PHYS 371 FINAL

explain the characteristics of energy conversion in the sun or a star

energy passing through the giant sphere each second must equal to the energy passing out of the sun’s surface each second which must be equal to energy created in suns core each second

is this true or false: nuclear reactions happen in the sun because its hot

false

TRUE or FALSE: the sun is hot because nuclear reactions within

true 

how do we measure angular size of the sun?

conversion factor for degrees x (physical size/distance)

how do we calculate the physical size of the sun?

distance x (angular size/conversion factor for degrees)

how do we measure how hot the sun is?

sun’s energy output is measured with spectrograph and thermal radiation spectrum revealing that surface temperature of photosphere is about 5800K

who discovered the orbital rules of motion?

kepler and newton

what are the characteristics of the interior surface of a star?

deeper you go inside the higher the gas pressure needs to be to support the weight of all the gas above it

what is the principle of hydrostatic equilibrium?

deeper you go inside the higher the gas pressure needs to be to support the weight of all the gas above it

what can the hydrostatic equilibrium principle and ideal gas law be derived for a star’s center?

(1/2) GMstar/NaKbRstar 

what does the hydrostatic equilibrium principle and ideal gas law in the center of a star depend on?

stars radius and mass (and fundamental constants)

what was the temperature of the center of the sun known to be?

15 million K before we knew nuclear fusion happens there

what are the characteristics of energy balance in a star?

for stars to remain stable there needs to be a constant flow of energy from center to the surface, if thermodynamics were alone stars would coool of with time and shrink, so there is a giant source of energy in the center of stars

what are the characteristics of energy conversion in a star?

nuclear energy processes create deadly radiation, fluffy buffer that converts deadly radiation to a thermal spectrum, buffing process takes a long time 

what does the joining of two protons form?

one proton becomes a neutron plus a positron pls a neutrino

can two protons stay together as an atomic nucleus?

no

what is a deuterium?

isotope of hydrogen

what is the mass of a photon

zero 

what is a positron?

anti-matter counterpart of an electron, has same mass but positive charge

what happens to the newly formed positron when protons combine?

quickly collides with an electron, mutual annihillation results in two gamma ray photons

how do neutrinos travel?

escape the sun at nearly the speed of light 

what is the mass of two protons?

2.014553 amu

what is the mass of a proton and neutron?

2.015941 amu

what is the mass of a deutron?

2.013551 amu

where does the missing mass from the proton proton chain go?

mass difference is converted to mass and energy of the positron adn enutrino following einsteins equaion, E = change in mass x c²

what is step one of the proton proton chain?

two protons fuse to make a deuterium nucleus (1 proton and 1 neutron), occurs twice in reaction 

what is step two of the proton proton chain?

deuterium nucleus and a proton fuse to make a nucleus of helium-3 (2 protons, 1 neutron), occurs twice in overall reaction

what is step three of the proton proton chain?

two helium 3-nuclei fuse to form helium-4 (2 protons, 2 neutrons) releasing two excess protons in the process

what does the proton proton chain reaction result in the formation of?

gamma rays

how do we measure the rate of mass conversion?

sun luminosity/energy created per kg 

how do we measure the nuclear lifetime of the sun?

suns mass/mass conversion rate

what can we conclude about the suns energy consumption?

theres enough fuel in the sun to keep it shining with its current power for at least another 5 billion years

what is another important factor in the energy conversion and balance in the sun?

suns core temperature is regulated to stay constant because the. gas in it obeys the ideal gas law of thermodynamics

what is the characteristic of energy release from nuclear fusion?

releases energy in form of very fast particles and gamma ray photons, at surface the sun emits mostly photons in visible part of spectrum

what are the actions of gamma ray photons in the sun?

in core of sun travel only few nm before deflected in collision with another electron or photon, overtime these interactions convert one energetic photon into many lower energy photons, takes long time for energy released by nuclear fusion to reach surface

is the net energy output of the sun variable?

super constant and very stable

does the sun follow gas like behaviour and if so what does this imply?

yes, if nuclear reaction rate increases the sun expands and cools, if rate lowers it is compressed and heats up back to average temp