HD 176693
Coordinates: 
18h 59m 08.6847s, +48° 25′ 23.5990″
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Draco |
| Right ascension | 18h 59m 08.6847s[1] |
| Declination | 48° 25′ 23.5990″[1] |
| Apparent magnitude (V) | 8.83 |
| Characteristics | |
| Evolutionary stage | Main sequence |
| Spectral type | F8V |
| B−V color index | 0.51[2] |
| Astrometry | |
| Radial velocity (Rv) | -54.9±0.2[3] km/s |
| Proper motion (μ) | RA: 4.704±0.013[3][3] mas/yr Dec.: 9.263±0.016[3][3] mas/yr |
| Parallax (π) | 11.218 ± 0.013[3] mas |
| Distance | 290.7 ± 0.3 ly (89.1 ± 0.1 pc) |
| Details[4] | |
| Mass | 1.05±0.04 M☉ |
| Radius | 1.253±0.051 R☉ |
| Luminosity | 1.864[5] L☉ |
| Surface gravity (log g) | 4.318+0.08 −0.089 cgs |
| Temperature | 608±65 K |
| Metallicity [Fe/H] | −0.138+0.043 −0.042 dex |
| Rotation | 12.89±0.19 d |
| Rotational velocity (v sin i) | 2.8±1.0 km/s |
| Age | 7.15±1.61[2] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 176693, also known as Kepler-408, is a F-type main-sequence star about 290 light-years away. The star is older than the Sun, at 7.15 billion years. It is slightly and uniformly[6] depleted in heavy elements compared to the Sun, having about 75% of the solar abundance of iron and other heavy elements.[4]
HD 176693 is a chromospherically inactive star,[2] although there is weak evidence for tidal spin-up due to star-planet interaction.[7]
Multiplicity surveys did not detect any stellar companions to HD 176693 by 2016.[8]
Planetary system[]
In 2014, a transiting Sub-Earth planet was detected on a tight 2.5 day orbit. Initially reported with a relatively low confidence of 97.9%,[9] it was confirmed in 2016.[10]
The planetary orbit is inclined to the equatorial plane of the star by 41.7+5.1
−3.5°. Such strong spin-orbit misalignment is unique for a sub-Earth transiting planet, and needs either additional giant planets in the system or a history of close stellar encounters to explain it.[4] The planet may also be a captured body originating from elsewhere.[11]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| — | — | 2.465024±0.000005 | — | 81.85±0.10° | 0.86±0.04 R
|