April 5, 2001

All fall and winter we watched the planets Jupiter and Saturn move across the sky from east to west. And yet they stayed in the same place.

These largest gas giants have been in the constellation Taurus the Bull all along. That is because they are so distant from the Sun, their orbits take about 12 and 30 years, respectively. If you consider that their paths in the sky pass through the twelve constellations of the Zodiac, it makes sense that they would remain in each one for at least a year.

Of course it is a coincidence that Jupiter and Saturn are in Taurus at the same time. This is when they provide the special visual treat of dancing do-si-do with the finest star clusters in our skies, for both the V-shaped Hyades and the glittery Pleiades are in Taurus.

There being twelve Zodiacal constellations, which appear to circuit the globe annually (mimicking what the Sun does daily), we can expect each one to move from east to west in approximately two seasons. And so that is why Jupiter and Saturn in Taurus are now doing their swan song in spring, falling into the western horizon shortly after sunset.

Watch the waxing crescent Moon join the group on the 25th, halfway between Saturn and the reddish star Aldebaran.