Our Sun
Why do we care about the Sun...
- Light, heat, life
- Space weather
solar wind (1,000,000 mph)
flares (UV, x-ray radiation)
disturb Earth's magnetic field
→ power surges
excess radiation bad for
satellites
Why do we care about the Sun...
- Light, heat, life
- Space weather
solar wind (1,000,000 mph)
flares (UV, x-ray radiation)
disturb Earth's magnetic field
→ power surges
excess radiation bad for
satellites
- ...one day it's gonna get us
Layers of the Sun
Core
- very very hot
(15 million K)
- thermonuclear
fusion (H → He)
- 4 million tons
of matter per
second converted
to energy
Radiative Zone
- heat transfer
through radiation
(surprise!)
- photons are absorbed
and re-emitted:
“random walk”
- few 100,000 years
Convective Zone
- heat transfer
through convection
(another surprise!)
- granulation
- core → surface:
~ 1 million years
Convection -- Granulation
Bright areas: hot pockets of gas move up
Dark lanes: cool pockets of gas sink down
Granules
Smaller granules join together,
expand, and then split up.
Atmosphere
- photosphere:
what you see!
(sunspots, granulation)
- the “surface”
Atmosphere
- chromosphere:
lower atmosphere
- we can see it
during eclipses
Atmosphere
- corona:
upper atmosphere
- very hot, tenuous gas
- we can see it
during eclipses
Atmosphere
- corona:
upper atmosphere
- very hot, tenuous gas
- we can see it
during eclipses
The corona is really hot, and no one knows why.
(It’s 250x hotter than the surface of the sun!)
. . .Magnetic field ?
Sunspots
Sunspots
Strong magnetic fields block convection cells
→ cooler areas (darker)
Sunspots
- on the photosphere
- formed by differential rotation
~equator: 25-day period
~poles: 35-day period
Sunspots
- on the photosphere
- formed by differential rotation
~equator: 25-day period
~poles: 35-day period
- they're picky about location
- high latitude → low latitude
- “butterfly
diagram”
Sunspots
11-year Solar Cycle
Prominences
loops of gas
Flares
eruptions of gas near sunspots
Coronal Mass Ejection (CME)
ejected bubbles of gas
Northern Lights
Charged particles interact with Earth’s magnetic field.
Northern Lights
Particles in Earth’s atmosphere get excited.