This Week’s Sky at a Glance, 2021 December 11 – 18
~by Curt Nason
The year’s best meteor shower radiates from near the star Castor in Gemini early this week, with Monday and Tuesday mornings being the peak times. Under ideal conditions the Geminids can average two shooting stars per minute, but don’t expect to see anywhere near that number. With Gemini rising soon after an early sunset and riding high just after midnight, convenient evening viewing is rewarded more often than for the showers from Perseus and Leo, which rise much later on their peak nights. This year the Moon sets around 3 am on the peak mornings, providing several hours of a darker sky for night owls and early risers.
The Geminids are relatively slow and easier to catch with the eye, and they often have a golden glow. Dress very warmly, get comfortable in a reclining position, face an unobstructed patch of sky away from artificial lighting, and hope for a cloudless sky. Viewing on the days before and after could also be worthwhile if the weather forecast isn’t promising for the peak times.
The parent “comet” for the Geminids is actually the asteroid 3200 Phaethon, which was discovered in 1983. It orbits the Sun in a little more than 17 months, crossing the orbits of Mars, Earth, Venus and Mercury. At perihelion its temperature can exceed 600 C, which can cause its carbon-water material to break down and release the pebbles and dust particles that give us meteors when they burn up in our atmosphere.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 7:51 am and sunset will occur at 4:33 pm, giving 8 hours, 42 minutes of daylight (7:53 am and 4:41 pm in Saint John). Next Saturday the Sun will rise at 7:56 am and set at 4:34 pm, giving 8 hours, 38 minutes of daylight (7:58 am and 4:43 pm in Saint John).
The Moon will be going through its waxing gibbous phase throughout the week, providing interesting evening views for binocular and telescope users, particularly this weekend. Venus is stationary on Friday and soon it will plummet sunward toward inferior conjunction on January 8. Jupiter and Saturn continue their westward crawl against the stars, while speedier Jupiter lengthens the distance between them. The shadow of its moon Io crosses the planet for telescope users between 5:38 and 7:54 pm Tuesday, with Io ending its transit about halfway between. Mars can be seen with binoculars in the morning sky, rising shortly after 6 am.
Comet C/2021 A1 Leonard, the best comet of the year, had been a binocular object in the morning sky for the past week. It makes its closest approach to Earth this weekend and therefore it is moving rapidly across the sky; unfortunately into twilight but it should be bright enough for a binocular view. Your best chance could be next Friday or Saturday around 5:30 pm in evening twilight when it passes about a binocular width below Venus.
Questions? Contact Curt Nason.