Skywatch for the week of March 9, 2020

Tue Mar 10, 2020 DIRT ON THE MOON When you look at that nearly full moon tonight, just consider that it’s covered in dirt. Where’d all this dirt - the scientific term is regolith - come from? Now, dirt on the earth makes sense: we have a lot of weathering and surface erosion, due to the action of wind, water, ice, and so on. But there’s no air or liquid water on the moon, so how come there’s dirt? Here’s a clue: when you’re on the moon, you’ll never see a meteor streak across the sky. That’s because there’s no atmosphere. There’s lots of dust in outer space, traveling along at a hundred thousand miles an hour or faster. When this dust plunges through earth’s atmosphere, compressional heating vaporizes it and it lights up the night sky as a meteor. But when dust hits the airless moon, the lunar surface gets pulverized. It’s like a cosmic form of sandblasting – countless micrometeorite bombardments that churn the moon’s crust into regolith.

Wed Mar 11, 2020 NAME THAT PLANET 2 Let’s play “name that planet.” I’ll give you the names of some of the features found on a particular planet, and you try to identify it. The first planet has features like Maxwell Mountain, Cleopatra, Amelia Earhart, Sacajawea, and Mead, plus two continent-sized land masses named Ishtar and Aphrodite. The planet is Venus, and its features are typically named after love goddesses or famous women in history. Now try, Tombaugh, Norgay Mountains, the Sputnik plains, Sleipnir, Tartarus, Balrog and Cthulhu. That would be Pluto. How about the plains of Utopia, Chryse and Amazonis, or the Hellas basin, the Tharsis bulge, the Argyre basin, the Mariner Valley or Mount Olympus? That’s Mars. Where do you find the Caloris basin, or craters named Lovecraft, Bach, Beethoven, Velazquez, Brahms, Cervantes, Chopin, Tolkien, van Gogh, Shakespeare or Mozart? These names of artists, musicians and writers can be found on Mercury.

Thu Mar 12, 2020 URANUS DISCOVERED/PLUTO DISCOVERY ANNOUNCEMENT On March 13, 1781, the planet Uranus was discovered by William Herschel. Herschel was a church organist and music director in the city of Bath, England. But he dabbled in other pursuits, and astronomy was his passion. Using a telescope he had built himself, he became the first person in history to discover another planet too faint to be easily seen with the unaided eye. About a hundred and fifty years after Uranus was discovered, the Lowell Observatory in Arizona announced the discovery of another planet. It had been found by a young observatory assistant, Clyde Tombaugh, and it was named Pluto. Back in 2006, an international group of astronomers who had nothing better to do with their time voted to demote Pluto to dwarf planet status, but the American Astronomical Society and NASA oppose this demotion. In the summer of 2015 a space probe named New Horizons flew past Pluto and radioed back some incredible images of this distant world and its moons.

Fri Mar 13, 2020 CAESAR AND THE IDES OF MARCH We’re coming up on the Ides of March, and it looks like this time around no Roman dictators will be killed. On March 15th in 44 BC Julius Caesar was assassinated, and many of us remember Shakespeare’s play, Julius Caesar, in which he was warned to beware the Ides of March. What are the Ides? The Romans divided their calendar month into three parts, with three specific days serving as benchmarks, based on the phases of the moon. The first day of the month was marked by the new moon and was called the Kalends (from which we get the word calendar;) A week later came the Nones, marked by the first quarter moon – and you can tell we don’t use a lunar calendar anymore because the moon is a waning gibbous today; and the middle of the month, the 13th day or in some cases the 15th, when the moon was full - that was the Ides. These terms are not familiar to us today, but they were well-known to the Romans, and also to Europeans in Shakespeare’s time.