Gazing Up At the Summer Sky
THE stars belong to everyone. Everyone, that is who takes time to look up. Come along; we're going to take a tour of the cosmos tonight. You won't need a telescope, just this article and map, and a flashlight to read by. If it's cloudy tonight, the map is good any other evening for the rest of June. It can be used anywhere in the world's north temperate latitudes.
Find a place with an open view of the sky and no lights nearby to blind your night vision. Bring the kids, the mosquito repellent, and perhaps a blanket to lie on.
First take a minute to learn how the map works. Note the directions around the outside, such as ``North Horizon.'' Hold the map straight out in front of you, and turn it so the horizon labeled with the direction you're facing is down. (See drawing on opposite page.) The star patterns above this horizon on the map now match the real ones in front of you in the sky.
The center of the map represents the sky directly overhead (the zenith). Stars halfway from the horizon to the map's center can be found in the sky halfway from the true horizon (horizontal from your eye) to the overhead point.
Lastly, remember the star patterns in the sky will appear much bigger than on the map.
Now we're ready to begin.
Face northwest at the end of dusk. (Northwest is a little to the right of where the sun went down.) Look high up. Slightly more than halfway to the zenith is the Big Dipper. Its handle points toward upper left, and its bowl is open to the right - just as on the map when it's turned so ``Northwest Horizon'' is down. Overall, the Dipper is a little longer than the width of your fully outstretched hand, from thumbtip to little finger, held at arm's length.
The stars of the Big Dipper are moderately bright, so you should be able to make them out even through the murky sky glow that washes out fainter stars near cities and towns. If you're fortunate enough to live far from populated areas, you may have trouble with too many stars! Look just for the brighter ones and you'll spot the Dipper pattern.
Find the two stars at the bottom of the Dipper's bowl. These are the Pointers, and what they point to is Polaris, the North Star. Polaris is rather dim, about 11/2 hands-spans-at-arm's-length to the right of the Pointers. Its claim to fame is that it stays essentially the same point in the sky day and night throughout the year. Whenever you face Polaris you are facing true north.
Go back to the Big Dipper and examine the middle star of the three in its handle. This is Mizar. If you look closely you may be able to spot its tiny but famous companion star Alcor, right next to it at the one-o'clock position.
Follow the arc of the Big Dipper's handle off to the left to locate the brilliant star Arcturus, as shown on the map. Arcturus has a pale-orange tint. It is a giant star 100 times more luminous than the sun, located 35 light years from us. The light you see from Arcturus tonight has been traveling toward us through space since about 1955.
Most of the stars visible to the naked eye are younger than the Earth, the sun, and the rest of the solar system, which are 4.6 billion years of age. But Arcturus is several billion years older than that. It is probably the oldest thing you have ever seen.
Continuing down toward the lower left we come to Spica, about a third of the way up the sky as you face southwest. This is a hot, blue-white star about 220 light-years distant; its light has been in flight since before the American Revolution.
Turn to the south. Here is Antares, a little lower than Spica - a fiery orange-red super-giant star some 500 light-years away pouring out 10,000 times the light of the sun. Scattered around it are the fainter blue-white stars of the constellation Scorpius, an array of diamonds setting off Antares' topaz.
Farther left and a little lower is the fainter constellation Sagittarius. In Greek mythology it is supposed to represent a centaur shooting an arrow, but its major stars (none very bright) form more of a teapot to modern eyes.
To the left of Sagittarius, low in the southeast, is the lone bright planet of the evening, yellow Saturn. Compare it to Antares. Does the star twinkle more than the planet? In general planets hardly twinkle at all, a useful point for recognizing them.
Turn to the east and look high up, two-thirds of the way to the zenith. There is sparkling-white Vega, the second-brightest star of the night after Arcturus. It forms the top of the so-called Summer Triangle with Daneb at the lower left, a white star about 1,600 light-years away, and Altair at the lower right, another white star just 16 light-years from Earth. Try to picture that Daneb is 100 times farther from us than Altair and 6,000 times more luminous.
Other bright stars and constellations can be identified around the sky just as easily using the map. With simple tools like this, anyone can master the heavens.