2023, January 7: Mercury, Inferior Conjunction, Evening Planet Display Continues


January 7, 2023: Mercury is at inferior conjunction between Earth and the sun.  Venus, Saturn, Jupiter, and Mars continue with their evening display after sundown.

Chart Caption – 2023, January 7: Mercury is between Earth and the sun, inferior conjunction, moving toward the morning sky, west of the sun. Notice Venus’ location in the evening sky, east of the central star.


by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 7:18 a.m. CST; Sunset, 4:36 p.m. CST.  Check local sources for sunrise and sunset times for your location.  Times are calculated from the U.S. Naval Observatory’s MICA computer program.

Sunrise is at its latest time.  This continues through the 10th.  The length of daylight slowly increases during January to ten hours by the end of the month.

Jupiter’s Great Red Spot’s transit times, when it is in the center of the planet in the southern hemisphere: 5:17 UT, 15:13 UT; Jan. 8, 1:09 UT. Convert the time to your time zone. In the US, subtract five hours for EST, six hours for CST, and so on.  Use a telescope to see the spot.  Times are from Sky & Telescope magazine.

Mercury is at inferior conjunction, between Earth and the sun, this morning at 6:57 a.m. CST.  It speeds into the morning sky, reaching its greatest separation from the sun near month’s end.

Mercury is not precisely between the Earth and sun, but it is 2.8° above the central. Mercury’s orbit is tilted 7.0° compared to the Earth-sun plane, known as the ecliptic.

When the speedy planet moves from the evening sky to a morning view it retrogrades.  The planet moves faster than Earth and passes it every 116 days.  When at the evening apparition, Mercury is east of the sun, and west of the sun during its morning appearance.  To move from evening to morning, the planet moves from east to west – or retrograde.  This illusion of retrograde occurs when Mercury and Venus pass Earth.   

Mercury stops retrograding on January 18th, and reaches its greatest separation from the sun on the 30th.

Here is today’s planet forecast:

Morning Sky

Chart Caption – 2023, January 7: The bright moon is below Castor and Pollux, the Gemini Twins, before sunrise.

The bright moon dominates the morning sky, seemingly whitewashing the dimmer stars view.  At one hour before sunrise, the lunar orb is nearly 20° above the west-northwest horizon.  It is 2.7° to the lower left of Pollux and 6.2° to the lower left of Castor.  The stars are the Gemini Twins. 

Likely the moon’s brightness overwhelms the nearby stars.  To see them, block the moon with your hand as you would to shield your eyes from the sun’s glare.

Each morning the moon is higher in the western sky and it begins to show its gibbous phase during the next few mornings.

Evening Sky

Chart Caption – 2023, January 7: Mars is in the eastern sky after sundown, to the upper left of Aldebaran, the brightest star in Taurus.

Forty-five minutes after sunset, the bright moon, 99% illuminated, is at the east-northeast horizon, casting its light across the sky.

At this hour Mars is 40° up in the east.  Still brighter than all the stars in this part of the sky, the Red Planet is dimming quickly as Earth moves away.

Mars’ illusion of retrograde ends in five nights when the planet resumes its normal eastward motion.  This evening it is 8.5° to the upper left of Aldebaran, the brightest star in Taurus.

Mars passes Aldebaran for the third time of a triple conjunction series on January 30th.

Chart Caption – 2023, January 7: Venus, Saturn, and Venus are along an arc from the southwest to south after sundown.

Farther westward, brilliant Venus is low in the southwest, less than 10° up in the sky.  Find a clear horizon to see it.  It is closing in on a January 22nd conjunction with Saturn.  This evening the gap between the planets is 17.0°.  The separation shrinks about 1° from evening to evening.

After the conjunction with Saturn, Venus moves toward Jupiter, passing it on March 1st.  For several days before and after the conjunction the two planets are close in the sky.  Their gathering is a spectacular sight to see.  The gap from Venus to Jupiter is 56.0° tonight, quite a separation to close during the next several weeks.

Jupiter (NASA Photo)

For sky watchers with telescopes, the Great Red Spot is in the center of Jupiter in the southern hemisphere at 7:09 p.m. CST.  From Chicago, the Jovian Giant is nearly 40° up in the southwest.  The long-lived storm is visible for about an hour before and after its center stage appearance as Jupiter’s rapid rotation brings it into view, then spins it away from view.



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