By now, you have almost certainly noticed dazzling Venus glowing in the western sky soon after sunset. On the evening of May 18, the brilliant planet will be joined by a slender crescent moon just 2.1 days past the new moon and only 7% illuminated.
Whenever these two objects pair off, they always attract attention even when they are not particularly close together.
Your clenched fist held at arm’s length measures roughly 10 degrees and on Monday evening, you will find our natural satellite situated about 3 degrees — or about one-third of a fist — to the right of Venus.
Ever wonder which is brighter, Venus or the crescent moon?
Many will probably say Venus because it appears as a small, sharp point of light, but it is the moon that is the brighter of the two. Currently, Venus shines at an eye-popping magnitude of -4.0, but the crescent moon, thin as it is, is magnitude -7.1 or 17 times brighter! It might be difficult to accept this, but the reason is that the moon‘s light is spread out over a much larger area compared to Venus, thus making it appear dimmer.
And of course, what we see is an illusion of perspective; the moon and Venus are nowhere near each other in space. The moon is 224,000 miles (360,000 km) from Earth, while Venus is 124 million miles (200 million km) away. But on Monday, they will be lined up in such a manner to appear relatively close to each other.
During May, Venus’s elongation from the sun increases from 24 to 32 degrees and from north temperate latitudes, making it easy to spot — hanging in the western sky at dusk and nearing the peak of its not very lofty 2026 apparition. It’s some 10 to 20 degrees to the east of the sun and 25 degrees above the horizon. Because a bright sky helps subdue Venus’s glare, this is a good time to inspect the planet telescopically, though its gibbous disk remains rather small and approximately seven-eighths illuminated.
Venus sets around 10:50 p.m. local daylight time. During the second week of June, when it will be at the pinnacle of its current evening visibility, it will set just after 11 p.m.
<em>Joe Rao serves as an instructor and guest lecturer at New York’s Hayden Planetarium. He writes about astronomy for Natural History magazine, Sky and Telescope, The Old Farmer’s Almanac and other publications.