Mon June 24, 2024 PLUTO AND ITS MOONS
On June 21st, 1978, Pluto's moon Charon was discovered by the American astronomer James Christy. In mythology, Pluto was god of the underworld. Charon was his ferryman, who transported souls across the river Styx to the other side. Styx is another, more recently discovered moon, along with three more – Hydra, Nix and Kerberos. Charon is the biggest one, it’s about half the size of Pluto. So when it orbits this distant world, Charon's mass has a substantial effect on Pluto, pulling it first one way, and then the other. In the year 2015, a space probe flew past Pluto and Charon, and sent back incredible pictures and information – ice mountains two miles high, vast nitrogen ice plains, and mysterious dark patches on Pluto’s farside. If you visit the website NASA dot gov, and enter the word “Pluto” in the search box, you can see these pictures for yourself.
Tue June 25, 2024 NAKED-EYE SKYWATCHING/TCAS MEETING
When you first get interested in astronomy, you're often tempted to go out and buy the biggest, best telescope you can get. But there are a lot of things you can observe with just your eyes alone. From the comfort of a lounge chair, you can gaze at the moon’s maria, dark basaltic lava basins that were once thought to be watery seas. Stars tend to twinkle, but planets, which also look like stars because of their great distances, shine with a steady light. Both stars and planets display subtle shades of color. And shooting stars, or meteors, also streak across the darkened sky, usually one or two such displays every 10 to 15 minutes. If you’re interested in looking at the sky, either with or without a telescope, then come to tonight’s get-together of the Treasure Coast Astronomical Society, which will be at 7:30 pm at the Science Center on the Fort Pierce campus of Indian River State College. This event is free and open to the public.
Wed June 26, 2024 ERATOSTHENES MEASURES THE EARTH
In late June, in the year 240 BC, the astronomer Eratosthenes calculated the size of the earth. He did it by using the changing angle of sunlight at different latitudes in Egypt. Eratosthenes made two assumptions: 1. the earth is round; 2. the sun is far away, so its rays fall parallel across the whole earth. At Alexandria, the sun is about 83 degrees, or 7.2 degrees off the zenith) at noon on the first day of summer. 500 miles to the south was a town called Syene, where on the same day, the sun’s image at noon could be seen reflecting off the water at the bottom of a deep well. There the sun was at 90 degrees altitude, directly overhead. The Alexandria - Syene distance must therefore be 7.2/360th, or a fiftieth of the earth’s circumference. Now Syene was 500 miles away, so he multiplied 500 by 50, and got 25,000 miles for an answer. He was off by a hundred miles – “pretty good work for 2,263 years ago!”*
*Carl Sagan quote from “Cosmos”
Thu June 27, 2024 HEBER CURTIS
The American astronomer Heber Curtis was born on June 27th, 1872. He 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 revealed that he had found novas, stars that periodically brighten and dim, nestled among many spiral nebulas. Because they were very dim, 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.”
Fri June 28, 2024 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. It 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, which 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.
