by Kim Malville
December 1: Soon after sunset look to the west for the line of planets: Saturn, Venus, and Jupiter. Saturn is highest and Jupiter is lowest. During the next two weeks, Jupiter gets lower and lower and finally vanishes around the 15th. Venus is closest to the earth and moves eastward fastest, eventually catching Saturn.
December 10: Look quickly westward after sunset to catch Venus and Saturn, which are less than 2° apart.
December 13-14: Venus has passed Saturn. Tonight and tomorrow there will be the Geminid meteor shower. In 2016 observers reported as many as 147 meteors per hour. The best time will between midnight and 4am when this year you might see some 20 meteors per hour. This shower seems to be under-appreciated compared to other major showers such as the Perseids in August, probably because it is colder in December than August. Most meteor showers are produced by the debris embedded in the “dirty” ice of the comet. That ice sublimates when the comet comes close to the sun, releasing some of the particles. In the case of the Geminids the source of meteor particles is a rock which heats up when approaching the sun. Its surface reaches 1500 degrees F and cracks, leaving dust particles behind it.
December 21: The longest night of the year in the northern hemisphere. Solstice occurs at 9:19 p.m. The sun experiences an annular eclipse, visible in a narrow path running from Saudi Arabia, though the Emirates, Oman southern India, across Malaysia to the Philippines. At this occasion the moon is too far from the earth in its elliptical path and is too small to cover the sun completely.
Constellation of the Month
Directly overhead at 8pm in early December is the constellation Andromeda and its famous galaxy, lying next to the Great Square of Pegasus. This galaxy is easily visible in our dark skies as a hazy blob and is the only object in the northern skies that is not a member of our own Milky Way Galaxy. All the stars we can see with our naked eyes are fellow passengers in our galaxy. The most distant star most people can see without a telescope is in the constellation of Cassiopeia at a distance of 16,308 light-years. The next most distant object is the Andromeda galaxy at distance of 2.5 million light years—a huge leap in distance. The Andromeda galaxy is a spiral galaxy similar to but larger than our Milky Way, containing around a trillion stars, twice as many as in our own. Unlike most of the billions of galaxies in the universe, it is moving toward us at a speed of 68 miles per second. We expect the collision will occur in 4.5 billion years. The fate of the earth and solar system is unknown, but we could be ejected from the combined galaxies as a result. At the center of Andromeda there lies a huge black hole containing as many as 200 million solar masses. I dare say, it will be far, far better to be ejected from the combined galaxies than to fall into the black center.
Andromeda in myth
Andromeda was the princess of Ethiopia, daughter of King Cepheus and Queen Cassiopeia. The queen was a boastful woman, and foolishly bragged that her daughter was more beautiful than Juno, the queen of the gods. In order to avenge the insult to his nymphs, Neptune sent a sea monster, Cetus, to ravage the Ethiopian coast. The horrified king consulted Ammon, the oracle of Jupiter, who said that Neptune could be appeased only by sacrificing Cassiopeia’s beautiful virgin daughter, Andromeda, to the monster. Andromeda was duly chained to a rock on the coast. Rocks in the harbor of Tel Aviv are now identified as the place where she was chained. Fortunately for her, the hero Perseus happened to be near, flying on the winged horse Pegasus (the progeny of the Gorgon Medusa) on his way back from killing Medusa, whose head he is carrying in a leather bag. Hearing her screams, Perseus pulls the bloody head of Medusa with her head of snakes out of his bag, and shows it to Cetus, who immediately turns to stone and sinks to the bottom of the sea. Perseus unchains Andromeda, careful not to expose the head to her, and they immediately fall in love. One hurdle remained, however. Her original suitor drops into their wedding ceremony and, like Dustin Hoffman in The Graduate, tries to spirit Andromeda away. Medusa comes to the rescue. Perseus pulls her head of his bag and quickly turns the suitor into stone. They had a happy marriage with nine children. If you don’t believe this story, check out the 1981 movie, Clash of the Titans, where is it all confirmed. Furthermore, in museums of the world, there are paintings of naked, chained Andromeda by painters such as Titian, Rembrandt, Rubens, Delacroix and Gustave Doré. Enjoy Andromeda in the sky!