Skywatch for the week of January 10, 2022
Mon Jan 10, 2022 RIDDLES IN THE DARK
J.R.R. Tolkien was born on January 3rd, 1892. In his fantasy story, “The Hobbit,” the hero Bilbo meets a strange creature named Smeagol down in a deep cave, and they ask each other riddles. One goes like this: “It cannot be seen, cannot be felt Cannot be heard, cannot be smelt. It lies behind stars and under hills And empty holes it fills.” And the answer is, “darkness.” Now, here’s an astronomy riddle I made up: “At weddings they appear; and at front doors it’s them we hear. They’re found on Elven hands and soda cans; ‘Round Saturn they appear.” And the answer is, “rings.” Let’s try another astronomy riddle. “It’s always on, and never off. It’s more when nearby, and less when far off; It keeps the sun from spilling out. And in the end, it stops us going up and about.” The answer is “gravity.”
Tue Jan 11, 2022 HERSCHEL DISCOVERS URANIAN MOONS
On January 11, 1787 the astronomer William Herschel discovered Uranus' moons Titania and Oberon. Herschel was a self-taught astronomer and telescope maker; but his day job was as church organist in Bath, England. But he dabbled in other pursuits, and astronomy was his passion. He built his own telescopes, and was so good at it that colleagues were amazed to find that his handmade instruments were far superior to the ones commercially available at the time. It was with just such a telescope that he became the first person in history to discover another planet telescopically, in 1781. He suggested naming it George, after the king of England. But eventually it became known as Uranus. And six years later, his improved observations led to the discovery of its two largest moons.
Wed Jan 12, 2022 JANUARY
January is named for Janus, the Roman god of new beginnings. He had two faces: one looked back toward the past; the other looked forward to the future. And so we now begin the calendar year. Take any given year – say the year 2024, which marks the next time that the continental U.S. experiences a total solar eclipse. That year, according to the calculations of a Roman monk, Dionysius Exiguus, (“Dennis the Small,”) marks the two thousand and twenty-fourth year following the birth of Christ – AD – Anno Domini – in the year of Our Lord - 2024. But Dionysius’s count was off by at least one year. Our calendar goes from 1 BC to AD 1 – there is no zero year, because the numerical concept of zero was not used in Europe back then. Well, no matter how you reckon time, the earth just keeps on rolling along.
Thu Jan 13, 2022 FATHER PIAZZI DISCOVERS CERES
On January 1st, 1801, the Italian astronomer Father Giuseppe Piazzi discovered Ceres, the first of the asteroids. Piazzi saw it in a place where there was no star recorded, so he marked its position on his star chart. Several nights later, he found that it had moved to a different spot. Obviously, this was no fixed star in the heavens, but a wanderer, a planet, a member of our own solar system that was close enough for us to observe its orbital motion around the sun. He informed the scientific community, and named his new world Ceres, after the Sicillian goddess of the harvest. In the years that followed, other astronomers found more asteroids (literally, “star bodies,” a term suggested by William Herschel, who discovered the planet Uranus;) and now, 220 years later, we’ve discovered over a million of these minor planets!
Fri Jan 14, 2022 GALILEO'S MOONS
In the year 1610 the astronomer Galileo wrote in his logbook: "On the seventh day of January… at the first hour of night, Jupiter presented itself to me. Beside the planet there were three starlets, small indeed, but very bright. Returning on January eighth I found a very different arrangement. On the thirteenth of January four stars were seen by me for the first time." Galileo then concluded that the four star-like objects were moons going around Jupiter. This was an astonishing discovery, because up until then it was believed that the planets were solitary objects, as their orbital motions would cause any attendant moons to fall behind in their wake. To see what Galileo saw, look at Jupiter with a small telescope in the southwest this evening; you’ll see Jupiter as a small, round disc, and its moons appearing as tiny stars, lined up on either side of the giant planet’s equator.