Sinus Iridum’s Golden Handle (Chris Vaughan, Starry Night Education)

This Week’s Sky: October 26 to November 1, 2020

As the Moon waxes to full just in time for Halloween, set your sights on its features and neighbours in the sky.

Tuesday, October 27 all night – Sinus Iridum’s Golden Handle

Sinus Iridum’s Golden Handle (Chris Vaughan, Starry Night Education)

On Tuesday night, October 27, the pole-to-pole terminator that divides the lit and dark hemispheres of the waxing gibbous Moon, will fall just to the left (or lunar west) of Sinus Iridum, the Bay of Rainbows. The circular, 155 mile (249 km) diameter feature is a large impact crater that was flooded by the same basalts that filled the much larger Mare Imbrium to its right (lunar east) – forming a rounded, handle-shape on the western edge of that mare. You can see it easily with sharp eyes and binoculars. A “Golden Handle” effect is produced by the way slanted sunlight brightly illuminates the eastern side of the prominent Montes Jura mountain range that surrounds the bay on the top and left (north and west), and by a pair of protruding promontories named Heraclides and Laplace to the bottom and top, respectively. Sinus Iridum is almost craterless, but hosts a set of northeast-oriented dorsae or “wrinkle ridges” that are revealed in a telescope at this phase.

Thursday, October 29 all night – Bright Moon near Mars

Bright Moon near Mars (Chris Vaughan, Starry Night Education)

In the eastern sky after dusk on Thursday, October 29, the nearly full Moon will be positioned only a few finger widths below (or 4 degrees to the celestial southeast) of Mars — close enough to appear together in most binoculars (red circle). As the duo crosses the sky together during the night, the diurnal rotation of the sky, and the Moon’s eastward orbital motion, will combine to shift the Moon clockwise around Mars – placing it a generous palm’s width to the upper left of the red planet in the western sky by sunrise on Friday morning.

Friday, October 31 around 05:02 GMT – Bright Moon occults star Xi1 Ceti

Bright Moon occults star Xi1 Ceti (Chris Vaughan, Starry Night Education)

Overnight on Friday, October 30, observers using binoculars and backyard telescopes (red circle) in most of North America can see the almost-full Moon occult the medium-bright star designated Xi1 Ceti (or ξ1 Ceti). The magnitude 4.35 star marks the top of the head of Cetus, the Whale. In the Great Lakes region, the occultation will run from approximately 2:38 a.m. to 3:27 a.m. EDT. Ingress and egress vary based on your latitude, so start watching a few minutes before the times quoted above — or use Starry Night or another planetarium app to look up the exact times for your town. 

Saturday, October 31 at 14:49 GMT – Small Full Blue Hunter’s Moon

Small Full Blue Hunter’s Moon (Chris Vaughan, Starry Night Education)

On Saturday at 10:49 am EDT, the second full Moon of October will occur. Since the full phase will occur on Saturday morning in the Eastern Time Zone, folks there will see that the Moon is slightly less than full on Friday night, and slightly past full on Halloween night. Use your binoculars or telescope to look for some texture in the craters along the Moon’s left-hand (western) rim on Friday and along its right-hand (eastern) rim on Saturday. Only people living in Eastern Europe, the Middle East and Eastern Africa will see the Moon rise when it’s exactly full.

This full Moon is traditionally called the Hunter’s Moon and, appropriate for Halloween, the Blood Moon, or Sanguine Moon (not to be confused with an eclipsed “blood moon”).

Indigenous groups have their own names for the full moons, which helped light the way of the hunter or traveller at night. The Anishinaabe people of the Great Lakes region call this Moon Binaakwe-giizis, the Falling Leaves Moon, or Mshkawji-giizis, the Freezing Moon. Cree peoples of central Canada call the October Moon Opimuhumowipesim, the Migrating Moon — the month when birds are migrating. The Haudenosaunee (Iroquois / Mohawk) of Eastern North America call it Kentenha, the Time of Poverty Moon.

This full Moon will occur only 20 hours after reaching its greatest distance from Earth, or apogee, producing the smallest full Moon of 2020. It’s the opposite of a “Supermoon” — perhaps this one should be called a Punymoon! Because the last full Moon occurred on October 1, this second one during the month will be a “Blue Moon,” but the Moon will not sport any unusual colouration at all.

Saturday, October 31 all night – Uranus at opposition

Uranus at opposition (Chris Vaughan, Starry Night Education)

Uranus will reach opposition on Saturday, October 31. On that night it will be closest to Earth for this year at a distance of 1.75 billion miles, 2.81 billion km, or 156 light-minutes. Its minimal distance from Earth will cause it to shine at a peak brightness of magnitude 5.7 and to appear slightly larger in telescopes for a few weeks. At opposition, planets are above the horizon from sunset to sunrise. During autumn this year, the blue-green planet will be located below the brightest stars of Aries, Hamal and Sheratan, while moving slowly retrograde westwards towards the constellation of Pisces.

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.

Editor’s note: The times of the Moon’s occultation of Xi1 Ceti were incorrect in an earlier version of the article. SkyNews apologizes for the error.