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◼ Mars is the sole bright planet visible throughout the evening. Mercury and Venus will be in close conjunction on 25 April, but hard to spot in bright evening twilight. The Lyrids meteor shower reaches maximum. Here’s what planets and other things can see in the night sky in April.
April’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 April 2021
The nights are getting shorter at more northern latitudes as summer approaches. As the sky darkens in early April, the winter constellations still hang on at northern latitudes, with Orion, the Hunter sinking in the southwest. Taurus, the Bull can be seen to his upper right, over the western horizon, followed down by Gemini, the Twins.
Auriga, the Charioteer, is high in the northwest, including Capella, one of the brighter stars in the sky. Ursa Major is now virtually overhead, the constellation that includes the familiar seven-star asterism of the Plough, or Big Dipper, and below it, due south, lies Leo, the Lion. Follow the curve of the handle of the Plough/Big Dipper to find bright star Arcturus, in the constellation of Bootes, the Herdsman, now high over the northeastern horizon.
From the southern hemisphere, Crux Australis, the Southern Cross, is overhead, with the pointers, alpha and beta Centauri, to its southeast. Canopus, the second brightest star in the sky, is high in the southwest, in the constellation of Carina, the Ship’s Keel, with the brightest star, Sirius, in Canis Major, hanging over the western horizon. Look northeast to see another bright star, Arcturus in the constellation of Bootes, the Herdsman.
The planets in April 2021
Mercury begins April in the morning sky, but too low in the pre-dawn glare to be seen from most northerly latitudes, such as Europe, the USA and Canada. From the southern hemisphere, it will be higher in the sky because the ecliptic is at a sharp angle to the horizon. Catch it as early as you can in the first week of April, because it swiftly heads back towards the Sun and will be lost by the end of the second week of the month.
On 25 April, Mercury will pass very close to Venus in the evening sky, though this conjunction will be very difficult to observe due to their low elevation in a brightly twilit sky. By the end of April, Mercury will have moved far enough from the Sun to be seen from northern hemisphere countries with clear western horizons.
Venus passed through superior conjunction, on the far side of the Sun, on 26 March and so is now technically an evening object. However, it will be some weeks before it emerges far enough from the Sun to be seen easily. Northern hemisphere observers might spot it very low in the western sky as the sky darkens, by the end of the month, if they have a clear, unobstructed horizon. As noted above, Venus and Mercury will lie close together on 25 April, but in a very bright sky.
The red planet’s rapid motion eastwards through the heavens means that it remains visible throughout the evening during the whole of April, not setting until the early hours. Mars is still steadily fading as it recedes from Earth. It starts April at magnitude 1.3 in the constellation of Taurus, and ends it at magnitude 1.6 in neighbouring Gemini.
It is now hard to see any detail on the planet, whose apparent diameter at the equator has halved since the start of the year. It is just 5.3 arcseconds at the start of April, reducing to 4.6 arseconds by the end of the month. The waxing crescent Moon will lie nearby on the 17th.
Read our guide to Mars.
Jupiter easy to spot from southern latitudes because of the sharp angle of the ecliptic, shining at magnitude -2.1. It rises more than three hours before the Sun at the start of April. Waning crescent Moon close by on the 7th. It will be difficult to see Jupiter from northern hemisphere locations at the start of the month, due to shallow angle of the ecliptic to the horizon, meaning it doesn’t get very high. The situation improves slightly as the month progresses, but you will need a clear, unobstructed horizon. By the end of April, it will be a lot easier, with Jupiter reaching an elevation of around 10 degrees above the horizon before twilight becomes too bright.
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 rises more than four hours before the Sun at the start of April from southern latitudes, and is high in sky by dawn.
From northern countries, Saturn rises around two hours before the Sun, but remains at a shallow angle to the ecliptic, so that it is still less than 10 degrees high before twilight becomes too bright at the start of the month. By the end of April, Saturn is rising about two and a half 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 6th.
Read more about Saturn.
Uranus is now sinking low in the west as the sky darkens. If you want to catch it, shining at magnitude 5.9 in the constellation of Aries, you will need to be quick as it will be near impossible after the first few days at northern latitudes, due to its rapid motion into the advancing glare of dusk twilight before it reaches conjunction with the Sun on the 30th. Binoculars are essential at the best of times. Read more about Uranus.
The outer ice giant Neptune is now in the morning sky, having reached conjunction on 11 March, and it will be very difficult to spot in the pre-dawn sky this month. Read more about Neptune.
The Lyrids meteor shower reaches its annual peak on the night of 21-22 April. This is a shower which favours the northern hemisphere, and in a good year, with dark skies, the zenithal hourly rate (ZHR) can reach 18 meteors an hour. Unfortunately, in 2021 the Moon will be at a bright, waxing, gibbous phase, which will drown out many meteors. The meteors are dust cast off by C/1861 G1 (Thatcher).
Another meteor shower, the Eta Aquariids, becomes active in late April, building to a peak next month, when rates could reach 50 an hour on the night of 4-5 May. Best viewed from the southern tropics, these meteors are debris left by Comet 1P/Halley. It is one of two showers produced by this comet, the other being the Orionids in October.
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.
Find bright asteroid Vesta
There may not be many planets to spot at the moment, but the brightest of the asteroids is now easy to find with binoculars. Vesta steadily brightened over the course of February, as it began to cross one of the more distinctive constellations in the night sky, Leo. It reached magnitude 5.8 on 4 March, when it was at opposition. The image below shows the track of Vesta. You can see a more detailed track in our main article on how to see asteroid Vesta shining at its brightest.
Losing the night sky to Starlink
As Stuart Atkinson was photographing the attractive spectacle of Mars closing in on the Pleiades and Hyades star clusters on the evening of 28 February, he realised that a steady stream of satellites were crossing the field and invading his images. They were the latest batch among hundreds of satellites being launched by Elon Musk’s SpaceX to provide global internet.
The arrival of vast constellations of such satellites in orbit, from SpaceX and rival corporations, is already having a huge and damaging impact on the work of professional and amateur astronomers alike. Yet surprisingly, the problem seems to have taken the astronomy world entirely by surprise, because there was no prior discussion with the scientific community.
Professor Andy Lawrence, of the Institute for Astronomy (IfA) of the University of Edinburgh, has written a non-technical ebook about the problem, called Losing the Sky. You can read about it and order a copy via his website.
Professor Lawrence comments: “These objects pollute the night sky, streak across our astronomical images, blare loudly and unpredictably at our radio telescopes, and increase the danger of spacecraft collisions, pushing us towards a space debris run-away that may make space industry unsustainable.”
SpaceX have responded to complaints by offering to make the Starlink satellites less reflective, and say they will be much less obvious anyway when they reach their eventual high orbits. But with newly launched batches becoming a regular event, they are likely to remain an astronomical nuisance for a long time yet.
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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