Sunday, December 27, 2009
Celebrate the 400th anniversary of modern astronomy
John Goss
John Goss is chairman of the Mid-East Region of the Astronomical League and a former president of the Roanoke Valley Astronomical Society.
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Blog
Many historians of science consider the end of 1609 and the beginning of 1610 to be the start of modern astronomy. During that period, the Italian physicist Galileo Galilei became the first person to scientifically examine the heavens with the newly invented telescope. That is why, 400 years later, the astronomical community has been celebrating 2009 as the "International Year of Astronomy."
In Galileo's eyes, his Jovian observations in early 1610 were his most significant, more so than his discoveries of the phases of Venus and of craters and mountains on our Moon's surface. Anyone, both then and now, who saw Jupiter through a small telescope could easily visualize a "miniature solar system" with Jupiter and its four moons representing the sun and the planets. This image helped reinforce the newly proposed, but still not widely accepted, idea that our sun -- not the Earth -- was at the center of the solar system.
The discovery of the moons began on Jan. 7, 1610, when Galileo pointed his small telescope toward Jupiter, shining brightly above the prominent constellation Orion. Like any good scientist, Galileo kept detailed records of what he saw, which later helped cement his claim of prior discovery. And like any good politician constantly looking for funding, he shrewdly named his new moons in honor of the family of his patron, Cosimo II de' Medici, the Grand Duke of Tuscany. As Galileo's fame and reputation grew, those moons became known as "the Medicean stars."
Imagine Galileo's anger two years later, when Simon Marius, an associate of the famous German physicist/mathematician Johannes Kepler, claimed to have seen Jupiter's moons on Dec. 29, 1609. Apparently, Galileo was scooped by nine days. He could no longer claim the all-important first discovery.
When Marius' records were examined, they were found to be lacking in detail, and there arose suspicions -- but no definitive proof -- that some of his work was plagiarized from Galileo's findings. It remains unclear today what Marius truly saw and when.
Galileo soon realized that, because of a case of "calendar juggling" 30 years earlier, he still could claim first discovery. In 1582, Pope Gregory ordered the Julian calendar, which was then in use by most countries, to be modified. In nearly 1,600 years of its use, certain inaccuracies had resulted in a noticeable mismatch between the calendar days and the Earth's orbit around the sun.
The Gregorian calendar came into existence with 10 days being added to the Julian calendar. The Protestant region of what is now Germany where Marius lived continued using the Julian calendar for another 100 years. When he added 10 days to Marius' records, Galileo found that Marius' key observation of Jupiter was conducted on Jan. 8, 1610 -- one day later than his own. Galileo retained first discovery!
But Simon Marius had the last laugh. The names he assigned to the four moons -- Io, Europa, Ganymede and Callisto -- are with us today.
You can easily see Galileo's four Medicean stars during the next few weeks. Look to the southwest for bright Jupiter. On the 400th anniversary of their first sighting, use a pair of steadily held binoculars to spot four pinpoints directly next to the planet. On Jupiter's upper left lie Europa and Ganymede while on its lower right sit Io and Callisto.
Start the new year right by seeing what Galileo first saw. By the way, if you like New Year's celebrations, consider that the first day of 2010 on the long-defunct Julian calendar corresponds to our Jan. 14. Go ahead -- celebrate two New Years!
