Monthly Archives: December 2008

Twilight beauty: the Moon, Venus and Jupiter conjunction

Vénus, Jupiter and the Moon will be conjunct today at 22º Capricorn.

If the sky is clear enough the triple conjunction will be visible on the western sky right after sunset.

Besides being a wonderful sight, this triple conjunction also provides a good opportunity to observe the difference between zodiacal latitude and longitude.

Although Venus and Jupiter are at the same zodiacal degree, 22º Capricorn, and therefore at the same longitude, they don’t seem to be perfectly aligned.

Venus (the brightest one) seems to be below and a little to the left of Jupiter; this is so because the planets have different zodiacal latitudes: Venus is at 2º33’ South and Jupiter 0º33’ South.

So, there are two factors to take in account: longitude, the degree of a given planet in a sign (in this case 22º Capricorn), and latitude, the distance from the planet to the ecliptic (which is the central line of the Zodiac).

When latitude and longitude coincide exactly, the planets form a perfect alignment, called occultation. In such cases, the planet closer to us (which in this case would be Venus) passes between the Earth and the other planet (Jupiter), and occults it from our sight.

However, this will not occur today, as Venus does not align Jupiter.

Instead, we’ll have the opportunity to admire the two planets and the Moon, in a beautiful and inspiring configuration. … That is, if the clouds would go away!

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Filed under Observing the sky