Skywatch for the week of September 23 , 2019
Mon Sep 23, 2019 FIRST DAY OF AUTUMN
It’s September 23rd: Autumn began at ten minutes of four, eastern daylight time, this morning. This is the autumnal or fall equinox, a point in time when, if you’re at the earth’s equator, the sun can be seen at the zenith, the top of the sky, at noon. Today, everyone around most of the world enjoys days and nights of pretty much equal length, hence the term “equinox,” which means “equal night”. From now until after the beginning of winter the sun will rise to the south of east and set to the south of west, and its noontime altitude will continue to decrease as well, as we view it from earth’s northern hemisphere. Our planet’s rotational axis is tipped 23 and a half degrees from straight up and down, as it orbits the sun. That axis does not flip back and forth – it acts more like a gyroscope, making the sun’s path across our sky lower and lower each day as we move toward winter. Now, south of the equator, spring begins: the seasons are reversed for earth’s southern hemisphere.
Tue Sep 24, 2019 CONSTELLATION SHOOTOUT AT TCAS
Tonight’s meeting of the Treasure Coast Astronomical Society will be held at the Hallstrom Planetarium on Indian River State College’s Fort Pierce campus. It will start at 7:30 pm. Every astronomy club meeting features a talk about the stuff of outer space, especially as can be viewed through a good telescope. But tonight’s talk will be a little different. Instead of a lecture on the stars, club members will be pointing out the stars on the planetarium’s domed ceiling, as they compete against each other in something I call a Constellation Shootout, a contest to see who can correctly point out the most stars, constellations and deep sky objects. We’ll even allow asterisms – those are unofficial star patterns like the Big Dipper and the Northern Cross. And there will be prizes, of course. If you want to come and see this competition, it’s free, and as I said, it starts at 7:30 tonight, Tuesday, September 24.
Wed Sep 25, 2019 HG WELLS, GUSTAV HOLST
Herbert George Wells was born on September 21st, 1866. Besides “The Invisible Man,” and “The Time Machine,” he wrote “The War of the Worlds,” which was published at the end of the 19th century, at a time when there was a really big “Mars mania” sweeping the planet. The American astronomer Percival Lowell had recently announced his discovery of canals on Mars (Lowell was mistaken by the way; his telescope allowed him to see natural features on Mars like the Mariner Valley, but didn’t give him enough resolution to see them as anything but vague lines which he interpreted to be canals.) But at the time it was thought that life must exist on the red planet. Wells shares his birthday with the composer Gustav Holst, born on September 21st, 1874. He was a musician, not an astronomer, but in 1915 he wrote a piece of music that you often hear on this radio station, and also quite a bit in planetariums. It's called, "The Planets", and in it Holst wrote music to describe each of the seven known planets.
Thu Sep 26, 2019 NEPTUNE’S DISCOVERY
Neptune was discovered by Johanne Galle on September 23rd, 1846. Working at the Berlin Observatory, Galle used the observatory’s nine inch refracting telescope to search for a possible eighth planet. Galle had been asked to search a particular spot in the sky by a French mathematician, Urbain Leverrier, where he’d calculated it to be. Through the eyepiece, Galle saw a tiny, faint blue dot – was it just another star? Galle and his assistant Heinrich d’Arrest opened up their book of star maps, something called, the Berliner Akademischen Sternkarte, (I think I said that right,) and found that his star was “not on the map!” The next night they found that the tiny dot had moved against the background of fixed stars - it was a wanderer, a planet. Neptune is still in our sky, over in the constellation Aquarius in the southeast after sunset tonight, and yes, even though our planet just passed it and it’s less than 2.7 billion miles away, you’ll still need a pretty good-sized telescope to see it.
Fri Sep 27, 2019 STAR CHARTS
With computers, ipads and smartphones, there are all kinds of star charts available to anyone who wants to look up at the heavens. I’m old-fashioned, and still like to look at star charts that are drawn on paper, with black dots on a white background, which gives the best contrast. Most star charts show the bright stars as big dots and the fainter stars as smaller dots. The brightest stars have Arabic, Greek, Latin or English names. When we run out of names, we use the Greek and Roman alphabets to designate stars from bright to dim: Antares in the southwest this evening is the brightest star in Scorpius and so is designated as Alpha Scorpii. The fourth brightest star, Dschubba, is Delta Scorpii, and so on until you run out of letters. We can also use Flamsteed numbers, named in honor of John Flamsteed, the first director of the Greenwich Observatory. The numbers go up as you move eastwards. Antares becomes 21 Scorpii, and Dschubba, near the west end of the constellation, is designated 7 Scorpii.