Mundus
Autumn
Four Seasons
Sept 1 02:05 Sept 15 01:10 Oct. 1 00:05 Oct.15 23:05 Nov. 1 21:00
Nov. 15
20:05
The following text appears on the plaque: “In autumn we view a sparsely populated region in an outer spiral arm of our galaxy known as the Perseus arm. For this reason, the autumn sky has the fewest bright stars of any season. The predominant autumn constellations are Perseus, a hero of Greek legend; Pegasus, Perseus’ winged horse; the mythical princess Cassiopeia; queen Andromeda, her mother; and Aries, the ram. Horn-shaped Andromeda is adjacent to the Great Square of Pegasus. Sirrah, one of Andromeda’s brightest stars, also forms the northeast corner of the Great Square. A blue- white star, Sirrah is 1.5 times the Sun’s diameter and lies 100 light-years from Earth.  Two other stars of equal brightness are located in Andromeda. They are Mirach and Almach. Almach is a triple star system located 260 light-years away. Two of its blue and yellow components can easily be seen through small telescopes.  The Andromeda Galaxy (M31) lies above the midpoint on a line from Sirrah to Almach. It is the most distant object visible to the unaided eye. Though no longer seen from Montreal, this vast stellar island appears as a faint, luminous spindle under very dark skies. Its spiral structure is slightly larger than the Milky Way and contains over 300 billion stars. Though the Andromeda Galaxy is 2.25 million light-years away, it is so vast that it stretches across the sky a distance equal to six full moons.  Aries, a small zodiac constellation, lies beneath Mirach. Its brightest star is Hamal, an orange giant 13 times the Sun’s diameter that is situated 60 light-years away.”
The blue mark indicates where to stand to see the alignment.
Designed by Katsuhiro Yamazaki; metalwork by Soheil Mosun, Ltd. and Alfred Pfattischer.