The Sun

3 Pages
Unlock Document

University of Massachusetts Amherst
Alexandra Pope

The Sun is not on fire: Chemical Energy / Total Luminosity= 10,000 years The Sun is not contracting: Gravitational Potential Energy / Luminosity = 25 million years The Sun is powered by nuclear energy (E=mc^2) Nuclear potential energy (core) / luminosity = 10 billion years Pressure and Gravitational Equilibrium: ● Weight of upper layers compresses lower layers Gravitational Equilibrium: ● Energy supplied by fusion maintains the pressure that balances the inward crush of gravity Energy Balance: ● the rate at which energy radiates from the surface of the Sun must be the same as the rate at which it is released by fusion in the core. ● Contraction stopped when fusion began. The Sun’s Dimension Radius: 6.9 x 10^8 m (109 times the earth) Mass: 2 x 10^30 kg (30,000 earths) Luminosity: 3.8 x 10^26 watts The Sun’s Structure Core: energy generated by nuclear fusion = 1 million K Radiation Zone: energy transported upward by photons Convection Zone: energy transported upward by hot rising gas Photosphere: visible surface of the sun = 6000 K Chromosphere: middle layer of the solar atmosphere = 10^4-10^5 K Corona: Outermost layer of the solar atmosphere = 1 million K Solar Wind: a flow of charged particles from the surface of the Sun REVIEW: ● The Sun shines because gravitational equilibrium keeps its core hot and dense enough to release energy through nuclear fusion. ● From inside out, the layers of the Sun are core, radiation zone, convection zone, photosphere, chromosphere, and corona. Fission: Big nucleus into smaller pieces (ie. nuclear power plants) Fusion: Small nuclei stick together to make a bigger one (ie. the Sun, stars) ● High temperatures enable nuclear fusion to happen in the core. ● The Sun releases energy by fusing four hydrogen nuclei into one helium nucleus. ● The proton-proton chain is how hydrogen fuses into helium in the Sun. ● Releases positron and neutrino (ionized plasma particle) binds with another. IN - 4 protons OUT - He nucleus, 2 gamma rays, 2 positrons, 2 neutrinos Total mass is lower than 0.7 % The solar thermostat keeps burning rate steady. ● Decline in core temp causes fusion rate to drop so core contracts and heats up ● Rise in core temp causes fusion rate to rise, so core expands and cools down ● Energy gradually leaks out of the radiation zone in form of randomly bouncing photons, which is how energy from fusion gets out of the Sun. Convection (rising hot gas) takes energy to the surface. Bright blobs on the photosphere show where hot gas is reaching the surface. We le
More Less

Related notes for ASTRON 100

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.