Apollo landing sites, as visible July 20, 2021. | SkyNews
Apollo landing sites, as visible July 20, 2021 (Chris Vaughan, Starry Night Education)

This Week’s Sky: July 19 to 25, 2021

View the Apollo landing sites on the anniversary of the first moonwalk. After the Moon reaches its full phase, watch as it passes Saturn and Jupiter.

Tuesday, July 20 – View the Apollo sites (all night)

Apollo landing sites, as visible July 20, 2021. | SkyNews
Apollo landing sites, as visible July 20, 2021 (Chris Vaughan, Starry Night Education)

It’s the 52nd anniversary of humankind’s first steps on another world! The six crewed Apollo Missions were sent to different regions of the Moon in order to carry out experiments and to bring back rock samples that help us determine the age and composition of the Moon’s surface. For safety reasons, Apollo 11 was sent to the flat and relatively featureless terrain of Mare Tranquillitatis “Sea of Tranquility.” Later missions landed in more rugged regions with complex geology. When the Moon approaches the full phase, all of the regions where the astronauts explored are illuminated by sunlight, including the most westerly site, Apollo 12 in Oceanus Procellarum.

Wednesday, July 21 – Venus passes Regulus (after sunset)

Venus passes Regulus after sunset on July 21, 2021. | SkyNews
Venus passes Regulus after sunset on July 21, 2021

For about an hour after sunset on Wednesday, July 21, and very low in the west-northwestern sky, the very bright planet Venus will gleam above the prominent double star Regulus in Leo. The orbital motion of Venus will carry it within a finger’s width to the upper right of (or 1 degree to the celestial north) of Regulus on Wednesday – close enough for them to be viewed together in a backyard telescope. Magnitude -3.93 Venus will outshine magnitude +1.34 Regulus by about 130 times. The duo will be observable in binoculars (red circle), with Mars to their lower right, for the entire week. (Ensure that the sun has set fully before pointing optics towards the western horizon.) (Image: Jul21-2021 at 9 pm – Venus Passes Regulus.jpg)

Friday, July 23 – Full Moon (at 2:37 GMT)

Full Moon on July 23, 2021. | SkyNews
Full Moon on July 23, 2021 (Chris Vaughan, Starry Night Education)

The Moon will reach its full phase on Friday, July 23 at 10:37 p.m. EDT (or 02:37 GMT on Saturday, July 24). The July full Moon, commonly called the Buck Moon, Thunder Moon, or Hay Moon, always shines in or near the stars of Sagittarius or Capricornus. The Ojibwe people of the Great Lakes region call this moon Abitaa-niibini Giizis, the Halfway Summer Moon, or Mskomini Giizis, the Raspberry Moon. The Cherokees call it Guyegwoni, the Corn in Tassel Moon. The Cree Nation of central Canada calls the June full moon Opaskowipisim, the Feather Moulting Moon (referring to wild water-fowl habits), and the Mohawks call it Ohiarihkó:wa, the Fruits are Ripened Moon. Because the Moon is full when it is opposite the Sun in the sky, full moons always rise in the east as the Sun is setting, and set in the west at sunrise. Since sunlight is striking the Moon vertically at that time, no shadows are cast; all of the variations in brightness you see arise from differences in the reflectivity, or albedo, of the lunar surface rocks.

Saturday, July 24 – Bright Moon below Saturn and Jupiter (all night)

Bright Moon below Saturn and Jupiter, all night on July 24-25, 2021. | SkyNews
Bright Moon below Saturn and Jupiter, all night on July 24-25, 2021 (Chris Vaughan, Starry Night Education)

While the Moon’s monthly visit with the gas giant planets will begin with Saturn on the previous evening, skywatchers who are outside on Saturday night, July 24 will find our slightly-less-than-full natural satellite shining very brightly below and between bright Jupiter on the left (or celestial northeast) and Saturn on the right (celestial northwest). After they finish rising around 9:30 p.m. local time the trio will make a nice wide-field photo opportunity when composed with some interesting scenery.

Sunday, July 25 – Gibbous Moon and Jupiter (all night)

Gibbous Moon and Jupiter on July 25, 2021. | SkyNews
Gibbous Moon and Jupiter on July 25, 2021 (Chris Vaughan, Starry Night Education)

After 24 hours, the Moon’s eastward orbital motion will move it to a slim palm’s width below (or 4.75 degrees to the celestial south) of Jupiter on Sunday night, July 25. The pair will be visible together in binoculars all night long after they rise in the east-southeast at about 10 p.m. local time. The scene will make another nice wide-field photo opportunity by adding Saturn well off to their right.

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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