Sunday, September 19, 2010

Shine On, Harvest Moon...

September 21... Jupiter Pays a Visit

All hail and behold the sky king! This year, giant Jupiter is closer than ever. Not since 1963 has Jupiter been so close, so bright, so easily seen—a result of its slow, oval orbit around the Sun that will take nearly 12 Earth years.

Jupiter rises at dusk, reaches opposition on the 21st, and shines at its brightest since 1963. At a magnitude –2.9, Jupiter dominates the sky all night long.

Interestingly, Uranus comes to opposition on the 21st, too, so the two worlds stand side by side, especially at midmonth.

Finding Jupiter should be easy. Look halfway up the southern sky for the night’s brightest star. This is Jupiter! Dazzling and astonishingly conspicuous against the faint stars of Pisces, it will be at its best at midnight this month.

September, 22... Autumnal Equinox

Fall begins. The autumnal equinox is defined as the point at which the Sun appears to cross the celestial equator from north to south. The celestial equator is the circle in the celestial sphere halfway between the celestial poles. It can be thought of as the plane of Earth's equator projected out onto the sphere. Another definition of fall is nights of below-freezing temperatures combined with days of temperatures below 70 degrees Fahrenheit. The word equinox means "equal night"; night and day are the same length of time. The spring equinox is in late March. In addition to the equal hours of daylight and darkness, the equinoxes are times when the Sun's apparent motion undergoes the most rapid change. Around the time of the equinoxes, variations in the position on the horizon where the Sun rises and sets can be noticed from one day to the next by alert observers.

The Harvest Moon

But around the date of the Harvest Moon, the Moon rises at almost the same time for a number of nights in our intermediate northern latitudes. Why is the Harvest Moon different? Well, remember that the zodiac is the band of constellations through which the Moon travels from night to night. The section of the zodiac band in which the full Moon travels around the start of autumn is the section that forms the most shallow angle with the eastern horizon.

Because the Moon's orbit on successive nights is more nearly parallel to the horizon at that time, its relationship to the eastern horizon does not change appreciably, and the Earth does not have to turn as far to bring up the Moon. Thus, for several nights near the full Harvest Moon, the Moon may rise as little as 23 minutes later on successive nights (at about 42 degrees north latitude), and there is an abundance of bright moonlight early in the evening, a traditional aid to harvest crews. By the time the Moon has reached last quarter, however, the typical 50-minute delay has returned.

September 23... Next Full Moon

The Moon has a personal relationship with us all, and folklore has it that courting and birthing are influenced by the Moon. Read on . . .

  • According to folklore, if a young woman sees a dove and glimpses the new Moon at the same instant, she should repeat: "Bright Moon, clear Moon, Bright and fair, Lift up your right foot, There'll be a hair." When she removes her shoe, she'll find a hair the color of her future husband's.
  • Marriages consummated during the full Moon are most prosperous and happy, according to ancient Greeks, while a waning Moon bodes ill for wedded bliss.
  • The full Moon is an ideal time to accept a proposal of marriage.
  • The Navajos, among others, believe that the full Moon's pull on a woman's amniotic fluids increases the chances of giving birth at this time. Some nurses and midwives claim the new Moon is also an active time for births.

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