I N S I D E T H I S I S S U E

Orbital OdditiesConjunction Junctionby Bruce McCurdy (bmccurdy@freenet.edmonton.ab.ca)Ihave long been captivated by the musicof the spheres. The interplay amongthe orbits of the planets, their satellites,and debris of the solar system, results inan enormous variety of harmonics,resonances, and variations on a theme.The cyclical interactions among afascinating cast of characters can rangefrom the subtle but steady rhythmicbuildup of an occultation series to thecymbal crash of a total eclipse.In this first article of what I hopebecomes a series, let’s look at interactionsbetween Earth and Venus, which arelargely played out in the “simple” timesignature of 13:8.I made my first acquaintance withthe planets in the winter of 1985. A friendpointed out a fine conjunction betweenMars and Venus, which I had neverpreviously identified despite havingachieved the ripe old age of twentysomething.I expected the more famous(at least in science fiction circles) Marsto be the more impressive object, but itwas a relatively faint red dot about 1% asbright as its companion. It was Venustherefore that left the lasting impressionof a neighbouring world; in fact, despiteMars’ reputation, in many ways Venus isthe more Earth-like planet in diameterand mass, not to mention its acid rainand greenhouse effect. Its large, steady,and brilliant spot of pure white is a sightthat to this day has never failed to bringme pleasure.As Sky & Telescope’s E. C. Krupp oncewrote in an attention-grabbing openingsentence, Venus was “named by theRomans for the voluptuous goddess oferotic love.” To the telescopic observer,The relationship between transits and occultations of Venus is depicted in this pair of diagrams.Whereas transits occur in pairs (as shown upcoming in 2004 and 2012) or even single events,occultation series last much longer due to perspective effects. In the first case Venus’ heliocentriclatitude (distance from the ecliptic) is greatly exaggerated by its close proximity to Earth; in theother it appears compressed due to the planet’s position beyond the Sun at superior conjunction.The chords of the successive occultations are therefore roughly six times closer together thanthose of the transits. In the transits shown, Venus moves east to west (left to right) relative tothe Sun near its descending node, and in the opposite direction near the ascending node duringthe occultations. Note that the chords are not precisely parallel due to the gradual eastwarddisplacement of the node from one event to the next (diagrams courtesy of Russell D. Sampsonand the author).however, Venus is downright demure,never shedding her atmospheric veil forany man, no matter what size hisinstrument! Surface details which arebrazenly strutted by the Moon and moregrudgingly revealed by Mars are foreverhidden on Venus by a bland yet crushinglydense, poisonous atmosphere. Theearthbound observer must therefore becontent watching dramatic changes inour sister planet’s size and shape as herdistance from us varies by a factor of sixduring each cycle.This past June Venus reached thefar side of its orbit as seen from Earth,its so-called superior conjunction. Butthis wasn’t any old superior conjunction;in 2000 June Venus was in fact occultedby the Sun, an unobservable but notuninteresting event that occurs on averageless than once per decade. This occultationapproximates the reverse of a still-rarerphenomenon: a transit of Venus acrossthe face of the Sun. One of the most eagerlyDecember/ décembre 2000 JRASC261