DSST Astronomy Practice Questions Answer Key
1. C: The Earth’s magnetic field protects it from solar wind. Solar wind is a stream of highly-charged radioactive particles that emanate from the Sun, and these particles are deflected by the magnetic field. The magnetic field is shaped like a bowl that covers the side of the Earth facing the Sun. It deflects most solar particles, but some are trapped in the Van Allen belt. Particularly strong bursts of solar wind allow particles to pass through this belt into the Earth’s ionosphere and upper atmosphere, creating geomagnetic storms and aurora.
2. D: The physical structure of the universe is thought to consist of filaments (walls of superclusters, clusters, and galaxies) that surround large, bubble-like voids. Filaments are the largest structures in the universe, with some forming huge structures like the Great Wall and the Sloan Great Wall.
4. A: The distance from the Earth to the Sun is equal to one astronomical unit. An astronomical unit (AU) is equal to 93 million miles, and is far smaller than a light year or a parsec. A light year is defined as the distance light can travel in a vacuum in one year, and is equal to roughly 64,341 AU. A parsec is the parallax of one arcsecond, and is equal to 206.26 ? 103 astronomical units.
5. B: The energy radiated by stars is produced by nuclear fusion. This is the process whereby the nuclei of individual atoms bind together to form heavier elements and release energy outward. By the time this energy, which is created in the star’s core, reaches the outer walls of the star, it exists in the form of light.
6. A: The stream of charged particles that escape the Sun’s gravitational pull is called solar wind. Solar wind is comprised primarily of protons and electrons, and these particles are deflected away from the Earth by its magnetic field. When stray particles do manage to enter the atmosphere, they cause the aurorae (Northern and Southern Lights) and geomagnetic storms that can affect power grids.
7. C: Venus is not a gas giant. The four gas giants are Jupiter, Saturn, Uranus, and Neptune. While these “gas giants” are larger than Earth and are comprised mostly of gases, Venus is a terrestrial planet that is comparable in size to the Earth.
8. D: The asteroid belt in our solar system is located between Mars and Jupiter. The asteroid belt is populated by asteroids and dwarf planets that are distributed thinly enough that spacecraft can pass though the belt with relative ease.
9. D: Gravitational collapse and high-energy collisions are both proposed explanations for the formation of black holes. Gravitational collapse occurs when the outward pressure exerted by an object is too weak to resist that object’s own gravity. Collisions that produce conditions of sufficient density could also, in theory, create black holes. The accretion of matter is considered observational evidence for the existence of black holes.
10. D: The first implies that the Earth was shaped by a series of quick, violent events, while the second implies that it changed slowly and incrementally. Catastrophism is the belief that the Earth was shaped by sudden, short-term catastrophic events. Uniformitarianism, also known as gradualism, is the belief among modern geologists that the forces, processes, and laws that we see in effect today have been in effect for a long period of time, that is, throughout geologic time. It involves the belief that the present is the key to the past, and that these relatively slow processes have shaped the Earth.