Zeta Ursae Majoris

Zeta Ursae Majoris (ζ UMa) is a star of the Constellation of the Grande Ourse and is the second star starting from the end of the Chariot. Its traditional name Mizar comes from the Arab ميزر mi' zar , meaning " ceinture". Mizar has a Magnitude connect of 2,27 and is of standard A1 V.

With a good sight, one can see a weak companion right in the east, called Alcor or 80 Ursae Majoris . Alcor has a magnitude of 3,99 and one spectral type A5 V. both are often called the horse and the rider, and the capacity to see the second is a traditional test of vision. Two stars are distant of more than one quarter of Light-year and although their own movements is shown that they move together, it still does not know if they form a true binary system , and not a binary optics as one currently thinks it.

Other components were discovered with the appearance of the telescope and the spectroscopy; being a beautiful easily separable visual target, Mizar was first binary the telescopic discovered one - most probably by Benedetto Castelli which required of Galileo Galilei in 1617 to observe it. Galileo then produced a report/ratio detailed on double star. Later, about 1650, Riccioli wrote that Mizar appeared double. The secondary star, Mizar B , has a magnitude of 4,0 and one spectral type A7, and is located at 380 WITH the primary elections; they put thousands of years to turn one around the other. Mizar has was then first the binary spectroscopic one discovered, by Pickering in 1889. The two components are both approximately 35 times more brilliant than the Sun, and turn one around the other in approximately 20 days. It was discovered later that Mizar B was also binary spectroscopic. In 1996 the components of the Mizar binary system has were visualized in very high-resolution by the Navy Prototype Optical Interferometer. The whole of the system of five stars is located at approximately 78 light-years of the Earth. The components all are members of the Courant of stars of Large Ourse, a group of strongly dispersed stars sharing a common origin, as their own movement shows it. The other stars of the Carriage, except Dubhe and Alkaid, also belong to this group.

External bonds

Mizar and Alcor articles in Jim Kaler' S Stars website
First very high resolution imaging off Mizar has (by Synthèse of opening)

Reference

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