The Sky at Night
With the clocks having 'sprung' forward at the end of March, reasonable darkness will only be obtained after 9pm so those wishing to view the night sky will have to venture out a bit later from April. Added to that, the great winter constellations have moved towards the west with Orion just above the western horizon at 10pm. Towards the south, Leo still dominates but below Leo is a rather bland area of sky occupied by the faint constellation Hydra. Virgo follows with its brightest star Spica, which acts as a marker for Virgo towards the south-east. Above Virgo is the bright star Arcturus which marks the base of the constellation Boötes, the Herdsman, a kite shaped constellation of rather fainter stars. Looking further upwards to almost overhead is the familiar shape of the Plough, the most recognisable star group of Ursa Major, the Great Bear. The area of sky around the Plough is rich in galaxies and a few of them can be seen with a pair of binoculars or small telescope. Three of my favourite galaxies are almost overhead in April and the first pair can be found by using the lower left star of the bowl of the Plough and following a line joining it to the upper right star. Extend that line about 15º and you will see two faint patches, close together. These are the galaxies named Messier 81 and 82 and are at a distance of 12 million light years. The larger, M81, is about the same size as the Milky Way and M82 is about half that size. The other galaxy is Messier 51, known as the Whirlpool Galaxy, and can be found about 5º southwards of the end star of the handle of the Plough. Like the other two, M51 appears as a faint patch of light but photographs show a beautiful spiral galaxy face on and interacting with another smaller irregular galaxy. Both of these galaxies are about 30 million light years distant.
April gives us the last chance until August to see some meteors. The April Lyrid meteor shower reaches a peak on the night of 22-23rd April when up to 15 meteors per hour may be seen. This meteor shower was first recorded in 687 BC and is associated with Comet Thatcher which was discovered in 1861. Small particles shed by the comet in its orbit round the Sun burn up in the Earth's upper atmosphere while travelling at 50 km/second. There have been occasional outbursts of activity, for example in 1982, when 100 or more were seen per hour. This year conditions are particularly favourable with a 3 day old Moon which will set quite early in the evening. Look towards the darkest part of your sky and there are likely to be more meteors after midnight.
Mercury will be most easily seen for a few days before and after the 11th April. It will be towards the west north-west at around 9pm at an elevation of 10º.
Venus will remain very bright in the west throughout the evenings of April and will reach an elevation of about 30º, setting after 1am.
Mars can be seen throughout the month high towards the south-west as the sky darkens after sunset and does not set until 3.30am. The planet has lost much of its brightness since its close approach last year but will retain its orange hue.
Jupiter is lost in the glare of the Sun throughout the month and will not be visible.
Saturn Saturn has moved away from the Sun this month, it rises at much the same time as the Sun and will not be visible.
The Moon is full on the 6th, at last quarter on the 13th, new on the 20th and at first quarter on the 27th April.