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Definitions of Equinox Names in the Northern and Southern Hemisphere

-- Carlos Daniel Trejos Angulo | March 5, 2021

Question:

Greetings from Costa Rica. My name is Carlos Daniel Trejos, I am a university student and I am in an astronomy group. My question is the following:

I know there are several names for the March equinox, such as…. “March Equinox”, “Vernal Equinox” and even “Spring Equinox” (although the latter I have heard is not well said because it depends on the hemisphere I am in) Is the vernal equinox always in March, or does it depend on the hemisphere we are in? (Implying that the term “vernal equinox” is the same as “spring equinox”).

This is a burning question that I can’t wait to know the answer, I have noticed that some websites contradict themselves and none are specific or reliable enough for me to know if in the southern hemisphere it is correct to say “the vernal equinox in September”. I would also like to corroborate if the name “vernal equinox” comes from “aries/vernal point”.

-- Carlos Daniel Trejos Angulo

Answer:

I think that the clearest terms to use to refer to the two equinoxes each year is to refer to them as the “March Equinox” and “September Equinox”. If you want to be completely clear, in the northern hemisphere the March Equinox is called the Vernal or Spring Equinox while the September Equinox is called the Autumnal or Fall Equinox. In the southern hemisphere the reverse is true: the March Equinox is called the Autumnal or Fall Equinox while the September Equinox is called the Vernal or Spring Equinox.

-- Jeff Mangum

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