Astro 7N Exam 3 (Answered) 74 Questions and
Correct Answers, 100% Correct. Updated Fall
2024/2025.
The sun is composed of mostly:
hydrogen (73%) and helium (25%)
How does the sun stay stable?
there is a balance of gravity that pushes inward, and gas pressure that pushes outward
What drives the gas pressure in the sun that pushes the sun outward?
Process called nuclear fusion that occurs at 15 million degrees Kelvin that produces energy
What is the conversion of the suns diameter to the earths?
One sun diameter is 109 earth diameters.
What is the conversion of mass from the sun to earth?
One sun mass is 333,000 earth masses
Luminosity
the true brightness of an object
How bright is the sun?
4 x 10^24 100-watt bulbs
99.9% of ALL THE MASS in the solar system is in the
Sun ALONE
How long has the sun been shining?
4.5 billion years and it will CONTINUE to shine for another 5.5 billion years
Sunspots
slightly cooler areas on the surface of the sun that (due to magnetic activity) prevent hot material from
rising in that region.
How long is a sunspot cycle
11 years
Nuclear fusion
the long-lasting source of energy in stars (the force that pushes against gravity to keep the sun in place)
, Under nuclear fusion, what happens?
4 protons combine to make helium and release energy through the subsequent gamma rays
The end result of what is made in nuclear fusion is called:
the Proton-Proton Chain
What is the first step of the proton-proton chain
two protons collide at a high speed and stick together. One of these then changes to a neutron to form a
deuterium nucleus and then releases energy
What is step two of the proton proton chain
The deuterium nucleus (one proton and one neutron) then collides with another proton and makes a
helium 3 nucleus. During this step, some more energy is released
What happens during step three of the proton-proton chain?
the helium 3 nuclei which both contain two protons and one neutron then collide together to form the
helium 4 nuclei
Where does the energy output from the p-p chain come from?
e = mc^2
sun's core
at the center; very high density and temperature; where all of the nuclear reactions occur and where the
gamma rays are produced
radiative zone
where the photons are repeatedly reabsorbed and reemitted; the process can take on average 170,000
years
convective zone
hot gas rises and cold gas sinks (light traverses in roughly one week)
photosphere
the surface of the sun that we see. the photons have been converted to visible light wavelengths and we
can see "granules" becuase of convection bringing material up and down.
(Temp is 5,780 K)
chromosphere
red or orange color (4,500 degrees kelvin) we can see through this down to the photosphere.
flare
an eruption coming out of the sun due to magnetic activity
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