Mizar Binary Star
Explanation:
Mizar (sounds like "My Czar") is a binary star.
In fact, most stars are binary stars.
In a
binary star system,
each star of the pair follows an elliptical orbital path.
Mutual gravity causes the stellar companions to
glide around their orbits
as if tied to the ends of an elastic string
passing through a balance point between them.
The balance point is the system's "center of mass".
Also known as
zeta Ursae Majoris,
Mizar is the middle star in the
handle of the Big Dipper and at a distance of 88 light years, was
the first binary star system
to be imaged telescopically.
Spectroscopic observations of the Mizar system show periodic
doppler shifts, revealing that
both stars, Mizar A and Mizar B,
are themselves binary stars!
But, the companions are too close to be directly observed as separate stars,
even by
the largest telescopes.
In developing a new optical
interferometer capable of extremely
high resolution while peering through the Earth's blurry atmosphere,
U.S. Naval Observatory and
Naval Research Lab astronomers have been
able to detect the companion star to Mizar A.
This composite image of their observations shows the
daily and monthly relative orbital motion in the binary system.
Binary stars are a boon to astronomers because these stars can be weighed
--
their orbits providing a direct measurement of star masses.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
