Gamma Virginis
| |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Virgo |
| Right ascension | 12h 41m 39.64344s[1] |
| Declination | –01° 26′ 57.7421″[1] |
| Apparent magnitude (V) | 2.74 (3.650/3.560[2]) |
| Characteristics | |
| Spectral type | F0 V/F0 V[2] |
| U−B color index | -0.05 |
| B−V color index | 0.36 |
| Variable type | unknown |
| Astrometry | |
| Radial velocity (Rv) | -19.5[3] km/s |
| Proper motion (μ) | RA: –614.76[1] mas/yr Dec.: 61.34[1] mas/yr |
| Parallax (π) | 85.58 ± 0.60[1] mas |
| Distance | 38.1 ± 0.3 ly (11.68 ± 0.08 pc) |
| Absolute magnitude (MV) | 2.38 (3.12/3.14) |
| Orbit[4] | |
| Companion | Gamma Virginis B |
| Period (P) | 168.93 ± 0.30 yr |
| Semi-major axis (a) | 3.662 ± 0.013" |
| Eccentricity (e) | 0.8825 ± 0.0010 |
| Inclination (i) | 148.82 ± 0.43° |
| Longitude of the node (Ω) | 213.79 ± 0.72° |
| Periastron epoch (T) | 2005.438 ± 0.067 |
| Details | |
| Mass | 1.56[3] M☉ |
| Surface gravity (log g) | 4.26[3] cgs |
| Temperature | 6,757[5] K |
| Metallicity [Fe/H] | –0.07[2] dex |
| Age | 1.14[6] Gyr |
| Other designations | |
| γ Vir A: HD 110379, HR 4825, LFT 937, LTT 4843 | |
| γ Vir B: HD 110380, HR 4826, LFT 937, LTT 4844 | |
Gamma Virginis (γ Virginis, abbreviated Gamma Vir, γ Vir), also named Porrima,[7] is a binary star system in the constellation of Virgo.
Name
γ Virginis (Latinised to Gamma Virginis) is the star's Bayer designation.
The traditional name Porrima derives from Ancient Rome, Porrima (also known as Antevorta) was one of the Camenae or goddesses of prophecy.[8] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[9] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[10] included a table of the first two batches of names approved by the WGSN; which included Porrima for this star.
In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Laouiyet al Aoua, which was translated into Latin as Angulus Latratoris, meaning 'the angle of the barker'.[11] This star, along with Beta Virginis (Zavijava), Eta Virginis (Zaniah), Delta Virginis (Auva) and Epsilon Virginis (Vindemiatrix), were Al ʽAwwāʼ, the Barker.[8]
In Chinese, 太微左垣 (Tài Wēi Zuǒ Yuán), meaning Left Wall of Supreme Palace Enclosure, refers to an asterism consisting of Gamma Virginis, Eta Virginis, Delta Virginis, Epsilon Virginis and Alpha Comae Berenices.[12] Consequently, Gamma Virginis itself is known as 太微左垣二 (Tài Wēi Zuǒ Yuán èr, English: the Second Star of Left Wall of Supreme Palace Enclosure.),[13] representing 東上相 (Dōngshǎngxiāng), meaning The First Eastern Minister.[14] 東上相 (Dōngshǎngxiāng), westernized into Shang Seang by R.H. Allen and the meaning is "the High Minister of State".[8]
Properties
Gamma Virginis is a binary star, consisting of two stars of approximately equal apparent magnitudes 3.65 and 3.56, and of spectral type F0V.[2] With an orbital period of 168.93 years,[4] it was an easy object for amateur astronomers until the beginning of the 1990s, but in 2011 the smaller apparent distance between the stars requires a larger telescope to resolve the individual components. The last time they were at periapsis was in 1836. The distance will again be wide enough in 2020 to view with a small telescope. The star system has a combined apparent magnitude of 2.9. The system is 39 light years away from the Sun.
As Gamma Virginis is close to the ecliptic, it can be occulted by the Moon and (extremely rarely) by planets. In June 2011, Saturn came within a quarter of a degree from Porrima.
Based upon X-ray emissions—an indicator of the strength of the stellar magnetic field—this system has an estimated age of 1.14 billion years.[6]
Changes of distance and position angle
This table shows the apparent distance between the two stars and their relative position angle: first three columns show data predicted from an orbit calculated in 1937, the next two columns show in 2006,[15] the next three columns show observations reported by the Hanwell Community Observatory.[16]
| Predicted from 1937 Strand orbit | Predicted from 2006 Docobo orbit | Observations 2003 to 2005 | |||||
|---|---|---|---|---|---|---|---|
| Year | distance | position angle | distance | position angle | Date | distance | position angle |
| 1995 | 2.5″ | 280 | 2.25″ | 277.6 | |||
| 2000 | 1.8″ | 267 | 1.50″ | 260.9 | |||
| 2002 | 1.5″ | 259 | 1.13″ | 247.5 | |||
| 2003 | 0.92″ | 236.6 | 2003 Dec. | 0.6″ | 219° | ||
| 2004 | 1.2″ | 246 | 0.68″ | 218.4 | 2004 Dec. | 0.4″ | 177° |
| 2005 | 0.44″ | 179.8 | 2005 April | 0.27-0.29″ | 161±0.6° | ||
| 2006 | 0.8″ | 221 | 0.41″ | 103.5 | |||
| 2008 | 0.4″ | 126 | 0.93″ | 41.0 | |||
| 2010 | 0.9″ | 44 | 1.39″ | 23.6 | |||
References
- 1 2 3 4 5 van Leeuwen, Floor (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752v1
, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357 Note: see VizieR catalogue I/311. - 1 2 3 4 Cayrel de Strobel, G.; Soubiran, C.; Ralite, N. (July 2001), "Catalogue of [Fe/H] determinations for FGK stars: 2001 edition", Astronomy and Astrophysics, 373: 159–163, arXiv:astro-ph/0106438, Bibcode:2001A&A...373..159C, doi:10.1051/0004-6361:20010525
- 1 2 3 Casagrande, L.; et al. (June 2011), "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s). Improved astrophysical parameters for the Geneva-Copenhagen Survey", Astronomy and Astrophysics, 530: A138, arXiv:1103.4651, Bibcode:2011A&A...530A.138C, doi:10.1051/0004-6361/201016276.
- 1 2 Mason, Brian D.; et al. (2006), "Speckle Interferometry at the US Naval Observatory. XII.", The Astronomical Journal, 132 (5): 2219–2230, Bibcode:2006AJ....132.2219M, doi:10.1086/508231
- ↑ Muñoz Bermejo, J.; et al. (May 2013), "A PCA approach to stellar effective temperatures", Astronomy and Astrophysics, 453: A95, arXiv:1303.7218, Bibcode:2013A&A...553A..95M, doi:10.1051/0004-6361/201220961.
- 1 2 Vican, Laura (June 2012), "Age Determination for 346 Nearby Stars in the Herschel DEBRIS Survey", The Astronomical Journal, 143 (6): 135, arXiv:1203.1966, Bibcode:2012AJ....143..135V, doi:10.1088/0004-6256/143/6/135
- ↑ "IAU Catalog of Star Names". Retrieved 28 July 2016.
- 1 2 3 Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 470. ISBN 0-486-21079-0. Retrieved 2010-12-12.
- ↑ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
- ↑ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
- ↑ Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society. 55: 429–438. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429.
- ↑ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- ↑ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ↑ (Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ↑ INTERNATIONAL ASTRONOMICAL UNION COMMISSION 26 (DOUBLE STARS)
- ↑ Christopher Taylor, Hanwell Community Observatory