2025, May 31: Jupiter Slowly Slips into Bright Evening Twilight, Mars and Moon near Regulus

May 31, 2025: After sundown, Jupiter slowly slips into bright evening twilight. The evening moon is near Mars.

2023, October 10: Venus, crescent Moon, and Regulus gather in the eastern morning sky before sunrise.
Photo Caption – 2023, October 10: Venus, crescent Moon, and Regulus gather in the eastern morning sky before sunrise.

by Jeffrey L. Hunt

Chicago, Illinois: Sunrise, 5:18 a.m. CDT; Sunset, 8:19 p.m. CDT.  Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.

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Photo Caption – 2023, February 13: Sunrise over the Gulf of Mexico.

As the month ends at Chicago’s latitude, daylight lasts 15 hours, 1 minute; twilight, 4 hours, 11 minutes; and darkness, 4 hours, 48 minutes. Until the solstice, daylight increases only 12 minutes.

Jupiter Slides into Evening Twilight

Jupiter, May 31, 2025
Chart Caption – 2025, May 31: Jupiter is low in the west-northwest at 45 minutes after sundown. Use a binocular to see Elnath, Taurus’ northern horn, to the planet’s right.

Two bright planets are in the evening sky.  Jupiter is low in the west-northwest after sundown.  It slowly slips into bright evening twilight as it heads toward solar conjunction on June 24th.  The bright planet can be seen near the horizon, unlike nearly every other celestial body besides the sun, moon, and Venus.

At 45 minutes after sundown, find the Jovian Giant 5° above the west-northwest horizon. Use a binocular to look for Elnath, the Bull’s northern horn, 7.5° to the planet’s right.

After solar conjunction, Jupiter appears in the eastern sky during morning twilight.  Venus overtakes Jupiter on August 12th for a pretty predawn conjunction.

Mars, Moon, and Regulus

Mars, Moon, Regulus, May 31, 2025
Chart Caption – 2025, May 31: An hour after sundown, find the crescent Moon, Mars, and Regulus spanning 14° in the west-southwestern sky.

The moon, 29% illuminated, is nearly 50° to Jupiter’s upper right. Wait about 15 minutes to see Mars, 4.9° to the lunar orb’s upper right and 9.1° to Regulus’ lower right, Leo’s brightest star.  The three celestial bodies span 14.0°.

Mars, marching eastward in front of the Lion, passes Regulus on June 17th.  Watch that gap close each evening.

Tonight, Jupiter sets only 78 minutes after the sun.  Mars and the Moon set after midnight and over four hours before sunrise.

While technically an evening planet, Mercury is one day past its superior conjunction and hides in bright sunlight.

Venus and Saturn

Venus, Saturn, May 31, 2025
Chart Caption – 2025, May 31: An hour before sunrise, Venus and Saturn are in the eastern sky.

This morning before daybreak, brilliant Venus gleams from low. Its rising time continues to mirror the beginning of morning twilight, which occurs 125 minutes before sunrise.  Through a telescope, the planet shows a phase that is nearly half full.  Tomorrow, the planet is at greatest elongation, over 45° from the sun, the limit of its separation from the sun.  It displays that 50% phase.

An hour before sunrise, Saturn is nearly 24° to Venus’ upper right and over 20° above the east-southeast horizon.  It rises nearly three hours before the sun and appears higher in the sky.  Its gap to Venus continues to open from Venus’ quick eastward movement.

Anticipating Neptune’s Appearance

This contrast enhanced color picture of Neptune was acquired by Voyager 2 at a range of 14.8 million kilometers (9.2 million miles) on August 14, 1989. (NASA photo)
Photo Caption – This contrast enhanced color picture of Neptune was acquired by Voyager 2 at a range of 14.8 million kilometers (9.2 million miles) on August 14, 1989. (NASA photo)

Neptune is in the same region with Saturn, but twilight is brighter than the planet, making the modern solar system’s most-distant planet invisible.  It becomes easier to see when it rises earlier and appears in a darker sky near Saturn. On June 29th, Saturn is 0.9° to Neptune’s lower right in a conjunction that occurs in equatorial coordinates.  (These articles use the ecliptic coordinates, based on the solar system’s plane.  A conjunction in this coordinate system occurs on February 20, 2026).  Neptune and Saturn are in the same binocular field for their observing season from late June until late February 2026. After this window of visibility, the two planets do not appear in the same binocular field again until 2061! 

Look for the four bright planets during nighttime hours.  See Jupiter before it slips into bright evening twilight.

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