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◼ Mercury puts on its best appearance of the year in the evening sky for northern hemisphere observers. Venus is in the evening sky too, but remains low in the twilight. The Eta Aquariids meteor shower is favourable for skywatchers at southern latitudes. Pacific regions and most of the America will see a Total Lunar Eclipse on 26 May.
May’s star chart
Click on the image above, or the following text for an interactive map of constellations visible in the sky. It can be adjusted for any time and date.
We also have a map of the night sky set up for mid-latitudes in the southern hemisphere.
The stars in May 2021
As northern skies darken, the familiar asterism of the Plough, or Big Dipper, lies overhead. Follow the curve of its handle to arrive at Arcturus, one of the brightest stars in the sky, in the constellation of Bootes, the Herdsman. If you continue the curve, you reach another bright star, Spica, in Virgo, which is now due south in the sky. Cassiopeia is at its lowest, above the northern horizon, its five brightest stars making a “W” pattern. In the north-eastern sky, Vega, in Lyra, and Deneb, in Cygnus, are rising. Binoculars, or a camera, will reveal the rich star clouds of the Milky Way in Cygnus.
From the southern hemisphere, the bright stars alpha and beta Centauri are virtually overhead, along with Crux Australis, the Southern Cross, to which those stars point. Brilliant star Canopus is low in the southwestern sky. Look north to see bright star Arcturus in Bootes.
The planets in May 2021
Mercury puts on its best show of the year for northern hemisphere observers in May. The planet, in Taurus, can be spotted from the start of the month if you have a clear, unobstructed WNW horizon. Its magnitude is -1.1 on 1 May, and though it gradually fades over subsequent days, it will move higher in the sky, making it easier to spot in the fading twilight. It is likely to be easiest to see in the second week of May, in the run-up to Greatest Elongation East when it will appear to be at its furthest from the Sun, at a distance of 22 degrees.
Southern hemisphere observers may also see the planet, though this is less favourable for them, and there will be a better show in September. A crescent Moon will lie close by Mercury on 13 May. On 28 May, Mercury will be close to Venus in the sky as it draws back in towards the Sun. This might be easier to see from southern latitudes, though Mercury will have faded to a challenging second magnitude. Read our full guide to seeing this evening apparition of Mercury.
Venus is back in the evening sky, but does not get very high in the sky from any part of the world before darkness falls. If you have a clear horizon, free of cloud and obstructions, then you may see it shining in the WNW as twilight falls, shining at magnitude -3.9. As noted above, Venus will lie close to Mercury on 28 May. We have a special article about this apparition of Venus, and how it will appear during 2021.
Mars spends the whole of May in the constellation of Gemini. It is still easy to spot in the evening sky, though much faded from its bright opposition showing last October. I now shines at just -1.6 at the start of May and 1.7 by month’s end. Mars’ rapid motion eastwards in the sky over the nights means it will remain an evening object for a few more months yet before it gets lost in evening twilight. A crescent Moon will lie close by on the 15th and 16th.
Read our extensive guide to Mars.
Jupiter is now in the morning sky and not difficult to see before dawn from northern hemisphere locations, though it still does not get terribly high in the sky before dawn. Lying in the constellation of Aquarius, it rises two hours before the Sun at the start of May and three hours by month’s end, shining at magnitude -2.4. From the southern hemisphere, Jupiter puts on a much better appearance, with its southerly position on the ecliptic allowing it to rise at around local midnight in mid-month, and getting high in the sky by the start of twilight. The Moon will lie close by on 5 May. If you have binoculars or a telescope, you can easily see the four brightest satellites of Jupiter, the Galilean moons Io Europa, Ganymede and Callisto. A telescope will also reveal the belts and bands in Jupiter’s cloud tops.
Saturn is another planet that is easy to spot from southern hemisphere, but less easy from northern latitudes due to its low altitude over the horizon. Saturn now rises in late evening from southern latitudes, and is high in the sky before dawn.
From northern countries, Saturn rises more than two and a half hours before the Sun at the start of May, but remains at a shallow angle to the ecliptic, so that it is still low in the sky before twilight becomes too bright at the start of the month. By the end of April, Saturn is rising about four hours before the Sun and so will be a bit higher and easier to see, given an unobstructed horizon. The Moon lies close by on the 4th.
Read more about Saturn.
Uranus passed through conjunction with the Sun on 30 April, so is not visible for most of May. Binoculars may pick it out before dawn towards the end of the month as it begins its new apparition. Read more about Uranus.
The outer ice giant Neptune is also in the morning sky, having reached conjunction in March, and may be spotted with binoculars or a small telescope, in Aquarius. Read more about Neptune.
The Eta Aquariids meteor shower became active in late April, and builds to a peak on the night of 4/5 May, when rates could reach 50 an hour. However, this is a shower best viewed from the southern tropics, because the radiant rises late in the night from northern latitudes, not long before the start of dawn twilight. The Eta Aquariids are debris left by Comet 1P/Halley. It is one of two showers produced by this comet, the other being the Orionids in October. Read our special guide to observing the Eta Aquariids meteor shower.
Remember that meteors can appear at any time on any night of the year. We see most when a meteor shower is active. But other meteors also randomly appear which cannot be identified with a known shower, and these are known as sporadic meteors, or simply sporadics. Here is more about these meteors, and how many appear from what is known as the anthelion source.
Total eclipse of the Moon
The Full Moon will enter the Earth’s dark shadow in space on 26 May, producing a total lunar eclipse. This wil be best seen in Pacific regions, with the eclipse already in progress when the Moon rises over Australia and the Far East, and with the whole spectacle visible from New Zealand. The main part of the eclipse begins just as the Moon is setting in parts of the eastern USA, Canada and South America. Places further west will see the Moon in eclipse before it sets. Sadly, no part of the eclipse will be visible for those of us in Europe and Africa, as the Moon will be below the horizon.
The Moon only just becomes fully immersed within the dark central part of the Earth’s shadow, just grazing its northern edge, so the northern part of the Moon may have a brighter tinge than the rest of the lunar surface.
The eclipse begins at 08.48 UT when the Moon enters the outer band of the Earth’s shadow, called the penumbra, and is slightly dimmed. Nearly an hour later, at 09.45 UT, it enters the dark central umbra, and it will look as if a bite is being taken out of the Moon. The Moon will be completely inside the umbra at 11.11 UT, and start to exit the umbra again just a few minutes later, at 11.26 UT. (Mid-eclipse occurs at 11.19 UT). The Moon leaves the umbra completely at 12.52 UT, then glides through the penumbra before exiting it at 13.50 UT, when the Moon will again shine with its full brilliance, due to reflected, unobstructed sunlight. Read our guide to eclipses of the Moon.
The Moon always makes a great target for a small telescope, which come into view as its phases change. We’ve a guide to where to find 50 of the best lunar features, plus a checklist to download so you can tick them off as you spot them! Don’t have a telescope? Here’s our guide to choosing one.
Fifty fantastic features – our amazing Moon
Here’s our guide to observing some of the finest sights on the Moon with small telescopes. Our pages of charts will help you find interesting features to seek out yourself, including craters, lava flows, mountain ranges and deep chasms!
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