April 16, 2024: After sundown, the bright winter stars shift westward each night. Bright Jupiter is visible during the evening, while Mars and Saturn appear before sunrise.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:08 a.m. CDT; Sunset, 7:33 p.m. CDT. Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.
Winter Stars Shift Westward
During the seasons, the bright stars and constellations seem to migrate westward. Select any bright star and note its location at about the same time on each clear evening. From week to week, it is farther westward, eventually disappearing into evening twilight.
As our planet revolves around the sun, we see the stars earlier each night, causing this westward shift. After disappearing into evening twilight, they reappear in the eastern sky. Jupiter, Saturn, Uranus, Neptune, and classic planet Pluto generally follow this pattern.
Saturn’s morning appearance, described below, follows this pattern. It rises earlier each morning and appears higher in the sky at the same time interval before sunrise.
In contrast, Mars marches eastward at a faster pace, about half Earth’s orbital speed, so that its appearance is slower.
After sundown, the bright stars that are prominent during winter’s evenings are in the western sky. Soon several of them disappear into bright evening twilight and reappear in the eastern morning sky.
Orion’s Rigel is first to slide into evening twilight, reaching its heliacal setting about April 30th at Chicago’s latitude. This evening it is less than 20° above the west-southwest horizon. Sirius, Orion’s belt stars, Aldebaran, and the Pleiades disappear approximately May 11th. Betelgeuse follows approximately eight nights later.
Sirius’ reappearance during mid-August brings considerable interest from Egypt aficionados and speculators because of the discussion around the Dog Star’s association with the ancient Egyptian calendar.
Stars Procyon, Castor, Pollux, and Capella disappear at later dates. During mid-May, Capella is visible before sunrise in the east-northeast. Along with Vega and Arcturus, the “little she-goat” star can appear before sunrise and after sunset at particular seasons.
Summaries of Current Sky Events
Summary for Venus as a Morning Star, 2023-24
Here is today’s planet forecast:
Morning Sky
Morning Planets
Four bright planets are west of the sun and considered morning planets, although Mercury and Venus are submerged in bright morning twilight.
At forty-five minutes before daybreak, Saturn and Mars are over 5° above the east-southeast horizon. Each morning their separation grows. This morning, they are 3.8° apart, fitting nicely into the same binocular field of view.
Mars marches eastward faster than Saturn and the Ringed Wonder seems caught up in the westward annual progress of the stars that appear higher in the east each morning. This is from Earth’s revolution around the sun. Mars moves in its solar orbit about half Earth’s speed. Its appearance in a darker sky takes longer, somewhat mirroring our planet’s speed. While Saturn rises two minutes earlier each morning, Mars rises one minute earlier compared to sunrise every two to three days.
Without the binocular, Saturn is marginally visible, depending on a viewpoint with an unobstructed horizon and a very clear sky.
Mars is slightly dimmer than Saturn. The Red Planet appears dimmer from its red color. Likely it evades viewing without the optical assistance.
Evening Sky
Evening Gibbous Moon
After sunset, the bright gibbous moon is high in the south-southwest. It is in front of Cancer’s dim stars, nearly midway from Pollux, a Gemini Twin, to Regulus, Leo’s brightest star.
The Beehive star cluster is near the moon this evening, but the moon’s light overwhelms the dimmer cluster.
Jupiter in west-northwest
Jupiter is the only bright planet in the sky tonight. One hour after sundown, find it low in the west-northwest. It is moving eastward in front of Aries and below the Pleiades star cluster, part of Taurus. The star cluster is a challenge to see in this moonlight.
Jupiter and Uranus
Jupiter is slowly overtaking a dimmer planet Uranus. The conjunction occurs in four evenings, but it is difficult to see in the increased moonlight and the planet duo’s low altitude after sunset. This evening, use a binocular to look for Uranus. First, place Jupiter in the center of the field and look for up to four of its largest moons, resembling stars near the bright planet. Considerably dimmer Uranus is above Jupiter.
Next, attempt to find Delta Arietis (δ Ari on the chart). It is brighter than Uranus, while numbered stars 53 Arietis (53 Ari) and 54 Arietis (54 Ari) are dimmer. Stars 53 and 54 might be washed out by the moonlight.
Uranus resembles an aquamarine star. Its globe appears through a larger telescope with significant magnification.
Jupiter sets two hours after sundown. The moon sets after the new day begins and about two hours before sunrise.
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