The Sun Flashcards
What holds sun together?
Sun made of gas so no rigidity. Held together by gravity
What stops sun collapsing?
Thermal pressure(atoms bouncing)
What is balance of pressure and gravity called?
Hydrostatic equilibrium
Why do we need hydrostatic equilibrium?
•if gravity too strong sun will collapse
•if pressure too strong sun will expand
Where is energy in sun generated?
The core
Explain nuclear fusion
•At high T atoms bounce very fast
•so fast 4 hydrogen fuse into helium
•releases tiny amount of energy
•so much hydrogen happens a lot powering entire sun
Where does the energy released in fusion come from?
Comes from binding energy of He
What are 3 ways of transporting energy?
Conduction, convection, radiation
What is radiation in sun?
Photons carrying energy
What is scattering?
Gas so dense so photons constantly getting absorbed and re-emitted. Photons random walk outwards
What is convection?
Boiling
Explain convection in sun
Lower parts of sun hotter so water expands becoming less dense than stuff above it so floats upwards transporting energy to top very fast
Ratio of radiation vs convection in sun
Radiation dominates lower 70%
Convection dominates upper 30%
What is helioseismology?
Measure of vibration patterns on suns surface
What is the photosphere?
Surface from which suns light comes to us
What is outside the photosphere?
The chromosphere and the corona
What does convection cause magnetic fields to do?
Bubble out of solar surface.
Sunspots and solar prominences
What do magnetic fields do?
Prevent hot surrounding plasma from entering the sunspot.
Are sunspots cooler or hotter than surrounding regions?
Cooler
Typical sunspot cycle
10-11 years
What happens to sunspots cycle when sun is hotter?
Cycle is shorter as more activity
When is sun most active?
When magnetic field lines tightly wound
What causes solar flares?
When magnetic field lines become too twisted they reconnect and release lots of energy
What is solar wind?
Continuous flow of charged particles caused by photons streaming out and pushing a tiny bit of matter along with it
What is CME?
Coronal mass ejection. Bubbles of gas erupting from solar surface
How is earth protected from solar wind and CMEs?
Magnetosphere. Charged particles can’t cross magnetic field lines so solar wind deflected. Visible as aurorae
When can one see solar corona?
X-rays or during solar eclipse
How is heliosphere inflated?
Solar wind
What does the heliosphere protect us from?
Very energetic galactic cosmic rays
What is heliopause?
End of heliosphere. Where wind buffets interstellar gas
