Dog days; the phrase is redolent of high summer days like today when the temperature is in the high thirties Celsius and the best idea is to stay indoors until the heat of midday dissipates. What I didn’t know until last night is the phrase’s astronomical origin, when a conversation with a friend brought up the Latin version canicula — little dog — which is also found in the Romance languages. The dog in question is Canis Major, the larger of the two dogs following Orion the hunter across the sky. Canis Major contains the brightest star in the sky, Sirius - the dog star - which rises with the Sun at the height of summer. At least, it did rise with the Sun at the height of summer when the phrase originated in ancient times; now, owing to the precession of the equinoxes, the so-called heliacal rising of Sirius is in September... So there you have it, from dog days to a little astronomy.