This week we will use the brightest star in the night sky to find a less than obvious constellation.
Canis Major, the Great Dog, was included in Ptolemy’s 2nd-century list of 48 constellations in his great work Almagest. This became the standard reference work for astronomy for a millennium, providing the basis on which the northern and equatorial skies are still divided into constellations.
The Almagest also championed the idea that Earth, not the sun, was the centre of the solar system, so it was not perfect.
The chart shows the view looking south-south-west from London at 2030 GMT on 17 March, although the view will be essentially the same all week.
Orion’s belt points to the brilliant dog star, Sirius, the brightest star in the night sky. From there, the rest of the dog’s shape can be traced using the fainter stars in the constellation. A dark sky will be useful for this.
Canis Major, and the nearby constellation Canis Minor (not shown on the chart), are Orion’s hunting dogs.
From the southern hemisphere, Canis Major rides high in the sky during the evening at this time of year. Face north-west and look for it, up near the zenith.
