March sky notes

Ken Kennedy of Dundee Astronomical Society has sent in his sky notes for March: “I always feel that spring is on its way when the crouching lion, Leo, begins to dominate the southern sky in the evenings,” he says.

“Perhaps next to the Plough and Orion, Leo is the most easily recognizable constellation in the northern sky with the sickle of stars clearly forming the head and neck.

“It is likely that this constellation was seen as a lion as long ago as 4,000 BC but it was Greek mythology that linked it with the first of the labours of Heracles.

“The brightest star of Leo is bluewhite Regulus at a distance of 77 light years. It is a multiple star consisting of at least four components but one of these can be seen close to the primary star using binoculars.

“The main star of the Regulus complex is about 3.5 times the mass of our sun and rotates on its axis in the remarkably short time of 15.9 hours, very much shorter than our sun’s 27–30 days’ rotation.

“Leo, like so many constellations, has a large number of double stars, many of which are binary rather than seen along lines of sight. This means that over time it is possible to see relative changes in their positions as they orbit each other. A number are able to be separated using binoculars or a small telescope so it is worth having a look at the brighter stars of Leo to find these.

“Leo contains a number of galaxies, some bright enough to be glimpsed using binoculars on a dark moonless night. A small telescope will be more useful in seeing these once their position has been noted, the brighter ones being situated just below the lion’s body.

“Talking of spring, March is the month of the Spring Equinox when the sun passes northwards over the equator. This year the crossing takes place on the March 20 at 10.30am. With this event comes the annual ritual of British Summer Time (BST) also known as Daylight