Lecture 18. The Sun
A. Class Business --
- Planet Viewing: what time?
- Midterm grades -- by Wed., I hope!
B. The Sun
- RADIATION -- again --
Look in different wavelengths, see different stuff!*
- different temperature gasses emit
THERMAL RADIATIONin different wavelengths -- two examples:
- hot corona (2 MK) emits in X-rays
- photosphere (5800 K) emits in yellow, visible
- photons in these various wavelength bands are ABSORBED and EMITTED by e-'s (electrons) orbiting atoms
-- so we also see SPECTRAL LINES
- the Sun is so hot, it has IONIZED much of its gas --
free e-'s and p+'s (protons) and IONS (atoms missing one or more e-) -- a PLASMA
- hotter particles move faster, colliding all the time
- at high enough T, collisions between them
cause e-'s to be knocked off of atoms
- if you have a plasma, you'll have MAGNETIC FIELDS
- Magnetic Fields
- "If it weren't for its magnetic field,
the Sun would be a pretty boring star." -- quite so!
- field lines -- show direction & strength of field
- i) also called "lines of magnetic FLUX"
-- impress your friends
- (all magnets have (+) & (-) poles -- BIPOLE
-- sunspots are bipolar)
- ii) lines run from (+) to (-) -- FOOTPOINTS of LOOPS
(can run in circles, too)
- iii) more field lines in a given space =
more flux = stronger field
- iv) charged particles must follow field lines:
- If you move lines, then particles move, too.
- If you move particles, then lines move, too.
- We say "flux is FROZEN IN to plasma."
- VIDEO