The Backyard Astronomer: Cassiopeia the Queen rules September nights

    1 of 3 2 of 3

      As the sun sets in the west, the sky slowly turns pastel shades, from light to dark blue. This is my favourite time of evening, as the brighter stars and planets begin to reveal themselves.

      Over the next 20 minutes, more tiny dots emerge, like celestial popcorn. About an hour after sunset, the sky is full of stars as viewed from the countryside on a moonless night.

      Gary Boyle

      Warm September nights still allow us to gaze at our lovely Milky Way, stretching from the heaviest concentration of stars in the south, which is the galactic centre, all the way to the northeast.

      This is where we see the iconic W formation that constitutes the constellation that symbolizes Cassiopeia the Queen. This is a circumpolar constellation, meaning it never sets as seen from Canadian soil. Although these five stars might look the same, they range in distance from 55 to 613 light-years away from Earth.

      In Greek mythology, King Cephus and Queen Cassiopeia ruled the land. She often boasted that she was the most beautiful of all. Legend states that the sea god Poseidon was not pleased with Cassiopeia’s vain statement and forced the king and queen to sacrifice their daughter, Andromeda, to the sea monster Cetus.

      However, the hero Perseus, who was returning from slaying Medusa, rescued Andromeda in the nick of time, riding off on his winged horse, Pegasus. This story depicting six constellations is sometimes referred to as the “Royal Family of Constellations”.

      To date, 26 exoplanets have been discovered orbiting 17 stars in the constellation. One star—catalogued as HD 219134 and located 21 light-years away—has seven planetary bodies circling it. The exoplanet closest to the star takes a mere three days to orbit it, while the farthest takes 2,220 days.

      Aside from the individual stars, there is a lovely star cluster, with catalogue number M52, located 500 light-years away. You will need binoculars to see this open cluster superimposed in front of the farther Milky Way stars.

      A beautiful object located in the nearby constellation Perseus is called the Double Cluster and consists of two side-by-side star clusters located 7,300 and 7,700 light-years away. The constellation Perseus is located below Cassiopeia's W. On a clear moonless night, away from light sources, the Double Cluster can be seen by the naked eye, meaning without using any optical aid.

      Cassiopeia constellation
      Gary Boyle

      A few hundred young hot supergiant stars reside in the two clusters. And that smudge to Cassiopeia’s right is the Andromeda Galaxy. At two-and-a-quarter-million light-years away, it is the closest galaxy to us.

      The light you see there left the Andromeda Galaxy when Homo habilus was walking the Earth two-and-a-quarter-million years ago.

      Till next time, clear skies.

      Known as “The Backyard Astronomer”, Gary Boyle is an astronomy educator, guest speaker, and monthly columnist for the Royal Astronomical Society of Canada as well as past president of the Ottawa Centre of the RASC. He has been interviewed on more than 50 Canadian radio stations as well as television across Canada and the U.S. In recognition of his public outreach in astronomy, the International Astronomical Union has honoured him with the naming of Asteroid (22406) Garyboyle. Follow him on Twitter: @astroeducator, Facebook and his website: