Starwatch: The triangle that spans the north’s spring sky

Many starwatchers are familiar with the so-called summer triangle of Vega, Altair and Deneb, but there is also a spring triangle to keep a watch for. The asterism joins three bright spring stars from three separate constellations. The stars usually chosen to represent the triangle are Arcturus in Boötes, the herdsman; Spica in Virgo, the virgin; and Regulus in Leo, the lion.

The chart shows the view looking south-south-east from London at 22.00 BST on 28 April, although the view will remain essentially the same all week. The full triangle spans such a large swathe of sky that some skywatchers prefer to place its apex at Denebola instead of Regulus.



Denebola is the second brightest star in Leo and truncates the triangle somewhat. Once the triangle has been located, use it as a marker to explore other areas of the spring sky. In particular, look below it to identify the faint constellations of Corvus, the crow; Crater, the wine-mixing cup; and Hydra, the water snake.

We will return to this triumvirate next week as they share a fascinating myth. From the southern hemisphere, the triangle can be easily seen in the northern sky – but should more accurately be referred to as the autumn triangle..