Lecture 11

Regarding poor RRRT Images ● Two potential issues: ○ High atmospheric ice crystals reflect a lot of Moon light which makes it very difficult to process out dust doughnuts (Moon was effectively full) ○ Telescope not pointing properly ● I suspect both issues are at play and me and another Professor are testing out the telescope to confirm or reject that ● Plan: Hold off until Monday to request new observations The Sun Goals for learning: ● Why does the sun shine? ● What is the Sun's structure? ● How do we know what’s happening in the Sun? ● What causes solar activity? Solar Composition (by mass) ● Hydrogen: 73.5% ● Helium: 24.8% ● Other: 1.7% Energy ● Energy is the ability to do work ○ The unit of energy is the joule (J) ○ 4.2 joules of energy are required to raise one gram of water one degree K ○ When I run at 10mph (4.4m/s) I have a kinetic energy of 1000 joules ○ A barrel of oil contains about 10 10 joules ○ In more natural units, 1 J = 1 kg m 2 /s 2 Power ● Power is the rate at which energy is being used ○ The unit of power is the watt = 1 joule/s ○ A 100 watt bulb uses 100 joules per sec ○ The Sun is giving off 3.82x10 26 ○ Astronomers use the term luminosity to describe the rate at which a star is giving off energy Why does the Sun shine? ● Is it on fire? Energy Generation ● In the 19th century, Lord Kelvin and Hermann von Helmholtz proposed that the Sun is powered by is gradual collapse