Hello everyone! We’ll have a waxing crescent Moon in our early evening skies this week but its light shouldn’t keep you from finding something glorious in the eastern sky although the pesky clouds of rainy season could be a problem.
There are other clouds in our summer sky besides those rain clouds. To find them, just motor to your favorite dark spot on the island and face east at about 8:00 p.m. If there aren’t too many rain clouds in that direction, you’ll see a band of clouds that doesn’t appear to move. Those clouds are far beyond the reach of earthly wind. They are the uncountable stars of our galactic home, the Milky Way. If you’re facing east, to your right you’ll see a giant fish hook in the sky. That’s the tail of Scorpius the Scorpion. The center of our galaxy is between the hook in the Scorpion’s tail and the spout of the teapot in Sagittarius.
Though you feel absolutely stationary as you lie in your lounge chair contemplating the galactic wonders, you are actually traveling in several different directions at once at incredible speed. If you contemplate the starry wonders for more than a few minutes, you’ll notice something interesting. If you find a star near the eastern horizon and look at it later, you’ll see that it’s higher in the sky. The star isn’t moving; you are, at 1006 mph as the Earth spins.
Next, look at your watch and note the exact time. Find the Scorpion’s tail in the southeastern sky and notice where it is in relation to the horizon or a coconut tree or some other landmark. Then next week, go back to the same spot at the same time and look for the Scorpion’s tail. It won’t be in the same place because your sky view has shifted. Earth, the giant spaceship we all ride, has traveled a significant distance in its orbit. As you sit there in your lounge chair, you are also travelling at 66,000 mph as the Earth goes around the Sun. Spaceship Earth travels significantly faster than most of the spaceships we’ve launched into space. As you absorb that incredible speed, you should also realize that you’re riding a much larger merry-go-round than Earth’s orbit around the Sun.
Our galaxy is huge; so big that it’s hard to grasp the size. Like all spiral galaxies, the Milky Way is a flatted disc of stars. It’s about 100 light years thick out here in the galactic suburbs and it’s about 100,000 light years across. It has the same proportions as a CD with a slightly bulging center. The Sun is located about halfway out on one of the spiral arms and the galactic center, there off the Scorpion’s tail, is about 25,000 light years away.
The Earth orbits the Sun because it has to; if it didn’t endlessly fall around the Sun, the Sun’s gravity would pull it in. The same is true of the Sun. Our Sun and all the other stars in the galaxy endlessly fall around the galactic center. The closer you are to a gravity mass, the faster you must go. Mercury orbits the Sun at over 100,000 mph and stars close to the galactic center must whirl around it at incredible speed. But hey, we’re way out here in the suburbs so how fast can the Sun go? The Sun orbits the galactic center at almost 500,000 mph. And we’re being dragged along for the ride. Have a great trip!
And speaking of great trips, I’m in Baton Rouge, Louisiana for the 21st meeting of the International Planetarium Society so the UOG Planetarium will be closed until 6 August. I hope to see all of you at a Planetarium show soon!