On the evenings around Thursday, September 12, Mercury and Venus will appear very close together in the sky. Let's find out how to observe the pair.
The speedy inner planets Mercury and Venus are both shifting steadily away from the sun in their orbits this week. Mercury starts this week much closer to the sun than Venus, but its faster orbital motion will cause it to overtake and then pass brighter Venus this Friday.
Look for the pair of planets very low in the western sky right after sunset. The planets will be less than half a finger's width apart. (20 arc-minutes, or two-thirds of the full moon's diameter, to be more precise.) Venus will be higher than (to celestial north of) Mercury until Sunday, after which time Mercury will be higher and on Venus' left. The best time to look will be at about 8:00 pm local time. Ensure that the sun has completely disappeared below the horizon before hunting for them in binoculars.
Mercury and Venus will appear together in binoculars and backyard telescopes at low power. Observers that live closer to the equator will have an easier time seeing them.