| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Leo |
| Right ascension | 11h 35m 03.75298s[1] |
| Declination | +20° 26′ 29.5637″[1] |
| Apparent magnitude (V) | +6.45[2] |
| Characteristics | |
| Evolutionary stage | giant star |
| Spectral type | G9 III[3] |
| B−Vcolor index | 1.010±0.015[2] |
| Astrometry | |
| Radial velocity (Rv) | −5.2±0.3[4] km/s |
| Proper motion (μ) | RA: –59.695[1]mas/yr Dec.: –1.047[1]mas/yr |
| Parallax (π) | 7.2613±0.0472 mas[1] |
| Distance | 449 ± 3 ly (137.7 ± 0.9 pc) |
| Absolute magnitude (MV) | 1.02[2] |
| Details[5] | |
| Mass | 2.2±0.1 M☉ |
| Radius | 8.8±0.1 R☉ |
| Luminosity | 40.8±0.3 L☉ |
| Surface gravity (log g) | 2.89±0.02 cgs |
| Temperature | 4,918±8 K |
| Metallicity [Fe/H] | 0.07±0.03[6] dex |
| Rotational velocity (v sin i) | 1.6±1.0[7] km/s |
| Age | 900±200 Myr |
| Other designations | |
| Formosa,BD+21° 2331,Gaia DR2 3979226627820659072,HD 100655,HIP 56508,HR 4459,SAO 81886,2MASS J11350375+2026295[8] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
HD 100655 is astar in thezodiacconstellation ofLeo, located 449[1] light years away from the Sun. It has anapparent visual magnitude of +6.45,[2] which makes it a challenge to see with the naked eye under ideal viewing conditions. The star is moving closer to the Earth with a heliocentricradial velocity of −5 km/s.[4] It has one confirmed planet.[7]
The star HD 100655 is namedFormosa. The name was selected in theNameExoWorlds campaign byTaiwan, during the 100th anniversary of theIAU. Formosa is the historical name of Taiwan used in the 17th century, meaning beautiful in Portuguese. The planet HD 100655 b is namedSazum, after the townshipYuchi and it means water in the language of theThao people.[9][10]
This is anevolvedgiant star with astellar classification of G9 III.[3] It is ared clump giant,[11] which means it is currently on thehorizontal branch and is generating energy throughhelium fusion at itscore. This star is around 900 million years old with 2.2 times themass of the Sun and has expanded to 8.8 times theSun's radius. It is radiating 4,918 times theSun's luminosity from its enlargedphotosphere at aneffective temperature of 4,918 K.[5]
The planetary companion, announced in 2011, was discovered by a Korean–Japanese planet search program by theradial velocity method. The motions of the host star displayedKeplerian variation, indicating a perturbing body in orbit. The best fit model suggests a body having a minimum mass of1.7 MJ and showing a 158-dayorbital period with asemimajor axis of 0.76 astronomical units (114 Gm) and a loweccentricity of 0.085.[7] This is one of the two least massive planets known around clump giants, as of 2012.[11]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b / Sazum | >1.7 MJ | 0.76+0.02 −0.04 | 157.57 ± 0.65 | 0.085 ± 0.054 | — | — |
