Depending on where you live worldwide, Venus and Saturn will snuggle up most closely together on the sky’s dome on December 10 or 11, 2019. On either date, though, Venus and Saturn will appear plenty close together in your sky. For the next several days, look for this bright pair of lights to pop out rather low in your southwest as dusk ebbs into nightfall.
Dazzling Venus – the 3rd-brightest celestial object, after the sun and moon – comes out first, around 30 minutes (or sooner) after the sun goes down; whereas Saturn – shining as brilliantly as a 1st-magnitude star – joins up with Venus perhaps 15 minutes or so after Venus’ initial appearance. Saturn, although respectably bright, pales next to Venus, which outshines Saturn by more than 60 times.
Be sure to catch this stunning planetary conjunction at dusk/nightfall (60 to 90 minutes after sunset) because these worlds will follow the sun beneath the horizon by early evening (about 2 hours after sundown). If you have binoculars, you can always aim them at Venus to spot Saturn all the sooner after sunset.
To optimize your sky watching pleasure, find an unobstructed horizon in the direction of sunset. Better yet, find a hill or balcony that’ll enable you to peek a little farther beyond the horizon. Venus and Saturn will set at nearly the same time for the next day or two, about 2 hours after sundown from virtually everywhere worldwide.
Two planets are said to be in conjunction where they are north and south of one another on the sky’s dome. At conjunction, Venus sweeps 1.8 degrees south of Saturn on December 11, 2019, at 4 Universal Time. For reference, your index finger at an arm length spans about 2 degrees of sky. After their conjunction, Venus will climb upward away from the sunset, while Saturn will fall sunward, to fade in the sunset glare by late December 2019 or early January 2020.
Venus and Saturn appear close together on the sky’s dome because they reside on nearly the same line of sight. But these worlds are not actually close together in space. Venus, the second planet outward from the sun, lies about 1.4 astronomical units (AU) from Earth, while Saturn, the 6th planet outward from the sun, resides nearly 8 times farther away, at 10.9 AU from Earth. For reference, one astronomical unit (AU) = sun-Earth distance.
Some people ask us how an inferior planet can have a conjunction with a superior planet in Earth’s sky? If a diagram is worth a thousand words, then perhaps the answer can be divined above.
On December 10 and 11, 2019, shortly after sundown, look low in the southwest, fairly close to the sunset point on the horizon, for the the conjunction of the bright planets, Venus and Saturn.