April 11, 2023: Jupiter is at solar conjunction. The sun is between Earth and Jupiter. Mercury is at its farthest from the sun in the evening sky. Venus continues its display with the Pleiades.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:17 a.m. CDT; Sunset, 7:27 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.
Jupiter appears to pass behind the sun – solar conjunction – today. The Jovian Giant’s motion, from evening to morning sky, is from Earth’s orbital motion. It revolves around the sun every 11.8 Earth years. While it gently moves eastward compared to the stars, its year-long cycle is from faster moving Earth. While recent articles have described Jupiter’s disappearance, this is a reflection of Earth’s orbital motion around the sun.
As seen from north of the solar system’s plane, the sun is between Earth and Jupiter that is over five times Earth’s distance from the sun. Also shown on the accompanying chart is Mercury’s greatest elongation position.
After conjunction, Jupiter moves into the morning sky, again from Earth’s motion. The first appearance occurs next month.
Additionally, Mercury is at its greatest separation from the sun today at 5:10 p.m. CDT. The planet stands about 10° above the horizon during the early evening. During spring evenings, the plane of the solar system is highly-angled with the western horizon, place the speedy planet in favorable views.
Mercury’s orbit is inside Earth’s solar path. The speedy planet seems to stay very close to the central, as a dog that is chained to a stake. It seems with wiggle from evening sky to morning and back again.
The accompanying chart shows the planet’s imaginary orbital path at sunset. Mercury is at the largest extent of its orbit. It never appears in the sky at midnight, only shining somewhat briefly either after sunset in the west or before sunrise in the eastern sky.
Mercury’s brightness continues to fade as it moves toward inferior conjunction – between Earth and sun – on May 1st. It quickly moves into the morning sky and to its morning greatest elongation on the 29th. At sunrise, it is difficult to see, only achieving an altitude of 10°, the height above the horizon this evening at 45 minutes after sunset. At 30 minutes before daybreak, the planet is a binocular object, only 4° above the east-northeast horizon.
During the late spring and summer, the ecliptic is unfavorably inclined to the eastern horizon. Mercury’s best morning appearances occur during autumn mornings when the ecliptic is favorably inclined to see it.
Summaries of Current Sky Events
Here is today’s planet forecast:
Morning Sky
An hour before sunrise, the gibbous moon, 71% illuminated, is about 20° above the southern horizon. It is in front of the Ophiuchus’ stars. The lunar orb is over 15° to the left (east) of Antares, the brightest star in Scorpius. The moon is west of Sagittarius.
The constellation Ophiuchus extends southward with its boundary farther south than Antares and north of the Scorpion’s stinger. Two stars, Shaula and Lesath, also known as the Cat’s Eyes, mark that fatal telson.
The moon is near the sun’s location at the summer solstice, although it is about 5° below that spot this morning.
Saturn is visible at this hour, but it is higher as morning twilight continues. Fifteen minutes later, the Ringed Wonder is about 10° above the east-southeast horizon. It rises earlier each morning and appears higher in the sky.
The planet is too low for telescopic observation. When viewing near the horizon, Earth’s atmosphere blurs the scene.
Evening Sky
Brilliant Venus and Mercury, at its greatest elongation, are in the western sky this evening. Brilliant Venus stands nearly 30° up in the west at forty-five minutes after sundown. The planet is stepping eastward in front of Taurus. The Pleiades star cluster is to the planet’s right, while the Hyades star cluster is to the upper left.
Aldebaran, 11.5° to Venus’ upper left, and the Hyades star cluster outline the Bull’s head.
Again, this evening, the Evening Star is near the Pleiades star cluster, 2.6° to the left of Alcyone, the stellar bundle’s brightest star. This is nearly the same separation as last night. Look at the scene with a binocular. It is a wonderous view with or without optical help. Wait until the sky is a little darker, but before the planet and star cluster are too low in the sky.
After Venus leaves the Pleiades, it continues eastward passing interesting starfields. Look each clear evening. From the Americas, tomorrow Venus is below and imaginary line from Aldebaran to the Pleiades. The next evening, it is above that line.
Mercury, 10.0° up in the west-northwest and nearly 20° to the lower right of Venus, is at greatest elongation. It sets 105 minutes after sundown and continues this setting time interval through the 15th, fading in brightness each evening. The planet is visible to the unaided eye, but use a binocular to initially find it.
Mars, marching eastward against Gemini, is about 35° to the upper left of Venus. The Red Planet’s eastward rate is about half of Venus’ trajectory. Watch the planet’s gap close during the next several weeks.
When the sky is darker, about 90 minutes after sundown, the stick figures of Gemini are visible with Mars near Mebsuta. This evening the planet is 1.4° to the lower right of the star.
Mars continues to dim as Earth opens space in the solar system with the fourth planet from the sun. It is about as bright as Pollux this evening.
Each clear evening, watch the planets continue their planetary dances in the western sky.
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