This Week’s Sky at a Glance, 2022 December 17 – 24
The most inconspicuous of the zodiac constellations is faint Cancer the Crab, which is nestled between Gemini and Leo. In mythology the crab was sent by the goddess queen Hera to distract Hercules while he was battling the Hydra. The crab was no match for the strongman’s stomp. Ancient Egyptians saw it as their sacred dung beetle, the scarab. In the first millennium BCE the Sun was in Cancer at the summer solstice, the time when it halts its northward motion and slowly starts heading south. This back and forth motion of the rising and setting Sun on the horizon was perhaps reminiscent of a crab sidling on a beach.
The constellation is recognized by a trapezoid of dim but naked eye stars as the crab’s body, with other stars representing the claws and legs. The trapezoid was also seen as a manger flanked by a pair of donkeys, Asellus Borealis and Asellus Australus. On a clear dark night we can see a hazy patch of hay within the manger, and binoculars reveal it as a beautiful star cluster called the Beehive, Praesepe (manger) or M44. Being near the ecliptic, the Moon and planets often pass through or near this cluster. The Beehive was once used to forecast storms, for if it could not be seen it was hidden by light clouds at the front of a weather system. Binoculars reveal another star cluster, M67, less than a fist-width south of M44.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 7:56 am and sunset will occur at 4:34 pm, giving 8 hours, 38 minutes of daylight (7:58 am and 4:42 pm in Saint John). Next Saturday the Sun will rise at 7:59 am and set at 4:37 pm, giving 8 hours, 38 minutes of daylight (8:01 am and 4:45 pm in Saint John). The Winter Solstice occurs on Wednesday at 5:48 pm: Winter has arrived.
The Moon is new on Friday, December 23, giving dark skies for observing over the Christmas weekend. The slim crescent Moon makes a tight triangle with Mercury and Venus, low over the southwest horizon, at 5 pm on Christmas Eve, but binoculars will be needed. Mercury is at greatest elongation from the Sun on Wednesday, within a wide binocular view to the upper left of brighter Venus. Saturn is setting before 9 pm by midweek, while Jupiter is at its highest around 8:30; around which time telescope users might catch its Great Red Spot on Monday. On Tuesday a telescope will show Jupiter’s icy moon Europa reappear from behind the planet at 6:14 pm, disappear into the planet’s shadow 12 minutes later, and reappear at 8:56. In Taurus, Mars continues to outshine all of the bright stars of the Winter Circle, but by next weekend it will have dimmed to the brightness of Sirius. The moonless sky on Thursday night improves our chances of seeing some meteors of the Ursid shower, which emanate from near the bowl of the Little Dipper in the north.
On Sunday evening at 8 pm, tune in to the Sunday Night Astronomy Show via the Facebook page or YouTube channel of Astronomy by the Bay.
Questions? Contact Curt Nason