Sky Power Blog Post #8 — Look Up! Meteor Showers and the Solstice

Look UP! Joe Jordan on Night Sky Happenings

What’s going on in the night sky? This week (Wed.,12/7 in U.S. time zones) the full moon “backslid” across bright Mars, so an “occultation” was visible in much of the country (where the sky was clear enough). As the earth rotates west-to-east on its axis, the sky appears to turn east-to-west — but the moon’s doing its own orbit west-to-east around the earth (taking about a “moonth” to go all the way around!), so moon’s apparent nightly westward motion is a tad slower than the stars & planets — so once in awhile it “backs over” something (as just happened with Mars). An “occultation” is basically an eclipse, or cutting off of something from our view. The root of the noun “the occult” (mysterious, strange) is “the hidden“: the moon is hiding some other celestial object from our view! …… +

+ …. Something still in the future (if you’re seeing this before Tues.,12/13) is the best meteor shower of the year: the Geminids — so named because the abundant “shooting stars” (maybe a couple a minute on average!) appear to be streaming out of constellation Gemini (the Twins), as we here on earth speed around the sun (at over 20 miles a second!) in that direction (roughly toward Gemini), while crossing the rich debris trail of an old asteroid — so we get the same visual effect (pattern radiating out from a central point) as when we drive at night through a snowstorm with the high beams on! (Some folks call that diverging movement pattern the “Star Trek effect”– as if we could be flying fast enough through stars and galaxies to make them stream out radially toward us.) This meteor shower is also great because (unlike many others) the Geminids are flashing and burning through our atmosphere all night long — from dusk to dawn.

About a week after the peak of the Geminid meteor shower, the December solstice occurs — starting northern hemisphere winter, at the same time as southern summer. And that time will be 1:48 PM PST, or 4:48 PM EST, or 9:48 PM “Universal” [Greenwich] Time — the moment when the sun will be directly overhead at some point along the Tropic of Capricorn: the southern limit of the band or belt around the earth where the sun can be seen overhead — a zone of latitudes centered on the equator, that’s 47 degrees wide (twice 23-and-a-half degrees). The sun at this time of year is (roughly) in front of constellation Capricorn — (and ~ Cancer at the June solstice) — hence the names for those tropics limit-latitude lines!

A note here on the meaning / origin of this word, “SOLSTICE” … Let’s say you’re tracking the shift, from day to day, of the sunset point along the western horizon. This time of year the sun is setting quite far to the south of due west, already — and it’s shifting farther and farther south at each successive sunset — but the southward march of that sunset point is slowing down now, to where the shift is barely perceptible from one day to the next. Right at the solstice, it turns around and starts the half-year march back northward — and when something turns around to reverse direction, it has to STOP for just a moment, right? … So that’s basically what the “sol-stice” means: “sun-stands-still“. On that day the sunset position reaches its farthest-south point, halting its daily progress from right-to-left along the western horizon. During all of the following half-year, its daily shifts will be from left-to-right (heading back northward toward the next turnaround at the June solstice).

All this and quite a bit more was recently discussed by this writer in a fun (and pretty funny at times!) radio interview that you can still (for some while longer) catch via the link at the top of this post or at the radio’s website home-page < http://KSQD.org > . … Enjoy! And, keep an eye on the sky! ***