The dog days of summer

The hottest days of summer are known as the dog days. There’s a fun bit of astronomy behind this expression: it’s the time of year when Sirius — also known as the dog star — rises just before the sun.

The August pre-dawn sky, with Sirius rising in the east just ahead of the sun. In 2020, Venus is also getting in on the act…
(Night Sky Map from

The dog star, which faithfully follows the hunter Orion across the sky, is easily our brightest star. It’s so bright, in fact, that the ancient Greeks believed it added to the heat of summer by rising at the same time as the sun. Hence, the dog days of summer.

Published by Graham Jones

Astrophysicist and science communicator