2022, December 13: Remembering Apollo 17, Bright Outer Planets


December 13, 2022: Fifty years ago, the Apollo 17 astronauts completed their exploration of the lunar surface.  Tonight, Mars, Jupiter, and Saturn are visible after sundown.

Photo Caption – (13 Dec. 1972) — Astronaut Harrison H. Schmitt, lunar module pilot, works near the Lunar Roving Vehicle (LRV) during the third Apollo 17 extravehicular activity (EVA) at the Taurus-Littrow site on the lunar surface. (NASA Photo)


by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 7:10 a.m. CST; Sunset, 4:20 p.m. CST.  Check local sources for sunrise and sunset times for your location.

Today’s sunset time is the earliest of the year.  This continues through the 14th.

Jupiter’s Great Red Spot’s transit times, when it is in the center of the planet in the southern hemisphere: 9:27 UT, 19:23 UT; Dec. 14, 5:19 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.

Photo Caption – (13 Dec. 1972) — The Apollo 17 Lunar Roving Vehicle (LRV) is photographed near a large lunar boulder during the third Apollo 17 extravehicular activity (EVA) at the Taurus-Littrow landing site.

This is the 50th anniversary of the last Apollo lunar mission – Apollo 17.  December 13, 1972, Eugene Cernan and Harrison Schmitt, the moon walkers, completed the third and final session of their lunar exploration.  They set up experiments and collected nearly 140 pounds of lunar samples, while they traveled over six miles in the lunar rover. This exploration period lasted several minutes longer than seven hours.

Photo Caption – Astronaut Eugene A. Cernan, Apollo 17 commander, is photographed next to the deployed United States flag during lunar surface extravehicular activity (EVA) at the Taurus-Littrow landing site.

The astronauts discarded equipment that they no longer needed.  They re-entered and pressurized the lunar module several minutes after midnight (EST) on the 14th.  The sixth lunar mission to explore the surface ended.  Twelve humans walked on the moon and minimally explored its surface.  Eugene Cernan was the last person to walk on the moon.

From NASA’s summary: “For the mission, the total time spent outside the LM was 22 hours 3 minutes 57 seconds, the total distance traveled in the lunar rover vehicle was 19.3 nautical miles (35.7 km), vehicle drive time was 4 hours 29 minutes, and the collected samples totaled 243.65 pounds (110.52 kg; official total in kilograms as determined by the Lunar Receiving Laboratory in Houston). The farthest point traveled from the LM was 25,029 feet. Good quality television transmissions were received during all three EVAs.”

Summaries of Current Sky Events

Here is today’s planet forecast:

Morning Sky

Chart Caption – 2022, December 13: The moon is near Leo before sunup.

The bright gibbous moon, 76% illuminated, is over 50° above the southwest horizon at one hour before sunup.  The lunar orb is approaching Leo.

The westward facing Lion is tilting toward the western horizon at this hour.  We look at the Lion in silhouette.  The head is outlined by a backwards question mark or sickle.  The haunches and tail are dotted by a triangle.  The tail – Denebola – as at the eastern edge of the bright stars.

Chart Caption – 2022, December 13: Mars is low in the west-northwest before sunrise.

Mars is quickly slipping from the morning sky at one hour before sunrise.  This morning it is over 6° above the west-northwest horizon, 9.2° to the lower right of Elnath, also known as Beta Tauri, Taurus’ northern horn.

Evening Sky

Chart Caption – 2022, December 13: Venus and Mercury are in the southwest during bright evening twilight.

Venus and Mercury continue to challenge our sky watching skills, low in the southwest after sunset.  At twenty minutes after sundown, the southwest-sky is bright, requiring a binocular to see the inner planets.

Brilliant Venus is less than 5° above the horizon and about one binocular field of view to the right of the southwest direction.  Find a spot with a clear, unobstructed horizon in that direction.

Mercury is 5.6° to the upper left of Venus.  Both are still in the same field of view, making Mercury reasonably easy to identify.

Venus sets 50 minutes after sundown, so there is a small window to look for the planet pair later during twilight.

Chart Caption – 2022, December 13: Jupiter and Saturn are in the southern sky during the early evening.

An hour after sundown, the three bright outer planets are easy to locate.  Starting eastward, Mars is nearly 20° up in the east-northeast.  It is bright, but dimmer than Jupiter.

Mars is retrograding – appearing to move westward compared to the distant starfield.  This illusion is from our faster-moving planet moving between the sun and Mars.  The line of sight, that normally moves eastward compared to the stars, shifts westward as Earth approaches, passes, and recedes from Mars.

The planet appears in front of Taurus, 9.4° to the upper right of Elnath and 8.8° to the upper left of Aldebaran, the constellation’s brightest star. Mars passes Aldebaran on December 26th and again on January 30, 2023.

Farther westward, bright Jupiter is about halfway up in the south-southeast.  The planet is moving eastward in front of Pisces’ dim stars.

Notice the stars Deneb Kaitos – meaning “the tail of the sea monster” – to Jupiter’s lower left and Fomalhaut – meaning “the mouth of the southern fish” – nearly 20° up in the south.

Saturn – dimmer than Jupiter and Mars, but brighter than most stars tonight – is about one-third of the way up in the southwest.  It is moving eastward compared to eastern Capricornus.  The Ringed Wonder is 1.8° to the upper right of Nashira.

Two hours after sundown, bright Jupiter is halfway up in the south; Mars is nearly one-third of the way up in the east; and Saturn is less than one-third of the way up in the southwest.

This display of outer planets continues each evening through early February, 2023.  Venus, Mercury, and the moon join them beginning December 24th.

The moon covers or occults Eta Leonis (η Leo) from the eastern US, southwestern Europe, and Africa.  By the time the moon rises in Chicago, the occultation is ending.  For more details see this source.

At 11:19 p.m. CST, when Jupiter is low in the western sky from Chicago, Jupiter’s Great Red Spot is in the center of the planet in the southern hemisphere. Sky watchers farther westward see the planet higher in a clearer sky.



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