Skywatch for the week of June 28, 2021
Mon June 28, 2021 HEBER CURTIS
Heber Curtis, born on June 27th, 1872, was an American astronomer who found strong evidence that the Milky Way was but one of many countless galaxies, what he called “island universes” in outer space. In 1920 he presented his work at a meeting of the National Academy of Sciences, citing the discovery of novas, stars that periodically brighten and dim, that could be found among many spiral nebulas. Based on their apparent faintness, he calculated that these novas were millions of light years away – too distant to be within the borders of our own galaxy. He was right! Curtis studied and photographed many nebulas and galaxies, discovered a jet of matter shooting out from the giant elliptical galaxy M87, (we now know it is powered by an enormous black hole at the galaxy’s core), and carefully observed nearly a dozen solar eclipses in his career. A deeply spiritual man, he declared, “The more I know of Astronomy, the more I believe in God.”
Tue June 29, 2021 SEASONAL CONSTELLATIONS
We are now a little over a week into the new season, and summer is definitely sizzling. The change of seasons has also brought a change in the sky and its constellations. The sun has moved from Taurus the Bull into Gemini the Twins, rendering that part of the sky difficult to see. The great constellations of winter, such as Orion the Hunter and Taurus the Bull, can now only be glimpsed just before sunrise, near the eastern horizon. Springtime star patterns such as Leo the Lion or the Big Dipper, which were once at the top of our northern evening sky, have now slipped over into the west, supplanted by Boötes the Herdsman, Hercules the Hero and Virgo the Maiden. And new star groups appear in the east – Libra and Scorpius, and the three bright stars of the Summer Triangle. The sky wheels about us, and the summertime constellations take their places in the heavens above.
Wed June 30, 2021 TUNGUSKA
Several years ago, an early morning fireball lit up the sky over Chelyabinsk, Russia. Shock waves from the impact shattered windows, injuring over a thousand people. Now this wasn’t the first time such a thing had happened. Back on June 30th, 1908, something really big blew up in the atmosphere above the Tunguska region in Siberia. Eyewitness reports sound a lot like the Chelyabinsk event. A brilliant blue light, like a second sun, flashed across the early morning sky. This was followed by a sonic shock wave that broke windows, killed wildlife, knocked people to the ground, and shook the earth. The Chelyabinsk impactor was a rock over fifty feet across. It came in at about 40,000 miles an hour – slow for a meteor – and it broke apart about ten to 15 miles above the surface. The total energy of the blast was roughly equal to that of dozens of atomic bombs. The Tunguska blast was at least five hundred times more powerful.
Thur Jul 1, 2021 CONSTELLATIONS VS. ASTERISMS
Today there are 88 official constellations. Now in the ancient world of the Mediterranean and Middle East, there were less than sixty constellations, owing partly to a lack of knowledge of stars to the south that were never seen from those latitudes. There are (and were) a great deal more unofficial star patterns, called asterisms. In order to be a constellation, everybody has to agree that that’s what it is. An asterism is more personal, and usually a lot easier to see or imagine. So the Great Bear, Ursa Major, includes the stars of the Big Dipper (what we call it here in America,) or the Plough (England,) or the Chariot (ancient Rome.) Cygnus the Swan becomes the Northern Cross, Scorpius becomes the Fish Hook, and Sagittarius the Archer looks like the crude outline of a teapot. When you first start to trace out the constellations, these asterisms will help make the more complex patterns easier to learn.
Fri Jul 2, 2021 4TH OF JULY COSMIC FIREWORKS
On the 4th of July in the year AD 1054, a bright star suddenly appeared in the eastern predawn sky. It was off in the direction of the constellation Taurus, just behind the forward horn tip of the bull. For the next several weeks this new star, this “nova,” was so bright that it could even be seen after sunrise, in the daytime! And then as summer drew to a close, the star faded out of sight and was seen no more. In the western world there is apparently no written record of this star’s appearance: either no one was looking up then, or more likely, the skies were overcast throughout the star’s appearance. But in the east, Chinese astronomers made note of this “guest star,” as they called it, and that’s how we know about it today. If you’re out before sunrise this month, aim your telescope at that part of space behind the forward horn tip of Taurus, and you’ll find the Crab nebula, the exploded remains of a supernova - cosmic fireworks from nearly a thousand years ago.