On a frosty northern winter evening, there is a jewel to be found in the evening sky: the brightest star in the night sky, Sirius, in the constellation of Canis Major, the great dog.
With a magnitude (the measure of a star’s apparent brightness in the night sky, the lower the brighter) of –1.46 , Sirius is roughly half the apparent brightness of Jupiter at present. But unlike Jupiter, which maintains a steady brilliance, Sirius twinkles because its light is deflected by the various layers and turbulence in our atmosphere. The same is true for all the stars, though only the brightest twinkle visibly. Planets remain steady because they are much closer and so actually appear as tiny discs to our eyes, which averages out the various effects produced by the atmosphere.
