BAS Observer November 2017

NOVEMBER 2017 17 Constellation of the month: Andromeda The constellation Andromeda (the Chained Maiden) is an ancient Greek constellation located in the northern celestial hemisphere; hence, it is low in our southern skies and often difficult to observe. In Greek mythology the maiden Andromeda was chained to a rock in the ocean by Cepheus as a sacrifice to the sea monster Cetus (the Whale). However, she was rescued at the last moment by Perseus on his winged horse Pegasus. So, the constellation Andromeda sits just below the constellation Pegasus, and locating the stars of the Great Square of Pegasus is a useful first step in locating Andromeda, which hides in the rear legs of the horse. The almost sole observing target that people head for in Andromeda is Messier 31 (the Andromeda Galaxy). This large galaxy is visible to the naked eye and is located 2.5 million light-years away. The galaxy played a major role in the early astronomical discoveries by Edwin Hubble that led to our understanding of the size and expansion of the Universe. Andromeda is heading towards our Milky Way Galaxy, and a massive silent collision is expected in about 2.5 billion years’ time. The planets While Neptune and Uranus have a slightly blue colour, which aids identification, a good set of detailed star charts showing the day-by-day location of these planets is a good tool to have available when hunting for these tiny planetary dots in a starry sky. Neptune will be about 4.7 billion kilometres away, and Uranus will be about 3 billion kilometres away. Neptune Uranus Observing target: • M31 – galaxy