Epoch J2000 Equinox J2000
|Right ascension||07h 27m 24.4991s|
|Declination||+05° 13′ 32.827″|
|Apparent magnitude (V)||9.872|
|U−B color index||1.115|
|B−V color index||1.571|
|Radial velocity (Rv)||+18.2 km/s|
|Proper motion (μ)||RA: 571.27 mas/yr
Dec.: -3694.25 mas/yr
|Parallax (π)||267.36 ± 0.79 mas|
|Distance||12.20 ± 0.04 ly
(3.74 ± 0.01 pc)
|Absolute magnitude (MV)||11.94|
|Surface gravity (log g)||5 cgs|
|Temperature||3,150 ± 100 K|
|Metallicity [Fe/H]||−0.16 ± 0.20 dex|
Luyten's Star (GJ 273) is a red dwarf in the constellation Canis Minor located at a distance of approximately 12.36 light-years (3.79 parsecs) from the Sun. It has a visual magnitude of 9.9, making it too faint to be viewed with the unaided eye. It is named after Willem Jacob Luyten, who, in collaboration with Edwin G. Ebbighausen, first determined its high proper motion in 1935.
This star is approximately a quarter the mass of the Sun and has 35% of the Sun's radius. Luyten's Star is at the maximum mass at which a red dwarf can be fully convective, which means that most if not all of the star forms an extended convection zone. It has a stellar classification of M3.5V, with the V luminosity class indicating this is a main-sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. The projected rotation rate of this star is too low to be measured, but is no greater than 1 km/s. Measurements of periodic variation in surface activity suggest a leisurely rotation period of roughly 116 days. The effective temperature of the star's outer envelope is a relatively cool 3,150 K, giving the star the characteristic red-orange hue of an M-type star.
At present, Luyten's Star is moving away from the Solar System. The closest approach occurred about 13,000 years ago when it came within 3.67 parsecs. The star is currently located 1.2 light years distant from Procyon, and the latter would appear as a visual magnitude −4.5 star in the night sky of a hypothetical planet orbiting Luyten's Star. The closest encounter between the two stars occurred about 600 years ago when Luyten's Star was at its minimal distance of about 1.12 ly from Procyon. The space velocity components of Luyten's Star are U = +16, V = −66 and W = −17 km/s.
In March 2017, two planets were discovered orbiting Luyten's Star. The outer planet, GJ 273b, is a Super Earth in its star's habitable zone. It has a mass of 2.89 ± 0.26 Earth masses and orbits at a distance of 0.09110 ± 0.00002 AU, completing one orbital period in 18.650 ± 0.006 days. While the planet is on the innermost edge of the star's conservative habitable zone, the incident flux is only 1.06S⊕, so it may be easily habitable if an atmosphere is present; depending on albedo, its equilibrium temperature could be anywhere between 206 and 293 Kelvin. The inner planet, GJ 273c, is one of the lightest exoplanets detected by radial velocities, with a mass of only 1.18 ± 0.16 Earth masses. However, it orbits much further in, with an orbital period of only 4.7234 ± 0.00004 days.
GJ 273b is one of the closest known planets in its star's habitable zone.
(in order from star)
|c||1.18 ± 0.16 M⊕||0.036467||4.7234 ± 0.0004||0.17||—||—|
|b||2.89±0.26 M⊕||0.09110 ± 0.00002||18.650 ± 0.006||0.10||—||—|
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