2023, May 13: Morning Saturn-Moon Conjunction, Mars Nears Castor-Pollux Alignment


May 13, 2023: The moon appears with Saturn in the southeast before sunrise.  Evening planet Mars marches toward an alignment with Castor and Pollux, the Gemini Twins.

Photo Caption – 2020: May 13: The gibbous moon appears 8.7° to the lower left of Saturn. The Jupiter – Saturn gap is 4.7°.


by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 5:33 a.m. CDT; Sunset, 8:02 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.

Summaries of Current Sky Events


Here is today’s planet forecast:

Morning Sky

Chart Caption – 2023, May 13: Saturn and the moon appear in the southeast before daybreak.

Before daybreak, the thick crescent moon, 41% illuminated, is nearly 20° above the southeast horizon and 5.1° to the lower right of Saturn.  Find a clear horizon toward that direction to easily seem them.

Saturn is slowly climbing higher into the predawn sky.  Rising nearly three hours before daybreak, it gains two to three minutes of rising time compared to sunrise each morning.

The moon continues its eastward hop each morning appearing noticeably eastward compared to the planets and distant stars.

Jupiter rises two hours after Saturn.  It is considerably brighter than the Ringed Wonder and becomes easier to see each morning.  Thirty minutes before sunrise, it is nearly 5° above the eastern horizon.  The assist of a binocular is still needed to see it in the bright blush of predawn’s light.

A razor-thin moon appears with Jupiter before sunrise in four mornings.  This might be one of the first mornings to see the Jovian Giant without a binocular.

Mercury is scampering into the morning sky for an unfavorable appearance early next month.  It rises about twenty minutes after Jupiter and is lost in the sun’s glare.

Evening Sky

Chart Caption – Venus moves in front of Gemini, May 7-June 2, 2023.

Brilliant Venus is “that bright star” in the west during the early evening.  At forty-five minutes after sundown, it is one-third of the way from the horizon to overhead. The planet is stepping eastward in front of Gemini, near Castor’s heel, Tejat Posterior, also known as Mu Geminorum (μ Gem on the chart).

Chart Caption – 2023, May 13: Venus and Messier 35 (M 35) appear in the same binocular field of view.

Through a binocular, Venus is in the same field of view with the star cluster catalogued as Messier 35 (M 35 on the chart). Hold the binocular so that Venus is near the top of the field of view.  The star cluster is toward the bottom.  This evening and tomorrow night are the last two evenings that Venus and the star cluster fit into the same binocular field for this appearance of the planet.  Venus appears again in the same binocular field with Messier 35, July 28-August 7, 2025 before sunrise.

Photo Caption – The Double Cluster in Perseus as from a sky survey at the upper left and the close up from the Hubble Space Telescope.

Open or galactic star clusters lie along the plane and spiral arms of the Milky Way. They have a few hundred stars in them and they are bunched together by the mutual gravitation of the other cluster stars. About 50 of them have been identified within 10,000 light years of the sun. 

Photo Caption – The Pleiades star cluster. (U.S. Naval Observatory)

The Pleiades, the most famous open cluster, is about 400 light years away.  In comparison, Messier 35 is about seven times more distant.

Photo Caption – Data from more than 1.8 billion stars have been used to create this map of the entire sky. Note the dark dust along the Milky Way. The northern hemisphere’s Great Rift begins near the center of the image and runs to the left. (ESA Photo)

From a location free from outdoor lighting, Gemini appears to be standing on the Milky Way.  The plane of the solar system, known as the ecliptic, crosses the galaxy’s plane near Castor’s foot where Messier 35 is located.  The cluster is a celestial milestone of sorts.  The moon and planets regularly pass it, and it is not far from the sun’s location at the summer solstice.

Chart Caption – 2023, May 13: Venus and Mars appear against Gemini after sundown.

Venus continues to step eastward in front of Gemini toward Mars, less than 20° to the upper left of the Evening Star and 5.7° to the lower left of Pollux.

Mars is fading in brightness from Earth’s increasing distance.  This evening it is dimmer than Pollux, but slightly brighter than Castor.

Return to the night sky about 90 minutes after sundown, to see the planetary duo against Gemini’s dimmer starfield, that looks like two side-by-side stick figures.  Venus is near Propus and Tejat Posterior, features on Castor’s foot.

Watch Mars step eastward and line up with Castor and Pollux.  Extend an imaginary line from Castor through Pollux.  Mars reaches that line in three evenings.



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