Sky Report

Stellar Vista Observatory Sky Report

John Mosley

December 12-18

The Sky Report is presented as a public service by the Stellar Vista Observatory, a nonprofit organization based in Kanab, Utah, which provides opportunities for people to observe, appreciate, and comprehend our starry night sky. Additional information is at www.stellarvistaobservatory.org. Send questions and comments to John@StargazingAdventures.org.

THE astronomical event this week is the finest meteor shower of the year. Although it’s the year’s best, few people watch it for the simple reason that it’s COLD in mid-December. Still, curious minds want to stay informed.

The shower is called the Geminids because the meteors radiate from the direction of the constellation Gemini, and Gemini is in the northeast beginning around 9 p.m. This means that you can begin seeing meteors as early as 9, although as the radiant point rises higher you’ll see more meteors. The peak is on the morning of the 14th, so the best time to look is late on the evening of the 13th and through that night with second choice being the following night. At maximum at 2 a.m. (when the radiant is at its highest) from a dark location you might see one meteor every minute or two, and these meteors are quite swift. Unfortunately bright moonlight will compromise the view.

Meteors come from comets, and they’re dust shed from the dirty snowball as it evaporates in warm sunlight. These particles follow along in the orbit of the comet, and when the earth passes near that orbit, as we do at the same time each year, we see a meteor shower. But the Geminids are different! They come from a puzzling object that is either a “dead” comet or an asteroid, and it’s named Phaethon. When discovered in 1983 it was classified an asteroid, one of the many thousands of rocky bodies that mostly orbit between Mars and Jupiter. It has no tail, but its highly elliptical orbit matches the orbits of the meteors so somehow they come from it — just how is not understood. Or it could be a comet that has lost all its ice and no longer has comet-like activity but somehow continues to shed particles. Either way, it produces a fine meteor shower.

Turning to planets, Mars was closest to earth just two weeks ago but it remains essentially as close – and as bright — into the new year. It now rises before sunset so you can see it rising in the east as the sky is growing dark. Mars is nearly overhead in the south at around midnight, and be sure to look for it low in the west at around 5 a.m. It’s brighter than any star, and its yellow-orange color comes from rusted minerals in its soil. Its red color caused earlier people to associate it with blood and with war. Mars is in Taurus, north of Orion.

Jupiter is twice as bright as Mars, and it’s high in the south as Mars is rising in the east. Jupiter sets at around midnight.

Last – and least – is Saturn. At 7 p.m. Saturn is half as high as Jupiter, to the 4 o’clock position from Jupiter. It’s only 1/20th as bright as Jupiter; it’s as bright as the brighter stars, but that’s still brighter than any stars that are near it.  

Phaethon is not quite 4 miles across, and at a distance of 1.1 million miles it appears point-like in all optical telescopes, but the giant Arecibo Telescope in Puerto Rico was able to bounce radar beams off it 5 years ago and create this blurry image. Credit: Arecibo/NASA/NSF.

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