Merak (star)
Star Merak (β Ursae Maioris) |
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β UMa in the constellation "Great Bear" | |||||||||||||||||||||||
AladinLite | |||||||||||||||||||||||
Observation dates equinox : J2000.0 , epoch : J2000.0 |
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Constellation | Big Bear | ||||||||||||||||||||||
Right ascension | 11 h 1 m 50.48 s | ||||||||||||||||||||||
declination | + 56 ° 22 ′ 56.7 ″ | ||||||||||||||||||||||
Apparent brightness | 2.35 likes | ||||||||||||||||||||||
Typing | |||||||||||||||||||||||
B − V color index | −0.02 | ||||||||||||||||||||||
U − B color index | 0.00 | ||||||||||||||||||||||
R − I index | −0.04 | ||||||||||||||||||||||
Spectral class | A1 IV | ||||||||||||||||||||||
Astrometry | |||||||||||||||||||||||
Radial velocity | (−13.1 ± 0.1) km / s | ||||||||||||||||||||||
parallax | (40.90 ± 0.16) mas | ||||||||||||||||||||||
distance | (79.7 ± 0.3) ly (24.4 ± 0.1) pc |
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Visual absolute brightness M vis | 0.49 mag | ||||||||||||||||||||||
Proper movement | |||||||||||||||||||||||
Rec. Share: | (81.43 ± 0.10) mas / a | ||||||||||||||||||||||
Dec. portion: | (33.49 ± 0.09) mas / a | ||||||||||||||||||||||
Physical Properties | |||||||||||||||||||||||
Dimensions | 2.6 M ☉ | ||||||||||||||||||||||
radius | 3.1 R ☉ | ||||||||||||||||||||||
Luminosity |
73 L ☉ |
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Effective temperature | 9500 K | ||||||||||||||||||||||
Metallicity [Fe / H] | −0.03 | ||||||||||||||||||||||
Other names and catalog entries |
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Merak (from Arabic مراقّ البطن, DMG marāqq al-baṭn 'soft parts of the abdomen' a ) is the proper name of the star Beta Ursae Maioris (β UMa) in the constellation Great Bear . Together with Dubhe (α UMa) it forms the rear end of the body of the Big Dipper , the extension of which points beyond Dubhe to the North Star . Merak has an apparent magnitude of 2.3 mag and is about 80 light years away.
properties
Merak is a white subgiant about 2.6 times the mass, 3 times the diameter and over 70 times the luminosity of the sun . Its surface temperature is around 9500 K. The star is slightly variable, it shows fluctuations in brightness of 0.05 mag and a projected equatorial rotation speed v ∙ sin i of around 30 km / s was measured for it.
With four other of the seven bright chariot stars, Merak belongs to the so-called group of bears , a moving cluster of over a hundred stars spread across half the sky. Our sun is in the range of this group, but moves in a different direction. Seen from Earth, there are two Messier objects - M 97, the Owl Nebula and M 108 , a spiral galaxy - in the immediate vicinity of the star. Both are too faint at about 10 mag to be seen with the naked eye.
designation
According to the “IAU Catalog of Star Names” of the Working Group on Star Names (WGSN) of the IAU for the standardization of star names, the name “Merak” was officially assigned to the star β Ursae Majoris in 2016.
Trivia
Merak is the namesake of the Maserati Merak sports car .
See also
Web links
Individual evidence
- ^ A b c d VizieR: Hipparcos, the New Reduction (van Leeuwen, 2007) - The Astrometric Catalog
- ↑ a b c VizieR: Stellar Photometry in Johnson's 11-color system (Ducati, 2002)
- ↑ a b VizieR: Extended Hipparcos Compilation (XHIP) (Anderson +, 2012)
- ↑ VizieR: Pulkovo radial velocities for 35493 HIP stars (Gontcharov, 2006)
- ↑ VizieR: Stars within 25 pc of the Sun (Woolley + 1970)
- ↑ a b c VizieR: Rotational velocities of A-type stars. IV. (Zorec +, 2012)
- ^ VizieR: Fundamental parameters of stars (Allende Prieto +, 1999)
- ^ VizieR: Linear polarization of nearby bright stars (Bailey +, 2010)
- ↑ Bulletin of the IAU Working Group on Star Names, No. 2. IAU Division C Education, Outreach and Heritage, 2016 ( PDF; 158 kB ).
- ↑ تعريف و معنى مراقّ في معجم المعاني الجامع - معجم عربي عربي (see entry 3.). Almaany.com, accessed January 18, 2017 (Arabic).
- ↑ J. Richardson, Ch. Wilkins, F. Johnson: A Dictionary, Persian, Arabic, and English; with a Dissertation on the Languages, Literature, and Manners of Eastern Nations. London 1829, p. 1384.