Mizar
Zeta Ursae Majoris
Distance (Light Years)
78.2 ± 1.1
Visual Magnitude
2.23
Color (B-V)
0.02
Names For This StarThis star is also known as Mizat or Mirza. The names derive from the Arabic Mi'zar meaning a girdle or waist-cloth. The name seems to have been applied to the star as the result of an error.
Description of the StarMizar is a hot, white A1VpSrSi main sequence star having a luminosity about 63 times that of the sun. The spectral type implies anomalously strong lines associated with strontium and silicon. This type of star is associated with an especially strong magnetic field.
The spectrum is peculiar for an A1V star, but the A1V spectral type implies an effective temperature of 9600 K, a diameter of more than twice that of the sun, and a mass about three times that of the sun.
The Mizar Star SystemMizar is a multiple star system. The primary Mizar A has a fainter companion Mizar B, at Visual Magnitude 3.95. Mizar B is also a type A main sequence star separated from A by 14 arc seconds, which corresponds to a projected separation of 340 AU or more than 8 times the diameter of the orbit of planet Pluto.
Spectral analysis reveals Mizar A itself to be a binary star consisting of two main sequence A2V stars orbiting around each other with a period of 20.5 days in a rather elliptical orbit having a semimajor axis of about 27 million miles.
Spectral analysis shows Mizar B itself to be a binary star, so that there are at least four stars in the Mizar system.
The Ursa Major ClusterThe fourth magnitude star Alcor can be seen at 12 arc minutes separation from Mizar, corresponding to a projected distance of more than 0.25 ly. However, since Alcor is about 3 ly farther from the earth than the Mizar system, it is unlikely that Alcor is a part of the Mizar system.
The Ursa Major ClusterAccording to Burnham, Mizar is part of a star cluster including at least 16 other stars from the Ursa Major area of the sky, as well as Alioth, Merak, Alcor, Phecda, and Megrez in the Big Dipper. The Ursa Major cluster represents an ellipsoidal volume of space about 30 ly long by 18 ly in width.
Zeta Ursae Majoris
Distance (Light Years)
78.2 ± 1.1
Visual Magnitude
2.23
Color (B-V)
0.02
Names For This StarThis star is also known as Mizat or Mirza. The names derive from the Arabic Mi'zar meaning a girdle or waist-cloth. The name seems to have been applied to the star as the result of an error.
Description of the StarMizar is a hot, white A1VpSrSi main sequence star having a luminosity about 63 times that of the sun. The spectral type implies anomalously strong lines associated with strontium and silicon. This type of star is associated with an especially strong magnetic field.
The spectrum is peculiar for an A1V star, but the A1V spectral type implies an effective temperature of 9600 K, a diameter of more than twice that of the sun, and a mass about three times that of the sun.
The Mizar Star SystemMizar is a multiple star system. The primary Mizar A has a fainter companion Mizar B, at Visual Magnitude 3.95. Mizar B is also a type A main sequence star separated from A by 14 arc seconds, which corresponds to a projected separation of 340 AU or more than 8 times the diameter of the orbit of planet Pluto.
Spectral analysis reveals Mizar A itself to be a binary star consisting of two main sequence A2V stars orbiting around each other with a period of 20.5 days in a rather elliptical orbit having a semimajor axis of about 27 million miles.
Spectral analysis shows Mizar B itself to be a binary star, so that there are at least four stars in the Mizar system.
The Ursa Major ClusterThe fourth magnitude star Alcor can be seen at 12 arc minutes separation from Mizar, corresponding to a projected distance of more than 0.25 ly. However, since Alcor is about 3 ly farther from the earth than the Mizar system, it is unlikely that Alcor is a part of the Mizar system.
The Ursa Major ClusterAccording to Burnham, Mizar is part of a star cluster including at least 16 other stars from the Ursa Major area of the sky, as well as Alioth, Merak, Alcor, Phecda, and Megrez in the Big Dipper. The Ursa Major cluster represents an ellipsoidal volume of space about 30 ly long by 18 ly in width.
Phecda
Gamma Ursae Majoris
Distance (Light Years)
83.7 ± 1.5
Visual Magnitude
2.41
Color (B-V)
0
Names For This StarOther names for this star are Phad, Phekda, Phegda, Phekha, or Phacd. These names derive from the Arabic term Al Falidh meaning "The Thigh (of the Bear)".
Description of the StarPhecda is a hot, white A0Ve main sequence star about 60 times as luminous as the sun. The spectral type implies a temperature of 9900 K, a mass of about 3 solar masses, and a diameter about 2.5 times that of the sun.
The Ursa Major ClusterAccording to Burnham, Phecda is part of a star cluster including at least 16 other stars from the Ursa Major area of the sky, as well as Alioth, Merak, Alcor, Mizar, and Megrez in the Big Dipper. The Ursa Major cluster represents an ellipsoidal volume of space about 30 ly long by 18 ly in width.
Gamma Ursae Majoris
Distance (Light Years)
83.7 ± 1.5
Visual Magnitude
2.41
Color (B-V)
0
Names For This StarOther names for this star are Phad, Phekda, Phegda, Phekha, or Phacd. These names derive from the Arabic term Al Falidh meaning "The Thigh (of the Bear)".
Description of the StarPhecda is a hot, white A0Ve main sequence star about 60 times as luminous as the sun. The spectral type implies a temperature of 9900 K, a mass of about 3 solar masses, and a diameter about 2.5 times that of the sun.
The Ursa Major ClusterAccording to Burnham, Phecda is part of a star cluster including at least 16 other stars from the Ursa Major area of the sky, as well as Alioth, Merak, Alcor, Mizar, and Megrez in the Big Dipper. The Ursa Major cluster represents an ellipsoidal volume of space about 30 ly long by 18 ly in width.
Aucun commentaire:
Enregistrer un commentaire