Skywatch for the week of November 9, 2020
Mon Nov 9, 2020 EDMUND HALLEY’S BIRTHDAY
Edmund Halley, the astronomer, mathematician and scientist was born on November 8th, 1656 near London. Now on the day of his birth, the calendar over his bed would have read October 29th, but when England adopted the Gregorian calendar in 1752, eleven days were lost and his birth-date was changed over to November 8th. Halley himself had died ten years before this conversion, but then again he also missed seeing the comet (that was named for him) return in late December of 1758. Halley had seen it in 1682, and after pestering Isaac Newton to write the equations he needed to solve the comet’s orbit and predict its return, he said he hoped that posterity would record that an Englishman had made the prediction. Incidentally, if you missed seeing the last appearance of Halley’s Comet in 1986, then you’ll want to hang around for its next apparition in the year 2061. I’ll be 108, and I’m looking forward to seeing it again.
Tue Nov 10, 2020 TYCHO’S COMET
On November 13th, 1577, the Danish astronomer Tycho Brahe saw a comet in the sky; from this and later observations, he was able to show that comets exist far out in space (previously it was thought that they 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 did this with the comet, gathering position information from different places in Europe, and he discovered that its 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. Comet appearances are a bit unpredictable, but we usually pick one up every ten years or so, and we’re definitely due!
Wed Nov 11, 2020 MOON, MERCURY AND VENUS IN PREDAWN
If you happen to be outside tomorrow morning, and the sky is clear, look off to the east horizon and you should be able to find the moon, along with three stars. The dimmest of the three stars is Spica, in the constellation Virgo. The two brighter stars are actually two planets of our solar system, which owing to their distances of millions of miles, merely look like stars – but if you watch closely, you’ll notice that while they shine with a steady light, Spica twinkles. That’s because Spica is not just millions of miles away, but trillions! The really bright planet is Venus, and it will be positioned below and slightly to the east of the old crescent moon. Draw a line from the moon down to Venus and then keep going, and it will lead you to Spica. Now head a little farther toward the east horizon, and you’ll discover Mercury.
Thu Nov 12, 2020 FARTHEST NAKED-EYE OBJECT
What’s the farthest thing you can see without a telescope? Off in the northeastern sky late this evening, you can find the answer to this question, but only if the skies are very clear, and very dark, and you know just where to look. It’s a very dim smudge of light that lies in the direction of the constellation Andromeda. But this small spot is neither little, nor does it have any physical connection with the stars of Andromeda, which are merely trillions of miles away. It’s not even a member of our Milky Way, but instead another galaxy, comprising 300 billion stars and approximately two and a half million light years away. One light year, the distance light can travel in a year, is roughly six trillion miles. So when you see the Andromeda Galaxy, you’re looking at something that is fifteen million trillion miles away – and that’s how far out your eye can see.
Fri Nov 13, 2020 LEONIDS
The Leonid meteor shower reaches peak activity this weekend. 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 staying up for. As a rule, meteor showers are best between midnight and dawn, but if that’s too late for you, 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 take this time to look at the stars, and see if you can find that famous constellation Orion the Hunter, which will also rise in the late evening.