The traditional name Hamal (also written Hemal, Hamul, Ras Hammel) derives from the Arabicرأس الحملrās al-ħamal "head of the ram", in turn from the name for the constellation as a whole, Al Ħamal "the ram".[15] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[16] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[17] included a table of the first two batches of names approved by the WGSN; which included Hamal for this star.[18]
The spectrum of this star matches a stellar classification of K2 III Ca-1, with the luminosity class of III indicating that it is an evolvedgiant star that has exhausted the supply of hydrogen at its core and is now on the red-giant branch.[21] The 'Ca-1' portion of the classification indicates that it shows weaker than normal lines of calcium in its spectrum. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[22] It is estimated to have about 50%[8] more mass than the Sun, while interferometric measurements show it to be 15[9] times larger in diameter. Despite its enlarged girth, this star is still spinning with a slightly faster equatorial azimuthal velocity than the Sun, having a projected rotational velocity of 3.44 km s−1.[8]
Hamal is radiating about 91[9] times the Sun's luminosity from its outer envelope at an effective temperature of 4,480 K.[9] This is cooler than the surface of the Sun, giving it the orange-hued glow of a K-type star. It is suspected to be slightly variable, with an amplitude of 0.06 magnitude.[5] The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is only around half that in the Sun.[9]
In 2011, the likely presence of a planet in orbit around this star was reported by Byeong-Cheol Lee, et al. It was detected using the radial velocity method, based upon measurements made between 2003 and 2010 at the Bohyunsan Optical Astronomy Observatory in Korea. The object has an orbital period of 381 days and an eccentricity of 0.25. The lower bound on this object's mass is about 1.8 times the mass of Jupiter. The estimated semi-major axis of the planet's orbit is 1.2 astronomical units (AU),[8] which would give it a periapsis distance of 0.9 AU and an apoapsis distance of 1.5 AU. By comparison, the star has a radius of 0.07 AU.[23]
Hamal's orientation with relation to the Earth's orbit around the Sun gives it a certain importance not apparent from its modest brightness. Between 2000 and 100 BCE, the apparent path of the Sun through the Earth's sky placed it in Aries at the northern vernal equinox, the point in time marking the start of spring in the Northern Hemisphere.[25] This is why most astrology columns in modern newspapers begin with Aries.[26] While the vernal equinox has moved to Pisces since then due to precession of the equinoxes,[25] Hamal has remained in mind as a bright star near what was apparently an important place when people first studied the night sky.[12] Currently (epoch J2000) its declination is almost exactly equal to the latitude of the Tropic of Cancer, meaning it can be used to find the position of that imaginary line when the Sun is not nearby.
^ abcdefvan 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, S2CID 18759600
^ abcdJohnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
^ abcHR 617, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line December 16, 2008.
^ abNSV 725, database entry, New Catalogue of Suspected Variable Stars, the improved version, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line December 16, 2008.
^Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, vol. 30, p. 57, Bibcode:1967IAUS...30...57E
^Carney, Bruce W.; et al. (March 2008), "Rotation and Macroturbulence in Metal-Poor Field Red Giant and Red Horizontal Branch Stars", The Astronomical Journal, 135 (3): 892–906, arXiv:0711.4984, Bibcode:2008AJ....135..892C, doi:10.1088/0004-6256/135/3/892, S2CID 2756572
^ abcdefLee, B.-C.; et al. (May 2011), "A likely exoplanet orbiting the oscillating K-giant α Arietis", Astronomy & Astrophysics, 529: A134, arXiv:1104.4431, Bibcode:2011A&A...529A.134L, doi:10.1051/0004-6361/201016293, S2CID 58906630
^ abcdefghiPiau, L.; et al. (February 2011), "Surface convection and red-giant radius measurements", Astronomy and Astrophysics, 526: A100, arXiv:1010.3649, Bibcode:2011A&A...526A.100P, doi:10.1051/0004-6361/201014442, S2CID 118533297
^Bonfanti, A.; et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics. 575. A18. arXiv:1411.4302. Bibcode:2015A&A...575A..18B. doi:10.1051/0004-6361/201424951. S2CID 54555839.
^Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN978-1-931559-44-7.
^ abHamal 2008-12-08 at the Wayback Machine, Stars, Jim Kaler. Accessed on line December 16, 2008.
^Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; et al. (July 1997), "The Hipparcos Catalogue", Astronomy and Astrophysics, 323: L49–L52, Bibcode:1997A&A...323L..49P
^Perryman, Michael (2010), "The Making of History's Greatest Star Map", Astronomers' Universe, Heidelberg: Springer-Verlag, Bibcode:2010mhgs.book.....P, doi:10.1007/978-3-642-11602-5, ISBN978-3-642-11601-8
^Allen, Richard Hinckley (1899), Star-names and Their Meanings, New York: G. E. Stechert, pp. 78, 80
^"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.
^"IAU Catalog of Star Names". Retrieved 28 July 2016.
^(in 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, ISBN978-986-7332-25-7.
^(in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 2011-01-29 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
^Stoesz, Jeffrey A.; Herwig, Falk (April 2003), "Oxygen isotopic ratios in first dredge-up red giant stars and nuclear reaction rate uncertainties revisited", Monthly Notices of the Royal Astronomical Society, 340 (3): 763–770, arXiv:astro-ph/0212128, Bibcode:2003MNRAS.340..763S, doi:10.1046/j.1365-8711.2003.06332.x, S2CID 14107804
^Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society, 25: 1319, Bibcode:1993AAS...183.1710G, retrieved 2012-02-04
^For a = 1.2 AU and e = 0.25, the periapsis is given by a × (1 - e) = 9 AU and the apoapsis is a × (1 + e) = 15 AU. The solar radius is 0.0046491 AU, so the star's radius is 14.9 × 0.0046491 = 0.069 AU.
^ abKaler, James B. (2002), The Ever-changing Sky: A Guide to the Celestial Sphere, Cambridge, UK: Cambridge University Press, pp. 151, 152, ISBN0-521-49918-6
^Raymo, Chet (1982), 365 Starry Nights: An Introduction to Astronomy for Every Night of the Year, New York: Simon and Schuster, p. 196, ISBN0-671-76606-6
GJ 84.3, entry in the Gliese–Jahreiß catalogue (Preliminary Version of the Third Catalogue of Nearby Stars, W. Gliese and H. Jahreiss, 1991, CDS ID V/70A.)
hamal, this, article, about, star, other, uses, disambiguation, designation, alpha, arietis, arietis, abbreviated, alpha, brightest, star, northern, zodiacal, constellation, aries, location, arietis, circled, observation, dataepoch, j2000, equinox, j2000, icrs. This article is about the star For other uses see Hamal disambiguation Hamal ˈ h ae m el 11 designation Alpha Arietis a Arietis abbreviated Alpha Ari a Ari is the brightest star in the northern zodiacal constellation of Aries 4 12 HamalLocation of a Arietis circled Observation dataEpoch J2000 0 Equinox J2000 0 ICRS Constellation AriesRight ascension 02h 07m 10 40570s 1 Declination 23 27 44 7032 1 Apparent magnitude V 2 00 2 CharacteristicsSpectral type K1IIIbU B color index 1 13 2 B V color index 1 15 2 V R color index 0 7 3 R I color index 0 62 4 Variable type Suspected 5 AstrometryRadial velocity Rv 14 2 0 9 6 km sProper motion m RA 188 55 1 mas yr Dec 148 08 1 mas yrParallax p 49 56 0 25 mas 1 Distance65 8 0 3 ly 20 2 0 1 pc Absolute magnitude MV 0 47 0 04 7 DetailsMass1 5 0 2 8 M Radius14 9 0 3 9 R Luminosity bolometric 91 6 9 L Surface gravity log g 2 57 9 cgsTemperature4 480 9 KMetallicity Fe H 0 25 9 dexRotational velocity v sin i 3 44 8 km sAge3 4 1 9 10 GyrOther designationsHemal Hamal Ras Hammel El Nath Arietis a Ari Alpha Arietis Alpha Ari 13 Arietis 13 Ari BD 22 306 FK5 74 GC 2538 GJ 84 3 GJ 9072 HD 12929 HIP 9884 HR 617 LTT 10711 NLTT 7032 PPM 91373 SAO 75151 3 4 Database referencesSIMBADdataWith an apparent visual magnitude of 2 0 2 it is the mean 50th brightest star in the night sky Based upon parallax measurements made with the Hipparcos astrometry satellite 13 14 Hamal is about 65 8 light years 20 2 parsecs from Earth 1 It is a giant star that may host an orbiting planet with a mass greater than Jupiter 8 Contents 1 Nomenclature 2 Properties 3 In culture 4 References 5 External linksNomenclature Edit Hamal is the brightest star in the constellation of Aries Alpha Arietis is the star s Bayer designation It also bears the Flamsteed designation of 13 Arietis The traditional name Hamal also written Hemal Hamul Ras Hammel derives from the Arabic رأس الحمل ras al ħamal head of the ram in turn from the name for the constellation as a whole Al Ħamal the ram 15 In 2016 the International Astronomical Union organized a Working Group on Star Names WGSN 16 to catalog and standardize proper names for stars The WGSN s first bulletin of July 2016 17 included a table of the first two batches of names approved by the WGSN which included Hamal for this star 18 In Chinese 婁宿 Lou Su meaning Bond asterism refers to an asterism consisting of Hamal b Arietis and g Arietis 19 Consequently the Chinese name for Hamal itself is 婁宿三 Lou Su san English the Third Star of Bond 20 Properties EditThe spectrum of this star matches a stellar classification of K2 III Ca 1 with the luminosity class of III indicating that it is an evolved giant star that has exhausted the supply of hydrogen at its core and is now on the red giant branch 21 The Ca 1 portion of the classification indicates that it shows weaker than normal lines of calcium in its spectrum Since 1943 the spectrum of this star has served as one of the stable anchor points by which other stars are classified 22 It is estimated to have about 50 8 more mass than the Sun while interferometric measurements show it to be 15 9 times larger in diameter Despite its enlarged girth this star is still spinning with a slightly faster equatorial azimuthal velocity than the Sun having a projected rotational velocity of 3 44 km s 1 8 Hamal is radiating about 91 9 times the Sun s luminosity from its outer envelope at an effective temperature of 4 480 K 9 This is cooler than the surface of the Sun giving it the orange hued glow of a K type star It is suspected to be slightly variable with an amplitude of 0 06 magnitude 5 The abundance of elements other than hydrogen and helium what astronomers term the star s metallicity is only around half that in the Sun 9 In 2011 the likely presence of a planet in orbit around this star was reported by Byeong Cheol Lee et al It was detected using the radial velocity method based upon measurements made between 2003 and 2010 at the Bohyunsan Optical Astronomy Observatory in Korea The object has an orbital period of 381 days and an eccentricity of 0 25 The lower bound on this object s mass is about 1 8 times the mass of Jupiter The estimated semi major axis of the planet s orbit is 1 2 astronomical units AU 8 which would give it a periapsis distance of 0 9 AU and an apoapsis distance of 1 5 AU By comparison the star has a radius of 0 07 AU 23 The Hamal planetary system 24 Companion in order from star Mass Semimajor axis AU Orbital period days Eccentricity Inclination Radiusb 1 8 0 2 MJ 1 2 380 8 0 3 0 25 0 03 In culture EditHamal s orientation with relation to the Earth s orbit around the Sun gives it a certain importance not apparent from its modest brightness Between 2000 and 100 BCE the apparent path of the Sun through the Earth s sky placed it in Aries at the northern vernal equinox the point in time marking the start of spring in the Northern Hemisphere 25 This is why most astrology columns in modern newspapers begin with Aries 26 While the vernal equinox has moved to Pisces since then due to precession of the equinoxes 25 Hamal has remained in mind as a bright star near what was apparently an important place when people first studied the night sky 12 Currently epoch J2000 its declination is almost exactly equal to the latitude of the Tropic of Cancer meaning it can be used to find the position of that imaginary line when the Sun is not nearby The other name of Hamal Hamul is used for the name of a U S Navy ship USS Hamul AD 20 References Edit a b c d e f van Leeuwen F November 2007 Validation of the new Hipparcos reduction Astronomy and Astrophysics 474 2 653 664 arXiv 0708 1752 Bibcode 2007A amp A 474 653V doi 10 1051 0004 6361 20078357 S2CID 18759600 a b c d Johnson H L et al 1966 UBVRIJKL photometry of the bright stars Communications of the Lunar and Planetary Laboratory 4 99 99 Bibcode 1966CoLPL 4 99J a b alf Ari SIMBAD Centre de donnees astronomiques de Strasbourg Retrieved December 16 2008 a b c HR 617 database entry The Bright Star Catalogue 5th Revised Ed Preliminary Version D Hoffleit and W H Warren Jr CDS ID V 50 Accessed on line December 16 2008 a b NSV 725 database entry New Catalogue of Suspected Variable Stars the improved version Sternberg Astronomical Institute Moscow Russia Accessed on line December 16 2008 Evans D S June 20 24 1966 Batten Alan Henry Heard John Frederick eds The Revision of the General Catalogue of Radial Velocities Determination of Radial Velocities and their Applications Proceedings from IAU Symposium no 30 University of Toronto International Astronomical Union vol 30 p 57 Bibcode 1967IAUS 30 57E Carney Bruce W et al March 2008 Rotation and Macroturbulence in Metal Poor Field Red Giant and Red Horizontal Branch Stars The Astronomical Journal 135 3 892 906 arXiv 0711 4984 Bibcode 2008AJ 135 892C doi 10 1088 0004 6256 135 3 892 S2CID 2756572 a b c d e f Lee B C et al May 2011 A likely exoplanet orbiting the oscillating K giant a Arietis Astronomy amp Astrophysics 529 A134 arXiv 1104 4431 Bibcode 2011A amp A 529A 134L doi 10 1051 0004 6361 201016293 S2CID 58906630 a b c d e f g h i Piau L et al February 2011 Surface convection and red giant radius measurements Astronomy and Astrophysics 526 A100 arXiv 1010 3649 Bibcode 2011A amp A 526A 100P doi 10 1051 0004 6361 201014442 S2CID 118533297 Bonfanti A et al 2015 Revising the ages of planet hosting stars Astronomy and Astrophysics 575 A18 arXiv 1411 4302 Bibcode 2015A amp A 575A 18B doi 10 1051 0004 6361 201424951 S2CID 54555839 Kunitzsch Paul Smart Tim 2006 A Dictionary of Modern star Names A Short Guide to 254 Star Names and Their Derivations 2nd rev ed Cambridge Massachusetts Sky Pub ISBN 978 1 931559 44 7 a b Hamal Archived 2008 12 08 at the Wayback Machine Stars Jim Kaler Accessed on line December 16 2008 Perryman M A C Lindegren L Kovalevsky J et al July 1997 The Hipparcos Catalogue Astronomy and Astrophysics 323 L49 L52 Bibcode 1997A amp A 323L 49P Perryman Michael 2010 The Making of History s Greatest Star Map Astronomers Universe Heidelberg Springer Verlag Bibcode 2010mhgs book P doi 10 1007 978 3 642 11602 5 ISBN 978 3 642 11601 8 Allen Richard Hinckley 1899 Star names and Their Meanings New York G E Stechert pp 78 80 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 IAU Catalog of Star Names Retrieved 28 July 2016 in 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 in Chinese 香港太空館 研究資源 亮星中英對照表 Archived 2011 01 29 at the Wayback Machine Hong Kong Space Museum Accessed on line November 23 2010 Stoesz Jeffrey A Herwig Falk April 2003 Oxygen isotopic ratios in first dredge up red giant stars and nuclear reaction rate uncertainties revisited Monthly Notices of the Royal Astronomical Society 340 3 763 770 arXiv astro ph 0212128 Bibcode 2003MNRAS 340 763S doi 10 1046 j 1365 8711 2003 06332 x S2CID 14107804 Garrison R F December 1993 Anchor Points for the MK System of Spectral Classification Bulletin of the American Astronomical Society 25 1319 Bibcode 1993AAS 183 1710G retrieved 2012 02 04 For a 1 2 AU and e 0 25 the periapsis is given by a 1 e 9 AU and the apoapsis is a 1 e 15 AU The solar radius is 0 0046491 AU so the star s radius is 14 9 0 0046491 0 069 AU Schneider Jean 2011 Notes for Planet alf Ari b Extrasolar Planets Encyclopaedia retrieved 2011 10 12 a b Kaler James B 2002 The Ever changing Sky A Guide to the Celestial Sphere Cambridge UK Cambridge University Press pp 151 152 ISBN 0 521 49918 6 Raymo Chet 1982 365 Starry Nights An Introduction to Astronomy for Every Night of the Year New York Simon and Schuster p 196 ISBN 0 671 76606 6External links EditJean Schneider 2011 Notes for star alf Ari Extrasolar Planets Encyclopaedia Retrieved 12 October 2011 GJ 84 3 entry in the Gliese Jahreiss catalogue Preliminary Version of the Third Catalogue of Nearby Stars W Gliese and H Jahreiss 1991 CDS ID V 70A Image of Hamal from Aladin The Constellations and Named Stars Purple Hell Retrieved from https en wikipedia org w index php title Hamal amp oldid 1125807394, wikipedia, wiki, book, books, library,
