Astro Study Guide - Midterm 1

Astro Study Guide - Midterm 1 - Astro Study Guide Midterm 1...

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Astro Study Guide – Midterm 1 Chapter 1 Scientific method – intellectual endeavor based on observation, logic, and skepticism. Requires that our ideas about the world be consistent with what we actually observe. Hypothesis – collection of ideas that seems to explain what is observed. Theory – collection of related hypotheses that are pieced together into a self-consistent description of nature. Importance of Skepticism – new hypotheses must be able to withstand the close scrutiny of other scientists. More radical hypotheses will receive more skepticism, which reduces the propagation of extraordinary theories. STARS Source of Sun’s Light - at center of Sun, thermonuclear reactions take place that convert hydrogen into helium. More massive stars have more thermonuclear fuel (hydrogen), but they consume that fuel so fast they live out their lives in just few million years. Less massive stars have less fuel to consume, but their thermonuclear reactions proceed so slowly that they live for billions of years. Nebulae - huge clouds of interstellar gas. In some nebulae stars are born from the gases of the nebula itself. Supernova – when the thermonuclear reactions of a massive star cease, a huge explosion of gases is released that blow the star apart and form a nebula. Pulsar – dead stars that spin dizzily at rates of tens or hundreds of rotations per second. Galaxy – stars grouped together in huge assemblages, sometimes containing hundreds of billions of stars. Quasar – very luminous objects that shine with the brilliance of a hundred galaxies, that draw their energy from material falling into black holes. Small Angle Formula – D = ad/206,265 where D is the linear size of an object, a is the angular size of the object in arcseconds, and d is the distance to the object. Parsec – at a distance of 1 parsec, a length of 1 AU subtends an angle of 1 arcsecond. CHAPTER 2
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Positional astronomy – study of the positions of objects in the sky and how these positions change. People who created Stonehenge aligned the stones to show where the sun rose and set at key times during the year. Anasazi Indians created stone carvings that were illuminated by the Sun on the first days of summer or winter. The great Egyptian Pyramids are oriented north-south and east-west with an accuracy of far less than 1 degree. Constellation – a grouping of stars, that on modern day star charts, the entire sky is divided into 88 regions. The Earth rotates from west to east, and because of this rotation the stars appear to rise in the East and set in the West, as do the Sun and the Moon. At 35 deg. North latitude, the North celestial Pole is 35 deg. above the northern horizon. In the Northern Hemisphere, as the Earth rotates from west to east, stars that are near the north celestial
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This note was uploaded on 04/07/2008 for the course ASTRO 1 taught by Professor Antonucci during the Fall '08 term at UCSB.

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Astro Study Guide - Midterm 1 - Astro Study Guide Midterm 1...

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