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

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

by Jeffrey L. Hunt

Chicago, IL: 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 throughout the 14^e.

Transit time of Jupiter’s Great Red Spot, when it is at the center of the planet in the southern hemisphere: 9:27 UT, 7:23 UT; December 14, 5:19 GMT. Convert the time to your time zone. In the US, subtract five hours for EST, six hours for CST, etc. Use a telescope to see the place. The hours are from Sky & Telescope magazine.

It’s the 50^e anniversary of the last Apollo lunar mission – Apollo 17. On 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 as they traveled more than six miles in the lunar rover. This period of exploration lasted several minutes longer than seven hours.

Astronauts got rid of equipment they no longer needed. They returned and pressurized the lunar module several minutes after midnight (EST) on the 14th^e. The sixth lunar surface exploration mission has ended. Twelve humans have walked on the moon and little 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 samples collected weighed a total of 243.65 pounds (110.52 kg; official total in kilograms as determined by the Lunar Receiving Laboratory Farthest point from the LM was 25,029 ft. Good quality television transmissions were received during all three EVAs.

Here is today’s planetary forecast:

morning sky

The bright gibbous moon, 76% illuminated, is more than 50° above the southwestern horizon an hour before sunrise. The lunar orb approaches Leo.

The west-facing Leo tilts towards the western horizon at this time. We look at the Lion in silhouette. The head is delimited by a question mark or an upside-down sickle. The hips and tail are dotted with a triangle. The tail – Denebola – as at the eastern edge of the shining stars.

Mars glides rapidly from the morning sky an hour before sunrise. This morning it is over 6° above the west-northwest horizon, 9.2° below the lower right of Elnath, also known as Beta Tauri, the northern horn of Taurus.

evening sky

Venus and Mercury continue to challenge our skywatching skills, low in the southwest after sunset. Twenty minutes after sunset, the southwestern sky is bright, requiring binoculars to see the inner planets.

Bright Venus is less than 5° above the horizon and about one binocular line of sight to the right of the southwesterly direction. Find a place with a clear, unobstructed horizon in that direction.

Mercury is 5.6° upper left of Venus. The two are always in the same line of sight, making Mercury reasonably easy to identify.

Venus sets 50 minutes after sunset, so there is a small window to search for the pair of planets later at dusk.

One hour after sunset, the three bright outer planets are easy to locate. Going east, Mars is nearly 20° up east-northeast. It is bright, but darker than Jupiter.

Retrograde Mars – appearing to be moving west relative to the distant star field. This illusion comes from our planet moving faster between the Sun and Mars. The line of sight, which normally moves east relative to the stars, moves west as Earth approaches, passes, and moves away from Mars.

The planet appears ahead of Taurus, 9.4° top right of Elnath and 8.8° top left of Aldebaran, the brightest star in the constellation. Mars passes Aldebaran on December 26^e and again on January 30, 2023.

Farther west, bright Jupiter is about halfway up in the south-southeast. The planet is moving east past the dark stars of Pisces.

Notice the stars Deneb Kaitos – meaning “Sea Monster’s Tail” – lower left of Jupiter and Fomalhaut – meaning “Southern Fish’s Mouth” – nearly 20° south.

Saturn – dimmer than Jupiter and Mars, but brighter than most stars tonight – is about a third of the way up in the southwest. It moves east relative to the east of Capricorn. The Ringed Wonder is 1.8° to the top right of Nashira.

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

This display of the outer planets continues each evening until the beginning of February 2023. Venus, Mercury and the moon join them from December 24^e.

The moon covers or occults Eta Leonis (η Leo) of the eastern United States, southwestern Europe, and Africa. By the time the moon rises in Chicago, the occultation ends. 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 at the center of the planet in the Southern Hemisphere. Skywatchers farther west see the planet higher in clearer skies.