Skywatch for the week of July 25, 2022
Mon Jul 25, 2022 THE DOG DAYS
These are the "dog days" of summer. The sun was highest in our noon sky on June 21st, but it takes the air a month to really sizzle. These are called the dog days because it's at this time of the year that you can first catch sight of the brilliant star Sirius, also known as the Dog Star, low in the southeast, rising just before the sun. Sirius is the brightest star in the night sky, partly because it’s a big, hot star, but mainly because it’s closer to us than most other stars, only about 54 trillion miles away! Its name is from the Greek word, "seirios," which means, “the scorcher.” Sirius is in the constellation Canis Major, the Big Dog, and that’s why it’s called the Dog Star. Sirius was feared and hated by the ancient Greeks and the Romans, who thought that when the sun and Sirius got together, their combined heat burned up the crops, drove dogs mad, and made everybody miserably hot.
Tue Jul 26, 2022 SUMMER STAR COMPARISONS
Stars vary in brightness and temperature, color, mass and size. Antares is a red supergiant in the southern sky this evening; it could fill half our solar system. High in the east is the blue giant star Vega, many times hotter and more massive than our sun. To the south of Vega is Barnard’s Star, a cool red dwarf so dim that it cannot be viewed without a telescope. There are also white dwarf stars only the size of the earth, plus compact neutron stars, more massive than the sun, but just a dozen miles across; or black holes, mere pinpoints of superdense matter, such as Cygnus X-1 in the middle of the Summer Triangle in the eastern sky. And overhead tonight, in the constellation Hercules, a great globular star cluster called M13, contains a million stars! Each star in the Universe is unique, possessing within it the secret of its own creation and demise.
Wed Jul 27, 2022 THOMAS HARRIOT BEATS GALILEO
Toward the end of July in the year 1609, the Englishman Thomas Harriot made the first detailed drawings of the moon as seen through a telescope. Galileo would make his drawings several months later, not quite as good as Harriot’s, but while Galileo became famous, hardly anyone has ever heard of Harriot. Galileo published his discoveries in a widely read book, “The Starry Messenger.” Harriot wrote manuscripts, but never published a book for public consumption. Harriot led an interesting life, accompanying Sir Walter Raleigh to the Roanoke colony in America, serving as mathematician, navigator and interpreter. He was briefly imprisoned in 1605 on account of suspicions that he had been part of the assassination attempt on King James 1. He was innocent and released, but this may have made him less eager to publish, not wishing to draw attention to himself.
Thu Jul 28, 2022 GALILEO SEES SATURN
On July 30th in the year 1610 Galileo set up a small, hand-made telescope on his veranda in Padua, and aimed it at a bright yellow, star-like object in the night sky – the planet Saturn. So what did he see? Just a big round blob of light, and on either side, two smaller blobs. Were these two large moons of Saturn? Did the planet have handles? Or ears? He couldn’t tell. His crude telescope only magnified objects about 30 times, which wasn’t enough to resolve the mysterious somethings that flanked the sixth planet. Galileo recorded what he saw, then moved on to other discoveries. It wasn’t until 1655 that better telescopes resolved those blobs into rings. Now, 400 years later, even small telescopes are good enough to see the rings of Saturn; late this evening you’ll find the ringed planet low in the southeastern sky in the constellation Capricornus.
Fri Jul 29, 2022 DELTA AQUARID METEOR SHOWER
A meteor shower is going on right now. It’s called the Delta Aquarid meteor shower, so named because these meteors come out of the constellation Aquarius, near its fourth brightest star, Delta Aquarii. Meteor showers are caused by tiny bits of comet dust; when this dust hits the earth’s upper atmosphere, it vaporizes, which then heats the air the dust passes through, lighting it up as a momentary streak of light in the night sky – that’s a meteor, also called a shooting star or falling star. This shower will be strongest after midnight. Go outside as late as you can and get away from bright streetlights. Dress warmly, protect yourself against mosquitoes, lie back in a lounge chair and look up high in the east for best results. This is a long-lasting shower which will continue until mid-August; but the best viewing will be the next two nights.