Still as while Saturn whirls

. . . his stedfast shade
Sleeps on his luminous ring
– Tennyson.

Saturn reaches, on August 21, a position called “east quadrature,” which means it is 90 degrees east (left, as seen from our northern hemisphere) of the Sun.

150821ev

This is a rather interesting stage in the orbits of the distant planets because we see as much as we can (not very much) of the narrow shadow along their left sides; but more so for Saturn because we have a view, far more generous, of its shadow thrown out across its rings.

SaturnEQuad2015
Part of an illustration in the Saturn section of Astronomical Calendar 2015.

Like any strong shadow, this shadow enhances the sunlight by contrast, causes the third dimension to spring out.

However, you may want to aim your telescope at Saturn a day or two before or after this date of quadrature, because of the Moon. It, too, is striding out eastward from the Sun, and will be at its First Quarter phase on Aug. 22, only 20 hours after it passes closest to Saturn. That stands to reason: a Quarter phase for the Moon, like quadrature for a planet, means being 90 degrees from the Sun, so if they happen to reach these phases of theirs at the same time they must be close together.

Meanwhile, over on the west of the Sun, things happen that you can only expect to see with the mind’s eye. Mars cruises in front of the star cluster in Cancer called the Beehive, or, more anciently, Praesepe, the “Manger.” Mars takes a couple of days to cross this sprinkling of stars, and is nearest to the middle of them about 18 Universal Time on Aug. 20.

150820mo

Also to be seen in the mind: Venus has just passed its inferior conjunction with the Sun and is on its way to rebirth in the morning sky – as we described for Aug. 15.

If you didn’t receive an email notification about that, please click here. I was using it to try to learn something else about the system, and the experiment may not have worked.

 

3 thoughts on “Still as while Saturn whirls”

  1. I’ve been hoping to watch Mars pass through the manger with binoculars.* The weather looks to foggy though, so I guess you’re right, I’ll have to use my mind’s eye.

    *Would you indulge this misplaced modifier by drawing me a cartoon of the God of War surveying his battlefield through a pair of binoculars?

    1. As Anthony watched Mars pass in front of the Beehive with binoculars, the bad-tempered god swung his binculars right around and told his bees: “I spy a nosy observer, sic himn!”

      I scheduled this post to go out on the morning of Aug. 19. when I would be away. I return to find something had gone slightly wrong: the first illustration, the sky scene, was not showing. It’s there now.

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