2023, July 20: Rare Venus, Mars, Moon, Regulus Gathering


July 20, 2023: Not until 2053 are Venus, Mars, Moon, and Regulus this close together.

Photo Caption – Venus, Jupiter, Mars, Mercury, Regulus, October 15, 2015.


by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 5:33 a.m. CDT; Sunset, 8:21 p.m. CDT.  Check local sources for sunrise and sunset times for your location.  Times are calculated by the U.S. Naval Observatory’s MICA computer program.

Photo Caption – July 20, 1969, Humans walk on the moon (NASA Photo)

Today is the 54th anniversary of the first human visit to the moon.

Summaries of Current Sky Events

Here is today’s planet forecast:

Morning Sky

Chart Caption – 2023, July 20: Jupiter is in the eastern sky during morning twilight.

Two planets are visible before sunrise.  Bright Jupiter is nearly halfway up in the east-southeastern sky at one hour before daybreak.  It is moving eastward against Aries, 11.9° below Hamal, the Ram’s brightest star.  Notice that the Jovian Giant is midway from Hamal to Menkar, Cetus’ nostril.

Jupiter rises nearly five hours before the sun. At 1:52 a.m. CDT, when the planet is low in the sky from Chicago, the Great Red Spot is visible through a telescope in Jupiter’s striped clouds at the planet’s center in the southern hemisphere.  At the same hour, Io – one of Jupiter’s largest satellites – is visible against the cloud tops and its shadow is near the Red Spot.  Sky watchers farther eastward see the planet higher and in a clearer sky.

Chart Caption – 2023, July 20: One hour before sunrise, Saturn is in the south-southwestern sky.

During morning twilight, Saturn is about 35° above the south-southwest horizon. It is retrograding in front of Aquarius. The stars are dim and difficult to see from urban and suburban settings.  Use a binocular to see Skat, 7.1° to Saturn’s lower left, and Lambda Aquarii (λ Aqr on the chart) 5.7° to the planet’s upper left.

The star Fomalhaut is about halfway from Saturn to the southern horizon.

Evening Sky

Chart Caption – 2023, July 20: Venus, Mercury, Mars, Regulus and the crescent moon are in the western sky as night falls.

Two days before the close gathering of Venus, Mars, and Regulus on July 19, 2053, the moon joins them in a circle 5.0° across, easily fitting into the same binocular field of view. This is when they are in close formation again and visible across the skies of the Americas, although they bunch together multiple times before then, not this compact.

Venus, Mars, and Regulus were gathered at their closest for the convergence of celestial cycles on July 9th when they fit into a circle 4.7° in diameter. The Red Planet passed Regulus the next evening.

This evening the quartet fits into a circle 9.0° across. Add in Mercury and the planets span 19.5° from the speedy planet to Mars.

This evening, find a clear horizon looking westward.  A view from a hilltop or elevated structure aids in seeing an obstruction-free horizon.  Begin looking about 35 minutes after sundown.

Brilliant Venus shines through the evening twilight’s palette of hues shortly after sunset, along with the crescent moon, 10% illuminated, 8.4° above the Evening Star.

While Mercury is fairly bright, use a binocular to find it over 11° to the right of Venus.

Chart Caption – 2023, July 20: Mars, the lunar crescent, and Regulus fit into the same binocular field of view.

As the sky darkens further, use the binocular to find Regulus, 3.9° above Venus, and Mars 3.4° to the lower left of the lunar crescent.  Mars, the lunar crescent, and Regulus fit into the same binocular field of view.

Gatherings of Mars, Moon, and Regulus are somewhat regular affairs, occurring about every other year.  The next one is June 29, 2025. Farther apart than tonight, but they tightly fit into a binocular’s field.

By 45 minutes after sundown, Venus is less than 5° above the horizon and Mercury is lower.

Photo Caption – 2022, July 30: The crescent moon with earthshine.

Look for earthshine on the moon from sunlight reflected from Earth’s oceans, clouds, and land.  It gently illuminates the lunar night.

Tomorrow evening the moon is to the upper left of the planets.

Chart Caption – 2023, July 20: Saturn is in the east-southeast three hours after sundown.

Saturn rises in the east-southeast about two hours after night falls. At three hours after sunset, find it nearly 15° above the horizon.

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