(by Monica Nardone).
The summer has already been
swept away by thunderstorms, but on Friday the 'goodbye' becomes
official with the autumn equinox at 10:02 pm local time.
Prior to that it will be possible to see the waxing crescent
moon as it glides past Jupiter just before the king of the
planets follows the sun below the horizon.
This will be "the last chance this year to observe an evening
alignment of Jupiter, which now hangs very low on the western
horizon, and the waxing crescent moon," said Paolo Volpini of
the Italian Astronomers Union(Uai).
The apparent alignment will be visible shortly after sunset.
The autumn equinox occurs when "the sun, on its apparent
motion along the Zodiac, crosses the celestial equator from
north to south," explained astrophysicist Gianluca Masi, who is
in charge of the Virtual Telescope Project.
This astronomic event also corresponds to equal hours of
darkness and light, "because when the sun is at the equinoxes it
remains for 12 hours above the horizon and 12 hours below it",
Masi added.
The term 'equinox' is derived from the Latin 'aequus',
meaning equal, and 'nox', night.
The date oscillates between September 21 and 24 and
corresponds to the spring equinox in the southern hemisphere.
However, generally speaking it falls on September 22 or 23 and
rarely on September 21 or 24.
For example, it has been a thousand years since the autumn
equinox fell on September 21, but this century it will happen on
two occasions, in 2092 and in 2096.
The event last fell on September 24 in 1931 and the next
occasion will be in 2303.
Among the traditions that accompany the autumn equinox is the
so-called harvest moon, or the full moon nearest to it. This
year it falls on October 5.
For several evenings before and after, the moon rises 20-30
minutes earlier than usual, resulting in an abundance of bright
moonlight early in the evening in which to harvest summer-grown
crops.
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