Sky Map: December 2019

Conjunction Junction—Venus Meets Saturn

By Jeff DeTray from AstronomyBoy.com
December 1, 2019
Sky Map December 2019
Jeff DeTray

Our December 2019 Sky Map highlights the December 10 Venus–Saturn conjunction! See a star chart that’s also printable—plus viewing information.

Just click here or on the image below to open the printable map—then bring outside!

December printable sky map

This month’s highlight: Conjunction Junction—Venus Meets Saturn

The song “Conjunction Junction” from the 1973 “Schoolhouse Rock” TV program sought to teach young learners about the proper usage of “and”, “but”, and “or.” For sky gazers, a conjunction is something completely different: a close meeting of two or more astronomical objects in the sky. During the first half of December, there is a delightful conjunction of the planets Venus and Saturn, with Jupiter in close attendance.

Venus, the second planet from the Sun (Earth is the third), has long been known as “Earth’s Twin.” The two planets are nearly equal in size, with Earth being slightly more massive and having a slightly larger diameter. The similarities don’t end there. Venus and Earth are both rocky planets, made of solid material, as opposed to planets like Jupiter and Saturn, which consist mainly of gases. It’s long been known that Venus has an atmosphere, a dense one, with thick clouds shrouding the entire planet. Venus also comes closer to Earth than any other planet, sometimes venturing as near as 24 million miles. So, there has always been much to suggest that Venus and Earth are indeed twin planets.

Before a visit by the Mariner 2 space probe in 1962, it was believed that Venus, like Earth, might harbor life. Yes, Venus was closer to the Sun than was Earth, so it was certainly the warmer of the two planets. In the absence of firm evidence to the contrary, it was easy to imagine Venus as a warm, cloudy, wet, swampy version of Earth. Perhaps it was populated by dinosaurs or even human-like Venusians!

These exciting prospects were dashed when Mariner 2 swept past Venus on December 14, 1962. Instruments aboard the spacecraft determined that the surface temperature of Venus was near 800∞ Fahrenheit, hot enough to melt lead. We’ve since learned that Venus is also utterly dry, a far cry from the lush, tropical environment once envisioned. But … there is always a “but” … a couple of billion years ago, scientific research suggests Venus might have been cooler and wetter than it is today. Maybe, just maybe, life once thrived on Earth’s Twin.

Almost exactly 57 years after she was visited by Mariner 2, you can spy beautiful Venus this December, low in the southwest sky, shortly after sunset. After the Sun and Moon, Venus is by far the brightest object in the sky, outshining every other planet and every star. It’s no wonder that the ancient Greeks and Romans both identified this dazzling planet with the goddess of love. (To the Greeks, she was Aphrodite.)

How to See the Venus–Saturn Conjunction

On the evening of December 10, Venus and Saturn are in conjunction, with very-much-brighter Venus just below Saturn. The planet Jupiter sits even lower, almost on the horizon, to the lower right of the pair.

For a few days before and after the December 10 conjunction, you can watch the position of Venus change from night to night. Compared to Saturn and Jupiter, which remain virtually stationary with respect to the background stars, Venus moves steadily toward the upper left each night. Our sky map shows the location of Venus in 3-day increments from December 4th to the 16th.

If your weather is warm enough, take a few minutes to enjoy other sights in the early December night sky. As shown on the map there are several distinctive asterisms (unofficial star patterns) and bright stars worthy of your attention.

December 2019 Sky Map

Click here or on map below to enlarge (PDF).

December 2019 Sky Map
Sky map produced using Chris Marriott’s Skymap Pro

Note: How to Read the Sky Map

Our monthly sky map does not show the entire sky which would be almost impossible. Instead, the map focuses on a particular region of the sky each month where something interesting is happening. The legend on the map always tells you which direction you should facing, based on midnight viewing. For example, if the map legend says “Looking Southeast,” you should face southeast when using the map.

The map is accurate for any location at a so-called “mid northern” latitude. That includes anywhere in the 48 U.S. states, southern Canada, central and southern Europe, central Asia, and Japan. If you are located substantially north of these areas, objects on our map will appear lower in your sky, and some objects near the horizon will not be visible at all. If you are substantially south of these areas, everything on our map will appear higher in your sky.

The items labeled in green on the sky map are known as asterisms. These are distinctive star patterns that lie within constellations. When getting your bearings under the stars, it’s often easiest to spot an asterism and use it as a guide to finding the parent constellation.

The numbers along the white “Your Horizon” curve at the bottom of the map are compass points, shown on degrees. As you turn your head from side to side, you will be looking in the compass direction indicated by those numbers. The horizon line is curved in order to preserve the geometry of objects in the sky. If we made the horizon line straight, the geometry of objects in the sky would be distorted.

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