The Night Sky in April
The spring constellations now take centre stage but lack the dynamic and bold appearance of the stars of winter and summer. The reason for this is simply that during spring and autumn we look out at right angles to the plane of our home galaxy, the Milky Way.
The main patterns on view include Leo the Lion. This backwardfacing question mark has the bright star Regulus as the punctuation dot. This unofficial pattern of stars or asterism is known as the Sickle.
You can locate Regulus using another famous asterism known as the Plough or Saucepan. At this time of year, this distinctive pattern of seven middle-brightness stars sits close to the overhead point in late evening. Identify its shape and extend the sides of the pan down where they converge – with a bit of artistic licence – at Regulus.
The rest of Leo consists of a roughly rectangular body heading east (left) of the Sickle. The end of the tail is marked by Denebola, a star almost twice the size of the Sun that rotates at 80 miles per second. However, Regulus spins even faster at 200 miles per second, a speed which takes it around three per cent short of its break-up velocity. Regulus would appear a very oblate star in close-up.
In mythology, Leo had an impressive tail, which was later reinterpreted to become a faint constellation known as Coma Berenices or Queen Berenice’s Hair. This lies north-east (upper-right) of Denebola and doesn’t contain any bright stars. A loose open cluster of stars called Melotte 111 creates a triangular mistiness, which is supposed to represent the queen’s hair. For most, the cluster appears to drift in and out of vision. If you’re having trouble seeing it, try using the technique known as averted vision; looking slightly to the side. This puts its dim light on to a more sensitive part of your retina.
South of Coma Berenices and south-east of Leo lies the second largest constellation in the night sky, Virgo the Virgin. Despite its size, Virgo isn’t that obvious. Its brightest star is Spica, which is the brightest in the low part of the sky towards the south, late evening. Look above Spica and you should be able to make out a large semicircular pattern of stars forming an asterism known as the Bowl of Virgo.
Our view allows us to see several galaxy clusters, gravitationally bound collections of external galaxies. Look through a telescope using a low-power eyepiece and these appear as dim grey smudges, each representing a collection upwards of a hundred million stars. Some monsters, such as M87, contain an estimated trillion stars.
Closer to home, the planets are still putting on a great show. After sunset, the planet Venus can be seen blazing away high in the west. However, towards the end of April, Venus begins to lose altitude as the sky darkens. On April 25-27, Venus is joined by the waxing crescent Moon as it slips to the south of the planet. Its closest approach is on April 16. If it’s clear, try to get a look at this conjunction as it’ll be the last time it is visible against a darkening evening twilight sky for some time.
Early risers will also get to see the bright planet Jupiter and Saturn. The last quarter Moon makes an attractive triangle with them on April 15 at around 04:30 BST. The following morning, around 05:00 BST, the now 37 per cent lit waning crescent Moon rises with mag. +0.6 Mars located nearby.
Finally, the new Moon on April 23 is perfectly timed for this year’s April Lyrid meteor display.