The moon will continue to dominate evening skies worldwide this week. As the moon waxes fuller the eastern side of the moon’s round face will be dramatically lit by slanted sunlight along the terminator — the pole-to-pole zone that divides the moon’s lit and dark hemispheres. Scan your binoculars along that strip of the moon, and then look again on subsequent nights to view new terrain in stark relief.
Starting on Tuesday evening and lasting until dawn, the nearly full moon will pass just to the north of the stars making up the triangular face of Taurus (the Bull). The bright star Aldebaran, which marks the bull’s more southerly eye, will still be visible against the moon’s brilliance. Due to Taurus’ position just south of the Ecliptic, the moon passes near, or through, his face every month.
On Wednesday night, the moon will move to sit between the horns of Taurus and then reach its full moon phase at 12:12 am EST (05:12 UT or Greenwich Mean Time) on Thursday. The December full moon, traditionally known as the Oak Moon, Cold Moon, Long Nights Moon, and the Moon Before Yule, always shines in or near the stars of Taurus. Since it’s opposite the sun on this day of the lunar month, the moon becomes fully illuminated, and rises at sunset and sets at sunrise. Full moons during the winter months at mid-northern latitudes reach as high in the sky as the summer noonday sun, and cast similar shadows.
Indigenous people have their own names for the full moons, which marked time and lit the way of the hunter or traveler at night before modern conveniences like flashlights. The Ojibwe of the Great Lakes region call the December full moon Mnidoons Giizis, the “Blue Moon” or “Big Spirit Moon”. For them it is a time of purification and of healing of all Creation. The Cree of North America call it Thithikopiwipisim, the “Hoar Frost Moon”, when frost sticks to leaves and other things outside.
On Thursday evening, the just-past-full moon will also pass within two finger widths to the lower right (or 2 degrees to the celestial south) of the rich, open star cluster named Messier 35. To see that cluster’s stars despite the bright moonlight, position the moon just outside your binoculars’ or telescope’s field of view.
For the rest of the week, the moon will wane in phase and rise in mid-evening — allowing it to linger into the morning sky.
We lose Jupiter within the evening twilight this week, but Venus and Saturn will remain to dance in the western sky after sunset. Venus’ orbit is currently drawing it away from the sun while Saturn is being carried west towards the sun by Earth’s motion. On Tuesday and Wednesday (December 10–11), ascending Venus will pass less than two finger widths to the lower left (or less than 2 degrees to the celestial south) of Saturn. Extremely bright, magnitude -3.9 Venus will greatly outshine magnitude 0.58 Saturn, but the pair will make a gorgeous sight to unaided eyes, in binoculars, and in backyard telescopes at low magnification. Both planets will set shortly before 7 pm local time this week.
This winter, evening planet-watchers will have to settle for Venus and the ice giant planets Uranus and Neptune. Despite their relatively dim magnitudes and small disk sizes, the delightful colours of those two remote planets make them worthy of a look in backyard telescopes — although they can be tricky to find.
Distant and dim, blue Neptune will set just before midnight local time this week, so you should try to observe it while it is highest in the sky — at 6 pm local time. Neptune is situated among the stars of eastern Aquarius (the Water-Bearer), and is positioned a thumb’s width to the right (or 1.5 degrees to the celestial west) of a medium-bright star named Phi (φ) Aquarii. Both blue Neptune and that golden-coloured star will appear together in the field of view of a backyard telescope at low power. When the bright moon is out of the night sky next week, magnitude 7.9 Neptune will be visible in binoculars. Find Phi Aquarii first and then locate nearby Neptune. Remember that binoculars will display the true positions of the objects, but your telescope will flip and/or mirror-image the view. (To find out what your telescope does to the image, see how it changes the appearance of the moon.)
Blue-green Uranus is located a generous palm’s width to the left (or 7 degrees to the celestial east) of the modest stars that form the “V” of Pisces (the Fishes). It’s also below (or to the celestial south of) the medium-bright stars of Aries (the Ram), and above the head of Cetus.
Uranus is observable from dusk until the wee hours of the night. Shining at magnitude 5.7, it is bright enough to see with or without binoculars under dark skies — and through small telescopes any time. If you view it at about 9 pm local time, it will be highest in the sky — and you’ll be looking through the least amount of Earth’s disturbing atmosphere.
Mercury and Mars are still putting on a show in the eastern pre-dawn sky. This week Mercury will be exiting the scene due to its descent sunward. You can look for medium-bright Mercury sitting very low over the southeastern horizon between 6:45 and 7 am local time.
Red-tinted Mars will rise at about 4:45 am local time and remain visible until dawn. On Thursday morning, Mars will pass very close to the medium-bright, white double star Zubenelgenubi in Libra (the Scales). The planet and the two stars will easily fit within the field of view of a telescope at medium magnification.
From now until October, 2020, Mars will continually grow in brightness — and will increase in apparent size when viewed in telescopes. In fact, the 2020 Mars opposition will be a terrific excuse to get a telescope now so you can practice viewing the planet during the spring and summer months of 2020!
Meteor Shower News 🌠
The Geminids Meteor Shower, always one of the most spectacular of the year, runs from December 4 to 16 annually — so you can begin to watch for Geminids this week. This shower will peak before dawn on Saturday, December 14, when up to 120 meteors per hour are possible under dark sky conditions. Geminids meteors are often bright, intensely coloured, and slower moving than average because they are produced by particles dropped by an asteroid designated 3200 Phaethon.
The full moon in Gemini on the peak night will overwhelm the majority of the meteors for this shower in 2019. Head outside on a clear evening early this week to catch a few while the moonlight is less intense!
The best time to watch for Geminids will be after midnight — but you can start looking for them after full evening darkness sets in. At about 2 am local time, the sky directly overhead, which will be positioned near the bright star Castor in Gemini (the Twins), will be plowing into the densest part of the debris field. True Geminids will travel away from that part of the sky, but don’t just watch that location — the meteors will be shortest there, and they can appear anywhere in the sky.
To see the most meteors, find a wide-open, dark location, preferably away from light polluted skies, and just look up with your unaided eyes. Binoculars and telescopes are not useful for meteors — their field of view are too narrow. Try not to look at your phone’s bright screen — it’ll ruin your night vision. And keep your eyes heavenward, even while you are chatting with companions. If the peak night is cloudy, a few nights on either side of that date will be almost as good. Happy hunting!
Astronomy Skylights for this week for the week of December 8th, 2019 by Chris Vaughan.
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