EUROPLANET OUTREACH - International Year of Astronomy

International Year of Astronomy 2009

Celebrating 400 years of planetary science

In 1609, Galileo Galilei turned a recent invention, the telescope, on the night sky. His observations of the Moon and his discovery of four small bodies orbiting Jupiter are the foundations of modern planetary science.

Four hundred years later, European planetary scientists are continuing his work observing and exploring the Solar System and understanding its place in the Universe.

Find out about IYA2009 activities in Europlanet countries:

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Galileo's Observations

In the spring of 1609, Galileo first heard of a new device for observing distant objects. Based on these reports, Galileo started to build his own telescopes, developing lens-grinding techniques to produce increasingly powerful magnification. By the end of the year, he was producing instruments that could magnify up to 20 times and he turned these on the night sky.

His observations of the Moon in December 1609 revealed a mountainous, uneven surface, instead of the perfect sphere claimed by the medieval followers of Aristotle. The following month, he noticed “three fixed stars” close to Jupiter and, observing them over several nights, found that they moved relative to Jupiter until one of them disappeared from view. He concluded that they were not stars but moons in orbit around Jupiter. A few days later, he observed a fourth moon. These four bodies were later named Io, Callisto, Europa and Ganymede and are still known as the Galilean moons in honour of his discovery.

Over the coming months, he continued to observe the moons, working out accurate estimates for their orbital periods. He also turned his telescope on other objects in the Solar System. Around Saturn, he spied mysterious lobes that disappeared when viewed at certain angles. These were later identified as rings by Christiaan Huygens in 1655.

Galileo observed that Venus phases similar to the Moon, providing strong evidence that the Earth orbited the Sun.

In 1632, Galileo published his Dialogue Concerning the Two Chief World Systems, comparing the Copernicus’s Sun-centred model of the Solar System with Ptolemy’s Earth-centred model. Shortly after publication, Pope Urban VIII prohibited distribution of the book and appointed a special commission to examine the contents. Galileo, though ill, was summoned to Rome for trial by the Inquisition and was convicted of “grave suspicion of heresy”. He placed under house arrest until his death in 1642.

Further information:
Biography of Galileo from the University of St Andrews: http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Galileo.html
Chronology and information from the Galileo Project: http://galileo.rice.edu/chron/galileo.html

Galileo's Legacy

Galileo’s design for a telescope was limited by a small field of view. By 1630, use of a combination of convex lenses first suggested by Johannes Kepler in 1611, spread through the astronomical community and became known as the astronomical telescope. By the 1730s, refracting telescopes had reached their limits. The first working reflecting telescope, using a combination of mirrors and lenses to increase magnification, was created by Isaac Newton in 1672. However, it took nearly half a century to overcome difficulties with the tarnishing of mirrors and to develop grinding techniques to produce regular curvature.

William Herschel’s innovations with mirror casting in the 1770s took reflecting telescopes to a new dimension. In 1781, Herschel used a seven-foot (2.1 metre) telescope with 227 times magnification to discover Uranus, the first planet to be discovered using a telescope. He later went on to make telescopes with 40-foot (12 metre) focal lengths. Herschel also discovered infrared radiation while experimenting with prisms and sunlight.

In the 20th Century astronomers began to develop instruments that could view wavelengths beyond visible light and new fields of astronomy, looking at the hottest and the coolest objects in the Universe, developed. The first astronomical radio source was detected in the 1930s and by the 1960s, astronomers were using balloons to carry experiments into the Earth’s upper atmosphere. With the advent of the space age, telescopes could be mounted above the absorption and distortion caused by the Earth’s atmosphere, allowing clearer images in visible and infra-red wavelengths and opening up the possibility for observations in ultraviolet, X-ray and gamma ray bands.

Today, European planetary scientists have a complete toolbox of ground-based telescopes, space-based observatories and robotic probes to observe the Solar System. Galileo’s legacy of observation, technological advance and scientific curiosity lives on.

Further information
The Galileo Project: http://galileo.rice.edu/sci/instruments/telescope.html
Herschel Museum: http://www.bath-preservation-trust.org.uk/index.php?id=46

Nodes Network News

The Europlanet National Nodes are the key contact points for all outreach activities in Europlanet member countries.
To date, there are Europlanet Nodes in thirteen countries who are responsible for developing and maintaining the national web pages hosted by the Europlanet outreach website and helping to build links with the national media, planetary research institutions and the outreach community.
The first Node meeting took place at EPSC 2009 in Potsdam.

Countries with Europlanet Nodes