MIZAR (ZETA (ζ) URSAE MAJORIS)
MULTIPLE STAR

Right Ascension:
13h 23m 52s

Best Seen:
3/1 - 9/15

Declination:
54º 55' 25" Combined
Magnitude:
2.23

Computer File:
mizar

Constellation:
Ursa Major

Apparent
Separation: 14.4"

Actual

Compared to Sun

Distance

78 l.y.

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Separation

47 billion miles

500 Earth/Sun

Orbital Period

~ 5000 years

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Actual Brightness

--

57 / 13 (Sun)

Magnitude

2.25 / 3.87

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Mass

Surface Gravity

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Surface Composition (by mass)

74% hydrogen 24% helium 2% everything else

same (Sun)

Spectral Type

A2 V / A1m

G2 V (Sun)

Density (gram/cubic cm)

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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.

  1. 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.

FOR GREG: Here’s the “old” stuff – is Mizar quadruple or quintuple?

  1. This is the middle star in the handle of the big dipper.

2a. The brighter of the visual is itself a double star; although the two stars are too close to each other to be seen seperatley.

2b. Other information for the primary pair: Actual brightness: each 35 times the sun’s brightness; separation: 18 million miles.

  1. The fainter of the visual pair is a triple star system. Periods of 182 days and 1350 days.

4a. Alcor is at least three light years away from Mizar. Although it is not a member of the Mizar system, it is part of the Ursa Majoris group.

4b. Alcor has a total brightness 15 times that of the sun and is itself a double star.

Item
Updated Notes

Coordinates 08-30-2002
just tweaked a bit

Combined Magnitude
08-30-2002
OK w/ Scott’s The Flamsteed Collection

Apparent Separation 08-30-2002
http://www.astronomical.org/constellations/uma.html

Distance
08-30-2002
OK w/ SIMBAD and Flamsteed

Separation
08-30-2002
http://www.astro.uiuc.edu/~kaler/sow/mizar.html

Orbital Period
08-30-2002
http://www.astro.uiuc.edu/~kaler/sow/mizar.html

Actual Brightness
08-30-2002
OK w/ Scott’s Flamsteed

Magnitude
08-30-2002
OK w/ Flamsteed

Mass

Surface Gravity

Surface Composition 01-06-2003
OK for all stars

Spectral Type
08-30-2002
OK with SIMBAD

Density

Other
08-30-2002
Item 2: http://leo.astronomy.cz/mizar/article.htm Item 3b,c: http://www.astro.uiuc.edu/~kaler/sow/mizar.html