HD 99109
Star in the constellation Leo
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HD 99109 is an orange-hued star with an exoplanetary companion in the constellation of Leo. It has an apparent visual magnitude of +9.10,[2] which is too faint to be visible to the naked eye. The distance to this system is 179 light-years based on parallax, and it is drifting further away with a radial velocity of +33 km/s.[1] The star is one and half degrees away from the celestial equator to the south.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Leo |
| Right ascension | 11h 24m 17.359s[1] |
| Declination | –01° 31′ 44.67″[1] |
| Apparent magnitude (V) | +9.10[2] |
| Characteristics | |
| Spectral type | G8/K0IV[3] |
| B−V color index | 0.874±0.002[2] |
| Astrometry | |
| Radial velocity (Rv) | +33.060±0.0025[4] km/s |
| Proper motion (μ) | RA: −178.689 mas/yr[1] Dec.: −159.528 mas/yr[1] |
| Parallax (π) | 18.178±0.017 mas[1] |
| Distance | 179.4 ± 0.2 ly (55.01 ± 0.05 pc) |
| Absolute magnitude (MV) | 5.62[2] |
| Details | |
| Mass | 0.93±0.02[5] M☉ |
| Radius | 0.90±0.03[5] R☉ |
| Luminosity | 0.56±0.02[5] L☉ |
| Surface gravity (log g) | 4.49±0.03[5] cgs |
| Temperature | 5,270±24[5] K |
| Metallicity [Fe/H] | 0.315±0.030[6] dex |
| Rotational velocity (v sin i) | 1.86±0.50[6] km/s |
| Age | 6±3 Gyr[5] ≥ 12.2[7] Gyr |
| Other designations | |
| Shama, BD−00°2437, HD 99109, HIP 55664, SAO 138182[8] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
The stellar classification of this star is G8/K0IV,[3] matching a late G or early K-type subgiant star. It appears to be past the end of its main sequence lifetime, having exhausted the supply of hydrogen at its core.[7] The star is 93% as massive as the Sun and has 90% of the Sun's radius.[5] It is spinning with a projected rotational velocity of ~2 km/s[6] and has over twice the abundance of iron relative to hydrogen than the Sun. The star is radiating 56% of the Sun's luminosity from its photosphere at an effective temperature of 5,270 K.[5] As of 2006, one extrasolar planet has been confirmed to be orbiting the star.[6]
The star HD 99109 is named Shama. The name was selected in the NameExoWorlds campaign by Pakistan, during the 100th anniversary of the IAU. Shama (شمع) is an Urdu literary term meaning a small lamp or flame. The exoplanet companion is called Perwana, meaning 'moth' in Urdu, alluding to the eternal love of an object circling a source of light.[9][10]
Planetary system
The planet HD 99109 b has an orbit comparable in eccentricity to the planet Mars in the Solar System but has a mass at least half that of Jupiter. Stability analysis reveals that Earth-size planets could have stable orbits in the planet's Trojan points, located 60 degrees ahead and behind the planet's position in its orbit.[7]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b / Perwana | >0.502 ± 0.070 MJ | 1.105 ± 0.065 | 439.3 ± 5.6 | 0.09 ± 0.16 | — | — |