Archive for September 28, 2021

09/28/2021 – Ephemeris – Andromeda, a damsel in distress

September 28, 2021 Comments off

This is Bob Moler with Ephemeris for Tuesday, September 28th. Today the Sun will be up for 11 hours and 50 minutes, setting at 7:28, and it will rise tomorrow at 7:38. The Moon, at last quarter today, will rise at 11:46 this evening.

In the east at 9 this evening can be found a large square of stars, the Great Square of Pegasus the flying horse. The square is standing on one corner. What looks like its hind legs stretching to the left from the left corner star is another constellation, Andromeda the chained princess. She is seen in the sky as two diverging curved strings of stars that curve upward. She was doomed due to her mother, Queen Cassiopeia’s boasting, which angered the god Poseidon. She was rescued by the hero Perseus, a nearby constellation, riding his steed Pegasus. Andromeda’s claim to astronomical fame is the large galaxy seen with the naked-eye just above the upper line of stars. The Great Andromeda Galaxy is two and a half million light years away.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT-4 hours). They may be different for your location.


Andromeda finder animation

Andromeda finder animation surrounded by the other constellations in her story, except the monster, which will rise later. Click on the image to enlarge it. Created using Stellarium and GIMP.

Andromeda Galaxy finder chart

Great Andromeda Galaxy finder chart. This image shows the galaxy almost to its fullest extent. In the finder animation above, the galaxy looks pretty much as it would to the naked eye. Click on the image to enlarge it. Created using Stellarium.

Astronomers often refer to this galaxy as M 31 for short. It was the 31st entry in Charles Messier’s catalog of objects that could be confused as being comets by comet hunters like himself. It was added in 1764. He didn’t care what these fuzzy objects were, just that they didn’t move against the background stars. Actually, M 31 is in the background. The stars are in the foreground, in our Milky Way Galaxy.