In January 1610 Galileo began using his newly invented telescope to observe the planets. After discovering Jupiter has moons, he must have been anxious to see what Venus might reveal.
After all, the goddess of love and beauty was the most brilliant of all the planets and its pattern of appearances was mystifying. Like Mercury — but unlike Mars, Jupiter, and Saturn — Venus was never seen far from the rising or setting Sun.
But alas, in January Venus was in the morning sky and old Galileo must have not been a morning person. Finally, by fall Venus was in the evening sky — just as it is currently in our evening sky. He was likely anticipating big things, but, boy, was he ever disappointed — at least at first.
All he saw in his primitive scope was a small fuzzy sphere — bright, yes, but no moons, no discernible features, and nothing else befitting a goddess of beauty. What a let down.
But being the good scientist he was, he continued observing Venus as it climbed further from the setting Sun over the next several months. And it’s good that he did.
His discoveries of Jupiter’s moons and our Moon’s mountainous features had already cast serious doubts about the then-accepted Earth-centered theory of the cosmos — the idea that everything moved around a stationary Earth.
What he began to note about Venus would put yet another nail in the coffin of the old theory and provide strong evidence in support of Copernicus’ revolutionary and heretical Sun-centered theory that everything revolved around the Sun, including Earth.
After a few weeks he observed that Venus was growing larger and less circular. By December it was twice the size as when he first saw it and its roundish shape had become semi-circular, and it continued to change almost nightly. It became even larger and by early February 1611 had become a thin crescent.
Being the bright guy he was, he realized the pattern of Venus’ phases, along with its pattern of appearances (never being seen far from the Sun) could only result if Venus orbited the Sun, not the Earth.
With this discovery Galileo became an open advocate for Copernicus’ Sun-centered theory, leading ultimately to his heresy trial and condemnation to the isolation of house arrest for the last decade of his life — a fine thank-you for one of history’s greatest scientists.
* Sep. 5 Sun. evening: Mars passes above slightly brighter Spica low in the west southwest with Venus to their left. * 8 Wed.: The Moon is new. * 10 Fri. evening: The crescent Moon is below Venus (left), Mars (higher above), and Spica (just above) low in the west southwest at dusk; the next evening the Moon is to their upper left. Sep. 11-24 all night: Uranus, looking like a faint star in binoculars, is within two moonwidths of Jupiter; in the evening Uranus is to Jupiter’s upper left and by morning to its upper right.
* 15 Wed.: The Moon is at 1st quarter.
* 22 Wed.: Autumn equinox, the beginning of fall in the northern hemisphere when night and day are of equal length.
* 22 Wed.: Jupiter and the Moon travel across the sky together all night.
* 23 Thu.: The full Moon is called the Harvest Moon, Fruit Moon, and Corn Moon.
• Naked-eye Planets. In the early evening brilliant Venus and fainter Mars (to its right) are low in the west southwest. Jupiter rises in the east soon after dark and by morning dominates the western sky. For a week or so around mid-month, Mercury is very low in the east as dawn breaks.
Stargazer appears every other week. Paul Derrick is an amateur astronomer who lives in Waco.