Luyten's Star
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Luyten's Star Template:IPAc-enTemplate:Cn (GJ 273) is a red dwarf in the constellation Canis Minor located at a distance of Template:Convert 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.<ref name=hcob900_1/> The star has two confirmed planets and two candidate planets,<ref name="PozuelosSuárez2020"/> of which Luyten b is in the circumstellar habitable zone.<ref name="Astudillo-Defru2017"/>
Properties
This star is approximately a quarter the mass of the Sun<ref name="RECONS"/> and has 35% of the Sun's radius.<ref name=apjss34_479/> 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.<ref name=aaa496_3_787/> It has a stellar classification of M3.5V,<ref name="RECONS"/> 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 starTemplate:Efn is too low to be measured, but can be no greater than 1 km/s.<ref name=aaa467_1_259/> Measurements of periodic variation in surface activity suggest a leisurely rotation period of roughly 116 days (which would give a velocity of ~0.15 km/s).<ref name=mnras452_3_2745/> 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.<ref name="mnras388"/><ref name=csiro/>
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.<ref name="García-Sánchez-etal-2001"/> The star is currently located 1.2 light years distant from Procyon, which would appear as a visual magnitude −4.5 star in the night sky of Luyten's Star's planets.<ref name=Schaaf-2008/> However, Luyten's Star would only have an apparent magnitude of 4.6 from Procyon's sky because it is much less luminous. 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.<ref name=Annot/> The space velocity components of Luyten's Star are U = +16, V = −66 and W = −17 km/s.<ref name=Annot/><ref name=Delfosse-etal-1998/><ref name=ARICNS/>
Planetary system
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In March 2017, two candidate planets were discovered orbiting Luyten's Star.<ref name="Astudillo-Defru2017"/> The outer planet, GJ 273b, is a super-Earth in its star's optimistic habitable zone. It has a minimum mass of Template:Nowrap and orbits at a distance of Template:Nowrap completing one orbital period in Template:Nowrap While the planet is on the innermost edge of the star's conservative habitable zone, the incident flux is only 1.06 Template:Mvar🜨, so it may be potentially habitable if water and an atmosphere are 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 Template:Nowrap However, it orbits much further in, with an orbital period of only Template:Nowrap<ref name="Astudillo-Defru2017"/>
GJ 273b is one of the closest known planets to Earth which lies in its star's habitable zone.<ref name="Astudillo-Defru2017"/>
Both planets are near 4:1 resonance; it is possible that, with still undiscovered ones, the entire inner part of this system is trapped in a single simple-mean-motion resonance chain like TRAPPIST-1.
In 2019, two more candidate planets were detected by radial velocity, making a potential total of four known planets in the system.<ref name=barnes/> If all four planets are present, their true masses must be close to their minimum masses for the system to be stable, with upper limits of Template:Val for b, Template:Val for c, Template:Val for d, and Template:Val for e.<ref name="PozuelosSuárez2020"/>
In October 2017, "Sónar Calling GJ273b", a project by METI and the Sónar music festival in Barcelona, Spain<ref name="Sónar-Barcelona"/> transmitted a series of radio signals towards Luyten's star from a radar antenna at Ramfjordmoen, Norway.<ref name=Economist-2017/> The signal consisted of a scientific and mathematical tutorial on how to decode the messages and was accompanied by 33 encoded musical compositions by various musicians. A second signal series was transmitted in May 2018. Were anyone listening, the soonest response would be received by 2042.
See also
Notes
References
External links
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