Mon July 14, 2025 CONSTELLATIONS VS. ASTERISMS
Today there are 88 official constellations. Now in the ancient world of the Mediterranean and Middle East, there were less than sixty constellations, owing partly to a lack of knowledge of stars to the south that were never seen from those latitudes. There are (and were) a great deal more unofficial star patterns, called asterisms. In order to be a constellation, everybody has to agree that that’s what it is. An asterism is more personal, and usually a lot easier to see or imagine. So the Great Bear, Ursa Major, includes the stars of the Big Dipper (what we call it here in America,) or the Plough (England,) or the Chariot (ancient Rome.) Cygnus the Swan becomes the Northern Cross, Scorpius becomes the Fish Hook, and Sagittarius the Archer looks like the crude outline of a teapot. When you first start to trace out the constellations, these asterisms will help make the more complex patterns easier to learn.
Tue July 15, 2025 HENRIETTA LEAVITT
On July 6, 1868, the American astronomer Henrietta Leavitt was born. She worked at Harvard Observatory, and while cataloging a class of stars known as Cepheid variables - named for the fourth-brightest star in the constellation Cepheus the King - Leavitt analyzed the light curves of various Cepheids. Variable stars change their brightnesses over time; this is caused by the star’s expanding and contracting as it reaches the end stages of its life. When the star expands, it becomes brighter, when it contracts, it dims a bit. Henrietta Leavitt discovered that there was a relationship: Cepheid variable stars that were intrinsically brighter, or larger, than others, took longer to go from bright to dim to bright again. This made it possible to figure out how far away distant galaxies were, and gave us a much larger measuring stick to determine how far away things are in the Universe.
Wed July 16, 2025 APOLLO 11 LAUNCH
On July 16, 1969, three astronauts were launched into space. On July 20th they would reach the moon. Six other men had preceded them, beginning with Apollo 8’s Frank Borman, Jim Lovell and William Anders; but they simply orbited the moon, they did not land on it. Beginning with the first rockets into earth orbit in the late 1950’s, then in America the manned training and preparation flights: a single astronaut aboard the Mercury spacecraft; two astronauts who orbited the earth in each of the Gemini missions, learning how to dock with other spacecraft, figuring out the best ways to maneuver while in a spacesuit outside the capsule; the loss of good people – Gus Grissom, Roger Chaffee, Ed White – in the Apollo 1 fire. Then to fix what had gone wrong, and continue the struggle, until at last the moon was within our reach. We went to the moon not because it was easy, but because it was hard.
Thu July 17, 2025 SEASONAL CONSTELLATIONS
We are now several weeks into summer. With the change of seasons also comes a change in the sky and its constellations. The sun has moved from Taurus the Bull into Gemini the Twins, rendering that part of the sky difficult to see. The great constellations of winter, such as Orion the Hunter and Taurus the Bull, can now only be glimpsed just before sunrise, near the eastern horizon. Springtime star patterns such as Leo the Lion or the Big Dipper, which were once at the top of our northern evening sky, have now slipped over into the west, supplanted by Boötes the Shepherd, Hercules the Hero and Virgo the Maiden. And new star groups appear in the east – Libra and Scorpius, and the three bright stars of the Summer Triangle. The sky wheels about us, and the summertime constellations take their places in the heavens above.
Fri July 18, 2025 ROBERT HOOKE
Robert Hooke, born on July 18, 1635, is best known for his pioneering work in analyzing insects, plants, all manner of things in nature, using a microscope. He made a lot of sketches, and first described the cell-like structure of living organisms. He was also a mortal enemy of Isaac Newton. In fiction, Sherlock Holmes had to combat Professor Moriarty; Superman had to fight Lex Luthor; and Batman had to deal with the Joker. For Isaac Newton, it was this guy – Robert Hooke. Newton had built a small reflecting telescope, the first of its kind, and he was persuaded to share his experiments on how the eye sees light. Hooke, who had done some work in this area, strongly criticized Newton, and Newton didn’t like it. Hooke also claimed to have worked out the laws of gravity long before Newton’s published work, Principia. Thus began a life-long battle between the two.
