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Birth of the Solar System
1. The first modern theory of the formation of planets and solar systems from a
nebular cloud was proposed by philosopher Immanuel _________ in the 1700s.
2. A collapsing gas cloud (nebula) that form a star system increases its rotation
rate because of the conservation of _________________ momentum.
3. The protostar is the early stage of a star that forms at the ____________ of
the collapsing gas cloud.
4. The Sun formed in the center of the nebular cloud about ______billion years
ago.
5. Elements heavier than hydrogen and helium are formed by
________________________.
6. Comet material was brought back to Earth by the _____________ spacecraft
in 2006.
7. Particles within the collapsing solar nebula disk begin to collide and collect
(accrete) from the _____________________ force.
8. Gravity takes over the formation of clumps in the early solar system when they
reach the approximate size of ____________________.
9. Bodies in the solar system greater than about __________ km across are
pulled into a spherical shape by gravity.
10. The Moon was most likely formed after the violent collision of a body the size of
Mars with ______________.
11. The two moons of Mars, Phobos and Deimos, are thought to be captured
________________.
12. The solar system’s _____________ line is a boundary outside of which water
is in a frozen state, allowing the giant gas and ice planets to form.
13. The blue-green color of the giant ice planet Uranus is due to an upper layer
of __________________ gas.
14. The likely explanation of the Moon’s craters having the same age, the large
number of icy bodies in the Kuiper belt, the motion of Neptune farther out in its
orbit, and the scattering of asteroids throughout the solar system at the same
time, was the occurrence of a resonance between the Jupiter-Neptune orbits
approximately ______ billion years ago.
15. The Sun will end its life in about ______ billion years, expanding beyond the
inner planets to form a red-giant star, then ending as a white dwarf.