Tonight – November 19, 2017 – you have a skywatching challenge ahead of you if you live in North America. If you live in Europe, Asia and Indonesia, this same challenge might have to wait until the evening on November 20. If you’re in the Southern Hemisphere … less of a challenge! You might see this sky scene – the young moon near the planet Mercury – both tonight and tomorrow.
From North America. Try catching the young moon and/or planet Mercury in the southwest sky after sunset on November 19. These two worlds will lurk close to the sunset point on your horizon, beneath the planet Saturn, at evening dusk. So don’t tarry when looking for the moon and Mercury! Chances are they will sink below your horizon before nightfall. Start your search no later than 45 minutes after sunset and bring along binoculars, if you have them.
From Asia, Indonesia, Australia and New Zealand. From Asia, Indonesia, Australia and New Zealand, you might have to wait until after sunset November 20 to spot the slender moon at evening dusk. That’s because – on November 19 – the moon will be closer to the sunset in your sky. Very tough to see! Easier on November 20, but still a challenge.
From the Southern Hemisphere. People south of the equator have the advantage for spotting the young moon and planet Mercury after sunset on November 19 and 20. The ecliptic – marking the path of the sun, moon and planets in our sky – makes a more perpendicular angle to the evening horizon as seen from your part of the world. So the moon and planets are more directly above the sunset, rather than to one side of it, as is the case from the Northern Hemisphere. At mid-northern latitudes, Mercury barely stays out for an hour after sunset (presuming a level and unobstructed horizon). At the equator, Mercury is in the sky for about one and one-third hours after sundown; and at temperate latitudes in the Southern Hemisphere, Mercury sets about one and three-quarter hours after sunset.
Click here to for a custom sunrise-sunset box; it’ll give you moonrise-moonset times, too, if you check the right box.
From around the world, the planet Saturn will stay out after the moon and Mercury have already set. Moreover, Saturn will stay out until (or after) nightfall. Tomorrow after sunset (November 20), as seen from around the world, the waxing crescent moon will have moved closer to Saturn on the sky’s dome.
Also, there’s a more subtle movement involving the two wandering worlds, Mercury and Saturn. Mercury is climbing away from the glare of sunset from day to day, while Saturn is sinking toward the setting sun daily. Near the end of the month – on November 28, 2017 – Mercury will pass 3o to the south of Saturn, to showcase a conjunction of these two worlds in the evening sky.
Bottom line: Will you catch the young moon and planet Mercury after sunset on November 19, 2017? Good luck!
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.