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ASTR 121 Study Guide - Spring 2018, Comprehensive Midterm Notes - Sun, Galaxy, Milky Way


Department
Astronomy
Course Code
ASTR 121
Professor
Derek Richardson
Study Guide
Midterm

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ASTR 121
MIDTERM EXAM
STUDY GUIDE
Fall 2018

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ASTR121 Lecture 1 Review of ASTR120
Logistics:
o Office is at PSC 1112
Office hours: M 10 11 am, W 2 3 pm
o Phone #: 301-405-8786
o E-mail: dcr@astro.umd.edu
o T.A.: Ms. Sara Frederick
o Learning assistant: Mr. Joe DeMartini
Whiteboards
o One person in group takes photo and shares with everyone; everyone uploads the
photo to ELMS.
Learning goals:
o Describe in general terms your place in the universe and your motion within it.
o Explain how a star’s spectrum can be used to determine its temperature,
composition, and relative radial motion.
o Give the net reaction in the proton-proton chain and predict how the Sun would
respond to a change in the reaction rate.
ASTR120 Lecture Topics
o Historical astronomy
o Moon phases
o Reasons for the seasons
o Nature of eclipses
o Kepler’s laws
o Newton’s laws
o Conservation laws
o Light and matter
o Spectroscopy
o Doppler effect
o Telescopes
o Overview of the solar system
o Formation of the solar system
o Surfaces and atmospheres
o Earth as a living planet
o Gas and ice giants
o Moons and rings
o Dwarf planets and comets
o Asteroids and dusts
o Impact hazard
o Solar structure and activity
o Exoplanets
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Beyond the Solar System
o Stars and gases
Eagle Nebula (M16)
Rosette Nebula
o The Milky Way
o Galaxies
o Our cosmic address:
Earth, Solar System, Milky Way, Local Group, Virgo Supercluster,
Universe
The Universe
o The sum total of all matter and energy (everything within and between the
galaxies)
o There are about 100 billion galaxies, each with 100 billion stars; this means that
the observable universe contains 10^22 stars (about 10 quadrillion).
o Since light travels at a finite speed c, we see heavenly objects as they were in the
past; we see the Sun as it was eight minutes ago, the Moon as it was one second
ago, and Andromeda as it was 2.5 million years ago.
o Humanity has been around for very little time, in relation to the age of the Earth
and the Universe.
In the so-called Cosmic Calendar, all of human history can be condensed
into the last fifteen seconds of the year (December 31, 11:59:45); the
voyage oc Columbus occurred at 11:59:59.
Cosmic Motions:
o Earth rotates on its axis at 1000 km/hr; it orbits the Sun at 100,000 km/hr; the Sun
moves among the stars at 70000 km/hr; the Milky Way rotates at 800000 km/hr.
How to Solve Problems:
o Understand the Problem
Will the solution be large or small? What units are you looking for?
What information do you need?
Would a diagram help?
o Solve the Problem
o Explain the Result
Does the answer make sense?
What did you learn?
o Make sure that the answer is in the correct units (if the question asks for length,
the answer should not be in years!).
o We can often deduce a form of an equation by looking at units.
By looking at the force exerted on an object in the wind, we can deduce
that the formula for this is:
 
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