Lecture Four Flashcards
What is the universe made up of?
99% hydrogen and helium (about a 20:1 ratio). The Big Bang created H and He (and a little bit of Li), but nothing else.
What are the characteristics of the Sun?
Largest body in the solar system (1,392,000 km diameter). Made up of H (94%), He (6%), other elements (0.013%)
Why does the sun shine?
Due to a huge nuclear fusion reaction.
This produces energy, neutrons and photons (light). Enough H in the sun to power it for 10 billion years.
What is the internal structure of the sun?
What are the characteristics of the core of the sun?
15,000,000 degrees C
H + H = He
Density ~ 150g/cm^3 (really really fucking dense)
What are the characteristics of the radiative zone of the sun?
7,000,000 degrees C
Radiation carried by protons take more than 1,000,000 years to get out.
Density ~20g/cm^3
What are the characteristics of the convective zone of the sun?
2,000,000 degrees C
Density ~20g.cm^3
What are the characteristics of the photosphere of the sun?
5,700 degrees C
Interaction between C, N, O, Ca and photons causes ‘boiling”
Density ~ 0.0000002g/cm^3
Not solid surfae
Layer ~ 100km thick
Where you find sun spots
What are sun spots?
Dark, irregularly shaped areas on the suns surface (photosphere).
~ 2000 degrees C
Vary in size from 16 - 160,000 km.
Pairs of positive and negitive magnetic areas.
Solar promenences and flares form at sun spots.
What is the solar maximum?
Occurs when the suns magnetic field reverses polarity.
This happens every 11-12 years.
Causes a large number of sunspots to appear, causing the suns irradiance output to grow.
Sun spots increase the amount of plasma (solar wind) escaping into space.
This interacts with Earth’s magnetic field.
This causes somecommunication systmes and satillites to be affected.
Where does everything come from?
In stars like the sun, H goes to He due to fusion reactions.
In older and/or larger starts, the reactions go furth and make larger elements.
What is the fate of the sun?
It will end up as a collapsed whit dwarf star, surrounded by a cloud of C and O rich gas, and the remains of our solar system.
What is the fate of larger stars (more than 8 times the sun’s size)?
These stars will explode to form super novae, mix heavier elements into the universe.
Then collapse back into neutron stars or black holes.
Explain the relationship and characteristics of nebula and galexies.
Stars are born out of nebulas (interstellar clouds of gas and dust).
Nebulas and most stars are found within galexies.
Uneven distribution of matter after the Big Bang causes each galexy to be its own clump of matter.
There are very few stars between galexies.
How do stars form and how are the born?
Formation:
Shockwave from supernova (dying star) passes thorugh a nebula (creates clumps).
Gravity pulls on particles in the nebula.
Gas and dust accumulate.
Accumulating matter spins as it becomes more dense.
If it passes critival mass, fusion begins.
Birth:
Solar winds blows away the unnacumulated gas and dust, revealing a solar system.
Rates of star formation was higher when the universe was younger.
Out sun is at least a second generation star, as Earth has Fe and other elements which could only exist due to the supernova of a very very large star.
