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December nights normally teem with beautiful celestial objects and breathtaking vistas, but this month also has some rare coincidences to make the skywatching experience even more exciting.
To begin with, Jupiter and Saturn will pair up at the closest conjunction in nearly 400 years and appear closer than they have in nearly 800 years. The two gas giants begin the month with about two degrees of separation from each other in the upper southwest after dark. That distance closes at one degree from 12 to 29 December. The conjunction peaks on 21 when the two are separated by only six arc seconds, about the equivalent of 0.0016 of a degree. The moon, in comparison, is about half a degree.
Try this: On the evening of December 21, train a moderately magnified telescope on Jupiter of magnitude ˗2.0 and on Saturn of magnitude +0.6 so that both spheres are within the same field of view. From this perspective, you will be able to observe both globes and their brightest moons in one go. They haven’t had this closer visible mating since 1226. They’re closer than you’ll likely ever see them, so take this conjunction while you can.
Although they may appear to do so with the naked eye, it is worth noting that at no time do they cross directly in front of each other, known as “mutual concealment”. That event is extraordinarily rare; the last time it occurred was about 8,000 years ago, according to Steve Albers, an associate researcher at NOAA Earth System Research Laboratory.
Another relatively rare event to watch for is the lunar occultation of Venus on December 12. Since the occultation occurs during the daylight hours, you will need a telescope to witness it.
Try this: Around 2:20 pm on December 12, find the 5% illuminated moon with the binoculars low to the west, then train the telescope on the pale lunar crescent to find the tiny Venus nearby. Watch the moon pass in front of Venus at 2:29 pm, hiding it from view. The whole event lasts about an hour, but the moon sets at 3:12 pm before Venus reappears.
Mars is rapidly coming out of its best appearance in over a decade, but there is still time for some reasonably decent observations of the planet’s surface. North of the ecliptic and in an excellent position, Mars hits the north / south meridian at around 8:30 pm at the beginning of the month and around 7:00 pm on the 31st. In medium-sized telescopes, the god of war is barely more than 10 arc seconds, slightly above the useful visibility limit. Moving from magnitude ˗1.1 to ˗0.3, Mars sets in the early morning hours by the end of the month.
The Geminid meteor shower peaks around 6:00 PM on December 13-14, coinciding with the new moon and occurs in dark skies. Most of them appear to radiate from Constellation Gemini, the twin brothers Castor and Pollux, higher above the eastern horizon around 2am on December 14, but they can cross any point in the sky. In very dark skies, the zenith hourly frequency of meteors, fireballs and yellowish-white, red, orange, blue and green fireballs can be as high as 150 per hour. Historically, the maximum meteor force is around 10 hours before and after rush hour, so this year’s display should be exceptionally good.
Unlike most meteor showers, Geminids do not come from streams of dusty debris left behind by comets. The material comes from a 3.1 mile wide asteroid called 3200 Phaethon after the son of Helios in Greek mythology. The “rocky comet” reaches within 12.9 million miles of the sun in its eccentric orbital period of 1.43 years, and the infernal solar radiation of 1,300 ° F explodes and removes the surface material. Rocks and dust ionize in Earth’s atmosphere at 79,000 mph, or 22 miles per second, as the planet passes through Phaethon’s orbital path.
Although few of us have the fortitude to spend 10 hours under the freezing December skies, it is important to keep in mind that, in order to see these “Gems”, the eyes of the sky watcher need about 20 minutes to adjust. adequately to the darkness. Prepare for the bitter cold and become familiar with the dangers in your viewing areas. If you’re going off-piste in search of this best shower, consider letting someone know about your plans.
It is noteworthy that the Perseid meteor shower had been considered the main meteor shower, but the Geminids now surpass them.
The winter solstice is at 3:02 am on December 21st, the beginning of winter and the longest night of the year.
The moon is full at 20:28 on December 29 and is called the Cold Full Moon.
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