Mon Jul 10, 2023 DECLARATION OF INDEPENDENCE
An observatory was built in 1769 in Philadelphia, a couple of hundred feet south of Independence Hall. It was built so that astronomers could observe a transit of the planet Venus that year. Transits occur when either Mercury or Venus passes directly between the earth and the sun; using strong filters, we can safely see those planets as small, dark round dots against the sun’s face. Transits of Venus are rare; they occur in pairs every hundred and twenty years. Seven years after colonial astronomers saw this transit the observatory’s balcony made an excellent platform for the first public reading of the Declaration of Independence, on July 8th,1776. During the Revolutionary War, the Philadelphia observatory housed British troops who occupied the city. And not too many years after the end of the war, the observatory fell into disuse, and sadly, is no longer there.
Tue Jul 11, 2023 FAREWELL SKYLAB
On July 11th, 1979 America’s first space station – Skylab - disintegrated when it re-entered earth’s atmosphere, its debris scattered across the south Pacific and Australia. Built from Apollo moon mission hardware, such as the Saturn 5 rocket’s third stage, it was launched in 1973. Over the next year, three different Skylab crews lived in it and made observations of the earth and the sun and the stars. And it provided lessons that would help us stay alive on future long duration missions, such as those aboard the current space station. There was even a racetrack reminiscent of the one seen in the movie “2001: A Space Odyssey”, where astronauts could run laps around Skylab’s inner circumference! One of my duties when I interned at the Hayden Planetarium was to provide daily updates on the anticipated re-entry time of Skylab. It was indeed a sad day when Skylab met its end.
Wed Jul 12, 2023 VEGA IN THE EAST – VULTUR CADENS
This evening, look toward the east. There’s a bright star over there – its name is Vega, and it’s the fifth brightest star in the night sky. Vega is from an old Arabic word meaning, “falling, (or “swooping,) eagle (or vulture)”. Vega is part of an ancient star pattern known as vultur cadens, which also means, “falling vulture,” although the official constellation here is Lyra, the Harp. On star charts you can sometimes see it pictured as a vulture with a harp inscribed within it. Above Vega are some fainter stars which trace out a simple letter H. The H stands for Hercules, and for his sixth labor, this mythical Greek hero shot arrows at this vulture, and also at two nearby constellations, Cygnus the Swan and Aquila the eagle, driving them away from Lake Stymphalus, where they had picked up the nasty habit of swooping down and attacking any unsuspecting people who wandered by.
Thu Jul 13, 2023 SEASONAL CONSTELLATIONS
We are now three weeks into summer. With the change of seasons also comes 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 Shepherd, 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.
Fri Jul 14, 2023 THE MILKY WAY AND THE LOCAL GROUP
The Milky Way, part of it at least, can be seen tonight under clear dark skies. It spreads across the eastern sky, from Cassiopeia in the north to Sagittarius in the south. The Milky Way is our home galaxy; we live on a planet orbiting a star about two-thirds of the way out from its center. We have satellite galaxies, most notably the Large and Small Magellanic Clouds. And there’s a bigger spiral galaxy about 2 and a half million light years away: its catalog number is M31, but we know it best as the Andromeda Galaxy. Now besides the Milky Way and M31, there are about 30 other, smaller galaxies in the immediate neighborhood (and by “immediate neighborhood,” we mean anything that’s within a million parsecs of here.) This cluster of galaxies is called the Local Group. Most of them are fairly small and contain only a billion or so stars. M31 and the Milky Way are the Group’s gravitational “anchors”.
