The Night Sky in April

Abstract

BETWEEN April 1 and 30, the nights shorten in the latitude of London by nearly two hours. Summer Time comes into operation on April 18. New moon occurs on April 11 at 5-2h and full moon on April 25 at 15-4h. If the evenings are clear, ‘earthshine’ on the moon may be observed from about April 13 until April 16. The planet Venus, which was conspicuous in the evening skies of last month, draws rapidly towards the sun's position until inferior conjunction takes place on April 18; next month it will be seen as a morning star. Mercury, which is usually rather a difficult object in the latitude of Great Britain for naked-eye observation, is at greatest eastern elongation (20° E.) on April 20. The planet is in conjunction with Venus on April 7 at 15h. On April 12 at 8h Mercury and Uranus are in conjunction, and at 12h on the same day there is a conjunction between Mercury and the moon which is then just over a day ‘old’. Mars rises before midnight and is placed not far from Antares. Jupiter is a morning star, rising at about 2Jh in the middle of the month. Saturn, rising in the dawn, is not conspicuous. By 22h in mid-April, the winter constellations of Taurus, Orion, Canis Major and Canis Minor with their bright assembly of stars have nearly set in their entirety, whilst Vega has risen in the north-east, and Arcturus is about 2J hours east of the meridian. The constellations on or near the meridian at this time offer several attractive objects for telescopic observation-the bright double stars of y Leonis (separation about 4″), Castor (4″), 5 Ursse Major is (1″), y Virginis (6″), and a Canum Venati-corum (20″). Messier 51 at R.A. 13h 28m, Dec. +474° (epoch 1950), which is one of the best known spiral nebulas, requires of course a large telescope and the photographic plate to resolve its structure. Messier 3 at R.A. 13.1 40m, Dec. -f 28-6° is a notable globular cluster 18′ in diameter, whilst the “Owl” planetary nebulse (Messier 97) is at R.A. llh 12m, Dec. 55-3 °. The Lyrid meteors may be looked for on and about April 21, their radiant, being near the star 104 Herculis. The northern sky should be scanned for appearances of the aurora-more particularly when a large sunspot is crossing the sun's disk.