AST201H1 Study Guide - Midterm Guide: Orbital Period

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pearwater-buffalo542

1 Jun 2011

School

UTSG

Department

Astronomy & Astrophysics

Course

AST201H1

Professor

Stefan Mochnacki

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AST201H1 Full Course Notes

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* the definition of universe: totality of all space, time, energy, matter; has no outside. * the age and size of the universe: 13. 7 billion years old. We look back in time when observing things far away, we see how things were when the light left it. * the observable universe: the contents and the limit to which we can see in the universe, can"t see past the observable universe. * light travel time and the light year. Light year: distance light travels in a year. Galaxy hundred billion light years away: light from there takes 100 billion light years to reach us. * the contents of the universe: planets, asteroids, comets, moons, stars, galaxies, solar system. * our location in the universe: in solar system, milky way galaxy. Acceleration: changes in velocity (either speed or direction), same for all objects, mass of object does not matter. Driving in a straight line is constant velocity, and no acceleration.

Related Questions

The great astronomer Edwin Hubble discovered that all distant galaxies are receding from our Milky Way Galaxy with velocities proportional to their distances. It appears to an observer on the Earth that we are at the center of an expanding universe. Figure 3.64 illustrates this for five galaxies lying along a straight line, with the Milky Way Galaxy at the center. Using the data from the figure, calculate the velocities: (a) relative to galaxy 2 and (b) relative to galaxy 5. The results mean that observers on all galaxies will see themselves at the center of the expanding universe, and they would likely be aware of relative velocities, concluding that it is not possible to locate the center of expansion with the given information.

Figure 3.64 Five galaxies on a straight line, showing their distances and velocities relative to the Milky Way (MW) Galaxy. The distances are in millions of light-years (Mly), where a light-year is the distance light travels in one year. The velocities are nearly proportional to the distances. The sizes of the galaxies are greatly exaggerated; an average galaxy is about 0.1 MlY across.

ceruleangiraffe295

An astronomiclal unit (AU) is equal to the average distance fromthe Earth to the Sun, about 92.9 x 10^6 mi. A parsec (pc) is thedistance at which 1 AU would subtend an angle of exactly 1 secondof arc. A light-year (ly) is the distance that light, travelingthrough a vacuum with a speed of 186,000 mi/s, would cover in 1.0year.

1. Calculate whether the setting sun floats or sinks into thePacific Ocean each night.
2. Use the size of the Universe, assume 200 billion galazies, ourown is average, and 200 billion stars per galaxy, our Sun isaverage, to calculate the density of the known Universe.

Based on counting the number of galaxies in a small patch of the sky and multiplying by the number of such patches needed to cover the entire sky, the total number of galaxies in the observable universe is estimated to be approximately

A) 100 million.

B) 1 billion.

C) 10 billion.

D) 100 billion.

E) 1 trillion.

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AST201H1 Study Guide - Midterm Guide: Orbital Period

AST201H1 Full Course Notes

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