Dec30-2020-at-328-GMT-Full-Oak-Moon
Full Oak Moon (Chris Vaughan, Starry Night Education)

This Week’s Sky: December 28, 2020 to January 3, 2021

Ring in the new year as the Earth reaches perihelion and a meteor shower streaks the sky.

Tuesday, December 29 – Full Oak Moon (at 10:28 p.m. EST)

Full Oak Moon (Chris Vaughan, Starry Night Education)

On Tuesday night, the Moon will reach its full phase at 10:28 p.m. EST (3:28 Greenwich Mean Time). The December full Moon, colloquially known as the Oak Moon, Cold Moon and Long Nights Moon, always shines in or near the stars of Gemini (the Twins). Since it is opposite the Sun on this day of the lunar month, the Moon becomes fully illuminated, rises at sunset and sets at sunrise. Full moons during the winter months at mid-northern latitudes reach as high in the midnight sky as the summer noonday Sun, and cast similar shadows.

Indigenous peoples have their own names for the full moons, which marked time and lit the way of hunters and travellers at night before modern conveniences like flashlights. Unlike the regulated western calendar, Indigenous peoples tend to link the full Moon to what is happening in the environment around them. Because this full Moon is occurring just before the start of January, the name for the December or January Moon may apply.

The Ojibwe of the Great Lakes region call the December full Moon Manidoo Giizisoons, the “Little Spirit Moon.” For them, it is a time of purification and of healing of all creation. Their January Moon is Gichi-Manidoo Giizis, the “Great Spirits Moon.” It is manifested through the Northern Lights, and is a time to honour the silence and realize one’s place within all of Great Mystery’s creatures.

The Woodland Cree of the central Canada call the December Moon Thithikopiwipisim, the “Hoar Frost Moon,” when frost sticks to leaves and other things outside. Their January Moon is Opawachikanasis, the “Frost Exploding Moon,” when trees crackle from cold temperatures and extreme cold weather arrives.

Editor’s note: A previous version of this story noted the full Moon was occurring on Wednesday, December 29 at 3:28 GMT. This is the correct time and date, but we changed the time zone in the subheadline to reflect when it would be visible from Canada.

Thursday, December 31 – Algol at minimum brightness (at 7:10 p.m. EST)

Algol at minimum brightness (Chris Vaughan, Starry Night Education)

Algol, also designated Beta Persei, is among the most accessible variable stars for skywatchers. Its naked-eye brightness dims noticeably for about 10 hours once every 2 days, 20 hours, and 49 minutes because a dim companion star orbiting nearly edge-on to Earth crosses in front of the much brighter main star, reducing the total light output we receive. On Thursday, December 31 at 7:10 p.m. EST (or 0:10 GMT on January 1), Algol will reach its minimum brightness of magnitude 3.4, which is almost exactly the same as the star Rho Persei (or ρ Per) that sits two finger widths to Algol’s right. When at its minimum, observers in the Eastern Time zone will find Algol high in the eastern sky. Five hours later, at 12:10 a.m. EST (or 5:10 GMT), Algol will be halfway up the western sky, and will have brightened to its usual magnitude of 2.1.

Saturday, January 2 – Earth at perihelion (at 14:00 GMT)

Earth at perihelion (Chris Vaughan, Starry Night Education)

On Saturday, January 2 at 14 GMT (or 9 a.m. EST and 6 a.m. PST), the Earth will reach perihelion, its minimum distance from the Sun for the year. At that time, Earth will sit 147.093 million kilometres from our star, or 1.67 per cent closer than our mean distance of 1.0 Astronomical Units. As winter-chilled Northern Hemisphere dwellers will attest, seasons on Earth are not controlled by our proximity to the Sun, but by the number of hours of daylight each hemisphere experiences.

Sunday, January 3 Quadrantids Meteor Shower peak (before dawn)

Quadrantids Meteor Shower peak (Chris Vaughan, Starry Night Education)

Named for a now-defunct constellation called the Mural Quadrant, the annual Quadrantids Meteor Shower runs from December 30 to January 12. This shower’s most intense period, when 50 to 100 meteors per hour can occur, lasts only about six hours surrounding the peak, which is predicted to occur on Sunday, January 3 at 10:00 GMT (or 5 a.m. EST). At that time, the Earth will be traversing the thickest part of the debris field. Quadrantids commonly produce bright fireballs owing to the shower’s source, an asteroid designated 2003EH. The best time for viewing Quadrantids will be before dawn, when the shower’s radiant, which lies beyond the tip of the Big Dipper’s handle, will be high in the northeastern sky. Unfortunately, a bright Moon will make it harder to see Quadrantids meteors this year.

Chris Vaughan is a science writer, geophysicist, astronomer, planetary scientist and an “outreach RASCal.” He writes Astronomy Skylights, and you can follow him on Twitter at @astrogeoguy. He can also bring his Digital Starlab portable inflatable planetarium to your school or other daytime or evening event. Contact him through AstroGeo.ca to tour the universe together.

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