Two planets orbiting orange dwarf TOI-4311 reveal dense super-Earth and sub-Neptune

Star system: TOI-4311 | Distance from the Sun: 440 light years

TOI-4311 is an orange dwarf star located between the Galactic thick disk and Hercules stream. This star hosts two planets: an ultra-short-period super-Earth and a longer period sub-Neptune. The super-Earth completes an orbit in about one day and is very dense, while the sub-Neptune has a longer orbit of around fifteen days. These planets were first detected by the TESS space telescope, and their properties were refined using CHEOPS and HARPS observations.

The study determined the radius and mass of both planets, confirming the planetary nature of the sub-Neptune and providing detailed measurements for the super-Earth. A third signal was found in the data, which may indicate another planet, but no transit was observed for this candidate. The analysis suggests that if this third planet exists, its orbit would be stable. The dense nature of the inner planet, TOI-4311 b, is notable given the star's motion and chemical makeup, which could challenge current ideas about how planets form in our galaxy.

Researchers used precise measurements to model the interior of TOI-4311 b, finding it unusually dense. The system's characteristics, including the possible third planet, offer valuable information for understanding planet formation. The findings highlight the importance of combining different observation methods to study planetary systems.

Key findings
- TOI-4311 hosts a super-Earth and a sub-Neptune with well-measured properties.
- A possible third planet is suggested by a periodic signal, though no transit was seen.
- The inner planet, TOI-4311 b, is very dense for its type.
- The system's properties may challenge current planet formation theories.
- Observations combined data from TESS, CHEOPS, and HARPS.

Scientific study

An Ultra-Short Period Super-Earth and a Sub-Neptune Orbiting the K dwarf TOI-4311 (external link)