Saturday, June 20, 2015

Planetary Pavane, Part 3; Matter of Perspective

Tonight I would like to direct your attention once again to the celestial show currently in progress in the western sky after sunset.  Again, we are observing the motions of Venus and Jupiter as they march toward conjunction at month's end; if you've been periodically checking you'll know the apparent distance between them is steadily decreasing from night to night.  This evening a new partner joins the dance, if only temporarily.

Once again, go outside about an hour after sunset and find a spot with a good view of the western sky.  You'll see brilliant Venus and somewhat dimmer Jupiter--now only six degrees apart from the point-of-view of terrestrial observers--and five degrees to the south-west of Jupiter lies the four-day-old crescent Moon, forming a lovely triangle in the gathering darkness.

While you admire the view, take a moment to consider its "depth of field".  In the foreground of the tableau lies our own Moon, practically next-door at nearly four hundred thousand kilometers' range, in the middle distance blazes the beacon of Venus at over eighty-nine million km, with Jupiter the most distant at almost nine hundred million km.

Put another way, the King of the Planets is ten times as far away from Earth as Venus, and over twenty-two hundred times as distant as our own Moon.

As Douglas Adams wrote, space is big.  Really big. Right now you are gazing at a yardstick of worlds marking off a distance of nearly a billion kilometers from where you stand!

(Oh, just to cement your feelings of cosmic insignificance, that spark of bluish light to the upper left of Jupiter is Regulus, brightest star of the constellation Leo; its distance has been determined to be seventy-nine light-years...roughly seven hundred and sixty trillion kilometers!)

Please, enjoy the show tonight--as usual I welcome your observations and feedback.

Courtesy NASA

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