International Year of Astronomy – Why 2009?

Copyright © 2009 by Bob Moler

It's finally here, the International Year of Astronomy (IYA) with the theme The Universe, yours to discover. But why 2009?

Four hundred years ago an Italian by the name of Galileo Galilei built a telescope after hearing that such a device had been invented in the Netherlands. To our knowledge he was the first to turn the telescope to the heavens, or at least was the first to write about it.

Galileo was the first modern scientist, performing experimental observations of falling bodies and other phenomena. With the telescope he single handedly proved the Copernican sun centered solar system to all who would look at his evidence, and look for themselves. His observations were recorded in his 1610 book Sidereus Nuncius or Starry Messenger. In it Galileo demonstrated that the moon had mountains and craters, and was not the perfect smooth sphere demanded by the prevailing cosmology of Aristotle, which stated that everything in the heavens from the moon on out were perfect and changeless. A non-smooth moon violated this.

Galileo also turned his telescope to the stars and found many more dim stars than could be seen with the unaided eye, and that his telescope didn't magnify the stars. They just appeared brighter. He looked at the Pleiades, Praesepe or what we call today, the Beehive cluster, and the Orion Nebula, though he missed the nebulosity, something I know can happen with a small telescope.

Finally Galileo observed the planet Jupiter and what he calls the Medician stars, after his patrons the Medici. The 4 are satellites of Jupiter. They are sill called the Galilean moons, and have the names he gave them: Io, Europa, Ganymede and Callisto.

The Starry Messenger was published in March of 1610 with these initial observations. Galileo made more observations with his telescope, the change in the size and the phases of Venus, proving that it orbited the sun and not the earth. He also observed Saturn, but mistook the rings for a pair of moons on each side of the planet. The rings were very thin in 1610, and went edge on in early 1613.

He also observed the sun, discovering sunspots. Though sunspots had been seen with the unaided eye, they were either dismissed as a transit of a planet like Mercury or something else. The sun, like the other heavenly bodies were supposed to be perfect and without blemish. Sun blemishes were another of Galileo's proofs of the error of the Aristotelean Universe. One of the erroneous myths of Galileo is that looking at the sun caused his blindness in later life. It isn't true. Early on, it is true that he looked directly at the sun with his telescope. He did it at sunrise and sunset. Later on he projected the sun's image.

This year we other astronomers around the world both amateur and professional will be showing the wonders of the universe to everyone we can. It's funny. We astronomers it seems cannot touch the objects of our affection, except when like Joe Brooks' collection, they are meteorites. But the photon of light is a particle, and when we look at a distant star or galaxy that photon, of the thousands of photons that spend their energy on our retina came from those objects. In the case of a galaxy the photons may have traveled for millions of years through the depths of intergalactic space to paint a picture of their source on our retinas. In that way, yes we do touch the object we view through the telescope, or really, they touch us.

Below is a table of observational and other activities that we can participate in this year. Some are annual and occur every year. The IYA is an occasion to highlight them. This table was created from entries on the calendars page of the United States IYA site at the address http://astronomy2009.us/calendar/. The main US site is http://astronomy2009.us/.

The table items for the start and end of the total eclipse of e (Epsilon) Aurigae is interesting. The star, the top one of the three stars in the narrow triangle of the Kids in Auriga, undergoes a total eclipse of one of its stars every 27.06 years. The brightness of the star will drop by 8/10^ths of a magnitude. Epsilon will be close to its dimmest most of the year, since the atmosphere of the eclipsing star is extensive, or there is a ring of material involved in the star's orbital plane.

There's lots of fun observing and sharing of the sky on tap this year. Come help your fellow members and the public explore the Universe!

Questions? Send Email to me at bob@bjmoler.org

Updated: 01/01/09