Astronomy 1000 Test 2 Review Chapter 6 – Formation of the Solar System Major Features of the solar system Eight planets with almost circular orbits in almost the same plane Sun – 99.9 % of the mass of the solar system Terrestrial planets o Mercury – metal and rock with large iron core, no atmosphere, heavily cratered o Venus – covered with clouds, high temperature due to greenhouse effect o Earth – Liquid water on the surface, with a large moon o Mars – Giant volcanoes, light atmosphere, water on the surface in the past Jovian planets o Jupiter – mostly H and He, rings, many moons o Saturn – similar to Jupiter, spectacular ring system o Uranus – smaller than Saturn and Jupiter, composed of H and He and H compounds, axis tilt is 98 degrees o Neptune – similar to Uranus in composition, unusual moon system. Pluto – dwarf planet, icy composition, one of many Kuiper belt objects and not even the largest known Clues to formation of the solar system All large bodies orbit in the same direction (CCW) and almost all rotate CCW Two main types of planets – terrestrial and Jovian with significant differences o terrestrial planets orbit close to the Sun, Jovians are far away o terrestrial planets have few or no moons, Jovians have many o Jovian planets have rings, terrestrial planets do not o Jovian planets are much larger than terrestrial planets. Dwarf planets also present, mostly beyond Neptune, seem to be icy objects like Pluto. This region is called the Kuiper Belt Asteroids, rocky objects mostly located between Mars and Jupiter (the only dwarf planet in the inner solar system is Ceres, an asteroid) Some exceptions to the rules above – Earth’s large Moon, Uranus’ axis tilt Any hypothesis must explain the clues above Nebular hypothesis The Sun and solar system condensed from a spinning cloud of gas and dust Planets formed by accretion (gradual growth, initially primarily through collisions, later by gravitational attraction) of smaller objects The participation of metal, rock, and/or hydrogen compounds in accretion depended on the distance from the sun and temperature of the solar nebula at that location (hydrogen compounds include water, methane, and ammonia) The frost line – the distance from the Sun where the solar nebula was cool enough for hydrogen compounds to solidify These facts can explain why most motion is counter-clockwise why Terrestrial and Jovian planets differ (formed inside and outside the frost line respectively) Exceptions to the “rules” – the Earth’s Moon, the retrograde rotation of Venus and Uranus, the moon system of Neptune Due to impacts of large planetesimals Earth’s Moon formation due to “Giant Impact”
Chapter 7 – Earth and the Terrestrial Worlds
You've reached the end of your free preview.
Want to read all 5 pages?
- Fall '08
- Solar System, Planet, Neptune, Pluto