Kruger 60

Coordinates: 22^h 27^m 59.4677^s, +57° 41′ 45.150″

Krüger 60 A/B

Krüger 60 Location of Krüger 60 in the constellation Cepheus
Observation data {{#ifeq:J2000|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| Epoch J2000      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000}}
Constellation	Cepheus
Krüger 60 A
Right ascension	22h 27m 59.55755s[1]
Declination	+57° 41′ 42.0806″[1]
Apparent magnitude (V)	9.93±0.03[2]
Krüger 60 B
Right ascension	22h 27m 59.79560s[3]
Declination	+57° 41′ 49.7468″[3]
Apparent magnitude (V)	10.3 – 11.4[4]
Characteristics
Spectral type	M3V/M4V[5]
Variable type	None/Flare star
Astrometry
Krüger 60 A
Proper motion (μ)	RA: −725.227[1] mas/yr Dec.: −223.461[1] mas/yr
Parallax (π)	249.3926 ± 0.1653[1] mas
Distance	13.078 ± 0.009 ly (4.010 ± 0.003 pc)
Krüger 60 B
Proper motion (μ)	RA: −934.098 mas/yr Dec.: −686.244 mas/yr
Parallax (π)	249.9668 ± 0.7414[3] mas
Distance	13.05 ± 0.04 ly (4.00 ± 0.01 pc)
Details
Krüger 60 A
Mass	0.271±0.010[6] M☉
Radius	0.301±0.015[7] R☉
Luminosity	0.00983±0.00025[8] L☉
Habitable zone inner limit	0.103[8] AU
Habitable zone outer limit	0.201[8] AU
Temperature	3,342±111[8] K
Metallicity	–0.04[9]
Krüger 60 B
Mass	0.176±0.007[6] M☉
Radius	0.209±0.017[7] R☉
Luminosity	0.00393±0.00016[8] L☉
Habitable zone inner limit	0.067[8] AU
Habitable zone outer limit	0.129[8] AU
Temperature	3,097±111[8] K
Orbit[10]
Primary	Krüger 60 A
Companion	Krüger 60 B
Period (P)	45.13+0.44 −0.43 yr
Semi-major axis (a)	2.45±0.02″
Eccentricity (e)	0.4131+0.0031 −0.0032
Inclination (i)	165.41+0.72 −0.71°
Longitude of the node (Ω)	152.6+3.3 −3.9°
Periastron epoch (T)	56,944+12 −11 MJD
Argument of periapsis (ω) (primary)	208.2+2.8 −3.3°
Other designations
BD+56°2783, GJ 860 A/B, HD 239960, HIP 110893, ADS 15972, G 232-075, LHS 3814/3815[11]
Database references
SIMBAD	The system
	A
	B

Krüger 60 (DO Cephei) is a binary star system located 13.1 light-years (4.0 parsecs) from Earth, being one of nearest stars. It is made up of a pair of red dwarf stars orbiting each other every 45 years.

The larger, primary star is designated component A, while the secondary, smaller star is labeled component B. Component A has about 27% of the Sun's mass and 30% of the Sun's radius. Component B has about 18% of the Sun's mass and 21% of the Sun's radius.^[6][7]

In 1951, Peter van de Kamp and Sarah Lee Lippincott announced that component B is a flare star.^[13] It was given the variable star designation "DO Cephei".^[14] Flares lasting as long as one hour have been recorded.^[15]

This system is orbiting through the Milky Way at a distance from the core that varies from 7–9 kpc with an orbital eccentricity of 0.126–0.130.^[16] The closest approach to the Sun will occur in about 88,600 years when this system will come within 1.95 parsecs (6.4 ly).^[17]

In 1890 Adalbert Krueger published a part of the AGK catalogue with stars with declination between +55 and +65. He noted which stars appeared to be double.^[18] Sherburne Wesley Burnham (1894) observed 67 of these candidate double stars, among which number 60 from his list, which later was called Kruger 60 (star 13170 from the catalogue of Krueger).^[19]

Krüger 60 was proposed as the origin of interstellar comet 2I/Borisov (formerly named C/2019 Q4 (Borisov)) in a preprint submitted to arXiv by Dybczyński, Królikowska, and Wysoczańska.^[20] These authors had from other work a list of stars and stellar systems that can potentially act as perturbers of the Oort cloud comets, and searched it for a past close proximity of 2I/Borisov at a very small relative velocity. While hampered by uncertainty about the orbit of 2I/Borisov and particularly its non-gravitational acceleration (due to cometary outgassing), they initially reached a conclusion that 1 Myr ago 2I/Borisov passed Krüger 60 at a small distance of 1.74 pc while having an extremely small relative velocity of 3.43 km/s. Perturbations of 2I/Borisov's incoming orbit altered the intersection distance with relatively small changes in the relative velocity. However, further study by the same authors presented in the revised version of the preprint instead ruled out the possibility of Krüger 60 as a home system for 2I/Borisov.^[20]

• James B. Kaler (22 March 2001). Extreme Stars: At the Edge of Creation. Cambridge University Press. p. 31. ISBN 978-0-521-40262-0. https://books.google.com/books?id=3kcjvYLh8xIC. 

• Hires LRGB CCD Image

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