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Zeta (ζ) Ursae Majoris

Mizar
Multiple Star System

Right Ascension 13h 23m 52s Best Seen 3/1 - 9/15
Declination 54° 55' 25" Combined Magnitude 2.23
Apparent Separation 14.4" Constellation Ursa Major

Actual
Compared
to Sun
Distance 78 ly --
Separation ~ 47 billion miles ~ 500 au
Orbital Period ~ 5,000 years --
Actual Brightness -- 57 / 13
Magnitude 2.25 / 3.87 --
Mass -- --
Surface Gravity -- --
Surface Composition (by mass) 74% hydrogen
24% helium
2% everything else
same
Spectral Type A2 V / A1m G2 V
Density (gram/cubic cm) -- --

What To Look For Through The Telescope


  1. Recommended eyepiece: 24mm or 40 mm.

  2. When people look through the telescope they should see two stars next to each other. One star should be slightly brighter than the other.

  3. The two stars they see are both called Mizar. Alcor can be seen in the finder some distance from Mizar.


Mizar Information:

  1. Mizar is the middle star in the handle of the Big Dipper.

  2. Mizar was the first multiple star discovered. In the early 1600s, a friend of Galileo’s discovered that it was really two stars.

  3. Each one of the two visible stars in Mizar is actually a multiple star itself!

    a. The two stars are spectroscopic multiples, meaning that their companions can’t be seen, only detected through spectroscopic analysis.

    b. The brighter star is really two stars so close to each other, they only take about 20 days to orbit each other.

    c. The fainter star is really – at least – two stars.

  4. Another star is near Mizar called Alcor. Alcor can even be seen with the unaided eye on a clear, dark night.

    a. Alcor is three light years from Mizar, so Mizar and Alcor are not part of the same system. However, Alcor is part of the Ursa Majoris group.

    b. Alcor has a total brightness 12 times that of the sun, is magnitude 3.99, and is spectral type A5V.

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References
Item Updated Notes
Coordinates 2002-08-30 just tweaked a bit
Combined Magnitude 2002-08-30 OK w/ Scott’s The Flamsteed Collection
Apparent Separation 2002-08-30 http://www.astronomical.org/constellations/uma.html
Distance 2002-08-30 OK w/ SIMBAD and Flamsteed
Separation 2002-08-30 http://www.astro.uiuc.edu/~kaler/sow/mizar.html
Orbital Period 2002-08-30 http://www.astro.uiuc.edu/~kaler/sow/mizar.html
Actual Brightness 2002-08-30 OK w/ Scott’s Flamsteed
Magnitude 2002-08-30 OK w/ Flamsteed
Mass --
Surface Gravity --
Surface Composition 2003-01-06 OK for all stars
Spectral Type 2002-08-30 OK with SIMBAD
Density --
Other 2002-08-30 Item 2: http://leo.astronomy.cz/mizar/article.htm
Item 3b,c: http://www.astro.uiuc.edu/~kaler/sow/mizar.html