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Chapter 14

Astromony Chapter 14 Notes

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Department
Astronomy
Course
Astronomy 1021
Professor
Trevor Kirsh
Semester
Winter

Description
Chapter 14: Our Star • Once we learned the Sun’s energy Examination of our Sun, the nearest output, scientists were at a loss to explain it until Einstein showed that star mass itself contains a tremendous amount of energy • The Sun shines with energy generated by fusion of hydrogen into helium in the Sun’s core Why does the Sun shine? • The Sun shines because gravitational • After a journey through the solar interior equilibrium keeps its core not and lasting several hundred thousand dense enough to release energy years, and then a 8min journey through through nuclear fusion space, a small fraction of this energy Gravitational equilibrium is the natural reaches Earth and supplies sunlight • and heat balance between two competing forces Gravitational equilibrium, the balance of the core, which is gravity pulling • inward and pressure pushing outwards between pressure and gravity, • The core originally became hot through determines the Sun’s interior structure the release of energy by gravitational and helps create a natural thermostat contraction, as gravity made the Sun’s that keeps the fusion rate steady in the birth cloud contract Sun • If the Sun were not so steady, life on • The Sun was born with enough hydrogen to steadily maintain its Earth might not be possible gravitational equilibrium for about 10 • The Sun’s atmosphere displaces its billion years own version of weather and climate, governed by solar magnetic fields What is the Sun’s structure? • Some solar weather, such as coronal mass ejections, clearly affects Earth’s • The Sun’s interior layers, from the inside magnetosphere out, are the core, the radiation zone, and the convection zone • Other claimed connections between • Atop the convection zone lies the solar activity and Earth’s climate but photosphere, the layer from which that may or may not be real photons can freely escape into space • The Sun is important not only because Above the photosphere, which is the it is our source of light and heat, but • also because it is the only star near surface, are the chromosphere and the enough for us to study in great detail corona • The sun is a ball of plasma, a gas in which many of the atoms are ionized because of high temperature 14.1 • Even sunspots are bigger than our planet Why was the Sun’s energy source a major mystery? • The Sun’s total output is called luminosity • Before we knew the difference between • Solar wind is the stream of charged Earth and Sun no one realized how particles continually blown outward much energy the Sun releases into from all directions of the Sun space • The outmost layer of the Sun is the corona, which emits Xrays • The next surface is the chromosphere •This is when photons bounce randomly where the temperature drops and emits among gas particles ultraviolet light •The migration of photons is called • The lowest layer is the photosphere, radiative diffusion, when photons slowly which is the visible surface of the sun make its way outward • The convection zone is the outer layer •After energy emerges from the
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