Astronomy Mid Semester Examination

1) Why was the use of the telescope by Galileo, 400 years ago, such a significant event in the history of astronomy?  (120 words, 2 marks)

The introduction of Galileo's refracting telescope was a significant event in history because of the conclusions Galileo proved using his instrument. He disproved the Roman Catholic Church's belief that the Earth was at the centre of the universe, instead of the Sun. He observed the moon-like areas on Venus that could only be true if the Sun was at the centre of the universe. He further discovered that the Moon did not have a smooth surface, but was covered with mountains and craters. Galileo also discovered the four largest moons of Jupiter, reinforcing that the Sun was at the centre of the universe. As all these primary discoveries were possible through a telescope, it laid the foundation for more telescopic developments and discoveries.

2) Pluto has recently been reclassified as a dwarf planet rather than a planet. How is a dwarf planet defined, and what led to this reclassification? (150 words, 3 marks)

The International Astronomical Union (IAU) defines a Planet as a celestial body:

1) that orbits the sun

2) is large enough to have formed its round shape due to the force of its own gravity

3) dominates its neighbourhood

IAU defines a dwarf planet as a celestial body that is neither a planet nor a satellite. It must:

1) be in direct orbit of the Sun

2) be large enough to have formed its round shape due to the force of its own gravity

3) not have cleared its orbital region of other objects

Pluto has defied the definition of a planet:

1) as it does not dominate its neighbourhood

2) Charon, one of its largest moons, is only half the size of Pluto, while other true planets are far larger than their moons

3) Astronomers estimate that there are at least 70,000 icy objects with the same composition as Pluto

Thus, Pluto is classified as a Kuiper Belt object.

3) There has been considerable controversy...