The tiny planet Mercury will make a close approach to the crescent moon in the evening sky tonight (Sept. 8), but the pair may be difficult to observe.
Mercury and the moon will be just above the western horizon at sunset, which means you won't have much time to observe Mercury before it, too, sinks below the horizon. Although the planet will be up in the sky before sunset, it can be difficult and dangerous to see it in the sun's bright glare.
In New York City, for example, the sun sets at 7:16 p.m. EDT tonight, less than one hour before Mercury sets at 8:06 p.m. local time, according to Time and Date. The day-old waxing crescent moon — which just reached new phase on Monday (Sept. 6) — sets shortly after Mercury, at 8:29 p.m.
Mercury and the moon reached a conjunction, meaning they shared the same celestial longitude while making a close approach, at 4:18 p.m. EDT (2018 GMT) today, according to the skywatching site In-The-Sky.org. The pair will remain close together in the sky all evening, but you may need binoculars or a telescope to see Mercury.
Because Mercury is so close to the horizon after sunset, it will be difficult or impossible to observe from northern latitudes. According to NASA, the planet should be observable at mid-northern latitudes and farther south. The closer you are to the equator, the better your view will be, as the planet will remain in the sky longer after sunset. In Miami, for example, the sun sets today at 7:32 p.m. EDT, while Mercury sets at 8:40 p.m. local time.
If you aren't able to spot Mercury tonight, you may have better luck looking for Venus, which is shining brightly to the south (left) of Mercury and is higher up in the sky. Venus sets in New York City at 8:48 p.m. local time but will be above the horizon in Miami until 9:30 p.m. local time.
To find out exactly what time the planets will rise and set from your location, check out this night sky calculator from Time and Date.