BD -22°5866

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**BD -22°5866**
Observation data Epoch J2000
Constellation (pronunciation)	Aquarius
Right ascension	22h 14m 38.364s
Declination	-21° 41' 53.15"'
Apparent magnitude (V)	10.1
Characteristics
Spectral type	K5
U-B color index	?
B-V color index	?
Variable type	None
Astrometry
Proper motion (μ)	RA: 161.7 mas/yr Dec.: 193.0 mas/yr
Absolute magnitude (M_V)	12.3
Astrometry
Distance	166 Ly
Binary orbit
Orbit period of BD 22°5866 A and B: (P)	9 years
Orbit period of BD 22°5866 A1 and A2: (P)	5 days
Orbit period of BD 22°5866 B1 and B2: (P)	55 days
Space between BD 22°5866 A and B:	5.8 AU
Space between BD 22°5866 A1 and A2:	0.06 AU
Space between 22°5866 B1 and B2:	0.26 AU
Details
Mass	? M_☉
Radius	? R_☉
Luminosity	? L_☉
Temperature	? K
Metallicity	?
Rotation	?
Age	500 million years
Other designations
NLTT 53279, LP 875-68, RBS 1834, 2MASS J22143835-2141535, CPD-22° 8173, PPM 273545, TYC 6384-505-1.
Database references
SIMBAD	data

BD -22°5866 is a quadruple-star system located 166 light years from Earth. The four stars are each about half the mass of the Sun and are approximately 500 million years old. The system is unusual in how closely the four stars are orbiting each other; one pair has an orbital separation of at most .06 AU and an orbital period of under five days, the other pair has a separation of at most .26 AU and a period of about 55 days, and the two pairs are separated by 5.8 AU and have an orbital period of less than nine years.^[1]

Since current theories of star formation indicate that stars like these could not form in such close proximity to each other, a favored explanation is that there may have been a single gaseous disk that forced them into such small orbits within the first 100,000 years of their evolution. The two pairs are currently moving farther apart due to tidal interaction, indicating that they were once even more closely associated than today.^[1]