May 1, 2023: The bright gibbous moon is in the southeastern sky after nightfall. Venus and Mars appear in front of stars soon to disappear into bright evening twilight.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 5:47 a.m. CDT; Sunset, 7:49 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.
As May opens, daylight lasts over 14 hours and grows another hour by month’s end.
Today is May Day, traditionally marked as the mid-point between spring equinox and the summer solstice. This year the actual mid-point occurs May 6th. These days that are the middle of the seasons are known as the cross-quarter days.
By the middle of spring in the northern hemisphere, the agricultural signs of the season are well established. Daylight is longer, flowers are blooming, the last frost date approaches, and the fields are ready for planting.
Some European countries celebrated the season with dances, decorated animals with flowers, and exchanged baskets of flowers. Spring is surely here. Celebrate the season. The Farmer’s Almanac has interesting stories about the day.
Mercury is at inferior conjunction, between Earth and the sun, today at 6:28 p.m. CDT. The planet enters the morning sky quickly, but the ecliptic is unfavorably tilted compared to the eastern horizon before sunrise. Mercury’s place is further complicated by its location south of the solar system plane. In a month at its best placement, speedy planet is less than 5° above the east-northeast horizon at 30 minutes before daybreak.
Summaries of Current Sky Events
Here is today’s planet forecast:
Morning Sky
Saturn is the lone bright planet that is visible before sunrise. Brighter than most of the stars in the sky this morning, but dimmer than Venus and Jupiter, the Ringed Wonder is over 15° above the east-southeast horizon at 45 minutes before sunrise. It rises nearly two hours, thirty minutes before daybreak.
After the April 11th solar conjunction, Jupiter slowly emerges from the sun’s glare, rising only 30 minutes before daybreak. When the planet is high enough for visibility, sunlight overwhelms its sighting.
Evening Sky
Brilliant Venus dominates the western sky after nightfall. Simply described, it is “that bright star” in the west. At forty-five minutes after sunset, it is nearly 30° above the horizon.
The Evening Star is moving between Taurus’ horns, Elnath and Zeta Tauri. The two stars are too far apart to fit into the same binocular field, but the binocular’s optical assist may help find Zeta Tauri, the dimmer star.
Venus steps quickly to the east against the distant sidereal backdrop. It is closing the gap to Mars, over 25° to the upper left.
Mars is marching eastward in front of Gemini, 6.3° to the lower left of Pollux. The Red Planet passes the star in a wide conjunction in a week.
Notice the bright stars in the western sky in the planets’ vicinity. These stars are slowly disappearing into the sun’s glare, to return to the morning sky during the summer months.
Sirius, nighttime’s brightest star, is 15° up in the southwest, likely twinkling wildly. It disappears into sunlight in about 10 days.
Rigel is the first star to leave the evening sky. It is part of Orion’s famous pattern. The star is about 5° up in the west-southwest. Can you find it this evening? It is overwhelmed by sunlight during the next few evenings.
Aldebaran, Taurus’ brightest star, leaves the evening sky a few evenings after Sirius, followed by Betelgeuse about a week later.
These final seasonal appearances of the stars in the western sky after nightfall is known as the heliacal setting.
Procyon, Pollux, Castor, and Capella disappear later in the season. Interestingly, Capella soon makes its first morning appearance, heliacal rising. The star is far enough north that it appears in the evening sky after sundown, and in the morning sky before daybreak. At Chicago’s latitude, this occurs approximately May 20th. The exact date depends on the clarity of the sky and whether the horizon is cloud free.
The bright moon, 86% illuminated, is in the southeast in front of the fainter stars in western Virgo and beneath Denebola, Leo’s tail.
The moon is at its Full phase in four days. This month’s moon is known as the Flower Moon.
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