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Celestial News: Jupiter and Saturn reach opposition

Jimmy Westlake
For Steamboat Pilot & Today
The solar system’s two giant planets will make close passes by the Earth this month: Jupiter on July 14 and Saturn on July 20. These telescopic views of the planets were taken through the historic 60-inch telescope at Mount Wilson Observatory near Pasadena, California. Jupiter shows off its cloud stripes and Great Red Spot (2012) and Saturn its icy rings (2017) Look for them in the southeastern sky in the early evening this month.
Jimmy Westlake/courtesy

Once every 20 years, the solar system’s two giant planets converge in the sky for what is called a Great Conjunction, and the year 2020 culminates with the greatest Great Conjunction of the past 400 years. On Dec. 21, Jupiter will pass only 0.1 degree from Saturn, the closest Great Conjunction since July 16, 1623. 

Meanwhile, this month, Jupiter and Saturn will light up our night sky side by side as each passes its opposition, or closest point to the Earth, only six days apart. It is during opposition that an outer planet is closest to the Earth and therefore best visible in our sky.

Jupiter and Earth are in a perpetual race around the sun, a race that the faster Earth always wins. Once every 13 months, the Earth gains a lap on Jupiter and pulls up alongside it in an event called opposition. Jupiter reaches opposition July 14, at a distance of 385 million miles. This will be the closest Jupiter has come to Earth since December 2012.

Saturn and Earth are also in a race around the sun. Once every 12 1/2 months, Earth gains a lap on Saturn for an opposition. Saturn reaches its opposition July 20, only six days after Jupiter does. This means that both of the giant outer planets will be big, bright and beautiful at the same time in our evening sky.

The gleaming planets will appear only about 7 degrees apart on the sky, less than the width of your clenched fist held at arm’s length. Saturn will be 836 million miles from Earth at this summer’s opposition, more than twice Jupiter’s distance. Still, this will be the closest Saturn has come to the Earth since May 2015.

Closer, larger Jupiter will shine 14 times brighter than Saturn. Look for them rising together in the southeastern sky as darkness falls, with Jupiter leading the way. Behind them will be the stars of the constellations Sagittarius and Capricornus.

Opposition is the best time to observe a planet through a telescope, too. If you own one, take a look at Jupiter’s dark cloud stripes and giant moons and Saturn’s icy rings in the weeks surrounding this double opposition. The very best observing time would be in the hours around midnight, when the two planets are as high in the sky as possible.

In other celestial news, a new comet might become visible to the unaided eye in mid-July. Comet NEOWISE, otherwise known as comet C/2020 F3, slingshotted around the sun July 3, and then shots up into our evening sky underneath the bowl of the Big Dipper. Tune in to the NASA website spaceweather.com for details and updates.

And finally, this month brings the much anticipated launch of NASA’s Mars 2020 mission, carrying the Perseverance rover to the dusty red surface of Mars to search for evidence of past life. Currently slated for a July 30 liftoff, Mars 2020 will arrive at Mars in February 2021.

Jimmy Westlake is the former full-time professor of physical sciences at Colorado Mountain College Steamboat Springs and former director of the Rollins Planetarium at Young Harris College. “Celestial News” appears monthly in Steamboat Pilot & Today. Check out Westlake’s astrophotography at jwestlake.com.


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