May new moon 2021: See Mercury, Venus and Mars in the moonless evening sky, ,

The new moon occurs Tuesday (May 11) at 3 p.m. EDT (1900 GMT). That same day the moon reaches apogee, the furthest point from Earth in its orbit, and in the days afterward the young moon will pass by Mercury and Venus in the evening sky.

New moons occur when the moon is directly between the Earth and sun, and the two share their celestial longitude, a projection of the Earth’s longitude lines on the sky. This position is also known as a conjunction. If you could see the dark sky during the day, the moon would only be noticeable as it blocked out stars. But the sun is so bright that it makes that kind of observation impossible from Earth. The exceptions are solar eclipses, in which the moon passes directly in front of the sun.

On average, the moon is about 239,000 miles (384,000 kilometers from the Earth, but the actual distance varies between as close as about 222,000 miles (356,000 km) and as far as about 239,000 miles (406,000 km), because the moon’s orbit is not perfectly circular. When the moon reaches new phase Tuesday, it will be 252,592 miles (406,508 km) away from Earth, according to NASA.

Related: 2021 Moon Phases Calendar

Visible planets

On the day of the new moon, Mercury and Venus will be in the evening sky, though only Mercury will be easily visible because Venus is so close to the setting sun. From New York City at about 8:30 p.m. local time — sunset is at 8:02 p.m. — Mercury will be about 13 degrees above the west-northwest horizon. The sky should be getting dark enough where it is visible by that time. Venus will only be about 3 degrees high; at sunset the planet is only at an altitude of 10 degrees. Venus is bright enough that a sharp-eyed observer might catch it against the glow of the sky at sunset.

The slender, crescent moon will make a close pass to Venus on Wednesday (May 12) and Mercury on Thursday (May 13). On Wednesday the moon will only be one day old, and so close to the sun that it will be very difficult to see — though an interesting and fun exercise is to see if you can catch a glimpse of it at sunset. The moon will pass about 42 arcminutes to the south of Venus at 6:03 p.m. local time in New York, according to the skywatching site In-The-Sky.org, and at sunset the moon and Venus will be about 6 degrees above the horizon.

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This sky map shows where Venus, Mercury and Mars will be visible from New York City on May 11, 2021, about 30 minutes after sunset. (Image credit: SkySafari app)

The conjunction with Mercury is an easier target. On Wednesday (May 12) at 1:58 p.m. EDT (1758 GMT) the moon will pass about 2 degrees to the south of Mercury. The event will be difficult to observe during the day, as the moon will still be quite close to the sun, the thin crescent easily lost in the sun’s glare.

Seeing the tiny planet Mercury will be very difficult without a telescope, and attempting to observe any celestial bodies in the vicinity of the sun can be dangerous. Accidentally looking through a telescope or binoculars at the sun, even for a moment, is an invitation to permanent retinal damage and even blindness.

It’s far better to wait until sunset, which will be at 8:04 p.m. in New York City. At that point Mercury will be about 19 degrees above the horizon with the moon to its left. If you can spot the two-day-old thin crescent of the moon, you can catch the innermost planet. Both will set by about 10 p.m. local time. As the sky darkens you can try to see Venus before it sets at about 9:08 p.m.

Related: Best night sky events of May 2021 (stargazing maps)

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The one-day-old moon will be in conjunction with Venus on May 12, 2021. (Image credit: SkySafari app)

Moving to the next planet out, Mars will be visible after sunset in the western sky. The Red Planet sets at about midnight, and by 8:30 p.m. on May 11 it is about 36 degrees above the horizon almost due west, in the constellation Gemini, the twins.

Jupiter and Saturn both remain predawn sights. Saturn rises first, at 1:45 a.m. local time in New York City, in the constellation Capricornus, the sea goat. Jupiter follows at 2:30 a.m., in the constellation Aquarius, the water bearer. By 5 a.m. Jupiter and Saturn will be 23 degrees and 27 degrees high, respectively, in the southeast. Saturn will be to the right of Jupiter.

Stars and constellations

The sun is setting later in mid-northern latitudes, and it doesn’t get dark until about 8:30 p.m., at the start of nautical twilight, when the sky will be dark enough for the stars to come out and the sun is at 6-12 degrees below the horizon. The winter constellations such as Orion, the hunter and Canis Major are all hugging the western horizon; they will set completely well before midnight.

Turning slightly northwards, you can see Capella, the brightest star in the constellation Auriga, the charioteer, which will still be relatively high, about one-eighth of the way to the zenith (the point directly overhead) from the horizon.

To the right and below Auriga you can spot the “W” shape of the constellation Cassiopeia, the legendary queen of Ethiopia who boasted that she and her daughter were more beautiful than the Nereids. Since the boast made Poseidon angry, she was forced to sacrifice her daughter Andromeda, but Perseus saved her. The legendary hero is just to the left of Cassiopeia in the sky, and to her right is her husband king Cepheus.

Straight up from the Cassiopeia is due north, and you will hit the Little Dipper and Polaris, the North Star. Opposite Polaris from Cassiopeia, you will see the Big Dipper, with the “bowl” upside down. The two stars at one end of the bowl (they will be on the left side) are Alpha Ursae Majoris and Beta Ursae Majoris, respectively called Dubhe and Merak. Those point to Polaris, the North Star. Following those “pointers” in the opposite direction, you find the constellation Leo, the lion, which will be almost at the zenith from mid-northern latitudes. The two stars at the back of the bowl point directly to the star Regulus, the brightest star in Leo. The more northerly star is called Megrez while the other is called Phecda.

If you think of Regulus as the front of Leo, with the sickle shape forming a head and mane, you can follow Leo’s gaze along the zodiac, the constellations the sun passes through as it moves against the stars during the year. If you’re facing so that Leo’s head is to the right (you will be looking just west of south), you can find the constellation Cancer, the crab, which forms a faint trapezoid shape in front of Leo. In the other direction, trailing Leo is the Virgo constellation, which will be to Leo’s right and towards the horizon. Following Virgo, just rising, is Libra, another faint constellation that is harder to see in urban areas.

As the night progresses observers can see Scorpio start to come over the horizon by about 11 p.m. At that point Antares, the bright star in the scorpion’s heart, will be about 10 degrees high in the southeast.

In the Southern Hemisphere, winter is approaching. In Melbourne, Australia, the sun sets at 5:21 p.m. on May 12 (the new moon occurs at 5 a.m. local time). By 7 p.m. when it is fully dark, the Southern Cross constellation will be just east of south — from Melbourne it is about 45 degrees above the horizon on May 12. The Southern Cross will be above the constellation Centaurus, which contains Alpha Centauri (otherwise known as Rigil Kentaurus), the closest star to our solar system. Turning east you can see the constellation Scorpius, the scorpion rising (though “upside down” from the Southern Hemisphere). Continuing to turn north observers will first spot Virgo, and then Leo, Cancer and Gemini.

Moving upwards from the Southern Cross — toward the north, and the zenith — Southern Hemisphere observers will find the three constellations that make up Argo, the ship: Puppis the deck, Vela the sail, and Carina the keel.

The Southern Cross can be used to locate south, much as the Big Dipper in the Northern Hemisphere can locate north. If you draw an imaginary line from the two brightest stars in the Southern Cross, which form the “vertical” post, extend it about four and a half times the length and drop a vertical line to the horizon, you are pointed due south.

The south celestial pole is in the constellation Octans, the octant, a relatively faint triangle of stars — there’s no equivalent of Polaris. So another way to locate it is to use the “pointers” in Centaurus, Alpha and Beta Centauri. Centaurus is the constellation just below the Southern Cross in the sky, and Alpha and Beta are its two brightest stars. If you draw an imaginary line from halfway between those two stars and another bright star, Achernar (the end of Eridanus, the river), the halfway point marks the pole.

Editor’s Note: If you snap an amazing night sky picture and would like to share it with Space.com’s readers, send your photos, comments, and your name and location to spacephotos@space.com.

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