Luyten's Star

Luyten's Star /ˈlaɪtənz/ (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.[10] The star has four confirmed planets,[11] of which Luyten b is in the circumstellar habitable zone.[12]

Luyten's Star
Observation data
Epoch J2000      Equinox J2000
Constellation Canis Minor
Right ascension 07h 27m 24.4991s[1]
Declination +05° 13′ 32.827″[1]
Apparent magnitude (V) 9.872[2]
Characteristics
Spectral type M3.5V[3]
U−B color index 1.115[2]
B−V color index 1.571[2]
Variable type None
Astrometry
Radial velocity (Rv)+18.2[4] km/s
Proper motion (μ) RA: 571.27[1] mas/yr
Dec.: -3694.25[1] mas/yr
Parallax (π)267.36 ± 0.79[5] mas
Distance12.20 ± 0.04 ly
(3.74 ± 0.01 pc)
Absolute magnitude (MV)11.94[2]
Details
Mass0.26[3] M☉
Radius0.35[6] R☉
Surface gravity (log g)5[7] cgs
Temperature3,150 ± 100[7] K
Metallicity [Fe/H]−0.16 ± 0.20[4] dex
Rotation115.6±19.4 d[8]
Age≳8[9] Gyr
Other designations
GCTP1755, BD +05°1668, GJ 273, G 089-019, LHS 33, LTT 12021, LFT 527, Vys 17, HIP 36208.
Database references
SIMBADdata

Properties

This star is approximately a quarter the mass of the Sun[3] and has 35% of the Sun's radius.[6] 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.[13] It has a stellar classification of M 3.5 V,[3] 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[lower-alpha 1] is too low to be measured, but can be no greater than 1 km/s.[14] 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).[8] 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.[7][15]

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.[16] 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.[17] 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.[18] The space velocity components of Luyten's Star are U = +16, V = −66 and W = −17 km/s.[18][19][20]

Planetary system
The Luyten's Star planetary system[11][9]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
c 1.18 ± 0.16 M⊕ 0.036467 4.7234 ± 0.0004 0.17 ~72°–90[lower-alpha 2]° —
b 2.89 ± 0.26 M⊕ 0.09110 ± 0.00002 18.650 ± 0.006 0.10 ~72°–90[lower-alpha 2]° —
d (unconfirmed) 10.8+3.9
−3.5 M⊕		 0.712+0.062
−0.076		 413.9+4.3
−5.5		 0.17+0.18
−0.17		 ~72°–90° —
e (unconfirmed) 9.3+4.3
−3.9 M⊕		 0.849+0.083
−0.092		 542±16 0.03+0.20
−0.03		 ~72°–90° —

In March 2017, two candidate planets were discovered orbiting Luyten's Star.[11] 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 1.06 S⊕, 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 1.18 ± 0.16 Earth masses. However, it orbits much further in, with an orbital period of only 4.7234 ± 0.00004 days.[12]

GJ 273b is one of the closest known planets in its star's habitable zone.[12]

In 2019, two more candidate planets were detected by radial velocity, making a total of four known planets in the system.[11]

In October 2017, "Sónar Calling GJ 273b", a project by METI and the Sónar music festival,[21] transmitted a series of radio signals towards Luyten's star from a radar antenna at Ramfjordmoen, Norway.[22] 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 on May 14, 15, and 16, 2018. Were anyone listening, the soonest response would be received by 2036.

See also

Notes
  1. This is denoted by v sin i, where v is the rotational velocity at the equator and i is the inclination to the line of sight.
  2. In a solution with 2 planets around Luyten's Star for Luyten b and Luyten c, the system was unstable when the inclination was below 50° and the planets were on very eccentric orbit,. However, with lower eccentricities, the 2 planet system tolerated the full range of inclinations.

References
  1. Perryman, M.A.C.; Lindegren, L.; Kovalevsky, J.; Hoeg, E.; Bastian, U.; Bernacca, P.L.; et al. (1997). "The Hipparcos Catalogue". Astronomy and Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P.
  2. Koen, C.; Kilkenny, D.; van Wyk, F.; Cooper, D.; Marang, F. (July 2002). "UBV(RI)C photometry of Hipparcos red stars". Monthly Notices of the Royal Astronomical Society. 334 (1): 20–38. Bibcode:2002MNRAS.334...20K. doi:10.1046/j.1365-8711.2002.05403.x.
  3. The One Hundred Nearest Stars (Report). Research Consortium On Nearby Stars. 2009-01-01. Retrieved 2009-09-03.
  4. Nidever, David L.; Marcy, Geoffrey W.; Butler, R. Paul; Fischer, Debra A.; Vogt, Steven S. (August 2002). "Radial velocities for 889 late-type stars". The Astrophysical Journal Supplement Series. 141 (2): 503–522. arXiv:astro-ph/0112477. Bibcode:2002ApJS..141..503N. doi:10.1086/340570. S2CID 51814894.
  5. Gatewood, George (2008). "Astrometric studies of Aldebaran, Arcturus, Vega, the Hyades, and other regions". The Astronomical Journal. 136 (1): 452–460. Bibcode:2008AJ....136..452G. doi:10.1088/0004-6256/136/1/452.
  6. Lacy, C. H. (August 1977). "Radii of nearby stars: An application of the Barnes-Evans relation". Astrophysical Journal Supplement Series. 34: 479–492. Bibcode:1977ApJS...34..479L. doi:10.1086/190459.
  7. Viti, S.; Jones, H. R. A.; Richter, M. J.; Barber, R. J.; Tennyson, J.; Lacy, J. H. (August 2008). "A potential new method for determining the temperature of cool stars". Monthly Notices of the Royal Astronomical Society. 388 (3): 1305–1313. arXiv:0805.3297. Bibcode:2008MNRAS.388.1305V. doi:10.1111/j.1365-2966.2008.13489.x. S2CID 18660955.
  8. Suárez Mascareño, A.; Rebolo, R.; González Hernández, J.I.; Esposito, M. (September 2015), "Rotation periods of late-type dwarf stars from time series high-resolution spectroscopy of chromospheric indicators", Monthly Notices of the Royal Astronomical Society, 452 (3): 2745–2756, arXiv:1506.08039, Bibcode:2015MNRAS.452.2745S, doi:10.1093/mnras/stv1441, S2CID 119181646
  9. Pozuelos, Francisco J.; Suárez, Juan C.; de Elía, Gonzalo C.; Berdiñas, Zaira M.; Bonfanti, Andrea; Dugaro, Agustín; et al. (2020). "GJ 273: On the formation, dynamical evolution, and habitability of a planetary system hosted by an M dwarf at 3.75 parsec". Astronomy & Astrophysics. 641: A23. arXiv:2006.09403. doi:10.1051/0004-6361/202038047. GJ 273 is a planetary system orbiting an M dwarf only 3.75 pc away, composed of two confirmed planets, GJ 273b and GJ 273c, and two promising candidates, GJ 273d and GJ 273e ... the system remained stable only for values of inclinations ranging from 90◦ to ∼72◦
  10. Luyten, W.J.; Ebbighausen, E.G. (September 1935). "A faint star of large proper motion". Harvard College Observatory Bulletin. 900 (900): 1–3. Bibcode:1935BHarO.900....1L.
  11. Tuomi, M.; Jones, H.R.A.; Anglada-Escudé, G.; Butler, R.P.; Arriagada, P.; Vogt, S.S.; et al. (2019). "Frequency of planets orbiting M dwarfs in the Solar neighbourhood". arXiv:1906.04644 [astro-ph.EP].
  12. Astudillo-Defru, N.; Forveille, T.; Bonfils, X.; Ségransan, D.; Bouchy, F.; Delfosse, X.; et al. (2017). "The HARPS search for southern extra-solar planets. XLI. A dozen planets around the M dwarfs GJ 3138, GJ 3323, GJ 273, GJ 628, and GJ 3293". Astronomy and Astrophysics. 602. A88. arXiv:1703.05386. Bibcode:2017A&A...602A..88A. doi:10.1051/0004-6361/201630153. S2CID 119418595.
  13. Reiners, A.; Basri, G. (March 2009). "On the magnetic topology of partially and fully convective stars". Astronomy and Astrophysics. 496 (3): 787–790. arXiv:0901.1659. Bibcode:2009A&A...496..787R. doi:10.1051/0004-6361:200811450. S2CID 15159121.
  14. Reiners, A. (May 2007). "The narrowest M dwarf line profiles and the rotation-activity connection at very slow rotation". Astronomy and Astrophysics. 467 (1): 259–268. arXiv:astro-ph/0702634. Bibcode:2007A&A...467..259R. doi:10.1051/0004-6361:20066991. S2CID 8672566.
  15. "The Colour of Stars". Australia Telescope. Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. 21 December 2004. Archived from the original on 22 February 2012. Retrieved 2012-01-16.
  16. García-Sánchez, J.; et al. (2001). "Stellar encounters with the solar system" (PDF). Astronomy and Astrophysics. 379 (2): 634–659. Bibcode:2001A&A...379..634G. doi:10.1051/0004-6361:20011330.
  17. Schaaf, Fred (2008). The Brightest Stars: Discovering the universe through the sky's most brilliant stars. John Wiley and Sons. p. 169. ISBN 978-0-471-70410-2.
  18. "Annotations on LHS 33 object". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-04-21.
  19. Delfosse, X.; Forveille, T.; Perrier, C.; Mayor, M. (March 1998). "Rotation and chromospheric activity in field M dwarfs". Astronomy and Astrophysics. 331: 581–595. Bibcode:1998A&A...331..581D.
  20. "ARICNS star page of GJ 273". Astronomisches Rechen-Institut Heidelberg. Retrieved 2010-04-21.
  21. "Sónar music festival". Sónar. Barcelona, ES.
  22. "How to send a message to another planet". The Economist. 16 November 2017. Retrieved 19 November 2017.


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