This year marks the 400th anniversary of the birth of telescopic astronomy, so the International Astronomical Union and UNICESCO have designated 2009 the International Year of Astronomy “to foster a global appreciation of the role and value of science and astronomy as a unifying activity for humanity.”

It could also be regarded as the symbolic 400th anniversary of the Copernican Revolution in which a scientific theory—that the Sun, not the Earth, was at the center of the universe — shook the foundations of western civilization. The international nature of IYA2009 is fitting as each of the major revolutionaries was from a different country.

The revolution began in earnest with the death of its namesake, the Polish Nicolaus Copernicus (1473-1543). In 1533 he set forth his theory in a book, On the Revolutions of the Celestial Orbs. But knowing his Sun-centered theory was at odds with the church-government’s view of things — and to disagree could be deadly — he arranged to have his book published upon his death, thus the first shot was fired in 1543. While many thought Copernicus’ view made sense, he offered no observational data to support his theory, so it simply circulated underground for several decades.

In the latter 1500s, the Dane Tycho Brahe (1546-1601), blessed with exceptionally keen eyesight and a penchant for meticulous record-keeping, amassed a wealth of observational data, including the precise movements of Mars over many years. Having little idea what to do with his data, he had the good sense to hook up with the German Johannes Kepler (1571-1630).

A brilliant mathematician, Kepler made good use of Tycho’s data. In 1609, he published Astronomia Nova in which he set forth the elliptical (rather than circular) nature of orbits. Thus he contributed important theoretical support for Copernicus’ theory — but firmer observational verification was still needed.

Enter the Italian Galileo Galilei (1564-1642). Upon hearing of the newly-invented telescopes made by the Dutch lens-grinder Hans Lippershey, Galileo in 1609 made his first telescope and began using it to study the night sky. His discoveries — such as the moons of Jupiter, the phases of Venus, and the mountains and craters of our Moon — finally began providing observational data to support Copernicus’ theory.

The final shot was fired decades later in 1687 by the Englishman Isaac Newton (1642-1727). “Standing on the shoulders of giants,” as he put it, Newton published Principia in which he set forth our modern understanding of gravity.

Thus, with two critically important turning points occurring in 1609, it seems fitting to celebrate 2009 as the symbolic 400th anniversary of the 144-year long Copernican Revolution.

• Sky Calendar:

• September 26th, Sat.: The Moon is at 1st quarter.
• September 29th, Tue. evening: Jupiter is below the bright gibbous Moon.
• Oct. 4th, Sun.: The full Moon, being the full Moon nearest the fall equinox, is this year’s Harvest Moon.
• Oct. 8th, Thurs. morning: Coming up an hour and a half before sunrise, Saturn is just to the upper left of brighter Mercury low in the west with Venus above them.

• Naked-eye Planets: Evening: Jupiter is the brightest “star” in the southeast. Morning: Venus rises shortly before dawn while much fainter Mars is well above it high in the east; later in the fortnight, Mercury, then Saturn, begin to rise at dawn.

• Astro Milestones: Using the calculated predictions of Urbain Jean Joseph Leverrier of France, Johann Galle & Heimrich d’Arrest discovered the planet Neptune from Germany’s Berlin Observatory Sept. 23, 1846.

Stargazer appears every other week. Paul Derrick is an amateur astronomer who lives in Waco. Contact him at 918 N. 30th, Waco, 76707, (254) 753-6920 or paulderrickwaco@aol.com. See the Stargazer Web site at stargazerpaul.com.