Gathered ‘round the campfire, folks don’t sit still. One draws close, another pulls back. Then the first pulls back, the other draws close. Folks adjust how much heat and light they get.
Nor do planets, orbiting the sun, sit still. Planets draw close and pull back, altering how much heat and light they receive.
Back in school, we learned that Earth orbits ninety-three million miles from the sun. True, but that’s an average. Right now – today – the Earth/sun distance is a mere ninety-one-and-a-half million miles. It will shrink a bit more, until the first week in January.
Earth draws closest to the sun in mid-winter, recedes farthest from the sun in mid-summer. Distance from the sun does not define the seasons (more on that in the future).
Mars, too, swoops in and out, toward and away from the sun. As Earth and Mars dance around the sun, they draw close to each other, then away. The two planets are at their closest right now, explaining the bright glow of the red-orange planet on recent nights.
Earth, sun and moon sometimes arrange themselves in a straight line. The word for such a line-up is “syzygy” (SIH-zih-gee). A syzygy that puts Earth between sun and moon occurs this Wednesday night, giving us a full moon.
Another, different syzygy also occurs Wednesday night: Earth, sun and Mars will line up, Earth in the middle. As with the moon, this syzygy gives us a “full Mars,” further explaining the planet’s bright glow.
The two syzygies will merge – briefly – into one, Wednesday night: Sun, Earth, moon and Mars will lie on the same line. For one hour and one minute, then, planet Mars will disappear.
Students of the occult seek hidden knowledge; the word “occult” relates to things hidden.
Just after 6:30 p.m. Wednesday, when sun, Earth, moon and Mars share the same syzygy, lie on the same line, Mars will be hidden – occulted – by the moon.
Wednesday’s Martian occultation begins just after 6:30. Head out before that, so as to catch Mars before it’s overwhelmed by the moon’s glare.
There’s another challenge: The four-way syzygy sets up shortly after moonrise, so the occultation will take place rather low on the eastern horizon. A good view of the eastern horizon will be needed to catch the occultation.
After the occultation, moon and Mars will remain close together in the sky all night, higher and easier to see.
The Artemis mission launched on its test flight toward the moon last month. Since then, the Orion crew capsule has flown far beyond the moon, circled back, and will return to Earth next weekend.
There’s no crew aboard Orion on this flight. The capsule’s reentry into Earth’s atmosphere – faster than the speed at which any Apollo capsule re-entered – is one of the mission’s major tests.
NASA will live-stream the ocean splash-down, off the coast of San Diego, Sunday morning.
CLASSES
A number of readers have inquired about classes. I’ll be starting a new science and nature class, for adults and older kids, in January. Please get in touch if you’re interested.
Al Stahler enjoys sharing science and nature with friends and neighbors, in The Union and on KVMR-FM. He teaches classes for both kids and grown-ups, and may be reached at a.a.stahler11@gmail.com.
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