Skywatch for the week of May 31, 2021
Mon May 31, 2021 MEMORIAL DAY
May 30th is the traditional date for Memorial Day, also called Decoration Day. It’s been observed since 1868, as those who fought and died on both sides of the American Civil War, the “War Between the States,” were remembered. In 1884, Oliver Wendell Holmes reminded us that both “…private and general stand side by side. Unmarshalled save by their own deeds, the army of the dead sweep before us, "wearing their wounds like stars." In another eulogy written by an unknown author, we are told that those who fought for our country are as the soft stars that shine at night. According to legend, General George Washington made the first sketch of a starry flag. But more likely it was Francis Hopkinson, a signer of the Declaration of Independence, who first urged the use of stars in our flag’s design. We invoke the stars as our beacons in the dark. They shine on us all, the astronomer, the poet, those who labor, those who create, those who fight to keep us safe, both in the sunlit day and in the starlit night.
Tue June 1, 2021 STAR TRAILS: AS THE WORLD TURNS
An elegant demonstration of the earth’s rotation is the motion of the stars across the heavens as the night progresses. Amateur astronomers have taken countless photographs of the sky at night, leaving their cameras open to record the stars as they rise and set. All it takes is a tripod, a camera that has a feature that allows you to leave the shutter open for minutes or hours, and a bit of patience. The result will be a photograph that shows star trails. Aim your camera east or west and you can get star trail lines that appear as diagonal streaks across the picture. Aim your camera south and you’ll get star trails that bend in broad, curving arcs that run along the southern horizon. But aim your camera north, with the star Polaris in the center of the viewfinder, and you’ll get star trails that move in nested circles around the North Celestial Pole. Even Polaris, the North Star, will show a very slight movement, as it is displaced from the earth’s pole by just under a single degree of angle.
Wed June 2, 2021 RAINBOWS AT SUNSET
Rainbows form when tiny water droplets in our atmosphere catch sunlight and, acting like prisms, break up the light into its separate colors. We sometimes see rainbows in the early morning, or more often, in the late afternoon, especially around sunset. Why at these hours instead of at midday, around noon? Rainbows always show up on the opposite side of the sky from where the sun is. At sunset, when the sun is near the western horizon, the rainbow appears well up in the eastern sky, its arc long and high. The lower the sun is, the higher the corresponding bow. That’s why you’ll never see a rainbow at noon, since it would place the sun below the horizon, unable to light up all those tiny water droplets. Sometimes you can see a secondary rainbow above the main one, but the colors are reversed: instead of the red being on the top of the arch and the violet at the bottom, the secondary bow has violet at the top and red at the bottom.
Thu June 3, 2021 IROQUOIS-NORSE STAR PATTERNS
In an old Iroquois story, the earth was created when all the animals came together in council to make a dry place where Ataensic, the sky woman, could live. Most all people long ago had creation stories, with similarities and differences. The Norse said that the earth was fashioned from the great body of the giant Ymir. And all around the world, constellations were invented that filled the heavens at night. In ancient Greece the Big Dipper, which is now high in the north after sunset, was part of the great bear Ursa Major. Many native American people saw a bear here as well. But to the Vikings, the Big Dipper was called Odin’s Wagon. This wagon or chariot must have been a pretty good ride, because it was passed down to Odin’s son Thor; and Ursa Minor, the Little Bear, also called the Little Dipper, was driven by Freya, Thor’s wife and the Norse goddess of love. And Thor himself may be represented by the constellation Orion, low on the west horizon at sunset this evening.
Fri June 4, 2021 JOHN COUCH ADAMS
John Couch Adams was born on June 5th in 1819. Adams was first to predict the location of Neptune. Astronomers had noticed that Uranus, thought at the time to be the outermost planet, did not follow its predicted path. The gravity of some massive object farther out was pulling on it, altering its orbit. In 1845, Adams deduced the location of the hidden gravity source, and in 1846, Neptune was discovered telescopically by J.G. Galle; but Galle had never heard of Adams! Galle used the predictions of the French mathematician Jean Leverrier instead, who had also arrived at a solution to the orbit problem a year after Adams. But Adams had sent his calculations to his supervisor, the Astronomer Royal, George Airy, who didn’t do anything with the information because Adams hadn’t shown all his work and didn’t follow through with Airy’s request for more information and never made an appointment to talk to him about it – definitely a “failure to communicate.”