Skywatch for the week of November 14, 2022
Mon Nov 14, 2022 TYCHO’S COMET
On November 13th, 1577, the Danish astronomer Tycho Brahe observed a comet and discovered that they exist far out in space (previously it was thought that comets were created in the atmosphere.) Brahe used parallax to prove this.
Hold your thumb up at arm's length, and look at it with first one eye, and then the other, and you'll see your thumb jump back and forth against the background. If you bring your thumb in closer, the parallax shift increases. Brahe noted the comet’s position against the background stars and compared his measurements with other astronomers and found that the comet’s parallax was less than the moon's, therefore farther away.
We haven’t had a bright comet appear in our sky since Comet Hale-Bopp, which a lot of people saw back in the spring of 1997.
Tue Nov 15, 2022 WILLIAM HERSCHEL BORN
William Herschel was born on November 15th, 1738. Herschel was a church organist in Bath, England. He also had a great interest in astronomy, and in telescopes. But most musicians don’t make much money, and telescopes were expensive. So he built his own.
It was with just such a telescope that in March of 1781, William Herschel discovered a planet. Herschel named it George, after the King of England. Many astronomers suggested the planet simply be called, Herschel. Eventually Uranus, who in mythology was the father of Saturn, was chosen.
Herschel also found four moons: Oberon and Titania, which orbit Uranus, and Mimas and Enceladus, which orbit Saturn. And Herschel mapped the stars of the Milky Way, concluding from their distribution that the galaxy in which we live was shaped like a giant disc.
Wed Nov 16, 2022 LEONIDS
The Leonid meteor shower reaches peak activity over the next couple of nights. The Leonids, so-called because these meteors seem to come from the direction of the constellation Leo the Lion, have been in a bit of a decline lately, but they’re still worth going out to see.
As a rule, meteor showers are best after midnight, but this year the bright 3rd quarter moon rises around midnight, making it hard to see these shooting stars, so catch the Leonids in the late evening hours. Protect yourself against mosquitoes, dress warmly, take along a lounge chair for comfort, find a clear, dark sky and face east, looking up toward the zenith.
You should be able to see several meteors an hour, but there can be stretches of ten or fifteen minutes sometimes, when nothing happens. So sit back and
enjoy the starry night sky.
Thu Nov 17, 2022 MESSIER’S FALL – November 6, 1781
On this day in the year 1781 the French astronomer Charles Messier lay bed-ridden after a very bad fall down a flight of stairs. It would take him a year to recover. Messier discovered over a dozen comets in his career, so many that King Louis the 15th dubbed him, “the comet ferret.” How’d you like to have that on your resume’?
Messier also made up a list of about a hundred fuzzy objects – we call them Messier objects, or M objects. These were things he saw in his telescope that turned out not to be comets at all, but star clusters like M13 in Hercules, or nebulas like M42 in Orion, or galaxies like M31 in Andromeda or the Whirlpool, M51!
Messier managed to survive the French revolution and lived to the ripe old age of 87. In 1806 Napoleon awarded him the Cross of the Legion of Honor.
Fri Nov 18, 2022 THE MOON AND TIDAL LOCKS
Just as we experience daylit and dark periods on earth, so the moon has both day and night. But the moon spins slowly; a lunar day lasts two weeks, followed by two weeks of lunar night. The moon’s rotation period matches its revolution, so it rotates once for every one orbit. This is called a tidal or synchronous lock, an effect of the earth’s tidal pull on the moon, which has slowed its rotational speed to match its revolution.
Because of this we can only see half the moon (lunar nearside;) the farside of the moon (sometimes wrongly called “the dark side,”) can never be seen from earth. Or as Pink Floyd tells us, ”There is no dark side of the moon; matter of fact, it’s all dark!” But the sun lights up the dark side, sorry, farside, just as much as lunar nearside.