61 Virginis

61 Virginis (abbreviated 61 Vir) is the Flamsteed designation of a G-type main-sequence star (G7V) slightly less massive than the Sun (which has a G4V mass), located about 27.9 light-years away in the constellation of Virgo. The composition of this star is nearly identical to the Sun.

61 Virginis

61 Vir as seen with a 12.5" telescope with a field of view of 45.1 arcminutes
Observation data
Epoch J2000      Equinox J2000
Constellation Virgo
Right ascension 13h 18m 24.31427s[1]
Declination −18° 18′ 40.3047″[1]
Apparent magnitude (V) 4.74
Characteristics
Spectral type G7V[2]
Apparent magnitude (B) 5.45
Apparent magnitude (J) 3.334
Apparent magnitude (H) 2.974
Apparent magnitude (K) 2.956
U−B color index 0.26
B−V color index 0.71
V−R color index 0.37
R−I color index 0.33
Astrometry
Radial velocity (Rv)–8.13[3] km/s
Proper motion (μ) RA: −1,070.36[1] mas/yr
Dec.: −1,063.69[1] mas/yr
Parallax (π)116.89 ± 0.22[1] mas
Distance27.90 ± 0.05 ly
(8.56 ± 0.02 pc)
Absolute magnitude (MV)5.07[4]
Details
Mass0.93[5] M☉
Radius0.9867±0.0048[5] R☉
Luminosity0.8222±0.0033[5] L☉
Surface gravity (log g)4.5[6] cgs
Temperature5538±13[5] K
Metallicity [Fe/H]−0.02[6] dex
Rotational velocity (v sin i)3.9 ± 0.9[7] km/s
Age6.1–6.6[8] Gyr
Other designations
BD-17°3813, FK5 1345, GCTP 3039.00, GJ 506, HD 115617, HIP 64924, HR 5019, LHS 349, LTT 5111, SAO 157844.
Database references
SIMBADdata
Exoplanet Archivedata
ARICNSdata
Extrasolar Planets
Encyclopaedia		data

61 Virginis (G7V) is the first well-established main-sequence star very similar to the Sun with a potential Super-Earth,[9] though it was preceded by COROT-7 (a borderline orange dwarf).

Description

61 Virginis is a fifth-magnitude G-type main-sequence star with a stellar classification of G7 V.[2] It is faint but visible to the naked eye south and east of the bright star Spica in the zodiac constellation of Virgo. The designation 61 Virginis originated in the star catalogue of English astronomer John Flamsteed, as part of his Historia Coelestis Britannica. An 1835 account of Flamsteed's work by English astronomer Francis Baily noted that the star showed a proper motion.[10] This made the star of interest for parallax studies, and by 1950 a mean annual value of 0.006″ was obtained.[11] The present day result, obtained with data from the Hipparcos satellite, gives a parallax of 116.89 mas,[1] which corresponds to a physical separation of 27.9 light years from the Sun.

This star is similar in physical properties to the Sun, with around 95%[9] of the Sun's mass, 98%[9] of the radius, and 85%[12] of the Luminosity. The abundance of elements is also similar to the Sun, with the star having an estimated 95%[6] of the Sun's proportion of elements other than hydrogen and helium. It is older than the Sun at around 6.1–6.6[8] billion years of age, and is spinning with a leisurely projected rotational velocity of 4[7] km/s at the equator. On average, there is only a low level of activity in the stellar chromosphere[6] and it is a candidate for being in a Maunder minimum state.[13] But the star was suspected as variable in 1988,[14] and a burst of activity was observed between Julian days [24]54800 (29 November 2008) and 55220 (23 January 2010).[15]

The space velocity components of this star are U = –37.9, V = –35.3 and W = –24.7 km/s. 61 Vir is orbiting through the Milky Way galaxy at a distance of 6.9 kpc from the core, with an eccentricity of 0.15. It is believed to be a member of the disk population.[12][8]

Planetary system

The ecliptic of the 61 Virginis system, as inferred from its dust disc, is inclined to the Solar system at 77°. The star itself is probably inclined at 72°.[15]

In 1988, a study surmised that 61 Virginis was a "possible variable", but no companions were then found.[14] A subsequent study, over eleven years, also failed to find any companion up to the mass of Jupiter and out to 3 AU.[16]

On 14 December 2009, scientists announced the discovery of three planets with masses between 5 and 25 times that of Earth orbiting 61 Virginis.[9][17] The three planets all orbit very near the star; when compared to the orbits of the planets in the Solar System, all three would orbit inside that of Venus. The outermost of these three, d, has not yet been confirmed in the HARPS data.[15]

A survey with the Spitzer Space Telescope revealed an excess of infrared radiation at a wavelength of 160 μm. This indicated the presence of a debris disk in orbit around the star. This disk was resolved at 70 μm. It was then thought to correspond to an inner radius of 96 AU from the star and outer radius at 195 AU; it is now constrained 30 to over 100 AU.[15] The total mass of the disk is 5 × 10−5 the mass of the Earth.[15][18]

On 27 November 2012, the European Space Agency declared that the debris disc (like that of the Gliese 581 planetary system) has "at least 10 times" as many comets as does the Solar system.

As of 2012, "planets more massive than Saturn orbiting within 6 AU" were ruled out.[15] The ESA has further ruled out Saturn-mass planets beyond that.[19]

Additional data is needed to confirm the possibility of more sub-Saturn planets between 0.5 (really, 0.3) and 30 AU from the star.[15] An Earth-mass planet in the star's habitable zone (which would still be too small to detect with current technology) remains possible.

The 61 Virginis planetary system[9]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 5.3±0.5[20] M⊕ 0.050201±0.000005 4.2150±0.0006 0.12±0.11 — —
c 18.8±1.1[21] M⊕ 0.2175±0.0001 38.021±0.034 0.14±0.06 — —
d[15] (unconfirmed) 23.7±2.7[22] M⊕ 0.476±0.001 123.01±0.55 0.35±0.09 — —
Debris disk 30[15]–>100[15] AU — —
  • 61 Virginis System

View from 61 Virginis

The Sun is barely visible from the system as a small star close to the much brighter Sirius. Arcturus (magnitude −1.01) is the brightest star of the night sky.[23]

See also

References
  1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
  2. Gray, R. O.; et al. (October 2003), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I.", The Astronomical Journal, 126 (4): 2048–2059, arXiv:astro-ph/0308182, Bibcode:2003AJ....126.2048G, doi:10.1086/378365
  3. Nidever, David L.; et al. (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
  4. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191.
  5. von Braun, Kaspar; et al. (2014). "Stellar diameters and temperatures - V. 11 newly characterized exoplanet host stars". Monthly Notices of the Royal Astronomical Society. 438 (3): 2413–2425. arXiv:1312.1792. Bibcode:2014MNRAS.438.2413V. doi:10.1093/mnras/stt2360.
  6. Perrin, M.-N.; Cayrel de Strobel, G.; Dennefeld, M. (February 1988), "High S/N detailed spectral analysis of four G and K dwarfs within 10 PC of the sun", Astronomy and Astrophysics, 191 (2): 237–247, Bibcode:1988A&A...191..237P
  7. Ammler-von Eiff, M.; Reiners, A. (June 2012). "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?". Astronomy & Astrophysics. 542: A116. arXiv:1204.2459. Bibcode:2012A&A...542A.116A. doi:10.1051/0004-6361/201118724.
  8. Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008). "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics". The Astrophysical Journal. 687 (2): 1264–1293. arXiv:0807.1686. Bibcode:2008ApJ...687.1264M. doi:10.1086/591785.
  9. Vogt, Steven; Wittenmyer; Paul Butler; Simon O'Toole; Henry; Rivera; Stefano Meschiari; Gregory Laughlin; Tinney (2010). "A Super-Earth and two Neptunes Orbiting the Nearby Sun-like star 61 Virginis". The Astrophysical Journal. 708 (2): 1366–1375. arXiv:0912.2599. Bibcode:2010ApJ...708.1366V. doi:10.1088/0004-637X/708/2/1366.
  10. Baily, Francis, ed. (1835). An Account of the Revd. John Flamsteed, the First Astronomer- Royal. By order of the Lords Commissioners of the Admiralty. p. 588.
  11. Staff (1950). "Stars, Parallax of: Stellar parallaxes determined photographically at the Cape Observatory (seventeenth list)". Monthly Notices of the Royal Astronomical Society. 110 (4): 405–412. Bibcode:1950MNRAS.110..405.. doi:10.1093/mnras/110.4.405.
  12. Porto de Mello, Gustavo; del Peloso, Eduardo F.; Ghezzi, Luan (April 2006). "Astrobiologically Interesting Stars Within 10 Parsecs of the Sun". Astrobiology. 6 (2): 308–331. arXiv:astro-ph/0511180. Bibcode:2006AsBio...6..308P. doi:10.1089/ast.2006.6.308. PMID 16689649.
  13. Lubin, Dan; Tytler, David; Kirkman, David (March 2012). "Frequency of Maunder Minimum Events in Solar-type Stars Inferred from Activity and Metallicity Observations". The Astrophysical Journal Letters. 747 (2): L32. Bibcode:2012ApJ...747L..32L. doi:10.1088/2041-8205/747/2/L32.
  14. Campbell, Bruce; et al. (1988). "A search for substellar companions to solar-type stars". Astrophysical Journal. 331: 902–921. Bibcode:1988ApJ...331..902C. doi:10.1086/166608., pages 904, 906, and 919
  15. Wyatt, M. C.; et al. (2012). "Herschel imaging of 61 Vir: implications for the prevalence of debris in low-mass planetary systems". MNRAS. 424 (2): 1206–1223. arXiv:1206.2370. Bibcode:2012MNRAS.424.1206W. doi:10.1111/j.1365-2966.2012.21298.x.
  16. Cumming, Andrew; Marcy, Geoffrey W.; Butler, R. Paul (1999). "The Lick Planet Search: Detectability and Mass Thresholds". Astrophysical Journal. 526 (2): 890–915. arXiv:astro-ph/9906466. Bibcode:1999ApJ...526..890C. doi:10.1086/308020.
  17. Tim Stephens (2009-12-14). "New planet discoveries suggest low-mass planets are common around nearby stars". UCSC News. UC Santa Cruz. Archived from the original on 23 December 2009. Retrieved 2009-12-14.
  18. Tanner, Angelle; et al. (October 2009). "Survey of Nearby FGK Stars at 160 μm with Spitzer". The Astrophysical Journal. 704 (1): 109–116. arXiv:0908.0049. Bibcode:2009ApJ...704..109T. doi:10.1088/0004-637X/704/1/109.
  19. ESA Herschel (27 November 2012). "Do missing Jupiters mean massive comet belts?".
  20. m sin i = 5.1. This true-mass value assumes about 75 degree inclination per Wyatt.
  21. m sin i = 18.2. This true-mass value assumes about 75 degree inclination per Wyatt.
  22. m sin i = 22.9 ± 2.6. This true-mass value assumes about 75 degree inclination per Wyatt.
  23. "The Chronicles of Local Space – 61 Virginis".

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.