VY Canis Majoris

VY Canis Majoris ( VY CMa ) este o stea hipergigant? ro?ie situat? la 1,2 kpc ^[1] de Terra in constela?ia Cainele Mare . Ea era cea mai mare stea cunoscut? ^[2] (1.420 de raze solare ) inainte de descoperirea stelei UY Scuti (1.708 de raze solare). Se afl? la aproximativ 3.900 de ani-lumin? fa?? de P?mant. Diametrul stelei este de circa 1.420 ^[3] de ori mai mare decat cel al Soarelui . De?i nu e cea mai str?lucitoare stea pe care o cunoa?tem, este clasat? intre primele 50. Fiind o stea a?a de mare, pierde foarte repede hidrogenul ?i poate rezista doar cateva milioane de ani.

Istorie [ modificare | modificare surs? ]

Mai intai, steaua a fost catalogat? de o magnitudine de 7, la 7 martie 1801 , sub numele de ?VY CMa” de astronomul francez Joseph Jerome Lefrancois de Lalande . ^[4]

Magnitudinea sa aparent? slab? ?i variabil? este estimat? la 7,9607, mai aproape de 8 decat de 7. Varia?ia luminozit??ii stelei a produs de mult timp b?nuiala prezen?ei unor stele inso?itoare. Observa?ii vizuale din 1957 , confirmate de imagini de inalt? rezolu?ie in 1998 , exclud aceast? ipotez?. ^[5]

M?rimea stelei [ modificare | modificare surs? ]

M?sur?ri directe ale m?rimii stelei VY Canis Majoris la lungimi de und? infraro?ii au dat valori de peste 3.000 de ori raza Soarelui (4 miliarde de kilometri), ceea ce dep??e?te limitele teorii stelare. ^[6] In 2006 , intr-un studiu nepublicat, profesoara Roberta M. Humphreys de la Universitatea din Minnesota estimeaz? raza stelei VY Canis Majoris de la circa 1.420 de ori cea a Soarelui. ^[7] Potrivit acesteia, steaua este o hipergigant? ro?ie foarte mare ?i luminoas?, cu estim?ri dep??ind limitele teoriei stelare. ^[8] VY Canis Majoris era cea mai mare stea cunoscut?, cu un diametru de circa 3 miliarde de kilometri, inainte de a fi fost dep??it? de UY Scuti . VY Canis Majoris, dac? ar inlocui Soarele, steaua VY Canis Majoris ar dep??i orbita planetei Saturn .

Al?i cercet?tori, ca Philip Massey, Emily Levesque, Bertrand Plez ?i Knut A. G. Olsen, cred c? steaua ar fi mai degrab? o supergigant? ro?ie de circa 600 de ori raza solar? , ceea ce ar include-o in modelele de structur? ?i de evolu?ie a stelelor. ^[9]^[10]

Referin?e ?i note [ modificare | modificare surs? ]

^ 1998A%26A...340L..39W&link_type=GIF ?Diffraction-limited speckle-masking interferometry of the red supergiant VY CMa” Verifica?i valoarea |url= ( ajutor ) , Astronomy and Astrophysics (in englez?), 340 , pp. 39?42, 1998
^ Alcolea, J.; Bujarrabal, V.; Planesas, P.; Teyssier, D.; Cernicharo, J.; Beck, E. De; Decin, L.; Dominik, C.; Justtanont, K.; Koter, A. de; Marston, A. P.; Melnick, G.; Menten, K. M.; Neufeld, D. A.; Olofsson, H.; Schmidt, M.; F. L. Schoier; Szczerba, R.; Waters, L. B. F. M. ( 1 noiembrie 2013 ), HIFISTARS Herschel/HIFI observations of VY Canis Majoris - Molecular-line inventory of the envelope around the largest known star (in englez?), 559 , Astronomy & Astrophysics, doi : 10.1051/0004-6361/201321683 , ISSN 1432-0746 0004-6361, 1432-0746 Verifica?i valoarea |issn= ( ajutor )
^ Wittkowski, M.; Hauschildt, P. H.; Arroyo-Torres, B.; Marcaide, J. M. ( 2012 ). ?Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry”. Astronomy & Astrophysics . 540 : L12. arXiv : 1203.5194   . Bibcode : 2012A&A...540L..12W . doi : 10.1051/0004-6361/201219126 .
^ en dsabs.harvard.edu/full/1971IBVS..599....1R Robinson L. J., (1971) Three somewhat overlooked facets of VY Canis Majoris , In: Information Bulletin on Variable Stars , volumul 599, Nr. 1 Arhivat in 13 iulie 2013 , la Wayback Machine .
^ en M. Wittkowsk, N. Langer, G. Weigelt (1998), Diffraction-limited speckle-masking interferometry of the red supergiant VY Cma , In: Astronomy and d'uneAstrophysics , volumul 340, pp. 39?42, Rezumat in: [1] 1998A%26A...340L..39W&li nk_type=GIF
^ en The Asymmetric Nebula Surrounding the Extreme Red Supergiant Vy Canis Majoris , Nathan Smith & alii, The Astronomical Journal, 2001
^ Wittkowski, M.; Hauschildt, P. H.; Arroyo-Torres, B.; Marcaide, J. M. ( 2012 ). ?Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry”. Astronomy & Astrophysics . 540 : L12. arXiv : 1203.5194   . Bibcode : 2012A&A...540L..12W . doi : 10.1051/0004-6361/201219126 .
^ Humphreys, Roberta ( 13 octombrie 2006 ). ?VY Canis Majoris: the astrophysical basis of its luminosity”. arXiV . arXiv : astro-ph/0610433   .
^ en Philip Massey, Emily M. Levesque, Bertrand Plez Bringing VY Canis Majoris Down to Size: An Improved Determination of Its Effective Temperature , In: The Astrophysical Journal, volume 646, pp. 1203?1208 , august 2006
^ en Philip Massey, Emily M. Levesque, Bertrand Plez, Knut A. G. Olsen, The Physical Properties of Red Supergiants: Comparing Theory and Observations , 2008, Rezumat, In: Proceedings of the International Astronomical Union, Symposium S250, volume 3, decembrie 2007, pp.97-110, Cambridge University Press, doi=10.1017/S1743921308020383|url text=http://journals.cambridge.org/download.php?file=%2FIAU%2FIAU3_S250%2FS1743921308020383a.pdf&code=bf824ea48d44cd78d990e75cf703ee45

Leg?turi externe [ modificare | modificare surs? ]

Portal Astronomie
Portal Stea

[Wittkowski-1] 1998A%26A...340L..39W&link_type=GIF ?Diffraction-limited speckle-masking interferometry of the red supergiant VY CMa” Verifica?i valoarea |url= ( ajutor ) , Astronomy and Astrophysics (in englez?), 340 , pp. 39?42, 1998

[2] Alcolea, J.; Bujarrabal, V.; Planesas, P.; Teyssier, D.; Cernicharo, J.; Beck, E. De; Decin, L.; Dominik, C.; Justtanont, K.; Koter, A. de; Marston, A. P.; Melnick, G.; Menten, K. M.; Neufeld, D. A.; Olofsson, H.; Schmidt, M.; F. L. Schoier; Szczerba, R.; Waters, L. B. F. M. ( 1 noiembrie 2013 ), HIFISTARS Herschel/HIFI observations of VY Canis Majoris - Molecular-line inventory of the envelope around the largest known star (in englez?), 559 , Astronomy & Astrophysics, doi : 10.1051/0004-6361/201321683 , ISSN 1432-0746 0004-6361, 1432-0746 Verifica?i valoarea |issn= ( ajutor )

[wittkowski-3] Wittkowski, M.; Hauschildt, P. H.; Arroyo-Torres, B.; Marcaide, J. M. ( 2012 ). ?Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry”. Astronomy & Astrophysics . 540 : L12. arXiv : 1203.5194   . Bibcode : 2012A&A...540L..12W . doi : 10.1051/0004-6361/201219126 .

[4] sabs.harvard.edu/full/1971IBVS..599....1R Robinson L. J., (1971) Three somewhat overlooked facets of VY Canis Majoris , In: Information Bulletin on Variable Stars , volumul 599, Nr. 1 Arhivat in 13 iulie 2013 , la Wayback Machine .

[5] M. Wittkowsk, N. Langer, G. Weigelt (1998), Diffraction-limited speckle-masking interferometry of the red supergiant VY Cma , In: Astronomy and d'uneAstrophysics , volumul 340, pp. 39?42, Rezumat in: [1] 1998A%26A...340L..39W&li nk_type=GIF

[6] The Asymmetric Nebula Surrounding the Extreme Red Supergiant Vy Canis Majoris , Nathan Smith & alii, The Astronomical Journal, 2001

[wittkowski2-7] Wittkowski, M.; Hauschildt, P. H.; Arroyo-Torres, B.; Marcaide, J. M. ( 2012 ). ?Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry”. Astronomy & Astrophysics . 540 : L12. arXiv : 1203.5194   . Bibcode : 2012A&A...540L..12W . doi : 10.1051/0004-6361/201219126 .

[humphreys-8] Humphreys, Roberta ( 13 octombrie 2006 ). ?VY Canis Majoris: the astrophysical basis of its luminosity”. arXiV . arXiv : astro-ph/0610433   .

[Massey-9] Philip Massey, Emily M. Levesque, Bertrand Plez Bringing VY Canis Majoris Down to Size: An Improved Determination of Its Effective Temperature , In: The Astrophysical Journal, volume 646, pp. 1203?1208 , august 2006

[10] Philip Massey, Emily M. Levesque, Bertrand Plez, Knut A. G. Olsen, The Physical Properties of Red Supergiants: Comparing Theory and Observations , 2008, Rezumat, In: Proceedings of the International Astronomical Union, Symposium S250, volume 3, decembrie 2007, pp.97-110, Cambridge University Press, doi=10.1017/S1743921308020383|url text=http://journals.cambridge.org/download.php?file=%2FIAU%2FIAU3_S250%2FS1743921308020383a.pdf&code=bf824ea48d44cd78d990e75cf703ee45

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]