Al Stahler: Looking for the center
Two bright points of light have hung in the southern sky for months now — one white, the other red: Venus and Mars, perhaps?
Problem: Mars is a “wanderer” … in Greek, a “planet.” Mars wanders through the zodiac, lurking first in this constellation, then in another. Whereas this red-colored object remains forever in the scorpion. It’s a star … it’s the heart of the scorpion.
Ancient sky-watchers noticed the resemblance between the scorpion’s heart and planet Mars, and named the star the “rival of Mars” … Anti-Ares … Ares (“airies) being the Greek equivalent of the Roman god of war. Say “Anti-Ares” fast and it becomes Antares — the name of the star that is the heart of the scorpion.
The white point of light, on the other hand, does wander. It is, indeed, a planet. But could it be Venus?
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Venus, remember, orbits closer to the sun than Earth. So, to see Venus from Earth, we’ve got to look more-or-less toward the sun, which is why Venus appears either as the “morning star,” in the east before sunrise (as it did last winter), or as the “evening star,” in the west after sunset (as it will this winter).
This planet we’re looking at now, though, hangs in the south. It’s planet Jupiter.
If you’ve got binoculars, and you brace your elbows on something solid, you’ll see, in your binocs, several other points of light — maybe four of them — forming a ragged line, to one side or the other, or on both sides of Jupiter.
These are moons of Jupiter, and they got the astronomer Galileo in big trouble. If you make note of the positions of the moons — I suggest you draw a diagram — then look again in an hour or two, you’ll see that they’ve moved — they’re still in a ragged line, but one or more will have moved sideways — closer to, or farther from Jupiter. Galileo realized that it was like watching a particular horse go ‘round on a carousel – it moves across your field of view, left to right, then right to left, over and over. Jupiter’s moons must be orbiting Jupiter.
Now, on Earth, we see sun, moon and stars rise in the east, move through the sky and set in the west. It would seem obvious, then, that sun, moon and stars are circling the Earth. Conclusion: Earth must be the center of the universe.
Or so it was thought, until Galileo presented his disturbing discovery concerning the moons of Jupiter. Perhaps Earth was not the center of the universe … which contradicted the teachings of the church, and got Galileo hauled before the inquisition.
This was not that long after the astronomer Giordano Bruno had been burned at the stake for doing astronomy, so we can forgive Galileo for admitting his error, for agreeing that Earth is the center of the universe.
Today we can safely say that Earth is not the center of the universe … that the sun anchors the solar system. But could the sun be the center of the galaxy … all the stars we see at night? Looking outward, we see the same number of stars in every direction … it sure looks like we’re at the center.
It was in the 1920s that an astronomer discovered something off-center in our sky: Great balls of stars – globular clusters – each composed of hundreds of thousands of stars. Dozens of such spheres … centered, not on the sun, but around something off in the direction of the constellation Sagittarius. He had discovered the center of the galaxy.
This Saturday night, local astronomers will set up scopes at the junction of state route 49 and the old Downieville Highway, to look at Jupiter and its moons; at globular clusters (some of the prettiest things you can see in a scope); and to enjoy Sagittarius, the scorpion, and a dozen other constellations. It’s free – bring the kids, and – especially – bring a sweater.
Al Stahler enjoys sharing nature with friends and neighbors. His science and nature programs may be heard on KVMR (89.5 FM), and he may be reached firstname.lastname@example.org.
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