2024, December 11-20: Mars Accelerates Westward

December 11-20, 2024: Mars retrograde accelerates and opens a gap to the Beehive star cluster. The Red Planet is part of a nightly planet display that begins with brilliant Venus after sunset.

Mars approaches Jupiter — Photo Caption – 2024, August 12: Mars nears a conjunction with Jupiter.

By Jeffrey L. Hunt

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Mars Accelerates Westward

Photo Caption – 2007, December 1: Late winter in the northern hemisphere shows clouds above the northern polar cap and some above the southern cap. (NASA Photo)

Mars accelerates westward after its retrograde began on the 6^th. Through a binocular it opens a widening gap with the Beehive star cluster.

Venus Leads Evening Display

Chart Caption – Venus clouds from the Hubble Space Telescope. The planet shows phases. (NASA photo)

Mars is part of a nightly planet parade that begins with brilliant Venus in the southwestern sky after nightfall. The Evening Star can be found as early as 30 minutes after the sun sets. Each evening it steps eastward against the background stars, currently Capricornus.

Venus is closing a gap to Saturn, less than 40° to Venus’ upper left on the 11^th. By the 20^th, they are over 28° apart. Venus passes the Ringed Wonder next month.

Saturn, the brightest star in the region, but considerably dimmer than Venus, is less than halfway up in the south at an hour after sundown. It is about 20° above the star Fomalhaut.

Jupiter, center, and its moon Europa, left, are seen through the James Webb Space Telescope’s NIRCam instrument 2.12 micron filter. Credits: NASA, ESA, CSA, and B. Holler and J. Stansberry (STScI) — Photo Caption – Jupiter, center, and its moon Europa, left, are seen through the James Webb Space Telescope’s infrared sensors. The Great Red Spot is the bright oval on the lower right of the planet’s globe. (Image Credit: NASA)

Jupiter, the second brightest starlike body, is nearly 15° up in the east. It retrogrades in front of Taurus – to the left of Aldebaran the constellation’s brightest star.

Mercury, Morning Planet

Photo Caption – Mercury as Never Seen Before. (NASA photo)

Mercury is one of the five bright planets, rising 65 minutes before the sun on the 11^th when it is about 6° above the horizon at 30 minutes before sunrise. By the 15^th, it rises 93 minutes before the sun and appears about 7° above the southeast horizon at 45 minutes before daybreak. By the 20^th, the speedy planet is nearly 10° up in the southeast at the same time interval before sunrise. Five bright planets are visible during the night, although four shine during the evening hours.

Mars through Binocular

Mars accelerates westward — Chart Caption – 2024, December 11-20: Through a binocular, Mars moves westward compared to Cancer.

Mars rises about three hours after sunset. It is in front of Cancer below Gemini’s Pollux. The planet is retrograding in front of Cancer near the Beehive star cluster, easily visible through a binocular, inside an irregular box made by Asellus Borealis, Asellus Australis, Theta Cancri (θ Cnc on the chart) and Eta Cancri (η Cnc).

Line of Sight Shifts Westward

Mars at opposition — Chart Caption – September 19, 2024-May 17, 2025: The orbits of Earth and Mars are displayed as opposition occurs January 15, 2025. As Earth overtakes Mars, the Red Planet appears to pass bright stars in Gemini and retrograde.

Retrograde is an illusion when our faster-moving world passes a planet farther from the sun, known as a superior planet. The line of sight from Earth to the planet and extended toward the distant starry background normally moves eastward. As Earth overtakes the planet and passes between the superior planet and the sun, the line of sight shifts westward compared to the stars. We see the planet appear to backup.

Mars, 2024-2025

Mars retrogrades over 1° during the 10 days displayed on the accompanying binocular diagram. This is about the diameter of two Full moons in the sky. In comparison, the Beehive star cluster covers three full-moon diameters.

Mars and Moon, September 6, 2020 — Photo Caption – 2020, September 6: Mars and Moon. (Composite image)

During the 10 days of Mars’ retrograde, the moon waxes to the Full (Cold) moon on the 15^th. It is near the Pleiades on the 13^th, followed by a pairing with Jupiter on the next evening. The waning moon is near Pollux on the 16^th and Mars on the evening of the 17^th. It appears near the Sickle of Leo on the 19^th.

Use a binocular to watch Mars accelerate westward compared to the starfield and the named stars. The chart is shown when the planet is high in the southern sky around four hours before sunrise. At other times, the field of view is rotated compared to the chart, but the stars and cluster are easy to recognize. It is useful when Mars is higher in the sky, such as from six hours after sundown until about 90 minutes before daybreak.

Watch Mars accelerate westward.

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