HD 104985
HD 104985, formally named Tonatiuh (/toʊnəˈtiːuː/), is a solitary star with a exoplanetary companion in the northern constellation of Camelopardalis. The companion is designated HD 104985 b and named Meztli (/ˈmɛstli/). This star has an apparent visual magnitude of 5.78 and thus is dimly visible to the naked eye under favorable seeing conditions. It is located at a distance of approximately 329 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −20 km/s.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Camelopardalis |
| Right ascension | 12h 05m 15.11770s |
| Declination | +76° 54′ 20.6385″ |
| Apparent magnitude (V) | 5.78 |
| Characteristics | |
| Evolutionary stage | Horizontal branch |
| Spectral type | G8.5IIIb |
| B−V color index | 1.029±0.005 |
| Astrometry | |
| Radial velocity (Rv) | −20.20±0.16 km/s |
| Proper motion (μ) | RA: 147.071 mas/yr Dec.: –92.204 mas/yr |
| Parallax (π) | 9.9146 ± 0.0706 mas |
| Distance | 329 ± 2 ly (100.9 ± 0.7 pc) |
| Absolute magnitude (MV) | 0.85 |
| Details | |
| Mass | 1.22±0.05 M☉ |
| Radius | 10.64±0.29 R☉ |
| Luminosity | 51±1 L☉ |
| Surface gravity (log g) | 2.43±0.06 cgs |
| Temperature | 4,685±15 K |
| Metallicity [Fe/H] | −0.36±0.02 dex |
| Age | 4.39±0.54 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The stellar classification of this star is G8.5IIIb, indicating this is an evolved giant star that has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. It is located in the red clump region of the HR diagram, suggesting it is on the horizontal branch and generating energy through core helium fusion. The star is approximately 4.4 billion years old with 1.2 times the mass of the Sun and has expanded to 10.6 times the Sun's radius. It is radiating 51 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,730 K.
In 2003, radial velocity measurements made by the Okayama Planet Search Program led to the announcement of an exoplanetary companion. It is orbiting at a distance of 0.95 AU (142 Gm) with a period of 199.5 days with an eccentricity (ovalness) of 0.09. Since the inclination of the exoplanet's orbital plane is unknown, only a lower bound on its mass can be determined. It has at least 8.3 times the mass of Jupiter.