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 6.5 The Conjunction and ConjunctionEvents Functions When two objects move close together in the sky, they are said to be in conjunction. The Conjunction function is useful for determining the approximate date of such an event. Conjunctions are usually of little astronomical importance, but they do make interesting events for casual observers to witness. A grazing occultation, however, can give detailed information about the shape and atmosphere of the occluding object. Determing the time of a conjunction. You can use Conjunction to find the approximate date when Jupiter and Mars align nearest a given date. The correct date for the nearest conjunction to 1995 January 1 is 1995 November 17, and you can determine this date precisely using Separation. Jupiter and Mars align 10 months after the given date on about 1995 November 17. In[45]:=Conjunction[Jupiter, Mars, {1995,1,1}] Out[45]= On 1995 November 17, Jupiter and Mars are just 1.2 degrees apart in the sky. In[46]:=Separation[Jupiter, Mars, {1995,11,17}] Out[46]= Precise Conjunctions A very precise conjunction between Venus and Mars took place in the year 1590. At the time of the conjunction, the angular radius of Venus is bigger than the Mars-Venus separation, so you can conclude that Venus totally occluded Mars on 1590 October 13. This was a very rare event. During 1590, Mars and Venus align on about October 14. In[47]:=Conjunction[Mars, Venus, {1590,8,1}] Out[47]= The precise time of the conjunction is October 13, at 15:58, at which point the separation is just 0.0016 degrees. In[48]:=Separation[Mars, Venus, {1590,10,13,15,58,0}] Out[48]= The angular radius of Venus is 0.0018 degrees, which is greater than the separation. In[49]:=ApparentDiameter/2 /. Appearance[Venus, {1590,10,13,15,58,0}] Out[49]= The ConjunctionEvents Function A related function is ConjunctionEvents, which finds all the conjunctions between major solar system objects during a given month. It returns a list of days in the month showing the objects that align, and how close they are to each other. Searching for conjunction events. Most objects in the solar system move near the ecliptic line, so chance alignments between pairs of objects are relatively common. A close conjunction between Venus and a new moon is a sight worth seeing. This shows all the conjunctions between the major solar system objects during November, 1993. It shows, for instance, that Jupiter is 0.4 degrees north of Venus on November 9. The Moon and the Sun are 0.2 degrees apart on November 15, so there is a solar eclipse visible at some location on the Earth on this date. In[50]:=ConjunctionEvents[{1993,11,17}] Out[50]=