TOI-5624 hosts four transiting sub-Neptunes and a fifth outer planet revealed by timing variations

Star system: TOI-5624 | Distance from the Sun: 331 light years

TOI-5624 is a Sun-like star about 100 parsecs away, now known to host a remarkable planetary system. Observations from TESS and CHEOPS revealed four transiting sub-Neptune planets with orbital periods of about 3.4, 7.9, 13.7, and 21.5 days. Their radii range from about 2.3 to 3.6 times that of Earth, and their masses are between 4.8 and 9.4 Earth masses. The outermost planet, TOI-5624 e, shows significant variations in its transit timing, which led scientists to search for additional planets.

By analyzing the timing variations and radial velocity data, researchers found evidence for a fifth, non-transiting planet, TOI-5624 f, with a minimum mass of about 13 Earth masses. This planet is likely in a 2:1 orbital resonance with TOI-5624 e, meaning it orbits the star once for every two orbits of the outermost transiting planet. The system is notable for the precision with which the planets' sizes and masses have been measured, rivaled only by the famous TRAPPIST-1 system.

These findings make TOI-5624 an important system for studying the dynamics and formation of multi-planet systems, especially those with closely packed sub-Neptunes and resonant companions.

Key findings
- Four transiting sub-Neptunes discovered around TOI-5624
- A fifth, non-transiting planet detected via transit timing variations
- Planets have well-measured sizes and masses
- The outer companion is likely in a 2:1 resonance with the outermost transiting planet
- The system is a valuable laboratory for studying planetary dynamics

Scientific study

The multi-planet system TOI-5624: four transiting sub-Neptunes with an outer companion revealed by transit-timing variations (external link)