Iota Andromedae

This article is about the star. For the galaxy, see Andromeda I. For another star, see 1 Andromedae.

"ι And" redirects here. For other uses, see And I (disambiguation).

Iota Andromedae, also named Rasalnaqa,^[13] is a single^[14] star in the northern constellation of Andromeda. It has the Flamsteed designation 17 Andromedae, while Iota Andromedae is the Bayer designation as Latinized from ι Andromedae. This object is visible to the naked eye at night as a faint, blue-white hued star with an apparent visual magnitude of +4.29.^[2] Based upon parallax measurements, it is located approximately 510 light years distant from the Sun.^[1]

Iota Andromedae

Location of ι Andromedae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Andromeda
Right ascension	23h 38m 08.200s[1]
Declination	+43° 16′ 05.06″[1]
Apparent magnitude (V)	+4.29[2]
Characteristics
Evolutionary stage	main sequence
Spectral type	B8 V[3][4]
U−B color index	–0.29[5]
B−V color index	–0.11[5]
Variable type	constant[6]
Astrometry
Radial velocity (Rv)	–0.5[2] km/s
Proper motion (μ)	RA: +27.163 mas/yr[1] Dec.: −1.246 mas/yr[1]
Parallax (π)	6.4313±0.1375 mas[1]
Distance	510 ± 10 ly (155 ± 3 pc)
Absolute magnitude (MV)	−1.63[7]
Details
Mass	3.1 M☉[4] 3.98±0.06[8] M☉
Radius	4.6[9] R☉
Luminosity	638[7] L☉
Surface gravity (log g)	3.35[6] cgs
Temperature	12,620[10] K
Metallicity [Fe/H]	−0.19±0.14[6] dex
Rotational velocity (v sin i)	70[11] km/s
Age	116[4] Myr
Other designations
Rasalnaqa, ι And, 17 And, BD+42°4720, FK5 891, HD 222173, HIP 116631, HR 8965, SAO 53216, PPM 64473[12]
Database references
SIMBAD	data

This object is a B-type main-sequence star with a stellar classification of B8 V. It is among the least variable stars observed during the Hipparcos mission.^[6] The star is 116^[4] million years old with 3.1^[4] times the mass of the Sun and is spinning with a projected rotational velocity of 70 km/s.^[11] It is radiating 638^[7] times the luminosity of the Sun from its photosphere at an effective temperature of 12,620 K.^[10] The star is somewhat metal-poor, although the abundance of helium is close to solar. The latter excludes it from membership among the class of peculiar stars.^[6] Iota Andromedae is a debris disk candidate, showing an infrared excess at a wavelength of 18 μm.^[15]

Name

In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Keff al-Salsalat (كف المسلسلة - kaf al-musalsala), which was translated into Latin as Manus Catenata, meaning hand of the chained woman (i.e. Andromeda).^[16] This name originally referred to a group of three stars – ι Andromedae, κ Andromedae, and λ Andromedae – also known in traditional Arabic astronomy as Ra’s al-Nāqa, the head of the she-camel.^[17] The IAU Working Group on Star Names approved the name Rasalnaqa for ι Andromedae on 8 May 2025 and it is now so entered in the IAU Catalog of Star Names; the name Kaffalmusalsala was given to κ Andromedae.^[13]

In Chinese, 螣蛇 (Téng Shé), meaning Flying Serpent, refers to an asterism consisting of ι 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, κ Andromedae and ψ Andromedae. Consequently, the Chinese name for ι Andromedae itself is 螣蛇二十二 (Téng Shé èrshíèr, English: the Twenty Second Star of Flying Serpent).^[18]