This trend continues until the traveler reaches the geographic not magnetic North Pole. At this point 90 degrees latitude , Polaris is 90 degrees above the northern horizon and appears directly overhead. Elmore further asked, "Did travelers in the past actually depend on the North Star to guide them? Thus, Polaris is a handy tool for finding the northern extent of one's position, or latitude, and was therefore heavily utilized by travelers in the pastespecially sailors.
Unfortunately, latitude alone is insufficient to pinpoint a location on the surface of the earth. Lines of constant latitude circle the earth parallel to the equator. With only latitude in hand, an individual knows just that he or she is on a particular "latitude circle. Although many cultures succeeded in making long ocean voyages using only the stars, weather and currents, the "longitude problem" plagued sailors for millennia and remained unsolved until the invention of a clock that could keep accurate time while a ship rolled, pitched and yawed on the sea circa Furthermore, Polaris is not an absolute guide to measuring latitude on the earth for Northern Hemisphere observers.
Its four faintest stars can be blotted out with very little moonlight or street lighting. The best way to find your way to Polaris is to use the so-called "Pointer" stars in the bowl of the Big Dipper , Dubhe and Merak.
Just draw a line between these two stars and extend it out about 5 times, and you eventually will arrive in the vicinity of Polaris. Interestingly, the Big and Little Dippers are arranged so that when one is upright, the other is upside down. In addition, their handles appear to extend in opposite directions.
Of course, the Big Dipper is by far the brighter of the two, appearing as a long-handled pan, while the Little Dipper resembles a dim ladle. Polaris is located at a distance of light-years from Earth and has luminosity nearly 4, times that of our sun. Polaris shines at 2nd magnitude.
On this astronomers' scale, smaller numbers represent brighter objects, with the brightest stars and planets in the night sky at around magnitude zero or even negative magnitudes. The North Star it is a "pulsing" star, a Cepheid variable , which appears to vary in brightness ever so slightly — only one tenth of a magnitude — over a time frame of just under four days.
If you have a small telescope and train it on Polaris, you just might notice a tiny companion star called Polaris B shining at 9th magnitude with a pale bluish tint. This companion was first sighted by Sir William Herschel in just a year later, Herschel would discover the planet Uranus. Astronomers believe that the two stars — A and B — are separated by about 2, astronomical units — one astronomical unit a. The orbital period of the two stars may number in the many thousands of years. So, if you live in, say, Paris at 48 o North, Polaris will be 48 o above the Northern horizon.
Put in another way - the North Star Polaris will be placed high on the sky when viewed from the Arctic 90 o from the Pole :. Limpus and J.
Click to obtain larger figure GIF, 35k. Some history During the Middle Ages, every Christian man with self-respect should visit Jerusalem at least once during his life. Bishop Nicolas from Iceland published a method to determine the altitude of the North Star and thereby to determine the geographical latitude in Figure 4. Click to obtain larger figure JPG, 85k. This method works the following way: Lie down on the ground and put your right hand above the knee, as shown on the picture.
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