This is Dudley Observatory’s Skywatch Line for Friday, December 11, through Sunday, December 13, written by Alan French.
With the Moon reaching new early Friday, the weekend will be dark and moonless. A young crescent Moon, however, will make a brief return to Sunday evening’s sky as darkness falls.
On Sunday at 5:00 pm look for the slender Moon just over 15 degrees above the southwestern horizon. As the Sun moves farther below the horizon the southwestern sky will darken and the Moon will move lower, but the Moon will not set until 6:54 pm.
If you were standing on the Moon a bright, nearly full Earth would be a lovely sight in your skies. Sunlight reflected from Earth shines on the entire visible face of the Moon, brightening the large area experiencing night there. This allows you to see the entire Moon – a bright crescent with the rest of the lunar surface aglow with Earthshine. It is a lovely sight, and with the right foreground could be the subject of a great photograph. Vary your exposures to get one with just the right balance between the crescent and the rest of the Moon. Too long an exposure and the crescent will be overly bright and details will vanish. Too short an exposure and the Earthshine will not show well. (Don’t forget a tripod to keep the camera steady during the relatively long exposures.)
The absence of the Moon is good news for sky watchers – this weekend starts the peak of the annual Geminid meteor shower. The shower will be at its peak on the night of Sunday, December 13 and morning of Monday, December 14, and night of December 14 and morning of Tuesday, December 15. The Geminids rivals the Perseids of August as the best and most reliable meteor shower of the year.
The weather is certainly more agreeable for the August Perseids, but there are no biting insects to provide a distraction in December. Just be sure to dress extra warmly so you won’t get chilled. Since you won’t be active you’ll need more layers than you need when outside for normal winter activities.
If you trace the path of the shower’s meteors backwards, they will all intersect in the constellation Gemini at what is called the “radiant.” As darkness falls, the radiant will be low and few meteors will be seen. If you do see one then it will likely be a long one. As the radiant rises higher, more meteors will be visible, and by about 10 pm the show should be in full swing.
The best views will be from dark skies away from city lights. A reclining lawn chair is ideal for meteor watching. Look high in the sky but facing toward the radiant, which is not far from the star Castor, in Gemini. It is high toward the east at 11 pm and was low in the north northeast early in the evening.