Astronomy 3 Midterm 1 Study Guide PDF
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This document is a study guide for a midterm exam in Astronomy 3, covering various topics including scientific notation, celestial sphere, and the history of astronomy.
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Astronomy 3: Study Guide for Midterm #1 Reading: Chapters 1 -‐ 6 Topics: Basics The Sky History ...
Astronomy 3: Study Guide for Midterm #1 Reading: Chapters 1 -‐ 6 Topics: Basics The Sky History Physics Fundamentals Light Telescopes The Solar System, Overview 1. Basics o What is scientific notation and how do we use it? o What is the definition of an AU? o What is the definition of a light year (recall: c=3x10^5 km/s) o How many seconds are there in a year? o What is the scale of the solar system (in AU)? o What is the scale of the Milky Way (in light years)? o Example: calculate the distance in a light year. 2. The Sky o What is the celestial sphere? o Define these terms relevant to the celestial sphere: right ascension, declination, the ecliptic, the celestial equator, equinoxes, the north celestial pole? o How many degrees are there in a circle? o How do we convert between degrees, arcmninutes, and arcseconds? o Example: Convert between arcseconds to arcminutes, and arcminutes to degrees? The full moon has a diameter of 0.5 degrees. Express this angular size in arcminutes and arcseconds. o What is Polaris? Where is Polaris? o Define these terms relevant to your local sky: altitude, azimuth, meridian, zenith o What is the cause of Earth's seasons? o What is Earth's axis tilt? What is precession? o What causes the phases of the Moon? o What causes a solar eclipse? A lunar eclipse? o What is the phase of the Moon during a total solar eclipse? A total lunar eclipse? 3. History o Who was Ptolemy? Aristarchus? Eratosthenes? o What is retrograde motion of the planets? o What is stellar parallax, and what causes it? o Who was Copernicus? Tycho? Galileo? Kepler? Newton? Why is each of these people famous? o What are Kepler's 3 laws of motion? o Example: How long does it take an asteroid at an orbit of 4 AU to orbit the Sun? 4. Physics Fundamentals o What are speed, velocity, and acceleration? o What is the difference between a vector and a scalar? o What is the difference between mass and weight? o What are momentum, force, and angular momentum? o What are Newton's three laws of motion? o Example: The same force, F, is applied to M1 and M2. M2 is 4 times more massive than M1. How do the accelerations of M1 and M2 (a1 and a2) compare? o What are three conserved quantities in a physical system that is not subject to any external forces? o Example: Consider a ball (projectile) thrown up in the air. Describe the relative amounts of kinetic and gravitational potential energy that the ball has at different points along its trajectory. o What are the units of Kinetic Energy? o What are the fundamental units of a Joule (in terms of kg, m, s)? o What is the difference between temperature and heat? o What is the expression for the gravitational force between two masses, M1 and M2, separated by a distance, d? o Example: What happens to the gravitational force when M1 increases by a factor of 3? When M2 decreases by a factor of 3? When d is 3 times larger? 3 times smaller? o What is Newton's version of Kepler's 3rd law? What is the approximation to this law when M1 is much greater than M2 (i.e., in the case of Earth and a baseball, or the Sun and any one of the planets in the solar system)? o Example: There is a planet 1 AU from a star. It takes this planet 3 years to complete one orbit. How does the mass of the star compare with the mass of the Sun? 5. Light o What is the wave / particle duality of light? o What is the relation between wavelength, frequency, and speed of light, c? o What is the relation between photon energy and frequency, and photon energy and wavelength? o What are the different regions of the electromagnetic spectrum? o Example: A blue photon has lambda=400 nm, while a green photon has lambda=500 nm. How do the frequencies compare for the blue and green light? What about the photon energies? o What is the difference between reflection and emission? o What are energy levels? What are the energy levels of the Hydrogen atom? o What are the two laws of thermal radiation we discussed in class -‐-‐ i.e., what does Wien's law state? What about the Stefan-‐Boltzmann law? o What is the Doppler shift? o Example: The rest wavelength of a certain emission line from ionized oxygen occurs at lambda_rest=500.7 nm. This feature is observed at lambda_obs=502.8 nm. What can you conclude about the motion of the gas cloud giving rise to that observed emission line? 6. Telescopes o How does a telescope's collecting area scale with primary mirror diameter? o Example: How does the collecting area of a 30 meter-‐diameter telescope compare with that of a 10-‐meter telescope? o How does a telescope's angular resolution scale with primary mirror diameter? o What are some of the key disadvantages of ground-‐based telescopes compared to those in space? 7. The Solar System, Overview o What are the relative masses of the Sun and the other planets in the Solar system? o What is the scale of the solar system? What is the separation between the Earth and the Sun in terms of the Sun's diameter? o What is the average radius of Jupiter's orbit? Neptune's? o Between which two planet's orbits is the asteroid belt located? o Do all planets orbit the Sun in the same direction? o Describe the relation between orbital and rotational motion for the planets in the Solar System (think in terms of the axis tilts of the various planets). o What is the relationship between axis tilt and seasonal variation? o Describe the key differences between the families of terrestrial and Jovian planets. o Describe the key phases of the formation of the solar system in the so-‐ called "nebular theory". o Which types of conservation laws are relevant for describing the formation of the solar system? o What is the frost line? o What is the current theory for how Earth's Moon formed? o How do we estimate the age of the Solar system? o What is Potassium-‐40? What is Argon-‐40? o What is a half-‐life?