Fall Constellations and the Andromeda Galaxy

Searching the Sky, Discovery Place’s sky watching feature

Fall Constellations and the Andromeda Galaxy

Discovery Place Nature

Welcome to the October edition of Searching the Sky, Discovery Place’s monthly sky watching and astronomy blog.

As discussed last month, we are now in astronomical fall. Fall is an especially great time to go sky watching since, due to the Earth’s tilt on its axis, the Sun will appear to set earlier in the evening and the nights will become longer. Additionally, there are many easily identifiable constellations visible in the fall night sky.

Perhaps the most distinctive fall constellation is Cassiopeia, which appears to be a great big “W” high up in the night sky. The stars that make up the “W” of Cassiopeia are so bright that they can be seen even in the light-polluted skies around Charlotte. This light pollution makes the unusual pattern of Cassiopeia even more obvious in the night sky, since it is the one of the only bright groupings of stars in its area of the sky.

In Greek mythology, Cassiopeia was the vain, beautiful queen of Ethiopia. Because she bragged about her beauty, the gods punished her by sending a sea monster to ravage the coast of her country. After consulting with her advisors and priests, Cassiopeia decided to sacrifice her daughter to the sea monster in an attempt to appease it.

Her daughter, Andromeda, can also be found in the fall night sky if we first make a detour to Pegasus. To find Pegasus, look for a large square right near Cassiopeia. This square, known as the autumn square, is the body of the winged horse Pegasus. He is flying upside down in the night sky, with his head and front legs stretched out above him. What appears to be his two back legs is actually an entirely different constellation: Andromeda.

Located in the constellation of Andromeda is the Andromeda galaxy, which looks like a blurry smudge when viewed with the naked eye. It is the only spiral galaxy, other than our own Milky Way, that we can see without the assistance of a telescope. Andromeda is the closest galaxy to the Milky Way, around 2.5 million light-years away from Earth. However, Andromeda is approaching the Milky Way and astronomers think that the two galaxies will collide in about 4 billion years. Although the Milky Way contains between 250 billion-300 billion stars and Andromeda contains around 1 trillion stars, these galaxies also contain so much empty space that it is likely that none of these stars will collide with each other when the two galaxies collide. The gravity of the stars and the two supermassive black holes at the center of these galaxies will interact when the galaxies collide, which may cause some of the stars to change position in space.

If you’re having trouble seeing the Andromeda galaxy in the night sky, try turning your head and looking at it with your peripheral vision. You also can use the middle of the “W” of Cassiopeia to point you towards where exactly the galaxy is located within the constellation of Andromeda. Good luck!

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Discovery Place Nature is located in the heart of Charlotte adjacent to Freedom Park.

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