What you can expect to see in April’s night sky

A meteor shower is named after the constellation from where the meteors appear to come from. In this case the constellation of Lyra the Lyre.

A meteor shower is formed from the dust trail left by a comet as it travels around the Sun. A comet is essentially a dirt snowball travelling through space.

When the Earth passes through these dust streams we see lots of meteors. These dust grains can hit the atmosphere with speeds of anywhere between 20 and 50 miles per second.

The Lyrids are the dust stream left behind by comet Thatcher which was discovered in 1861. Comet Thatcher returns to the inner part of the solar system every 415 years. This meteor shower is one of the oldest known with records going back to 687BCE. Normally we would expect to see around 20 meters per hour but there have been outbursts with this shower, the most recent being in 1982 when 90 meteors per hour seen. This means it is always worthwhile having a look for the Lyrids.

I normally talk about the very brightest stars in the sky and ones that can be easily seen but this month I want to start with the constellation of Cancer the Crab, the least conspicuous constellation of the zodiac. If Cancer was not part of the zodiac it is doubtful that it would be considered important at all.

Cancer can be found in the area of sky between Regulus in Leo and Castor and Pollux in Gemini. Cancer is noteworthy because it contains one of the brightest galactic clusters which actually has two names, the first being Praesepe (The Manger). There are two faint stars one above and one below Praesepe. The northern star is called Asellus Borealis and the southern one is called Asellus Australis. The word Asellus means Ass, as in the animals feeding in the stable where Jesus was laid in the manger. This term was first used around 2,000 years ago.

The alternative name for the cluster is The Beehive, a name which appears to have first been used by someone using a telescope shortly after they were invented, in the early seventeenth century. The observer described the cluster as looking like a swarm of bees.

Praesepe was also used in ancient times as a weather indicator, when observers said that the invisibility of this object in what otherwise might be considered a clear and starry sky forecasted the approach of a violent storm.

Praesepe can be seen in good clear, dark skies and looks like a small nebulous object. It is around 550 light years away and contains about 200 stars.

The seasonal change over in the sky is more or less complete and can be observed on April evenings. The symbol of winter, Orion, has to all intents and purposes disappeared, although it is true that the northern part of the constellation does not set until midnight. Of the other winter stars, Aldebaran in Taurus and Sirius in Canis Major have now set, while only Capella in Auriga, Procyon in Canis Minor and Castor and Pollux in Gemini are easy to see.

The Plough is now directly overhead which means that the ‘W’ of Cassiopeia is at its lowest in the sky in the north, although it is not difficult to find. Two of the stars of the summer triangle; Vega in Lyra and Deneb in Cygnus are now above the horizon and will be very easy to spot in the summer months.

The winter night sky is often described as being the best, with many bright stars to be seen, making it a difficult act for the spring sky to follow. This is rather unfair because there are some spectacular sights to be seen.

We begin our tour around the spring sky with the Plough, which is overhead at the moment. Follow the curve of the handle down and around and you will come across a bright orange star called Arcturus, the brightest star in the constellation of Bootes the Herdsman. There are no definite legends connected with this constellation, although one story says that Arcturus was the person who invented the two oxen plough. Arcturus is an orange giant star around 36 light years away. Its orange colour indicates that it is cooler than the Sun, its temperature being only around 4,000 degrees centigrade compared to the 5,800 degrees centigrade of the Sun. If you imagine Arcturus as the bottom of a large letter ‘Y’ in the sky, move upwards to the star Epsilon and then the two arms of the ‘Y’ lead to the star Gamma on the right and to a star called Alphekka on the left, which is actually the brightest star in the constellation of Corona Borealis, the Northern Crown.

Corona Borealis does resemble a crown in the sky with its stars forming a little semi-circle. There are two remarkable variable stars, one of which is called ‘R Corona Borealis’, a star normally just at the limit of naked eye visibility but which occasionally fades away so it can only be viewed through a telescope. The other is ‘T Corona Borealis’, a star which has brightened twice, in 1866 and 1946, starting from below naked eye visibility and becoming a bright star. We never know when the star might brighten again, so it is always worth watching this constellation. T Corona Borealis is referred to as ‘The Blaze Star’

If the line drawn from the handle of the plough towards Arcturus is continued down and around, it will reach the bright white star Spica in the constellation of Virgo the Virgin.

The southern sky is dominated by Leo, the celestial Lion.

Leo is the most splendid of the spring constellations. Its brightest star, Regulus, is not as bright as Arcturus but it does have a very distinctive shape. To find Regulus, return to the Plough and go to the two pointers; these are the two stars furthest from the handle. We normally use the pointers to find the North Star by drawing a line from the right hand pointer through the left pointer and up. However, to find Regulus we go the other way; a line drawn from the left hand pointer star through the right one and then continued downwards will take you to Regulus which is a less bright star located at the bottom of a quite distinctive backwards question mark in the sky.

The last star to mention in the spring sky is Alphard in the constellation of Hydra the Water Snake. Although it is the largest constellation in the sky, Hydra contains very few bright stars except the red star Alphard, which can be found by continuing the line from the pointers past Regulus and continuing down towards the horizon. As Alphard is in such a featureless part of the sky it is often referred to as ‘The Solitary One’

Phases of the Moon for April: Last Quarter 4th New Moon 12th First Quarter 20th Full Moon 27th

The Full Moon in April is called the Egg Moon due to the increasing amount of daylight which results in hens, ducks and geese laying more eggs.