Polaris. the North Star, is the Brightest Star of the Nighttime Sky

Not so... It actually ranks as the 49th brightest star in the heavens, if the sun is included. Polaris is relatively easy to spot even from an urban location, but its real importance stems from the fact that its position is near the place where the Earth? axis intersects the heavens. As a result, the Earth's rotation causes the heavens to appear to wheel around this star, making it an excellent marker to determine the direction north. The brightest star of the nighttime sky is Sirius, the Dog Star. Follow the three stars of Orion's belt downward to this gem of the winter sky.

Polaris has Always Been the North Star

Because the Earth's axis wobbles like a top, completing one cycle during a period of 26,000 years (precession), the direction in the sky where the axis points, slowly changes. At present, the axis projects very near to the star Polaris, but 5,000 years ago, when the Great Pyramid at Giza, and Stonehenge I were being constructed, the Earth? axis pointed fairly close to Thuban, a star in Draco, the Dragon. About 12,000 years into the future the Earth's axis will be directed towards the star Vega, in the constellation of Lyra, the Harp.

The Big Dipper is a Constellation

The star pattern known by the name of the "Big Dipper" is most familiar to Americans. It is called the Plow in England, and the Wagon in Germany. During the Civil War, slaves escaping the South through the network of safe havens known as the underground railroad, referred to the Dipper as the Drinking Gourd. Its location is always found in the northern part of the sky, so the Drinking Gourd made an easy marker to follow as blacks made their way north to freedom. The Dipper is really an asterism, a group of stars which form a picture, but which has not been officially recognized by professional astronomers as a constellation. Ursa Major, the Great Bear, is the official name of the constellation which Americans refer to as the Big Dipper. The Great Bear is difficult to see from urban locations, so the Big Dipper has continued to remain more popular in this country than the official constellation.

Constellations are Groupings of Stars in the Sky which Form Pictures

Constellations are very much like states with official borders. Within these boundaries certain stars may be found to form a picture, but all stars within the boundary are considered members of the constellation. There is no official strategy with regards to how the stars of a particular constellation are to be connected to form a picture. Eighty-eight constellation boundaries encompassing the entire sky were sanctioned in 1928 by the International Astronomical Union, a world-wide congress of professional astronomers which deal with such matters. Constellations are useful to modern astronomers because they allow for approximate locations of objects in the sky.

Alpha Centauri is the Closest Star to the Sun

The Alpha Centauri system is the closest stellar system to our sun. The principal star, Alpha, is really a double star with its two components, A and B, separated by about 17 seconds of arc. About 2.2o away from Alpha lies very faint Proxima Centauri, also thought to be part of the Alpha Centauri system and currently on the sunward side of its orbit. Therefore, technically, Proxima is the closest star to our sun. Its distance is about 4.3 light years or 25 trillion miles.

Stars are Burning Hydrogen

Although it is customary for astronomers to use the words "Hydrogen burning" in connection with the energy production inside of stars, nothing could be farther from reality. Combustion is a chemical process which releases energy. The atoms which partake in the reaction are not changed in any way because of the reaction. The "burning" which takes place inside of stars results in the creation of new atoms through a process called nucleosynthesis. In the sun four hydrogen protons are fused into one helium nucleus. The process is much more complicated than that, but the concept is a valid one. In the fusion process some mass is converted into energy as helium atoms are created. This is the mechanism which powers most of the stars that we see in the sky.