TOI-178
TOI-178 is a planetary system in the constellation Sculptor, which appears to have at least five, and possibly six, planets in a chain of Laplace resonances, which constitute one of the longest chains yet discovered in a system of planets. The system also has unusual variations in the densities among the planets.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Sculptor |
| Right ascension | 00h 29m 12.30s |
| Declination | −30° 27′ 13.46″ |
| Apparent magnitude (V) | 11.95 |
| Characteristics | |
| Evolutionary stage | Main sequence |
| Spectral type | K7V |
| Astrometry | |
| Radial velocity (Rv) | 57.4±0.5 km/s |
| Proper motion (μ) | RA: 149.95±0.07 mas/yr Dec.: −87.25±0.04 mas/yr |
| Parallax (π) | 15.92 ± 0.05 mas |
| Distance | 204.9 ± 0.6 ly (62.8 ± 0.2 pc) |
| Details | |
| Mass | 0.650+0.027 −0.029 M☉ |
| Radius | 0.651±0.011 R☉ |
| Luminosity (bolometric) | 0.132±0.010 L☉ |
| Surface gravity (log g) | 4.45±0.15 cgs |
| Temperature | 4316±70 K |
| Metallicity [Fe/H] | −0.23±0.05 dex |
| Rotational velocity (v sin i) | 1.5±0.3 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
The system is 205 light-years away, which is relatively close, implying that such systems may be relatively common. The brightness of the star, TOI-178, facilitates followup observations, which make it an ideal system in which to expand our understanding of planet formation and evolution.
The planetary system was confirmed by data provided by five different planet search projects. After TESS provided first hints at a system with an interesting resonant chain, additional observations to refine the measurement and confirm the finding were provided by CHEOPS, ESPRESSO, NGTS and SPECULOOS. Over the coming years, observations of transit-timing variations in the transits of the various planets, which are expected to range from minutes to tens of minutes, should help pin down the planetary masses and uncover the eccentricities of the various orbits.