They precisely determined the orbital periods and masses of six planets, including resolving ambiguities for HIP 41378 d and e, and notably revised the mass of the ultra-low-density "super-puff" planet HIP 41378 f. The authors also identified a new long-period planet candidate, HIP 41378 h, and employed Gaussian Process modeling to robustly disentangle planetary signals from stellar activity.

Key Takeaways

1
The paper provides definitive orbital periods and masses for six planets in the HIP 41378 system, resolving previous ambiguities for planets d and e.
2
The mass of the "super-puff" planet HIP 41378 f was significantly revised upwards, yet its extremely low density was confirmed, posing challenges for formation theories.
3
A new long-period planet candidate, HIP 41378 h, was detected, expanding the known architecture of this unique multi-planetary system.

Conceptual Flow

HIGH LEVEL

Methodology: How was it done?

Scientists gathered light from a star over many years, then used smart computer programs to find tiny wobbles caused by planets and figure out what each planet is like.

Star Light Data

Wobble Measurements

Analyze with Computers

Planet Orbits

Planet Sizes

Planet Weights

Results: What did they find?

They found six confirmed planets and one possible new one, including a giant fluffy planet, all orbiting a star, with the outer planets being very light for their size.

Six Known Planets

One New Candidate

Measure Properties

Precise Orbits

Updated Masses

Very Low Densities