Most of us can point out The Big Dipper when stargazing. It is easily observable without a telescope most of the year. When asked if we know it’s other attributes, however, we fall sadly short. It is actually called an asterism, (pattern of stars), inside of the constellation Ursa Major. It is, and has been throughout history, used as a starting point for astronomers and layman alike, to find constellations and other stars across the sky. Some of these are Cassiopeia, Pegasus, Andromeda, and Polaris, also known as the North Star. It has also been used as a navigational tool for travelers since ancient times. Understanding it’s role in history, and unique place in mythology, will help us appreciate astronomy in other ways.
The 7 stars that make up The Big Dipper are:
1. Alkaid
2. Mizar
3. Dubhe
4. Merak
5. Alioth
6. Phecda
7. Megrez
Alkaid (going from east to West of Big Dipper) is a main sequence star (or dwarf), and not part of the Ursa Major constellation.
Mizar, the second star, is the brightest star of the Big Dipper, and a multiple star system. It has 2 double stars Mizar A and Mizar B. Without a telescope, another star can be seen right above it, a dwarf star called Alcor, which is not part of The Big Dipper. Whether or not Alcor is Mizar’s companion star is still being speculated.
Dubhe and Merak are called pointer stars because they point towards the North Star (Polaris).
Alioth is the third star on the handle of The Big Dipper, an Ap star, and the brightest of Ursa Major.
Phecda, a main sequence star, is located on the bottom left of The Big Dipper.
Megrez is located on the upper left of the cup. It is also a main sequence star.
Ursa Minor, known as The Little Dipper, is considered to be the son of Ursa Major.
There are different variations in Greek mythology of how Ursa Major and Ursa Minor became constellations. One version is that the God, Zeus had seduced a young maiden named Callisto. Callisto became pregnant and had a son, Actas. Zeus’ wife, Hera, became so enraged when she found out, she turned Callisto into a “Great Bear”, to take away her beauty. Callisto’s son grew up to become a strong hunter. He was out hunting one day and saw the bear his mother had become. Callisto was so excited at seeing her son she had forgotten she was a bear, and ran to him. Actas was just about to kill her, when Zeus, taking pity on the boy, changed him into a “Little Bear” and placed him in the sky next to his mother, becoming the Big and Little Bear constellations. In the Latin language, Big Bear and Little Bear translates to Ursa Major and Ursa Minor. Most of us have to look hard to see any resemblance of a bear, but the names of the constellations came from the imaginations of our ancestors, not from a scientific standpoint.
Scientifically speaking, if planning on viewing The Big Dipper and other constellations, make sure to have a planisphere. A planisphere is defined as, “A star chart that can be adjusted to display the night sky for any given latitude, time and date,” by wikipedia.com. It will significantly help the starting out astronomer in finding constellations.
Next, make sure to be away from city lights. It is best to be in a dark area, such as a field, away from any lights that will prohibit sight.
After that is accomplished, set up the telescope for observing. Be patient and observe the stars. Relax. Use the planisphere as your guide for finding The Big Dipper. Once found; set your sights on finding the North Star, Sagittarius, and Little Dipper. With 88 constellations in the sky, you can now look forward to numerous nights stargazing.
Simply by looking upon The Big Dipper, our ancestors could ascertain the location of the North Star. With this significant knowledge, slaves in the Underground Railroad utilized the Big Dipper for needed direction. Uneducated, so consequentially illiterate, slaves before the Civil War would communicate through songs. The Big Dipper was referred to as “The Drinking Gourd”. The slaves disguised songs would convey information, telling other slaves to head north.
Next time we look upon The Big Dipper when we are stargazing, let us appreciate the significance of The Big Dipper, and share our newfound knowledge with someone else.
Maybe they could join us in our new explorations.
http://en.wikipedia.org/wiki/Main_sequence
http://en.wikipedia.org/wiki/Big_Dipper
http://homepage.mac.com/kvmagruder/bcp/aster/general/dipper.htm
http://www.mindspring.com/~stardancer/whatsup7.htm
