December 29, 2022: The evening planet display is ending as Mercury begins to retrograde and fade in brightness. Look for Venus, Mercury, Jupiter, Moon, and Mars after sundown.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 7:18 a.m. CST; Sunset, 4:28 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 January 10th.
Jupiter’s Great Red Spot’s transit times, when it is in the center of the planet in the southern hemisphere: 2:48 UT, 12:43 UT, 22:39 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.
Summaries of Current Sky Events
Here is today’s planet forecast:
Morning Sky
The bright planets are in the evening sky. They are strung from the eastern skyline to the southwest horizon. Connecting them with an imaginary line shows us the plane of the solar system.
Before sunrise, four stars approximately indicate the ecliptic’s location. Antares, marking the heart of the Scorpion, is over 5° above the southeast horizon. The star is 4.6° below the ecliptic. The sun is closest to the star about December 1st each year.
Farther westward, Spica is less than halfway up in the south. Meaning “the ear of corn,” the star is 2.0° below the ecliptic. The sun seems to pass the star on October 17th.
Regulus – meaning “the prince” – is nearly halfway up in the west-southwest. The star is the closest bright star to the ecliptic, only 0.5° above the solar system plane. Because of its proximity to the ecliptic, the planets can pass it in close conjunctions. The sun passes through about August 23rd each year.
Pollux, one of the Gemini Twins, is one-third of the way up in the west-northwest. It is 6.7° north of the ecliptic. The sun is closest on July 15th. Because of this larger separation, only the moon passes reasonably close to the star.
Evening Sky
Mercury begins to retrograde today, or move westward compared to the fainter starfield. The planet passed its greatest separation from the sun, appearing at its maximum distance from our central star, over a week ago. This change in apparent direction is an indicator that the speedy planet is quickly catching up to our planet on an inside orbit where Mercury revolves faster.
Mercury quickly catches our planet, then moves into the morning sky. Inferior conjunction occurs on January 7, when it is between our world and the sun. It appears low in the southeast at the end of January.
The inner planets – Mercury and Venus – retrograde because of their faster speed around the sun than Earth. The outer planets retrograde from Earth’s faster motion than the more-distant worlds.
The five planets are visible again this evening, but Mercury is receding into brighter twilight and fading in brightness. At forty-five minutes after sundown, the Evening Star is less than 5° above the southwestern horizon, a little to the right or north of the southwest point. Find an observing spot with a clear horizon in that direction.
Mercury is slightly brighter than Saturn and 1.7° to the upper right of Venus. Both easily fit into the same binocular field of view. Can you see Mercury without the optical assist?
The moon is at the First Quarter phase at 7:21 p.m. CST. At forty-five minutes after sundown, the lunar orb is over halfway up in the south-southeast, 6.4° to the left of Jupiter. The planet is very bright, although dimmer than Venus.
Saturn is less than one-third of the way up in the southwest, about one-third of the way from Venus to Jupiter. Do not confuse the planet with the star Fomalhaut that is lower in the south-southwest.
Mars is in the eastern sky near Aldebaran. The planet is considerably brighter than the star. Notice Betelgeuse, below Mars and near the horizon. It rises at sunset in a few days.
As the sky darkens further, the celestial wonders appear farther westward. Venus and Mercury set.
At two hours after sunset, Mars is in the eastern sky with Taurus as the sidereal backdrop. The planet is retrograding, 8.3° to the upper left of Aldebaran. For Mars retrograde ends on January 12th.
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