Double stars in Lyra's parallelogram on August 21, 2022 | SkyNews
Double stars in Lyra's parallelogram on August 21, 2022 (Chris Vaughan, Starry Night Education)

This Week’s Sky: August 15 to 21, 2022

After the Moon meets the bluish Pleiades and red Mars, it goes on its way to third quarter, allowing deep-sky objects to shine through

Every week, SkyNews publishes a list of key events in the Canadian sky in This Week’s Sky. This series gives you all the latest news in Solar System movements, including where the planets are in our sky and Moon phases. From eclipses to meteor showers, This Week’s Sky keeps you updated on the best in upcoming astronomical highlights.

Monday, August 15 – Two shadows and the Great Red Spot cross Jupiter (from 3:59 to 05:39 UTC)

Two shadows and the Great Red Spot cross Jupiter on August 15, 2022 | SkyNews
Two shadows and the Great Red Spot cross Jupiter on August 15, 2022 (Chris Vaughan, Starry Night Education)

The small, black shadows of Jupiter’s Galilean moons are visible through a backyard telescope when they cross the planet’s disk. On Monday night, August 15, two shadows will cross at the same time, accompanied by the Great Red Spot! Io’s small shadow will began to cross at 11:25 p.m. EDT on Monday evening. A few minutes after midnight EDT the larger shadow of Ganymede and the red spot will rotate into view. Io’s shadow will complete its passage at 1:39 a.m. EDT, while Ganymede’s shadow and the spot will depart at 3 a.m. and 4 a.m. EDT, respectively. Observers on Canada’s west coast will only be able to observe the later stages of the event, underway as Jupiter rises in late evening.

Tuesday, August 16 – Vesta passes the Helix Nebula (all night)

Vesta passes the Helix Nebula on August 16, 2022 | SkyNews
Vesta passes the Helix Nebula on August 16, 2022 (Chris Vaughan, Starry Night Education)

For several nights centred around Tuesday, August 16, the orbital motion (red path with dates:time) of the main belt asteroid Vesta will carry it a thumb’s width above (or 1.6 degrees to the celestial northwest of) the Helix Nebula (aka NGC 7293) in southern Aquarius. The magnitude 5.7 asteroid and the magnitude 7.6 nebula will be close enough to share the view in a low magnification telescope eyepiece or binoculars (green circle), but you’ll need a dark-sky location to see the large, but faint ring of that spectacular planetary nebula. The nebula will be more visible when it is highest in the sky, around 2 a.m. local time. Southerly observers, where both objects will culminate higher in the sky, will have the best views.

Wednesday, August 17 – The Moon hops Uranus (all night)

The Moon hops Uranus on August 17, 2022 | SkyNews
The Moon hops Uranus on August 17, 2022 (Chris Vaughan, Starry Night Education)

On Wednesday night, August 17 in the Americas, the blue-green, magnitude 5.7 speck of Uranus will be positioned a slim palm’s width to the lower left (or 4.5 degrees to the celestial east-northeast) of the waning gibbous Moon, close enough for them to share the view in binoculars (green circle). Reddish Mars and the Pleiades cluster will shine to their lower left. The duo will rise in the east after 11 p.m. local time, and then climb high into the southern sky towards dawn. By then, the easterly orbital motion of the Moon will shift it much closer to Uranus. Hours later, observers from Micronesia to most of Hawaii and the Bering Sea can see the Moon occult Uranus at around 16:00 UTC on August 18 — the eighth in a series of consecutive lunar occultations of that planet.

Thursday, August 18 – Moon, Mars and the Pleiades (overnight)

Moon, Mars and the Pleiades meet on August 18, 2022 | SkyNews
Moon, Mars and the Pleiades meet on August 18, 2022 (Chris Vaughan, Starry Night Education)

Once the waning, half-illuminated Moon clears the treetops in the eastern sky a little before midnight local time on Thursday, August 18, the bright, reddish dot of Mars will be shining a few finger widths to its lower left (or 3 degrees to the celestial east), with the bright Pleiades star cluster (a.k.a. the Seven sisters or Messier 45) shining to the Moon’s upper left. The trio will remain binoculars-close (green circle) all night long. By dawn, the Moon will have shifted between Mars and the cluster.

Friday, August 19 – Third quarter Moon (at 04:36 UTC)

Third quarter Moon on August 19, 2022 | SkyNews
Third quarter Moon on August 19, 2022 (Chris Vaughan, Starry Night Education)

The Moon will complete three quarters of its orbit around Earth, measured from the previous new Moon, on Friday, August 19 at 12:36 a.m. EDT or 04:36 GMT, which converts to Thursday, August 18 at 9:36 p.m. PDT. At the third (or last) quarter phase the Moon appears half-illuminated, on its western, sunward side. It will rise around midnight local time, and then remain visible until it sets in the western daytime sky in early afternoon. Third quarter moons are positioned ahead of the Earth in our trip around the Sun. About 3.5 hours later, Earth will occupy that same location in space. The week of dark, moonless evening skies that follow this phase are the best ones for observing deep-sky targets.

Saturday, August 20 – The Teapot tilts west (evening)

The Teapot tilts west on August 20, 2022 | SkyNews
The Teapot tilts west on August 20, 2022 (Chris Vaughan, Starry Night Education)

Moonless August evenings are ideal for viewing the deep-sky objects (indicated by the red labels) near one of the best asterisms in the sky, the teapot-shaped stars of Sagittarius, the Archer. This informal star pattern features a flat bottom formed by the stars Ascella on the left (east) and Kaus Australis on the right (west), a pointed spout on the right (west) marked by the star Alnasl, and a pointed lid marked by the star Kaus Borealis. The stars Nunki and Tau Sagittarii form a handle on the left-hand (eastern) side. The bent line of three stars named Kaus Borealis (north), Kaus Meridianalis (centre) and Kaus Australis (south) refer to the archer’s bow. The centre of our galaxy sits only a palm’s width to the right of Alnasl. When the asterism reaches its maximum height above the southern horizon, around 9:30 p.m. local time, it will be tilted west, as if it’s serving its hot beverage, and the Milky Way represents the rising steam.

Sunday, August 21 – Double stars in Lyra’s parallelogram (all night)

Double stars in Lyra's parallelogram on August 21, 2022 | SkyNews
Double stars in Lyra’s parallelogram on August 21, 2022 (Chris Vaughan, Starry Night Education)

Each corner of Lyra’s parallelogram is marked by a double star. Zeta Lyrae (ζ Lyr), the corner closest to bright Vega, can be split with binoculars. Both components are white, one star slightly brighter than the other. Each of these stars also has a partner that is too close together to split visually. Moving clockwise, the southwest corner star is Sheliak, the brightest of a tight little grouping of stars visible in a telescope. Sheliak itself has a close-in, dim companion in an eclipsing binary system with a 13-day period. The hot, blue giant star Sulafat sits at the farthest corner from Vega. 620 light-years-distant Sulafat is much larger than Vega, an old star on its way to becoming an orange giant many years from now. Add the slightly dimmer stars Lambda Lyrae and HD 176051 to its south and west, respectively to form a naked-eye triple. Delta Lyrae (δ Lyr) marks the northeast corner of the parallelogram. Sharp eyes and binoculars will easily split the double into one blue and one red star. The blue star is one hundred light-years farther away than the red one; they just happen to appear close together along the same line of sight.

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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