  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda[1] |
| Right ascension | 23h 40m 24.508s[2] |
| Declination | +44° 20′ 02.16″[2] |
| Apparent magnitude (V) | 4.139[3] |
| Characteristics | |
| Evolutionary stage | main sequence[4][2] |
| Spectral type | B9 IVn[5] |
| U−Bcolor index | −0.221[3] |
| B−Vcolor index | −0.067[3] |
| Astrometry | |
| Radial velocity (Rv) | −12.7±0.8[6] km/s |
| Proper motion (μ) | RA: +79.998mas/yr[2] Dec.: −19.011mas/yr[2] |
| Parallax (π) | 19.4064±0.2104 mas[2] |
| Distance | 168 ± 2 ly (51.5 ± 0.6 pc) |
| Absolute magnitude (MV) | +0.59[1] |
| Details[7] | |
| Mass | 2.768+0.1 −0.109 M☉ |
| Radius | 2.303+0.039 −0.016 R☉ (equatorial) 1.959+0.033 −0.028 (polar) R☉ |
| Luminosity | 62.60±9.83 L☉ |
| Surface gravity (log g) | 3.968+0.028 −0.025 cgs (equatorial) 4.296+0.019 −0.012 (polar) cgs |
| Temperature | 10,342+384 −138 K (equatorial) 12,050+448 −39 (polar) K |
| Rotational velocity (v sin i) | 142.2+13.1 −21.1 km/s |
| Age | 47+27 −40 Myr |
| Other designations | |
| Kaffalmusalsala,κ And,19 Andromedae,BD+43°4522,FK5 1619,HD 222439,HIP 116805,HR 8976,SAO 53264,PPM 64525[8] | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
Kappa Andromedae,Latinized from κ Andromedae, also namedKaffalmusalsala,[9] is a star in the northernconstellation ofAndromeda. It is visible to the naked eye with anapparent visual magnitude of 4.1.[3] Based on the star's ranking on theBortle Dark-Sky Scale, it is luminous enough to be visible from the suburbs and from urban outskirts, but not from brightly lit inner city regions.Parallax measurements place it at a distance of approximately 168light-years (52parsecs).[2] It is drifting closer with aradial velocity of −13 km/s,[6] and there is a high likelihood (86%) that it is a member of theBeta Pictoris moving group.[10] The star has one knownexoplanet,Kappa Andromedae b.[11]
In traditional Arabic astronomy, the starsι Andromedae, κ Andromedae, andλ Andromedae were known asKaff al-Musalsala, the hand of the chained woman (i.e. Andromeda), and asRa’s al-Nāqa, the head of the she-camel.[12] TheIAU Working Group on Star Names approved the name Kaffalmusalsala for κ Andromedae on 8 May 2025 and it is now so entered in the IAU Catalog of Star Names; the name Rasalnaqa was given to ι Andromedae.[9]
InChinese,螣蛇 (Téng Shé), meaningFlying Serpent, refers to an asterism consisting of κ Andromedae,α Lacertae,4 Lacertae,π2 Cygni,π1 Cygni,HD 206267,ε Cephei,β Lacertae,σ Cassiopeiae,ρ Cassiopeiae,τ Cassiopeiae,AR Cassiopeiae,9 Lacertae,3 Andromedae,7 Andromedae,8 Andromedae,λ Andromedae,ι Andromedae, andψ Andromedae. Consequently, theChinese name for κ Andromedae itself is螣蛇二十一 (Téng Shé èrshíyī, English:the Twenty First Star of Flying Serpent).[13]
Thestellar classification of Kappa Andromedae is B9 IVn, indicating that it is asubgiant star in the process ofevolving away from themain sequence. The star has an estimated 2.8 times themass of the Sun and is radiating 62.6 times theSun's luminosity.[7] It is spinning rapidly, with aprojected rotational velocity of 162 km/s. Its true rotational velocity is 283.8 km/s, which is about 85% of its critical rotation rate (the rate at which it would break up).[7] With such a rapid rotation rate, the star is deformed into an oblate spheroid, such that while the polar radius is 1.959 R☉, the equatorial radius is significantly larger, at 2.303 R☉.[7] The outer envelope of the star is radiating energy into space with aneffective temperature of10,342 K at the equator and12,050 K at its poles, producing a blue-white hue.[7]
The age of Kappa Andromedae has been the subject of debate. The discovery paper for Kappa Andromedae b[11] argued that the primary's kinematics are consistent with membership in the Columba Association, which would imply a system age of 20-50 million years, while a subsequent work derived an older age of220±100 million years based on the star's position on theHertzsprung-Russell diagram position[14] assuming that the star is not a fast rotator viewed pole-on. Direct measurements of the star later showed that Kappa Andromedae A is in fact a rapid rotator viewed nearly pole-on and yield a best-estimated age of 47+27
−40 million years.[7]
In November 2012, members of theStrategic Explorations of Exoplanets and Disks with Subaru (SEEDS) survey reported the discovery of a faint, directly-imaged companionKappa Andromedae b.[11] Follow-up photometry and spectroscopy of kappa And b with theSubaru Telescope,Keck Observatory, andLarge Binocular Telescope constrained its mass to be about 13 Jupiter masses, temperature to be between 1700 K and 2150 K, and orbit to be highly eccentric with a semimajor axis likely greater than about 75 AU. The companion's spectrum shows evidence for water and carbon monoxide molecules and suggests the object has a low surface gravity.[15][16][17]
| Companion (in order from star) | Mass | Semimajor axis (AU) | Orbital period (years) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 17.3±1.8 MJ | 103.6+132.4 −46.2 | 630+1,520 −430 | 0.77+0.13 −0.17 | 130±17° | 1.42±0.06 RJ |
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