Skywatch for the week of April 26, 2021
Mon Apr 26, 2021 APRIL’S FULL MOON
The full moon rises in the east this evening once the sun has set in the west. Since spring is underway, the Sioux Indians call April’s full moon, the Moon of Greening Grass; to the Winnebago, it is Planting Corn Moon. The Seneca Indians, the Keepers of the Western Door, recognize this as the time of the strawberry dance, while the Keepers of the Eastern Door, the Mohawk, know it as “Onerahtokha,” the budding time, which is similar to the Kiowa’s Leaf Moon, as this is the time of year when new leaves form on trees. The Cheyenne Indians speak of it as the Moon When the Geese Lay Eggs. To the Mandan Indians of North Dakota, it is simply the Planter’s Moon; it was under the light of this full moon many people planted tobacco, potato, and the Three Sisters - the seeds of corn, squash and bean. Other tribes call this the grass moon. And to the Cherokee it is “kawohni,” the flower moon.
Tue Apr 27, 2021 SHAPLEY-CURTIS DEBATE
On April 26th, 1920, a great debate took place concerning the earth's place in our Milky Way Galaxy. Some astronomers like Heber Curtis thought we were at the center of our galaxy, for when you looked along the milky band of stars that defines the galactic disc, you saw roughly the same number of stars throughout. Curtis also thought that spiral nebulas were distant galaxies, like our Milky Way, but very far away. Other astronomers, notably Harlow Shapley, suggested that interstellar dust clouds blocked our view of the galactic center, and that a concentration of star clusters in the direction of the constellation Sagittarius was where the true center of the galaxy was. It turns out that our solar system is not at the center of the Milky Way, but about halfway out, in one of its spiral arms. And those other spiral nebulas – they really are other galaxies, other island universes, far, far away.
Wed Apr 28, 2021 ONWARD CAME THE METEORS!
Back on April 26 in 1803, there was a great bombardment of meteorites in France. This phenomenon was so spectacular that it convinced astronomers that these rocks had come from outer space. When a rock is out in space, prior to its hitting our atmosphere, it’s known as a meteoroid. When it does enter our atmosphere, it’s called a meteor, or more commonly, a shooting or falling star. Big rocks make fireballs, but most meteors are just tiny bits of dust or ice, or a small pebble, that burns up in our atmosphere. The heat of its passage lights up the air around it, which causes the brief flash of light that you see. If a larger rock tumbles to earth, something as large as a bowling ball, say, then there's a good chance that it won't burn up completely, but strike the ground, and become a meteorite, a rock from outer space. That’s what they got back in 1803.
Thu Apr 29, 2021 STARING AT THE SUN
The sun is so bright that it's difficult to look anywhere near it, even with sunglasses, because of its blinding brilliance. And yet it has been carefully studied since long before the invention of the telescope and safe protective filters. The ancient Greeks observed and described large sunspots, at least 40,000 miles across, that sometimes appeared on its face. They did this by watching the sun only during sunrise or sunset when it was dim and red. And on a misty day in the year 1612 in Bavaria, the Jesuit astronomer Father Scheiner first observed sunspots directly through a telescope. As you may have guessed, these methods are definitely NOT safe: even though the amount of visible light is cut down by clouds or by the thick column of air at the horizon, the sun still emits invisible radiation which can blind you. So never stare at the sun, even when it’s cloudy, not even at sunrise or sunset.
Fri Apr 30, 2021 SUN IN ARIES
The earth revolves about the sun, which causes the sun to slowly drift through our sky from west to east. The sun has now entered the constellation Aries, the Ram. This means that because of the earth’s revolutionary motion, the sun is now directly between us and the stars which make up Aries. This obviously is a bad time to be looking for the constellation of the Ram, because the bright sun blocks our view of this part of space. If today’s your birthday, you may have been told that you’re a Taurus, meaning the sun was in Taurus when you were born. But the sun isn’t in Taurus, it’s in Aries, and will be for the next several weeks. When astrology was in its heyday thousands of years ago, the sun would have been in Aries, but because there’s a very slow wobble in the earth’s rotational axis, all the zodiacal signs have been offset by one constellation, turning bulls into sheep, sheep into fish, and so on.