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Class Information for PHYS/ASTR 1050 can be found at: • www.physics.utah.edu • Click on courses • Click on The Solar System (George Cassiday…that’s me) • Everything about the class HW, Exams, Syllabus, etccan be found by following the appropriate links.
The Solar System CHAPTER 1 Astronomy and the Universe
1. How exploring other planets provides insight into the origins of the solar system and the nature of our Earth 2. Stars have a life cycle—they form, evolve over millions or billions of years, and die 3. Stars are grouped into galaxies, which are found throughout the universe 4. How astronomers measure the positions and sizes of celestial objects 5. How to express very large or very small numbers in convenient notation 6. Why astronomers use different units to measure distances in space 8. What astronomy can tell us about our place in the universe Coming up in this lecture
The Crab Nebula Crab Pulsar
Milky Way Galaxy You are here • Actually, this is our sister galaxy, Andromeda, about 2 MLY away! • Our galaxy contains about 200 billion stars — Andromeda is a little smaller.
Angular Measure • 1 arc minute (arcmin) = 1/60 degree • 1 arc second (arcsec) = 1/60 arcmin
Circumference of Circle: C = 2πR • C/R = 2π (radians) This is the angle of a full circle. • 2π radians is equivalent to 3600 α = L / R (in radians) L α If L = C then α = 2π radians R If L = R then α = 1 radian 3600 = 2π radians 1 radian = 57.30
Powers of 10 • 10-1 = 0.1 • 10-2 = 0.01 • etc. • 101= 10 • 102 = 100 • etc.
Light Years and Parsecs Distance Light Travels in 1 Year … 1 LY = c T c = 3 x 108 m/s T = 1 Yr= 3.15 x 107 s 1 LY = (3 x 108m/s) x (3.15 x 107s) = 9.5 x 1015m
Key Ideas • Astronomy, Science, and the Nature of the Universe: The universe is comprehensible. The scientific method is a procedure for formulating hypotheses about the universe. These are tested by observation or experimentation in order to build consistent models or theories that accurately describe phenomena in nature. • Observations of the heavens have helped scientists discover some of the fundamental laws of physics. • The Solar System: Exploration of the planets provides information about the origin and evolution of the solar system, as well as about the history and resources of Earth. • Stars and Nebulae: Studying the stars and nebulae helps us learn about the origin and history of the Sun and the solar system.
Key Ideas • Galaxies: Observations of galaxies tell us about the origin and history of the universe. • Angular Measure: Astronomers use angles to denote the positions and sizes of objects in the sky. The size of an angle is measured in degrees, arcminutes, and arcseconds. • Powers-of-Ten Notation is a convenient shorthand system for writing numbers. It allows very large and very small numbers to be expressed in a compact form. • Units of Distance: Astronomers use a variety of distance units. These include the astronomical unit (the average distance from Earth to the Sun), the light-year (the distance that light travels in one year), and the parsec.