Skywatch for the week of December 13, 2021
Mon Dec 13, 2021 GEMINID METEORS
For the next two nights, the Geminid meteor shower will send us “shooting stars,” which seem to come out of the constellation Gemini. Under clear, dark skies the Geminids usually produce a few dozen meteors each hour. This year, the moon is just past half full, making it difficult during the evening hours to see all but the brightest fireballs. So you may want to watch for the Geminids after midnight, which is when most meteor showers are at their best anyway. And of course, if it’s cloudy, you won’t be able to see the meteors at all. But if it’s clear, then find a place that’s away from house and street lights, protect yourself against mosquitoes, dress warmly, take a lounge chair that leans all the way back, and face toward the east. The top of the sky should be about the best area to watch. You won’t need a telescope or binoculars, in fact such things would limit your view.
Tue Dec 14, 2021 SUNRISE, SUNSET, AND SEASONS
We speak of the sunrise in the east and sunset in the west, but there are only two times during the year when this occurs – at the beginning of spring and at the beginning of autumn. After the spring equinox, the sun rises to the north of east and sets to the north of west, and after the autumnal equinox, the sun rises to the south of east and sets to the south of west. In the summer, the sun’s path across the sky is long and high, the daylight period is longer than the night, and the weather turns warm. In the fall and in the spring, the sun’s path is lower in the sky than it was in summer. The period of daylight and dark is roughly equal, and the air is cooler than in summer, but not so cold as in winter. Lastly, at winter’s beginning, the sun’s path is very short and low; the daylight period is short, the night is long. Air temperatures drop quite a bit during this time, and the weather turns cold.
Wed Dec 15, 2021 TYCHO BRAHE
Tycho Brahe was born on December 14th, 1546. He was a Danish nobleman whose most notable feature was an artificial nose made of brass - it replaced the one he had lost in a fencing duel over an argument with another scholar about a math problem (That actually happens a lot. Not the duel, the arguing.) Also, he had a pet moose and his own court jester. But he was above all, a great astronomer. Tycho proved by its parallax that a comet was far beyond the moon; it used to be thought that comets were simply gases in the atmosphere. From Tycho’s island observatory, and before telescopes were invented, he made incredibly accurate measurements of star and planet positions. After twenty years and thousands of observations, his last assistant and associate, Johannes Kepler, was able to use them to figure out that the shapes of the orbits of planets about the sun are not round, but elliptical.
Thu Dec 16, 2021 SUMMER TRIANGLE IN WINTER/THE NORTHERN CROSS
Three bright stars – Vega, Altair, and Deneb - form a large triangle in the heavens; and because they can be found high overhead in summertime, Vega, Altair and Deneb are often called the Summer Triangle. Each star marks a separate constellation: Vega is in Lyra the Harp; Altair is in the wing of Aquila the Eagle; and Deneb represents the tail feathers of Cygnus the Swan. It’s often difficult to recognize these old fanciful star pictures, so sky watchers have come up with easier shapes to find. In the constellation of Cygnus the Swan, there is a simpler pattern called the Northern Cross. The tail of Cygnus, the star Deneb, marks the top of the cross; while the bird’s beak, the star Albirio, is at the foot of the cross; and the wings of Cygnus form the crosspiece. During early winter evenings, the Summer Triangle has moved toward the west, and the Northern Cross now stands upright on the west horizon after sunset.
Fri Dec 17, 2021 DECEMBER FULL MOON
This weekend the moon will be rising at the time of sunset as it waxes toward full. It will be at its fullest tomorrow night, when it appears above the constellation Orion and between the horns of Taurus the Bull. December’s full moon is known as the Big Winter Moon – that’s according to the Creek and the Seminole Indians. To the Algonquin Indians and to colonial settlers, this is the Long Night Moon, another reference to the beginning of winter, when days are short and nights are long. The Sioux call this the Moon of Popping Trees, perhaps because the cold air freezes water, causing the trees to crack and pop. The Winnebago name it the Big Bear’s Moon, and the Cheyenne say it is the Moon When the Wolves Run Together - pack hunters searching for food before the snows of winter.