Introduction to the Solar System

What object accounts for over 98% of the solar system's total mass?

• The Sun

• Jupiter

• Earth

• All planets combined

Which ancient Greek astronomer proposed a sun-centered model of the universe, but was largely ignored?

• Ptolemy

• Aristotle

• Aristarchus of Samos

• Johannes Kepler

Which of the following statements about planets in our solar system is true?

• All planets are larger than any moon.

• All planets have at least one moon.

• Inner planets are generally small and rocky, while outer planets are large with thick atmospheres.

• Planets orbit the Sun in random directions, like bees around a hive.

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How did the initial cloud of gas and dust that formed the solar system change as it collapsed?

• It expanded and became less dense.

• It remained spherical but became hotter.

• It flattened into a disk and began to spin faster.

• It broke into many smaller, independent clouds.

What is the primary reason that inner planets like Earth are rocky, while outer planets like Jupiter are gas giants?

• Inner planets formed from heavier elements, while outer planets formed from lighter elements.

• The sun's strong gravity pulled all the rocky material inward.

• Inner planets were too warm to retain light gases like hydrogen and helium, while outer planets were cool enough to accumulate them.

• Outer planets experienced more collisions, leading to larger sizes and gas accumulation.