Appropriately, the first 'Star of the Week' is Polaris--the North Star.
Polaris is not an especially exceptional star. It is the brightest star in Ursa Minor (hence it has the name Alpha Ursae Minoris) but with an apparent magnitude of around 2 it is the 46th brightest of stars (in both hemispheres). Were it not for it's location, Polaris would be no more familiar than Alphard, the brightest star in the constellation Hydra, which has a similar apparent magnitude. But, what a location it has, for Polaris has a distinguished position close to celestial north pole. This means that to observers in the northern hemisphere, Polaris wobbles in place ever so slightly while all the other stars trace circles around it. It also means that at night, one can find north by finding the appropriately nicknamed North Star. Moreover, should anyone ask you to find Polaris during the day, although you cannot see it, you can confidently point north.
|Stars traverse the sky at night, but not Polaris, which sits|
like a king in the center of a court.
Photo : Ashley Dace under Creative Commons Attribution Share-alike
The fact that there is a star near the celestial north pole is a happy coincidence of both time and space. At the moment, Polaris happens to be located above the axis of Earth's rotation. However, the orientation of Earth's axis of rotation wobbles, a process called the precession of the equinoxes. As a result Polaris was not the North Star for the Ancient Greeks and in the coming centuries, it will be drift further and further away from north.
One can find Polaris by using a simple trick involving one of the most easily identifiable constellations, Ursa Major (also known as the Big Dipper). Using the two stars on the leading edge of the dipper section (the two stars away from the handle) follow up from the bottom star. The next bright star you find is Polaris. One can also locate the star at the edge (back end) of the handle part of the Littler Dipper (Ursa Minor) but because that constellation has many dim stars, it is difficult to find it in places with even moderate light pollution.
Besides finding north, one can also use Polaris to get a rough estimate of latitude or distance above the equator: the height of the star roughly corresponds to one's latitude. At the North Pole, it is overhead, whereas at the Equator it is skimming the horizon.
In a post later this week, I'll detail information about the nature of the star. Sneak Peak: What we call the North Star actually more than one star!