Double Stars - Celestron NexStar 90 MAK Instruction Manual

essentially the same for all of these cities, and any
other place along this line of latitude.
More than anything else, latitude determines what
you can see in the sky. The North Star is not visible
from the Southern Hemisphere, as are most of the
stars and constellations near it. And there are all
sorts of stars and constellations visible from the
Southern Hemisphere that we never get to see in the
North (the Moon and planets are visible from both
hemispheres). TheSkyX can show you what the sky
would look like from any place in either
hemisphere.
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Double Stars

A little more than half of all stars actually travel in
pairs, orbiting each other in space. The American
astronomer Henrietta Leavitt once quipped that
three stars out of every two are double. Most of
them appear as single stars to the naked eye. You
need good binoculars or a small telescope to resolve
them as double stars (there are also triple stars and
groups consisting of four or even more stars).
Some double stars are true binaries, meaning they
are gravitationally bound to each other and orbit a
common point in space. Others only appear to be
double because they happen to lie along the same
line of sight from Earth, but are in fact many light
years apart and not tied to each other by gravity.
One of the best-known double stars in the sky is
called Mizar. It's located in the handle of the Big
Dipper.
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