features of the suns Flashcards
The James Webb Space Telescope
(JWST)
observ es at infrared wav elengths
how many earths could fit inside the sun
About one million Earths could f it inside the Sun
The Sun
A large sphere of hot, dense,
mostly ionized gas (plasma),
bound together by grav ity.
Energy is produced in the Sun’s
core and makes its way to the
surf ace.
The Sun consists of dense gas
by mass: 70% H, 28% He, 2% other
(90% of all the atoms are Hydrogen)
* Density = Mass / Volume
* Average Density of the Sun = 1.4 g/cm3
(density of water is 1.0 g/cm 3
Most common elements in the Sun
H 90%
He 8.7%
O 0.08%
C 0.04%
N 0.01%
Si 0.004%
Mg 0.004%
Ne 0.004%
Fe 0.003%
S 0.002%
The Solar Atmosphere: Photosphere
visible surface of the Sun
* Temperature 5700K
* Density 10−9 kg/liter
* 400 km thick
tops of the cells on the Sun’s ‘surface’ (photosphere
graunualtion
The photosphere of the Sun is
an apparent surface: you would notice little change as you
go through it, like flying through a cloud
Sunspots are dark because
they are cooler (4000K
v s. 6000K) than the regions around them
The Sun rotates once
every 4 weeks
Differential rotation:
* 26 days at the equator
* 38 days at the poles
Sun’s Magnetic Field
produced by the flow of plasma in the interior
Sunspots occur when the
when the Sun’s
magnetic field bursts through the surface
* Magnetic field
lines prevent
hotter plasma
from rising into
the sunspot
* Sunspots come
in pairs, with
opposite
polarities
Sunspots vary in an
an 11-year sunspot cycle
The number of sunspots and solar activity in general peaks
every 11 years
The Solar Atmosphere: Chromosphere
lay er abov e the photosphere
* T ~ 15,000 K.
* 1,000 km thick
spicules
magnetic jets and loops
The Solar Atmosphere: Corona
Outermost lay er,
v ery thin but hot,
T > 1 million K
* Visible during
a total
solar eclipse
The corona is much hotter than layers below i
The Sun’s magnetic f ield acts like a pump
that accelerates the particles in the corona.
Very hot gas can be seen in
x-rays
Solar prominences
are created by plasma looping along
magnetic f ield lines
Solar Flares
Two prominences short
out, releasing huge burst
of energy (million H
bombs)
Solar Wind
The solar wind (charged particles) escapes
through coronal holes, seen in X-ray images.
The Sun is ev aporating! (but very slowly)
solar wind what it is
electrons and
protons streaming away
f rom the corona
Earth’s magnetic f ield
def lects
most of the solar
wind around the Earth,
collects the rest in the
Van Allen belts.
Coronal Mass Ejection
Coronal Mass Ejection
A solar flare or coronal mass ejection (CME)
can trigger the aurora borealis
Aurora
When the low-density gas
of the upper atmosphere is
heated, it emits an
emission-line spectrum.
Aurora Borealis
