A guide to what's up in the sky for Southern Australia

Previous Articles

OCTOBER’S DEEP SKY HIGHLIGHT (29th Sep 2024)

M31—The Andromeda Galaxy Distance: 2.5 million Light Years

M31 has played a pivotal historical role in astronomy. Early observers saw the
soft, foggy patch of glowing light as just another spiral nebula but weren't yet
equipped with the knowledge to appreciate its nature. The true nature of M31
began to become clear in 1923. In that year Edwin Hubble, using the just
completed 100 inch Hooker telescope at the Mount Wilson observatory, made his
monumental discovery of Cepheid Variable stars in M31 and in one stroke forever
changed the astronomical paradigm of the universe as we know it.

Appropriately interpreting the cepheid data, Hubble was the first to appreciate the faint nebula in Andromeda as an "island universe", an immense galaxy in its own right, similar to our Milky Way. Hubble's work opened the door to the moderninterpretation of the universe which we now know consists of countless galaxies all receding from each other.