Day 11 Notes

Louis Lackey

Day 11 Notes

Chapter 10 Our Star

Section 10.1 a closer look at the sun

            The sun is not on fire because it would not have enough fuel to burn for longer than 10,000 years. The sun is powered by nuclear energy, nuclear fusion. Gravity balances high pressure through gravitational equilibrium. Thermal energy released by fusion in the core balances radiated energy lost from the surface. Gravitational contraction provided energy that heated the core as the sun was forming. Contraction stopped when the fusion started replacing the energy radiated into space.

-illustration of the suns structure on P289 F10.31.2012

Radius: 6.9x10^8 m

Mass: 2x10^30 kg

Luminosity 3.8x10^26 W

            Solar wind is a flow of charged particles from the surface of the Sun. The outer layer is the corona. The chromosphere is the middle layer of the solar atmosphere. The photosphere is the visible surface of the sun. The convection zone is where energy is transported upward by rising hot gas. The radiation zone is where energy is transported by photons. The core is where energy is produced by fusion, ~15m K.

Section 10.2 Fusion in the sun

            Fusion happens in the core of the sun because of high temperatures. The high speed forces nuclei to overcome electromagnetic force to come close enough for the strong force to bind them together. Four protons (hydrogen) combine into helium with two neutrons, releasing energy. This is called the proton-proton chain.

The mass is 0.7% lower. 4 protons in, ^4He (2P 2N) nucleus, 2 gamma rays, 2 positrons, 2 neutrinos out.

The core expands and contracts accordingly with temperature, changing pressure, changing the rate of fusion, readjusting the size and temperature. This solar thermostat balances the cores temperature.

We learn about the inside of the sun from mathematical models, observing solar vibrations, and observing neutrinos. The patterns on the surface on the sun can tell us about the inside of the sun.

Section 10.3 the sun earth connection

            Solar activity is like weather, sunspots, solar flares, and solar prominences. These are all related to magnetic fields.

Sunspots are cooler regions, with strong magnetic fields. Magnetic activity causes solar flares that send bursts of Xrays and charged particles into space. Coronal mass ejections send bursts of charged particles out. Solar wind is charged particles coming from the sun. Sunspots follow an 11 year cycle. This is based on the twisting of the sun’s gravitational field.