What month was it when Odysseus saw Orion in 1000BC? (Advanced)

I would like to know in which months people can see Orion in ca. 1000 BC.

I am an MA student in Classics at Queen's University, Kingston, Ontario. While reading Homer's Odyssey, we encountered a small technical problem. We don't know the starting date of one of Odysseus' voyages. The book only says he saw Orion in the sky. I think he set sail in the winter, but I need more proof to convince the class.

This inquiry should lead to a second question: by how much have the constellations shifted their position in the past 3000 years? i.e. If a constellation is first visible in February, in which month would we first see it 3000 years ago?

The phenomena you are talking about is the precession of the equinoxes. The autumnal and vernal equinoxes are the times of the year when the day and night are exactly equal lengths. The position of the Sun in relation to the constellations at these times shifts, with a total period of 26,000 years. This means they shift around 1.5 degrees every century, or just over 40 degrees in 3000 years! That's almost an eighth of the way round the sky! In the year 1 the spring equinox was just moving into Pisces, and it moves backwards along the ecliptic plane changing constellation every 2000 years or so. I think that this means that the vernal equinox was in Aries in 1000 BC. Orion is about opposite Scorpius on the sky, so when the Sun is in Scorpius we see Orion. The Sun moves through a constellation a month through the year, so starting with Aries in March we should be able to work out which month the Sun was in Scorpius and Odysseus could see Orion:

Aries March Aquarius
Taurus April Pisces
Gemini May Aries
Cancer June Taurus
Leo July Gemini
Virgo August Cancer
Libra September Leo
Scorpius October Virgo
Sagittarius Nov Libra
Capricorn Dec Scorpius
Aquarius Jan Sagittarius
Pisces Feb Capricorn

So it looks like Odysseus could see Orion in September/October/November (to give us some leeway). He set sail in the Autumn!


This page updated on June 27, 2015

About the Author

Karen Masters

Karen Masters

Karen was a graduate student at Cornell from 2000-2005. She went on to work as a researcher in galaxy redshift surveys at Harvard University, and is now on the Faculty at the University of Portsmouth back in her home country of the UK. Her research lately has focused on using the morphology of galaxies to give clues to their formation and evolution. She is the Project Scientist for the Galaxy Zoo project.

Twitter:  @KarenLMasters
Website:  http://icg.port.ac.uk/~mastersk/

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