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Gliese 65 A/B

Gliese 65, as seen during the Digitized Sky Survey
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cetus
Gliese 65 A (BL Ceti)
Right ascension	01 39 01.3773
Declination	–17° 57′ 02.587″
Apparent magnitude (V)	12.8
Gliese 65 B (UV Ceti)
Right ascension	01 39 01.6377
Declination	–17° 57′ 01.001″
Apparent magnitude (V)	12.8
Characteristics
Gliese 65 A (BL Ceti)
Spectral type	M5.5V
U−B color index	1.10
B−V color index	1.87
Variable type	UV Cet
Gliese 65 B (UV Ceti)
Spectral type	M6 V
Variable type	UV Cet
Astrometry
Parallax (π)	371.92 ± 0.42 mas
Distance	8.770 ± 0.010 ly (2.689 ± 0.003 pc)
Gliese 65 A (BL Ceti)
Proper motion (μ)	RA: 3385.316 mas/yr Dec.: 544.386 mas/yr
Absolute magnitude (MV)	15.7
Gliese 65 B (UV Ceti)
Proper motion (μ)	RA: 3178.694 mas/yr Dec.: 584.061 mas/yr
Absolute magnitude (MV)	15.7
Orbit
Period (P)	26.38±0.002 yr
Semi-major axis (a)	2.0584±0.0097" (5.459±0.002 AU)
Eccentricity (e)	0.6172±0.0001
Inclination (i)	128.0±0.1°
Longitude of the node (Ω)	325.9±0.1°
Periastron epoch (T)	41333±8 MJD (17 January 1972)
Argument of periastron (ω) (secondary)	103.2±0.1°
Details
Gliese 65 A
Mass	0.122±0.002 M☉
Radius	0.165±0.006 R☉
Luminosity	0.00147±0.00005 L☉
Surface gravity (log g)	5.092±0.015 cgs
Temperature	2784±58 K
Metallicity	−0.03±0.20 dex
Rotation	0.2430±0.0005 days
Rotational velocity (v sin i)	28.2±2 km/s
Gliese 65 B
Mass	0.116±0.002 M☉
Radius	0.159±0.006 R☉
Luminosity	0.00125±0.00005 L☉
Surface gravity (log g)	5.113±0.015 cgs
Temperature	2728±60 K
Metallicity	−0.12±0.20 dex
Rotation	0.2268±0.0003 days
Rotational velocity (v sin i)	30.6±2 km/s
Other designations
GJ 65, G 272-61, L 726-8, PLX 343.1
Gliese 65 A: BL Ceti, LHS 9, LP 768-27
Gliese 65 B: UV Ceti, LHS 10, LP 768-26
Database references
SIMBAD	The system
	A (BL Cet)
	B (UV Cet)

Gliese 65, also known as Luyten 726-8, is a binary star system that is one of Earth's nearest neighbors, at 8.8 light-years (2.7 parsecs) from Earth in the constellation Cetus. The two component stars are both flare stars with the variable star designations BL Ceti and UV Ceti.

Star system

The star system was discovered in 1948 by Willem Jacob Luyten in the course of compiling a catalog of stars of high proper motion; he noted its exceptionally high proper motion of 3.37 arc seconds annually and cataloged it as Luyten 726-8. The two stars are of nearly equal brightness, with visual magnitudes of 12.7 and 13.2 as seen from Earth. They orbit one another every 26.5 years. The distance between the two stars varies from 2.1 to 8.8 astronomical units (310 to 1,320 Gm). The Gliese 65 system is approximately 2.63 parsecs (8.58 ly) from Earth's Solar System, in the constellation Cetus, and is thus the seventh-closest star system to Earth. Its own nearest neighbor is Tau Ceti, 0.98 pc (3.20 ly) away from it. If ${\displaystyle R_{v}=+29}$ km/s then approximately 28,700 years ago Gliese 65 was at its minimal distance of 2.21 pc (7.2 ly) from the Sun.

Gliese 65 A was later found to be a variable star and given the variable star designation BL Ceti. It is a red dwarf of spectral type M5.5V. It is also a flare star, and classified as a UV Ceti variable type, but it is not nearly as remarkable or extreme in its behavior as its companion star UV Ceti.

Soon after the discovery of Gliese 65 A, the companion star Gliese 65 B was discovered. Like Gliese 65 A, this star was also found to be variable and given the variable star designation UV Ceti. Although UV Ceti was not the first flare star discovered, it is the most prominent example of such a star, so similar flare stars are now classified as UV Ceti type variable stars. This star goes through fairly extreme changes of brightness: for instance, in 1952, its brightness increased by 75 times in only 20 seconds. UV Ceti is a red dwarf of spectral type M6V.

Both stars are listed as spectral standard stars for their respective classes, being considered typical examples of the classes.

In approximately 31,500 years, Gliese 65 will have a close encounter with Epsilon Eridani at the minimal distance of about 0.93 ly. Gliese 65 can penetrate a conjectured Oort cloud about Epsilon Eridani, which may gravitationally perturb some long-period comets. The duration of mutual transit of two star systems within 1 ly from each other is about 4,600 years.

Gliese 65 is a possible member of the Hyades Stream.

Candidate planet

In 2024, a candidate super-Neptune-mass planet was detected in the Gliese 65 system via astrometry with Very Large Telescope's GRAVITY instrument. If it exists, it would orbit one of the two stars (it is unclear which) with a period of 156 days. The planet's properties change slightly depending on which star it orbits, but in general its mass is estimated to be about 40 M_E and the semi-major axis is about 30% of an astronomical unit. It is estimated to be about seven times the size of Earth based on mass-radius relationships.

Notes

1. The parameters are slightly different depending on whether the planet orbits star A (above) or star B (below).

References

1. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
2. ^ Houdebine, Éric R.; Mullan, D. J.; Doyle, J. G.; de la Vieuville, Geoffroy; Butler, C. J.; Paletou, F. (2019). "The Mass-Activity Relationships in M and K Dwarfs. I. Stellar Parameters of Our Sample of M and K Dwarfs". The Astronomical Journal. 158 (2): 56. arXiv:1905.07921. Bibcode:2019AJ....158...56H. doi:10.3847/1538-3881/ab23fe. S2CID 159041104.
3. ^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
4. ^ Kirkpatrick, J. Davy; Henry, Todd J.; McCarthy, Donald W. Jr. (1991). "A standard stellar spectral sequence in the red/near-infrared - Classes K5 to M9". Astrophysical Journal Supplement. 77: 417. Bibcode:1991ApJS...77..417K. doi:10.1086/191611.
5. ^ "Query= BL Cet". General Catalogue of Variable Stars. Centre de Données astronomiques de Strasbourg. Archived from the original on 2016-03-03. Retrieved 2009-12-16.
6. ^ "Query= UV Cet". General Catalogue of Variable Stars. Centre de Données astronomiques de Strasbourg. Archived from the original on 2016-03-03. Retrieved 2009-12-16.
7. ^ Abuter, R.; et al. (GRAVITY Collaboration) (May 2024). "Astrometric detection of a Neptune-mass candidate planet in the nearest M-dwarf binary system GJ65 with VLTI/GRAVITY". Astronomy & Astrophysics. 685: L9. arXiv:2404.08746. Bibcode:2024A&A...685L...9G. doi:10.1051/0004-6361/202449547.
8. ^ Kervella, Pierre; et al. (October 2016), "The red dwarf pair GJ65 AB: inflated, spinning twins of Proxima. Fundamental parameters from PIONIER, NACO, and UVES observations", Astronomy & Astrophysics, 593, arXiv:1607.04351, Bibcode:2016A&A...593A.127K, doi:10.1051/0004-6361/201628631
9. ^ MacDonald, James; et al. (June 2018), "The Magnetic Binary GJ 65: A Test of Magnetic Diffusivity Effects", The Astrophysical Journal, 860 (1): 15, arXiv:1711.09434, Bibcode:2018ApJ...860...15M, doi:10.3847/1538-4357/aac2c0
10. ^ Barnes, J. R.; et al. (October 2017), "Surprisingly different star-spot distributions on the near equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB", Monthly Notices of the Royal Astronomical Society, 471 (1): 811–823, arXiv:1706.03979, Bibcode:2017MNRAS.471..811B, doi:10.1093/mnras/stx1482
11. Luyten, W. J. (December 1949). "New stars with proper motions exceeding 0.5" annually". The Astronomical Journal. 55: 15. Bibcode:1949AJ.....55...15L. doi:10.1086/106322.
12. "Annotations on V* UV Cet object". Centre de Données astronomiques de Strasbourg. Archived from the original on 2014-11-23. Retrieved 2010-04-14.
13. Beskin, G.; Karpov, S.; Plokhotnichenko, V.; Stepanov, A.; Tsap, Yu. (January 2017). "Discovery of the subsecond linearly polarized spikes of synchrotron origin in the UV Ceti giant optical flare". Publications of the Astronomical Society of Australia. 34. arXiv:1702.06660. Bibcode:2017PASA...34...10B. doi:10.1017/pasa.2017.3. S2CID 125084280.
14. Potemine, Igor Yu. (April 2010). "Transit of Luyten 726-8 within 1 ly from Epsilon Eridani". arXiv:1004.1557 .
15. Montes, D.; et al. (2001). "Late-type members of young stellar kinematic groups - I. Single stars". MNRAS. 328 (1): 45–63. arXiv:astro-ph/0106537. Bibcode:2001MNRAS.328...45M. doi:10.1046/j.1365-8711.2001.04781.x. S2CID 55727428.

Further reading

• Durand, E.; Oberly, J. J.; Tousey, R. (1949). "Analysis of the First Rocket Ultraviolet Solar Spectra". The Astrophysical Journal. 109: 1. Bibcode:1949ApJ...109....1D. doi:10.1086/145099.
• Luyten, W. J. (1949). "New stars with proper motions exceeding 0.5" annually". The Astronomical Journal. 55: 15. Bibcode:1949AJ.....55...15L. doi:10.1086/106322.
• Geyer, David W.; Harrington, Robert S.; Worley, Charles E. (June 1988). "Parallax, orbit, and mass of the visual binary L726-8". Astronomical Journal. 95: 1841–1842. Bibcode:1988AJ.....95.1841G. doi:10.1086/114781.
• Delfosse, Xavier; et al. (December 2000). "Accurate masses of very low mass stars. IV. Improved mass-luminosity relations". Astronomy and Astrophysics. 364: 217–224. arXiv:astro-ph/0010586. Bibcode:2000A&A...364..217D.

External links

• http://www.aavso.org/vstar/vsots/fall03.shtml Archived 2004-03-05 at the Wayback Machine
• http://www.solstation.com/stars/luy726-8.htm Archived 2009-03-27 at the Wayback Machine

v t e Constellation of Cetus
List of stars in Cetus Cetus in Chinese astronomy
Stars	Bayer α (Menkar) β (Diphda) γ (Kaffaljidhma) δ ε ζ (Baten Kaitos) η θ ι κ κ λ μ ν ξ ξ ο (Mira) A B π ρ σ τ υ φ φ φ φ χ Flamsteed 1 2 3 6 7 9 13 14 20 46 49 56 (υ) 63 64 69 75 77 79 81 84 94 25 Ari Variable T UV YZ ZZ AY BL BW DK HR 10 72 159 228 500 672 870 HD 984 1690 2638 4747 5319 6718 7449 11506 11964 15115 16008 224693 (Axólotl) Other 2MASS J01225093−2439505 BD-07 436 BD−17 63 (Felixvarela) Cayrel's Star CFBDS J005910.90–011401.3 DENIS-P J020529.0−115925 GD 40 Gliese 65 Gliese 105 GJ 1002 GJ 1005 HIP 5158 HIP 11952 LHS 1140 NGC 156 NGC 158 NGC 302 NGC 308 NGC 310 PSR J0108−1431 SDSS J001820.5−093939.2 SDSS J0106−1000 ULAS J003402.77−005206.7 WD J2356−209 WASP-20 WASP-26 WASP-44 WASP-71 (Mpingo) WISE J0254+0223 WHL0137-LS
Exoplanets 79 Ceti b 81 Ceti b 94 Ceti b BD−17 63 b HD 1461 b HD 2638 b HD 5319 b HD 11506 b c HD 11964 b c HD 224693 b HIP 5158 b c HIP 11915 b τ Ceti e f
Nebulae NGC 246
Galaxies	Messier 77 NGC 17 35 45 47 50 54 59 61 62 64 65 66 73 77 102 107 113 114 116 117 118 120 124 132 135 142 143 144 145 151 154 155 157 161 163 165 166 167 168 170 171 172 173 177 178 179 187 191 192 195 196 197 201 207 209 210 216 217 219 223 227 230 232 235 237 239 244 245 247 255 259 263 268 270 271 273 274 275 276 277 279 283 284 285 286 291 293 297 298 301 303 307 309 320 321 325 327 329 331 333 335 336 337 340 341 342 343 344 345 347 349 350 351 352 353 355 356 357 359 363 364 367 369 377 391 413 417 426 428 429 430 435 442 445 448 450 478 480 481 487 493 497 519 521 533 540 541 545 547 554 555 560 570 584 585 596 615 622 655 681 682 690 701 720 747 755 779 800 806 833 838 864 874 880 895 908 936 945 950 960 965 966 985 988 1009 1015 1019 1022 1032 1042 1052 1055 1073 1087 1090 1128 1142 1153 1218 7808 7828 7829 Other Arp 146 Arp 147 Arp 256 3C 75 Cetus Dwarf HCM-6A HD2 Holmberg 15A HXMM01 IC 1613 IC 1623 IRAS 01003-2238 Markarian 1014 Markarian 1018 MCG -03-04-014 PGC 2456 SDSS J0303-0019 SXDF-NB1006-2 9Spitch TON S180 UGC 711 UGC 1775 Wolf–Lundmark–Melotte
Galaxy clusters Abell 133 Abell 222 Abell 223 Abell 370 Abell 400 Arp 251 Gioiello IRC 0218 JKCS 041
Astronomical events SN 2005E SN 2005gj
Category

• M-type main-sequence stars
• BY Draconis variables
• Flare stars
• Binary stars
• Hyades Stream
• Local Bubble
• Cetus
• Gliese and GJ objects
• Objects with variable star designations
• Hypothetical planetary systems