BD−11 4672

BD−11 4672 is a single star with a pair of orbiting exoplanets in the southern constellation of Scutum, the shield. The designation BD−11 4672 comes from the Bonner Durchmusterung star catalogue, which was published during the nineteenth century in Germany. With an apparent visual magnitude of 9.99,^[3] the star is much too faint to be viewed with the naked eye. It is located at a distance of 89 light-years from the Sun, as determined from parallax,^[2] but is drifting closer with a radial velocity of −87.5 km/s.^[5] This was recognised as a high proper motion star by German astronomer Max Wolf in 1924^[8] and is traversing the celestial sphere at an angular rate of 0.401 arcsec yr⁻¹.^[9]

BD−11°4672

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Scutum[1]
Right ascension	18h 33m 28.832s[2]
Declination	−11° 38′ 09.72″[2]
Apparent magnitude (V)	9.99±0.05[3]
Characteristics
Evolutionary stage	main sequence[3]
Spectral type	K7 V[4][3]
Apparent magnitude (B)	11.21±0.10[3]
Apparent magnitude (J)	7.651±0.023[1]
B−V color index	1.263±0.009[1]
Astrometry
Radial velocity (Rv)	−87.515±0.0011[5] km/s
Proper motion (μ)	RA: −288.440 mas/yr[2] Dec.: −235.615 mas/yr[2]
Parallax (π)	36.7534±0.0157 mas[2]
Distance	88.74 ± 0.04 ly (27.21 ± 0.01 pc)
Details[3]
Mass	0.651+0.031 −0.029 M☉
Radius	0.639+0.020 −0.022 R☉
Luminosity	0.157+0.019 −0.017 L☉
Surface gravity (log g)	4.642+0.027 −0.025 cgs
Temperature	4,550±110 K
Metallicity [Fe/H]	−0.48±0.07[6] dex
Rotation	~25 d
Rotational velocity (v sin i)	1.0±0.5 km/s
Age	7.4+4.5 −4.9 Gyr
Other designations
BD−11 4672, Gaia DR2 4154598526336121600, GJ 717, HIP 90979, PPM 234703, Wolf 1462, TYC 5699-2129-1, GSC 05699-02129, 2MASS J18332885-1138097[7]
Database references
SIMBAD	data
Exoplanet Archive	data

The spectrum of BD−11 4672 matches a K-type main-sequence star, an orange dwarf, with a stellar classification of K7 V.^[4] Its age is not well constrained, but is probably older than the Sun. It is a metal-poor star, showing an iron abundance that is 35% of solar.^[6] No significant flare activity was detected.^[10] The star shows evidence of a Sun-like magnetic activity cycle with a period of 7–10 years.^[3] It has 65% of the mass and 64% of the radius of the Sun. The star is radiating 16% of the luminosity of the Sun from its photosphere at an effective temperature of 4,550 K.^[3]

Planetary system

In 2010, a team of astronomers led by astronomer C. Moutou [fr] of the High Accuracy Radial Velocity Planet Searcher performed a radial-velocity analysis, which led to the suspicion of a gas giant exoplanet in orbit around BD−11 4672.^[4] The existence of this exoplanet was confirmed in 2014.^[11] In 2020, a second exoplanet was detected on an interior and much more eccentric orbit near the inner edge of the star's habitable zone.^[3]

The BD−11 4672 planetary system^[3]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
c	≥15.37+2.97 −2.81 M🜨	0.30±0.01	74.20+0.06 −0.08	0.40+0.13 −0.15	—	—
b	≥0.65+0.05 −0.06 MJ	2.36±0.04	1634+13 −14	0.05+0.05 −0.03	—	—

See also

• list of exoplanets discovered in 2014 (BD-11 4672b)
• list of exoplanets discovered in 2020 (BD-11 4672c)