Exploring Our Night Sky: April 2021

As the days lengthen and the nights shorten there is still plenty to see in this month’s night sky. The winter constellations will gradually disappear beyond the western horizon as the spring constellations of Leo and Virgo dominate our southern sky. Also, after a gap of a few months, shooting stars return in the form of the Lyrids meteor shower, which peaks on the night of 21-22 April. 

A shooting star from the Lyrid Meteor Shower flying across the night sky above Loch Sunart

The Constellations

This month, the sun sets around 8:30 pm and the stars and the constellations start to become visible from about 10:00 pm onwards. So, once it is getting dark, look directly above your head and you’ll see the Plough, which is an asterism that is familiar to a lot of people. This makes it an excellent starting point from which to navigate your way around the southern night sky.

If you trace a line from the Plough down to the southern horizon, you will find Regulus, the brightest star in the constellation of Leo (The Lion) about halfway down. This star is at the bottom of a backwards question-mark which is made up of a total of 6 stars and called The Sickle. This asterism is the back of The Lion’s head and the six stars in it are Epsilon Leonis, Mu Leonis, Zeta Leonis, Gamma Leonis, Eta Leonis, and Alpha Leonis. Follow a line left and slightly up from Regulus and you’ll come to Denebola. This forms the bright tip of The Lion’s tail and its name comes from the Arabic for lion’s tail.

​Up from and to the right of Regulus, you will find Castor and Pollux, the two stars which mark the heads of the Twins, Gemini. The bodies of the Twins are the two lines of stars which extend towards Orion (The Hunter), which will be low on the horizon out to the west and will be best found by identifying Betelgeuse, the bright red star which forms the Hunter’s left shoulder at the top of the constellation.

The Constellation of Virgo Image Credit: Till Credner [CC Share Alike 3]

Up from and to the right of Regulus, you will find Castor and Pollux, the two stars which mark the heads of the Twins, Gemini. The bodies of the Twins are the two lines of stars which extend towards Orion (The Hunter), which will be low on the horizon out to the west and will be best found by identifying Betelgeuse, the bright red star which forms the Hunter’s left shoulder at the top of the constellation.

Southern Night Sky - April 2021
Created using SkyPortal Mobile App

Northern Night Sky - April 2021
Created using SkyPortal Mobile App

Below and to the left of Leo is the constellation of Virgo (The Virgin), with its brightest star Spica sitting down towards the horizon.  In some cultures, Virgo is the "Wheat-Bearing Maiden" or the "Daughter of the Harvest” and is depicted holding several spears of wheat in each hand and Spica is one of the ears of grain hanging from her left hand. If you can’t find Spica, try going back up to the Plough and follow the curve of its handle round, through the very bright star, Arcturus and then down to Spica, which will be way down low in the sky.

If you are at a location with little or no light pollution, you may be able to pick out Hydra (The Water Snake), which wriggles along the southern horizon and is the largest constellation in the night sky. Most of its stars are faint, but Alphard, its brightest star, is quite easy to find if you look below and to the right of Leo’s brightest star, Regulus (See above). Alphard is from the Arabic for "the solitary one" as there are no other bright stars near it. You might also be able to pick out the head of the Water Snake. It is an almost square set of four stars about halfway between Regulus and Procyon, the brightest star in Canis Minor, which sits below Castor and Pollux.

The Moon

​We start the month with an almost full moon because we had a full Moon on 28 March. The last quarter Moon (a half moon) is on 4 April and there is a new Moon (no Moon) on 12 April. If it’s clear on the mornings of 6 and 7 April, have look low down on the south-east horizon at about 6:30 am and you will be able to see a crescent Moon below Jupiter and Saturn. 

If it’s clear on the evening of 16 April, have look out to the west in the first couple of hours after dark and you will see a very thin crescent Moon in between the red star Aldebaran and the red planet Mars, while on 17 April, the crescent Moon will be right next to Mars.

This month’s full Moon occurs early on the morning of 27 April, but you can see it rise on the evening of 26 April. It is often called the Pink Moon because of the pink flowers – phlox – that bloom in early spring in North America. This will be the second of 4 supermoons this year, making it at Pink Supermoon. On that day, it will be 222,212 miles from Earth, its second closest approach of the year. It will therefore appear as second-largest and second-brightest moon of the year, but the best supermoon will be on 26 May, when it will be 221,117 miles from Earth.

This month’s full Moon is also known as the Egg Moon or the Paschal Moon because it is used to calculate the date for Easter. For those you who wonder why Easter does not occur on the same date each year, the rule is that Easter falls on the Sunday next following the Saturday that falls on or after the Full Moon next following the Vernal/Spring Equinox. This means that Easter can occur on any date from March 22 through to April 23. As this year’s Equinox was on March 20 and the next full Moon was on March 28, Easter Sunday falls on 4 April.

​The Planets

Jupiter and Saturn and Mercury are now in the early morning sky, sitting quite close together, rising above the south-eastern horizon at about 4:30 am.
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Meanwhile, in the western evening sky you will find Mars. Over the last month, it has moved away from the red giant Aldebaran, marking the eye of Taurus the bull and you will now find it near the Castor and Pollux, the twin stars in Gemini. It will be visible from just after sundown until about 1:30 am, when it dip below the western horizon.

Towards the end month, Venus will begin to make an appearance after sunset, low down on the west. It will set just after 9:00 pm, but it should be bright enough for you to spot it in the twilight after sunset.

Meteor Showers 

After several months without any major meteor showers, we now have the Lyrid meteor shower this month. It starts on 16 April and reaches its peak on the night of 21-22 April, when its dust particles that originate from the comet Thatcher hit our atmosphere are expected to produce around 15-20 meteors per hour. However, a good number of meteors can usually be seen on the night before and the night after the peak. 
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The meteors will appear to emanate from the constellation of Lyra (The Lyre) at a point near Vega, the constellation’s brightest star and the fifth brightest star in the night sky. You will find Vega over in the north-eastern night sky from 10:00 pm, although you don’t need to look there to see meteors as they’ll appear across the whole night sky. 

This year, the moon will be about 65% full and bright enough to drown out a lot of the meteors, so the best time to look for them will be between moonset and sunrise, or from about 4:00 am and 6:00 am. However, as the meteor shower’s radiant point in Lyra will be high in the sky by midnight, you could start watching for them from then.