The Night Sky in April
Notice how light the evenings are becoming? This is because the sun’s apparent position against the background stars has it moving north at its fastest rate for the year this month, peaking on March 20 at the northern hemisphere’s spring equinox (autumn equinox for the southern hemisphere). The effect is enhanced on March 26 when the UK’S clocks go forward an hour from GMT to BST. Welcome to spring!
Head outside around 10pm GMT and look overhead where you’ll find the familiar pattern of the Plough or Saucepan. If you imagine a saucepan, extending the length of the pan away from the handle brings you to two fainter stars, converting the saucepan into a frying pan. Keep going and you’ll arrive at a solitary star called Muscida.
The Saucepan is part of Ursa Major, the Great Bear. It represents the bear’s rump and abnormally long tail which, according to legend, stretched when Zeus used it to swing the creature around his head before releasing it into the sky. The extended frying pan pattern adds the bear’s torso, Muscida marking its head. Below are three pairs of stars of similar brightness stars representing three of the bear’s paws.
The 13th-century Arabic astronomer, Ulugh Beg, described the pairs as the footprints of a leaping gazelle, the creature startled by a swish of Leo the Lion’s tail. Leo is
found south of Ursa Major, the Lion’s head marked by the distinctive Sickle asterism resembling a backward question mark. The bright star Regulus is the punctuation dot. Lodged between the Great Bear’s paws and Leo, is Leo Minor the Little Lion, a “modern” constellation first depicted in 1687 by Johannes Hevelius. Before this it was regarded as an undefined region of the night sky, devoid of any major patterns. It’s probably best described as looking like a squashed diamond with a tail.
Leo Minor is tricky to pick out, but it’s a walk in the park compared with the linear constellation of Lynx, located west of Ursa Major. Lynx represents, well, a lynx, but it’s not easy to visualise. It was said the name was attributed because you’d need eyes like a lynx to see anything interesting in this part of the sky!
Much easier to spot are the various planet and moon conjunctions happening this month.
On the evening of March 20, an extremely slender 1 per cent-lit waxing crescent moon sits very near Jupiter. Spot them low above the western horizon in the evening twilight, visible around 19:00 GMT. On the evening of March 24, it’s the turn of Venus to get a visit from the now thicker waxing crescent moon. As it sets, the moon will also be four apparent moon diameters from the binocular planet Uranus. On the evening of March 25, the 20 per cent-lit waxing crescent moon will be close to the Pleiades open cluster when it is approach setting.
Then, on the evening of March 27, it’s Mercury and Jupiter having a meet up. Visible very low in the west after sunset, Mercury is only just dimmer than Jupiter. The pair will appear separated by three times the apparent diameter of the moon. On March 28 the now 39 per cent-lit waxing crescent moon lies near orange-hued Mars, a planet which, now appears significantly dimmer than of late. The following evening, on March 29, binoculars will show Mars just to the north of a rich open cluster of stars known as M35, located in Gemini.