Skywatch for the week of October 26, 2020
Mon Oct 26 2020 THE STORY OF PERSEUS AND ANDROMEDA
Well-placed in the eastern sky this evening are four stars which form a large square – this is the great square of the constellation Pegasus the Flying Horse. To the north of the square there’s Cassiopeia, which resembles a letter W. Queen Cassiopeia was a boastful woman who compared her beauty to that of the mermaids. In punishment, the sea god Poseidon sent Cetus, the sea monster, a scattering of stars below Pegasus, to devour Cassiopeia’s daughter, the princess Andromeda, marked by several stars between Cassiopeia and Pegasus. But the hero Perseus, a scattering of stars to the east of Cassiopeia, came to the rescue by showing Medusa’s head to the sea monster. Cetus looked at the gorgon’s snake-infested head, turned to stone and sank. Then Perseus flew off with Andromeda on the back of Pegasus, and a happy family reunion.
Tue Oct 27 2020 HOW MANY STARS?
How many stars are there in the Universe? Well, on a clear dark night you can see a couple thousand up there above you. The best estimates of the number of stars in the Milky Way suggest there are over 200 billion stars in our home galaxy. Beyond the Milky Way there are other galaxies, hundreds of billions of them, each containing billions or trillions of stars. So, how many stars? Here’s a good way to get an idea. Next time you’re at the beach, count the number of grains of sand you can hold in your hand. You’ll be at it a while; there’s roughly 10,000 sand grains in each handful. Now count all the grains of sand on the entire beach. Follow that up by counting all the grains of sand on all the beaches of Florida, and then for extra credit, count all the grains of sand on all the beaches of the world. There are more stars than that in our Universe. Of course, if those stars have planets that have sandy beaches, that’s really a lot of sand!
Wed Oct 28 2020 TREFRACTORS VS REFLECTORS, 50 POWER RULE
Most department store telescopes are refractors. A refractor has a large glass lens at the front end, usually two or three inches across. You can also find reflecting telescopes or reflectors in department stores. A reflector has a large mirror, usually between 3 and 10 inches, mounted in the bottom of the tube. Reflectors typically cost less than refractors, because mirrors are cheaper to make than lenses. So the reflector is a better buy; you can get a larger, or wider telescope for the same money. And the wider the mirror, the more light it can gather, which means more magnification. A good rule of thumb is fifty power for every inch of aperture. If a scope has only a three-inch lens or mirror, then you really should only expect it to magnify up to about a hundred and fifty power – after that, the image looks dim and fuzzy. Buy a reflector that has a mirror at least four inches to six inches across. That will give you the ability to magnify images up to 200 power or more.
Thu Oct 29 2020 CREATURES OF THE NIGHT
With the coming darkness, the constellations above your heads recall monster stories from very long ago. The three stars in the summer triangle, overhead this evening, represent man-eating birds that were chased from the Stymphalian swamps by the hero Hercules. At sunset, the constellations of Scorpius the scorpion, Serpens the snake and Lupus the wolf are sinking into the southwest. A scattering of stars in the southeast this evening mark the location of Cetus the Whale – a sea monster in Greek mythology. Perseus the hero, over in the northeast, holds out the snake-haired head of the gorgon Medusa, while Draco the dragon guards the northern skies tonight. After midnight, Canis Major rises in the southeast. He is associated with the three-headed dog Cerberus who guarded the gates of the Underworld. And as dawn approaches, Leo the Lion and Ursa Major the Great Bear, rise up out of the eastern sky, hunting for fresh prey.
Fri Oct 30 2020 FULL OCTOBER MOON
The full moon, now among the stars of the constellation Pisces, rises at sunset this evening. October’s full moon is often called the Hunter’s Moon, because hunters in colonial America found its light useful when pursuing their own dinner in the dark. This is also the Sioux Indians’ Moon of Falling Leaves; the Big Wind Moon of the Zuni tribes; or the Cheyenne’s Moon When the Water Begins to Freeze on the edge of the Stream - must be getting cold up north. The Ponca Indians, in observance of the time when food is harvested for the winter, call this the Moon When They Store Food in Caches, while the Kiowa simply call it the Ten Colds Moon, a harbinger of the freezing weather that follows. October’s full moon was also called the blood moon in medieval England, a reference to the reddish coloring often displayed by the rising full moon of October.