Iota Serpentis

ι Serpentis, Latinized as Iota Serpentis and abbreviated Iot Ser, is a triple star^[7] system in the constellation Serpens, in its head (Serpens Caput). It is approximately 190 light years from Earth.^[1]

Iota Serpentis

Location of ι Serpentis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Serpens
Right ascension	15h 41m 33.05469s[1]
Declination	+19° 40′ 13.4380″[1]
Apparent magnitude (V)	4.51[2]
Characteristics
Evolutionary stage	main sequence
Spectral type	B9V + A1V[3]
B−V color index	+0.062±0.003[2]
Astrometry
Radial velocity (Rv)	−17.20[4] km/s
Proper motion (μ)	RA: −60.86[1] mas/yr Dec.: −43.69[1] mas/yr
Parallax (π)	17.16±0.67 mas[1]
Distance	190 ± 7 ly (58 ± 2 pc)
Absolute magnitude (MV)	+0.69[2]
Orbit[5]
Period (P)	8015.0±6.3 d
Semi-major axis (a)	0.21033±0.00047″
Eccentricity (e)	0.0941±0.0028
Inclination (i)	83.608±0.043°
Longitude of the node (Ω)	69.684±0.033°
Periastron epoch (T)	54,180±33 HMJD
Argument of periastron (ω) (secondary)	80.5±1.8°
Details
A
Mass	1.999[3] M☉
B
Mass	1.984[3] M☉
Other designations
ι Ser, 21 Serpentis, BD+20°3138, GC 21102, HD 140159, HIP 76852, HR 5842, SAO 101682, ADS 9744, CCDM J15416+1940[6]
Database references
SIMBAD	data

At the centre of the system is a spectroscopic binary, Iota Serpentis A and B. These are both white main sequence dwarfs and both have apparent magnitudes of +5.3. This binary has an orbital period variously reported as 11^[8] or 22^[5] years. First discovered as an astrometric binary, the pair have now been resolved and visual orbits have been derived.^[5]

There are two visual companions, Iota Serpentis C, a 13th magnitude star 143 arcseconds away and Iota Serpentis D, a 12th magnitude star 151 arcseconds distant.