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Planet Watch 2021

by Perry Pezzolanella

Every evening this year will have at least one bright planet visible with Mars ruling the early months, Jupiter and Saturn the late mid-year, and Venus the finale. The night sky is always full of beauty and wonder, sometimes punctuated with bright, shimmering aurora; flashy, streaking meteors; or a fuzzy, delicate comet. There are beautiful lunar and planetary conjunctions, countless asteroids and satellites, and the International Space Station.

Eclipses return in 2021 with a near-total lunar eclipse during the wee hours of November 19. The partial eclipse begins at 2:18 A.M., reaching maximum eclipse at 4:02 A.M. when the Moon will be 97% eclipsed, and ends at 5:47 A.M. The next total lunar eclipse visible locally will occur on May 15-16, 2022. There will be a beautiful, if challenging, partial solar eclipse at sunrise on June 10, 2021 with the sun rising as a stunning crescent around 77% eclipsed. The eclipse is annular over the Hudson Bay with the Moon a little smaller than the Sun so it can never be total. The result is a rather thin, sharply pointed crescent worthy of dramatic photography. The eclipse ends at 6:36 A.M. with another, less dramatic partial solar eclipse occurring on October 14, 2023.

A productive 2021 starts off with Mars as the lonely bright planet and will gradually fade into the evening twilight by September. Neptune, followed by Uranus, will descend into the sunset glow by March. Mercury will briefly come into view low in the northwest for the first three weeks of May to steal the spotlight from Mars. Venus emerges in the bright twilight low in the west during June and slowly grows higher, although still low for the rest of the year. Saturn will rise not long after sunset by July followed closely by Jupiter. Both will dominate the remainder of the summer and into autumn before succumbing to bright twilight during December leaving Venus as the lone bright planet symbolically as a Christmas Star. Uranus and Neptune will be at their best from September through the end of the year, although never bright. Here is the breakdown for each planet in the evening sky during 2021:

Mercury: This elusive planet is always very low on the horizon and immersed in bright twilight, but it is easiest to see in the evening from May 1-22, being highest above the horizon on May 15. Mercury will grow steadily through this period from 6 to 10 arcseconds across as it approaches Earth, but its magnitude will dim from -1 to +2. It will go through phases like a tiny, coppery version of the waning Moon, from nearly full to a thin crescent.

Venus: This dazzling planet has a poor evening apparition later this year as it barely rises above the tree and roof tops until early December and even then, its highest appearance will be brief as it reaches inferior conjunction between the Sun and Earth on January 8, 2022. It will be at its greatest eastern elongation from the Sun on October 28 and well away from the Sun for good viewing, but very low. It will brighten to magnitude -4.7 in the weeks ahead and grow into a large, thinning crescent nearly an arcminute across by New Year’s Day. It will be the perfect Christmas Star and will make several beautiful pairings with the crescent Moon.

Mars: This is an off year for Mars as it is small and distant before becoming lost in the twilight by September. The best views will be in January when it is around 10 arcseconds across and shining at magnitude 0 before shrinking to barely 4 arcseconds across and fading to magnitude +1.8 by June. Mars will be back for a modest opposition during December 2022.

Jupiter: This stormy world will perform a class act for the public as it will be nearly at its largest and brightest possible, and this will occur in the balmy summer months to boot. Jupiter is at opposition on August 19 in Capricornus and will be 48.9 arcseconds across and blaze at magnitude -2.9. The huge size will allow for plenty of detailed viewing of Jupiter’s clouds including the Great Red Spot. It should be possible to see the tiny discs of the larger moons, Callisto and Ganymede, and to compare their size to smaller Europa and Io. It might even be possible to detect slight color differences among them. Jupiter will become lost in the evening twilight during December as it fades to magnitude -2.0 and shrinks to 33 arcseconds across.

Saturn: The beautiful rings are steadily closing as the years go by, but Saturn is still a showstopper at star parties and will continue to do so as oppositions are occurring during the warmer months. It is at opposition in Capricornus on August 2 when it will be 18.6 arcseconds across and shine at magnitude +0.2. The balmy nights offer the perfect opportunity to examine the rings and detect the Cassini Division. The cloud belts and polar hood are often quite obvious. The largest moon, Titan, shines around 8th magnitude and takes nearly 16 days to orbit once around Saturn and it is a fun project to plot its changing position. Saturn will slowly fade to magnitude +0.6 and shrink to around 15 arcseconds across by December when it becomes lost in the twilight glow.

Uranus: Seeing the unusual turquoise hue of Uranus is worth the hunt and its small disc is easy to discern among the stars. It is at opposition on November 4 in Aries when it will be 3.7 arcseconds across and shine at magnitude +5.7. Uranus rises before midnight during September and gradually fades into the evening twilight by April 2022.

Neptune: Seeing the icy bluish tint of Neptune gives the chills and seeing this rare color is also worth the hunt making it easier to distinguish it from the stars. It is at opposition on September 14 in Aquarius when it will be 2.4 arcseconds across and shine at magnitude +7.8. Neptune will rise before midnight during August and disappear into the evening twilight during February 2022. A finder chart for Uranus and Neptune will appear in the August issue of Telescopic Topics.

Pluto: The challenge of hunting Pluto and finally seeing it is considered a major accomplishment for all who make the effort. Unfortunately, the challenge will only increase during the decades ahead as Pluto dims towards magnitude +15 around 2040 and remains very low along the ecliptic in Sagittarius and eventually lower Capricornus. It is at opposition on July 17, southeast of the Teaspoon asterism of Sagittarius, and above a small asterism that looks like a fainter version of the Southern Cross. Pluto is nothing more than a faint spark at magnitude +14.3 and will be only 0.1 arcseconds across.