Masses and orbits of young giant planets in the HIP 67522 system measured

HIP 67522 is a young star system, aged only 17 million years, which hosts two giant planets. By observing the timing of when these planets cross in front of their host star—an event known as a transit—researchers can detect subtle shifts in the schedule caused by the gravitational tugging between the two worlds. These variations in timing, known as transit timing variations, serve as a precise tool for calculating the masses and orbital characteristics of these infant planets.

The research analyzed 55 transits for planet b and 29 transits for planet c gathered from 11 different facilities. By comparing these observations against mathematical models of gravitational interaction, the masses and shapes of the planetary orbits were determined. The data confirm that both planets maintain low orbital eccentricities, meaning their paths around the star are nearly circular.

The findings suggest that the planets possess low masses despite their large physical size. This configuration aligns with models of gas dwarf formation, where a planet retains a contracting atmosphere in its early stages of development. These results provide critical evidence for understanding how common types of planets evolve in the Galaxy.

Key findings
- HIP 67522 b has a mass of approximately 23.1 Earth masses.
- HIP 67522 c has a mass of approximately 9.7 Earth masses.
- Both planets exhibit low orbital eccentricity of less than 0.1.
- The system is positioned near a 2:1 mean-motion resonance.
- Observed planetary dimensions support a contracting atmosphere model of formation.

Scientific study

Toddlers in Resonance I: low masses and eccentricities of the 17 Myr giant planets HIP 67522 bc from transit timing variations (external link)