2024, April 20: Jupiter-Uranus Conjunction

April 20, 2024: The Jupiter-Uranus conjunction occurs tonight.  Mars and Saturn are visible before sunrise.

Venus, Uranus, March 8, 2020
2020, March 8: Venus is 2.2° to the upper right of Uranus.

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by Jeffrey L. Hunt

Chicago, Illinois: Sunrise, 6:02 a.m. CDT; Sunset, 7:38 p.m. CDT.  Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.

Jupiter-Uranus Conjunction

Jupiter-Uranus conjunction
Chart Caption – 2024, April 20: The Jupiter-Uranus conjunction is shown through a binocular.

Tonight, Jupiter passes 0.5° to the lower left of planet Uranus in a narrow conjunction.  The two planets easily fit into the same binocular field of view.

Such conjunctions are rare because of the slow pace they revolve around the sun.  Jupiter completes a solar circuit every 11.8 years, but Uranus takes 84 years. 

In the sky Jupiter’s journey in front of the distant zodiacal stars takes that 11.8-year period. When Jupiter passes Uranus again on September 8, 2037, the more distant planet has only moved two constellations eastward, Taurus and Gemini, but Jupiter moves one complete circuit and an additional 63° from tonight’s position.

Jupiter, Uranus, and the moon appear in the same binocular field again on September 6, 2037. They snugly fit into the field of view.  On October 3, 2037, they easily fit into a binocular field and inside a circle only 3.6° in diameter.

This is an image of the planet Uranus taken by the spacecraft Voyager 2 in 1986. The Voyager project is managed for NASA by the Jet Propulsion Laboratory.
Photo Caption – This is an image of the planet Uranus taken by the spacecraft Voyager 2 in 1986. The Voyager project is managed for NASA by the Jet Propulsion Laboratory.

This evening the view of Uranus and the distant starfield is hampered by the low altitude of the conjunction and the bright moon.  An hour after sundown, the two planets are less than 10° above the west-northwest horizon.  This altitude is unfavorable because of the air’s filtering effects that dims and blurs celestial objects. 

When looking toward the horizon, a celestial body’s light travels through more air than when overhead. This longer track makes celestial objects appear redder, blurred, and dimmer.  This is noticed in the red-orange colors of a rising and setting sun or moon.

Secondly, the bright moonlight from the lunar orb in the eastern sky washes across the sky and hides dimmer stars.

Conjunction through a Binocular

The accompanying chart shows an ideal view of the scene, without moonlight and atmospheric effects.  Place Jupiter at the center of the field of view.  Appearing as a star, the moon Ganymede is immediately to Jupiter’s upper left.  It is slightly brighter than aquamarine Uranus to Jupiter’s upper right.

Star Delta Arietis (δ Ari), brighter than Uranus, is to Jupiter’s upper right.  Stars 53 Arietis (53 Ari) and 54 Arietis (54 Ari), dimmer than the more-distant planet, are to the right.

Uranus, rings and Moons from NASA's Webb Space Telescope
Photo Caption – Uranus, rings and Moons from NASA’s Webb Space Telescope (NASA Photo)

In more favorable conditions, Uranus is visible to the unaided eye in a dark location.  The planet was first documented as a star possibly as early as 128 BC by Hipparchus.  Through a telescope during the 18th century, William Herschel noted that it moved slowly compared to the distant starfield – a new planet. Herschel wanted to name it after England’s king, but tradition held with a mythological character.

While Jupiter and Uranus appear close together in the sky, they are far apart in space.  Tonight, Jupiter is over 550 million miles from Earth, but Uranus is nearly 3.5 times that distance.  This separation is about 1.5 times Saturn’s solar distance.

Try this challenging observation tonight.  As Jupiter appears to move away and open a gap to Uranus, the pair is lower each evening and even more challenging to see until they disappear into brighter twilight.

Summaries of Current Sky Events
Summary for Venus as a Morning Star, 2023-24

Here is today’s planet forecast:

Morning Sky

Morning Moon

Two hours before sunrise, the bright gibbous moon is low in the sky, above the west cardinal direction.

Four bright planets are west of the sun and potentially visible before sunrise.  Mercury and Venus are veiled by bright morning twilight.

Morning Planets

Mercury speeds toward an unfavorable appearance in the eastern morning sky, while Venus slowly moves toward a solar conjunction and a wide swing into the western evening sky.

2024, April 20: Mars and Saturn are in the east-southeast before sunrise.
Chart Caption – 2024, April 20: Mars and Saturn are in the east-southeast before sunrise.

Mars and Saturn are in the east-southeast before sunrise.  This region of the celestial vault does not have any bright stars nearby to provide reference points.  At 45 minutes before sunrise, Saturn is nearly 10° above the horizon.  A binocular may be necessary to initially identify it. In the binocular field, Mars is 6.4° to Saturn’s lower left.

2024, April 20: Mars and Saturn fit into the same binocular field of view.
Chart Caption – 2024, April 20: Mars and Saturn fit into the same binocular field of view.

Depending on the binocular’s characteristics, this might be the last morning until 2026 to see them in the same field.

Saturn appears higher in the sky each morning as it rises two minutes earlier each day.  Mars marches eastward, opening a wider gap with Saturn.  The Red Planet rises one minute earlier every two to three days.

Evening Sky

Evening Gibbous Moon

2024, April 20: After sundown, the gibbous moon is in the southeast with Virgo.
Chart Caption – 2024, April 20: After sundown, the gibbous moon is in the southeast with Virgo.

Three nights before the Full (Pink) moon, the bright gibbous moon is less than halfway up in the southeast after sundown.  It is in front of Virgo, nearly 25° to Spica’s upper right.

Earlier today, the lunar orb occulted or eclipsed the star Zavijava, also known as Beta Virginis, for sky watchers in eastern Europe and western Asia.  In the Americas, the star is 2.4° to the lunar orb’s upper right.  Use a binocular or cover the moon with your hand to see the star.

Jupiter

Jupiter-Uranus conjunction
Chart Caption – 2024, April 20: One hour after sundown, Jupiter is low in the west-northwest.

One hour after sundown, bright Jupiter is less than 10° above the west-northwest horizon in its conjunction with Uranus.  Jupiter is about 10° below the Pleiades star cluster.

Jupiter sets less than two hours after sundown.  The moon and the muted starry background appear farther westward during the night.  One hour before sunrise tomorrow, the moon is above the western horizon before twilight begins.

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