Jupiter Now and Then
Published on Sep 13, 2007 at 11:55 pm.
3 Comments.
Filed under planets, skywatching.
Earlier this week, I did a laboratory exercise with my students that required them to know the current coordinates of a planet. That planet was Jupiter. I thought that I might mention a few things about that.
Jupiter takes nearly 12 years to orbit the Sun. Right now, it appears to be in the constellation Scorpius, as shown in the diagram below. This time of year, if you go out soon after sunset, Jupiter is in the southwestern sky. There is no mistaking it. Jupiter will be the brightest object in that part of the sky (or any other part of the sky, for that matter). Right below Jupiter in the sky will appear the bright reddish star Antares.
Since Jupiter takes about 12 years to go around the sky, it appears to move eastward one constellation per year. In one year, Jupiter will be in Sagittarius, as seen in the next diagram. At that time, in September, 2008, Jupiter will be as far south as it will be getting this time around, at over 23 degrees south of the celestial equator. It will be in prime position then and for the next few years for observers in the southern hemisphere. But, it will still be great to look at for those of us in the northern hemisphere.
Since Jupiter takes about 12 years to orbit the Sun, and passes through 12 constellations along the way, it takes about a year to move from one to another. This turns out to be important to the historical Chinese calendar. Jupiter was the “year star” for the ancient calendar. Whatever Chinese constellation Jupiter appeared to be in that year defined how the year was identified (year of the horse, rat, dragon, etc).
Of course, for those of us who have been watching the sky for a number of years, Jupiter also helps us mark time. I remember the last times it was in Scorpius. The more times that you can remember the event, the older you are! I also remember when Saturn was in Scorpius, too. Saturn, though, takes about 29 years to make a complete circuit of the heavens, so it will be a few years more until it gets back to where I first saw it.
So, go out and look for Jupiter, and think about where it will be next year!
-Astroprof
Star charts created using Starry Night Pro
A ler…-- Rastos de Luz on September 14, 2007 at 6:31 am: 1
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Mike S. on March 12, 2008 at 8:32 pm: 3
Wikipedia describes the 12 Chinese constellations as if they have no actual representation in the sky - and since they are now used as a 12-year cycle, this is now true. (while I didn’t search exhaustively, I didn’t see anyone disputing this view) But did the 12 animals at one time correspond to real stars, and if so where? It’d be cute to plot Jupiter’s orbit and try to locate them, because it would allow you to say that people were “really” born in some other year/constellation of the Chinese zodiac than is commonly accepted, besides shedding some light on ancient constellations.