Ch 10 Jane Lucas

Jane Lucas
Astronomy 100-Week 11 – Chapter 10
Guillermo Haro
The Earth is mainly nitrogen
10.1 - A Closer Look at the Sun
10.2 - Nuclear Fusion in the Sun
10.3 - The Sun-Earth Connection
The class lecture started with a history of the Mexican Astronomer Guillermo Haro.  He discovered a type of star forming region.
You started that the Earth is mainly nitrogen.
Chapter 10.1 was introduced by the question: Why does the Sun shine?  Chemical Energy Content/Luminosity~10,000 years.  Gravitational Potential Energy/Luminosity~25 million years.  Nuclear Potential Energy (core)/Luminosity~10 billion years.  Gravitational equilibrium gravity pulling in and balances the pressure pulling out.  Energy balance is when thermal energy is released by fusion in core balances radiative energy lost from service.  Gravitational contraction is provided energy that heated the core as the sun was forming.  Contraction stopped when fusion started replacing energy radiated into space. 
Figure 10.3 is the basic structure of the Sun.  The radius of the Sun is 696,000 km.  The mass of the Sun is about 300,000 times the mass of the Earth.  The other basic properties are listed on Table 10.1 in the textbook.  
Solar wind is a flow of charged particles from the surface of the Sun.  The Corona is the outer most layer of the atmosphere.  The photosphere is the visible surface of the Sun.  The convection zone is the energy that is transported upward by rising hot gas.  The radiation zone is the energy transported upward by photons.  The core is where energy is generated by nuclear fusion.  
Why does the Sun shine? – Chemical and gravitational energy and sources could not explain how the Sun could sustain its luminosity for more than about 25 million years.  The Sun shines steadily because nuclear fusion in the core maintains both gravitational equilibrium between pressure and gravity and energy balances between thermal energy released into  the core and radiative energy lost from the Sun’s surface.
The Sun’s structure from inside out: core, radiation zone, convection zone, photosphere, chromosphere, and corona.  
Chapter 10.2 is about nuclear fusion in the Sun.  Figure 10.4 is illustrated as nuclear fission splits a nucleus into smaller nuclei, while nuclear fusion combines smaller nuclei into larger nucleus.  Higher temperatures enable nuclear fusion to happen in the core.  The Sun releases energy by fusing four hydrogen nuclei into one helium nucleus.  Gamma rays and subatomic particles known as neutrinos and positrons carry off the energy released in the reaction.  
Chapter 10.3 is about the Sun-Earth Connection.  The causes of solar activity are the convection combined with the rotation pattern of the Sun and the faster at the equator than at the poles which causes the solar activity because the gas motions stretch and twist the Sun’s magnetic field.  Sunspots are regions kept cooler than the surrounding atmosphere by strong magnetic fields.  Gas in the Sun’s chromospheres and corona becomes trapped in giant loops called solar prominences.  Solar storms are when magnetic fields winding through sunspots and prominences undergo dramatic and sudden changes.  The most dramatic of all the solar storms are the solar flares.  These solar flare storms send bursts of X-rays and fast moving charged particles shooting into space.  Coronal holes are regions of the corona that barely show up in X-ray images, because they are nearly devoid of hot coronal gas.  Coronal mass ejections are bursts of charges particles from the Sun’s corona that travel outward into space.  Sunspots are blotches on the surface of the Sun that appear darker than the surrounding areas.  The sunspot cycle is a the period of about 11 years over which the number of sunspots on the Sun rises and falls.
Chapter 10 we examined the Sun.  We discussed how the Sun shines and its basic properties.  We also learned how nuclear fusion occurs in the Sun and about the proton-proton chain.  The solar thermostat was discussed along with solar neutrinos, sunspots, and magnetic fields.  We also took a look at the solar storms, coronal holes, and coronal mass ejections.  We went through the sunspot cycle in detail.  It was a chapter all about the nearest star, our Sun.