ركبة الجاثي الشمالية

ركبة الجاثي الشمالية
Hercules constellation map-ar.png
تصوير تاريخي لكوكبة الجاثي حيث يظهر النجم τ، بأسفل اليسار، كـ "ركبة الجاثي الشمالية".
بيانات الرصـد
الحقبة J2000      اعتدال J2000
الكوكبة Hercules
الصعود المستقيم 16h 19m 44.43666s[1]
الميل 46° 18′ 48.1123″[1]
القدر الظاهري (V)3.91[2]
3.83 to 3.86[3]
الخـصـائص
النوع الطيفيB5 IV[4]
U-B دليل الألوان−0.569[2]
B-V دليل الألوان−0.151±0.009[2]
النوع المتغيرSPB[3]
علم القياسات الفلكية
السرعة القطرية (Rv)−15.5±0.5[2] كم/ث
الحركة الحقيقية (μ) RA: −13.33[1] mas/yr
Dec.: 38.48[1] mas/س
اختلاف المنظر (π)10.61 ± 0.11[1] mas
المسافةس ض
( ف ن)
القدر المطلق (MV)−0.96[2]
التـفـاصـيل
الكتلة4.01[5] M☉
نصف القطر3.55±0.19 R☉[6]
3.80±0.25[7] R☉
جاذبية السطح (log g)4.02±0.05[6]
الضياء574[2] L☉
درجة الحرارة15,615±301[6] ك
سرعة الدوران (v sin i)32[5] كم/ث
تسميات أخرى
Rukbalgethi Shemali، τ Her، 22 Her، BD+46°2169، FK5 608، GC 21987، HD 147394، HIP 79992، HR 6092، SAO 46028، CCDM J16197+4619A[8]
مراجع قواعد البيانات
SIMBADdata

ركبة الجاثي الشمالية إنگليزية: Rukbalgethi Shemali أو Tau Herculis نجم تابع لكوكبة الجاثي، يبعد 314 سنة ضوئية عن الأرض. يعدّه الفلكيون نجمًا عملاقًا أزرق-أبيض and is visible to the naked eye at night with an apparent visual magnitude that fluctuates around 3.91.[2] The star is located at a distance of approximately 307 light years from the Sun based on parallax,[1] but it is drifting closer with a radial velocity of −16 km/s.[2]

The stellar classification of Tau Hercules is B5 IV,[4] and it serves as a standard spectrum in the modern Morgan–Keenan (MK) classification.[9] It is estimated to be just 26 million years old with a relatively low projected rotational velocity of 32 km/s.[5] Slowly rotating B-type stars are often chemically peculiar, so the mostly normal spectra of this star suggests we may be viewing it from near pole-on.[10] The abundance of most heavier elements in this star are about 85% of those in the Sun.[11] The star has four times the mass of the Sun[5] and around 3.8[7] times the Sun's radius. On average, it is radiating 574[2] times the luminosity of the Sun from its photosphere at an effective temperature of 15,615 K.[6]

During the Hipparcos mission,[12] Tau Hercules was discovered to be a variable star of the slowly pulsating B-type. These are mid-B main sequence stars that vary with a period of about a day;[12] the brightness of Tau Hercules varies by 0.03 magnitude[3] over a period of 1.24970±0.00008 days. The radial velocity of the star varies at a different rate than the photometric period, with the object showing both radial and non-radial pulsation modes.[12][13]

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الأهمية التاريخية وأصل الاسم

Small white disks representing the northern stars on a black background, overlaid by a circle showing the position of the north pole over time
The path of the north celestial pole among the stars due to the precession.

Tau Herculis is located within 1° of the precessional path traced across the celestial sphere by the Earth's North pole. It could have served the northern pole star around the year 7400 BCE, a phenomenon which is expected to reoccur in the year 18,400 due to precession.[10]

Preceded by Pole Star Succeeded by
Iota Herculis 18,400 AD Alpha Draconis

Its traditional name, Rukbalgethi Shemali, is of Arabic origin and shares certain etymological characteristics with the stars Ruchbah and Zubeneschamali, signifying Hercules' "northern knee".[14][مطلوب مصدر أفضل]

In Chinese, 七公 (Qī Gōng), meaning Seven Excellencies, refers to an asterism consisting of τ Herculis, 42 Herculis, φ Herculis, χ Herculis, ν1 Boötis, μ1 Boötis and δ Boötis.[15] Consequently, the Chinese name for τ Herculis itself is 七公二 (Qī Gōng èr, إنگليزية: the Second Star of Seven Excellencies.)[16]


انظر أيضا


الهامش

  1. ^ أ ب ت ث ج ح van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  2. ^ أ ب ت ث ج ح خ د ذ Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  3. ^ أ ب ت Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports 61 (1): 80, doi:10.1134/S1063772917010085, Bibcode: 2017ARep...61...80S. 
  4. ^ أ ب Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics 11: 29, doi:10.1146/annurev.aa.11.090173.000333, Bibcode: 1973ARA&A..11...29M. 
  5. ^ أ ب ت ث David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal 804 (2): 146, doi:10.1088/0004-637X/804/2/146, Bibcode: 2015ApJ...804..146D. 
  6. ^ أ ب ت ث Fitzpatrick, E. L.; Massa, D. (March 2005), "Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry", The Astronomical Journal 129 (3): 1642–1662, doi:10.1086/427855, Bibcode: 2005AJ....129.1642F. 
  7. ^ أ ب Gordon, Kathryn D.; Gies, Douglas R.; Schaefer, Gail H.; Huber, Daniel; Ireland, Michael (2019), "Angular Sizes, Radii, and Effective Temperatures of B-type Stars from Optical Interferometry with the CHARA Array", The Astrophysical Journal 873 (1): 91, doi:10.3847/1538-4357/ab04b2, Bibcode: 2019ApJ...873...91G. 
  8. ^ قالب:Cite simbad
  9. ^ Garcia, B. (June 1989), "A list of MK standard stars", Bulletin d'Information du Centre de Donnees Stellaires 36: 27, Bibcode: 1989BICDS..36...27G. 
  10. ^ أ ب Kaler, James B., TAU HER (Tau Herculis), University of Illinois, http://stars.astro.illinois.edu/sow/tauher.html, retrieved on 2018-04-27. 
  11. ^ Adelman, Saul J.; Caliskan, H.; Kocer, D.; Kablan, H.; Yüce, K.; Engin, S. (June 2001), "Elemental abundance analyses with DAO spectrograms. XXV. The superficially normal B and A stars alpha Draconis, tau Herculis, gamma Lyrae, and HR 7926", Astronomy and Astrophysics 371 (3): 1078–1083, doi:10.1051/0004-6361:20010408, Bibcode: 2001A&A...371.1078A 
  12. ^ أ ب ت Masuda, Seiji; Hirata, Ryuko (April 2000), "Line-profile variation in tau Herculis", Astronomy and Astrophysics 356: 209–212, Bibcode: 2000A&A...356..209M. 
  13. ^ Briquet, M.; Aerts, C.; Mathias, P.; Scuflaire, R.; Noels, A. (April 2003), "Spectroscopic mode identification for the slowly pulsating B star HD 147394", Astronomy and Astrophysics 401: 281–288, doi:10.1051/0004-6361:20030086, Bibcode: 2003A&A...401..281B. 
  14. ^ Kurt Vonnegut. "Constellations: Hercules 'the Strongman'". The BBC (British Broadcasting Corporation). Retrieved 2010-11-14.
  15. ^ (in صينية) 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.
  16. ^ (in صينية) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 26 日
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الإحداثيات: خريطة السماء 16س 19ق 44.437ث, +46° 18′ 48.12″

الكلمات الدالة:
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