This Week’s Sky at a Glance, 2021 November 13 – 20
~by Curt Nason
At the mercy of the weather, night-owl stargazers or very early risers could be treated to a deep partial lunar eclipse on Friday morning. This is our first lunar eclipse since January 2019, as we missed one that started at moonset in May.
Although the full Moon starts slipping into Earth’s dark shadow, called the umbra, at 3:18 am, look for subtle gray shading on the lunar surface beginning a half hour sooner. This is the penumbra, a lesser shadow created when Earth partly covers the Sun as seen from the Moon. From 3:18 the umbra will creep across the lunar surface, reaching maximum eclipse at 5:03 with 97% of the Moon in shadow and creating a diamond ring effect. Note that the umbra appears on the left side, which indicates the Moon is moving eastward in its orbit rather than the westward motion we see as our planet rotates. Also, note the curvature of the shadow. Aristotle noticed this in the fourth century BC and correctly assumed it was because the Earth is spherical.
The Pleiades star cluster, also called the Seven Sisters and M45, will be just above the Moon. Use binoculars to watch for more stars to appear in the cluster as the sky darkens toward maximum eclipse. The partial phase lasts for three and a half hours, ending at 6:47 am. The Moon could take on a red or orange hue during mid-eclipse, caused by our atmosphere acting like a lens and bending the red part of the sunlight toward the Moon. Moonset occurs before the end of the penumbral phase but it would be too difficult to see it then anyway. The next lunar eclipse, a total one, will occur on May 15/16 next year.
This Week in the Solar System
Saturday’s sunrise in Moncton is at 7:17 am and sunset will occur at 4:49 pm, giving 9 hours, 32 minutes of daylight (7:20 am and 4:56 pm in Saint John). Next Saturday the Sun will rise at 7:27 am and set at 4:42 pm, giving 9 hours, 15 minutes of daylight (7:29 am and 4:49 pm in Saint John).
The full Moon passes almost completely within Earth’s shadow on Friday morning, a deep partial eclipse.
With the time change Saturn now sets around 10:10 pm this weekend, followed by Jupiter at 11:30. Venus is a few weeks away from being at its brightest and commands attention in the southwest as evening twilight fades. Mars can be seen, with luck, rising an hour before sunrise while Mercury is plunging sunward. The Leonid meteor shower peaks on November 17/18 but don’t expect much for fireworks. A few times over the past two centuries this shower has produced meteors at a rate of greater than ten per second.
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.