The International Year of Astronomy 2009

Astronomy, perhaps the oldest science, has played an important role in most, if not all, cultures throughout history. The International Year of Astronomy 2009, a global celebration of the contribution of astronomy to society and culture, stimulated worldwide interest in astronomy and science, with particular emphasis on young people.

The International Astronomical Union (IAU) was the central hub for the IYA2009. Its secretariat liaised continuously with National Nodes, Task Groups and Partners as well as with Organizational Associates, the media and the general public to ensure progress in all aspects of IYA2009.

IAU astronomers are working together to build on the achievements of IYA2009 in the years ahead, fostering a global sense of wonder about the Universe. It is hoped that this will lead to the development of new generations of scientists and citizens, ready to use the sky as an inspiration for innovation and to foster a global vision.

Developed in cooperation with the European Space Agency (ESA), Universe Awareness was a Cornerstone project to acknowledge that astronomy needs to be developed in three key areas: professionally (universities and research); publicly (communication and media); and educationally (schools and informal education structures). It noted the multicultural origins of modern astronomy, using the sky and children’s natural fascination with it as common ground.

While a calendar year is defined as the number of days between two successive Gregorian dates, astronomers use different measures of time to describe the Earth’s orbit around the Sun and its rotation on its axis. The most familiar is the Gregorian solar year, which includes 365 days in each of the 12 calendar months, or the Besselian year, named after 19th century German astronomer Friedrich Bessel, who devised it. Other measurements include the tropical, sidereal and anomalistic years.

The real breakthrough in astronomical measurement came with the invention of the telescope, first in the 17th century. It was this invention that allowed Italian astronomer Galileo to sketch the surface of the Moon, discover Jupiter’s main moons and sunspots on the Sun and much more. His work catalysed the rebirth of science in Renaissance Europe, and his revelation that the Earth was not at the center of the universe but orbited around the Sun with other planets and their moons – the heliocentric model – was a major step forward in our understanding of the cosmos.