College of the Desert

A 001

The Galilean Moons of Jupiter
Name: Yesenia Rosales
Goal: To study the orbital motions of Jupiter’s four largest
moons.








The four largest moons of Jupiter were discovered in 1610by the Italian astronomer















with his simple telescope. Contrary to popular belief, he did not invent the
telescope, which was invented in Holland several years earlier. He was, however, the first
person known to apply the new invention to astronomy. Galileo made many discoveries with
his telescope besides the moons of Jupiter. He discovered that the Moon’s surface is rough
and irregular, and that Venus has phases. H e also rediscovered sunspots, and, by watching
their motion across the Sun, deduced that the Sun rotates on its axis.
At the time, the most accepted model of the universe, perfected by        !"
had the Earth in the center and everything revolving around it. All celestial objects were
perfect spheres However,        had challenged this model and had postulated a model
with the Sun in the center (as had certain anent Greeks). All the planets including the Earth
revolved around the Sun. Galileo’s discoveries either cast doubt on the old model or directly
supported the new model. For example, his discovery of small bodies orbiting Jupiter proves
that the Earth is not the center of all orbital motion in the universe.
These four moons were important for other reasons.      # later showed
that their orbits obeyed his three laws just as the orbits of the planets around the Sun do. Later
researchers were able to use Kepler’s third law for these moons to measure the mass of
Jupiter.
Galileo’s first book, Siderius Nuncius, was published in 1610. The Roman Catholic
Church, which endorsed the geocentric model, order him to stop supporting the Copernican
model in 1616. Galileo refused and published his second book, A Dialogue Concerning the
Two Chief World Systems, in 1632. This angered the church, which charged him with
suspicion of heresy in 1632. Convicted in 1633. Galileo’s difficulties with the church,
however, did not stop his discoveries from becoming widely known Copernicus’s heliocentric
model from becoming accepted. Pope John Paul 2 formally pardoned Galileo in 1992.








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When Galileo’s fist turned his new telescope on Jupiter he recorded in his noteboo