Lecture 10: Our Star, the Sun
& Solar System Formation
What does the Corona mainly emit?
UV and X Ray wavelengths
Solar Corona during an Total Solar Eclipse
Chromosphere during Solar Eclipse
Note the:
Photosphere,
Chromosphere,
and
Corona (PCC)
in this diagram.
Polar regions are slower ~36 days
How many Earths will fit across the Sun?
~110 Earth’s
What is the density of water and is the Sun more or less dense than this?
The Sun is more dense, than water which is 1000 kg/m^3
What happens to the temperature of the Sun as you go below and above
the surface?
It gets hotter, up to 1-2 million K in the corona & 15.5 million K in
the core.
The Sun is the Largest Object in
the Solar System
• The Sun contains more than 99.85% of the
total mass of the solar system
• If you put all the planets in the solar system,
they would not fill up the volume of the Sun
• 110 Earths or 10 Jupiters fit across the
diameter of the Sun
An X-ray look at the Sun.
http://bcs.whfreeman.com/universe6e/pages/bcs-main.asp?v=category&s=00110&n=01000&i=18110.07&o=|18000|01000|&ns=0
The Sun goes through periods of
relative activity and inactivity
If the magnetic field comes out of
the photosphere, that makes a pair
of sunspots.
The luminosity of the Sun increases
a little when there are sunspots.
During the period 1645 to 1715 the
Earth was unusually cold.
http://sohowww.nascom.nasa.gov/sunspots/
Sun Spots have looping magnetic
fields entering and leaving them &
thus have a North and South pole,
like a horseshoe magnet.
Sun Spot Cycle
The Sun’s interior has three
layers:
(1) core [nuclear f_ _ ion]
(2) radiative zone
(3) convective zone
Energy generated in the core of the Sun propagates outward
through these different layers, and finally, through the
atmosphere of the Sun. This process takes tens of thousands
of years or more.
The Sun’s atmosphere also has three
layers…
• Photosphere - the layer we see, 5800 K
• Chromosphere - the red layer observed
using a hydrogen filter, 10,000 K
• Corona - the incredibly thin outer
atmosphere, 1,000,000 + K
Granulation caused by convection
http://bcs.whfreeman.com/universe6e/pages/bcs-
main.asp?v=category&s=00110&n=01000&i=01110.03&o=|02000|01000|&ns=0
(go to Ch 18 “Seething Granules around a Sun Spot”)
The
photosphere is
the visible
layer of the
Sun
Sunspots are
the most well
known
feature on the
Granulation caused by convection
photosphere
Sunspots are the most well known feature in the
photosphere. Monitoring sunspots reveals the
Sun’s rotation.
http://bcs.whfreeman.com/universe6e/pages/bcs-main.asp?v=category&s=00110&n=01000&i=01110.03&o=|02000|01000|&ns=0
(go to chaper 18, the motion of a small sun spot )
Galielo
viewed the
movement of
sunspots and
this revealed
the Sun’s
rotation,
which
takes…
about 4 weeks for one rotation
The annual change in numbers of sunspots reveals
that the Sun experiences an 11-year Sun Spot cycle
Maximum
number
Minimum
number
Magnetic field lines connect sunspots on the Sun’s photosphere
Above the photosphere, the chromosphere is
characterized by its red color –
from Ha emission.
Solar magnetic fields also create
other atmospheric phenomena
• prominences
(a type of filament)
are large regions of
very dense, cool gas
held in place by
magnetic fields.
Solar magnetic fields also create
other atmospheric phenomena
• prominences
• solar flares – are
large explosions in the
Sun's atmosphere
that can release large
amounts of energy.
Some solar flares and some prominences are
powerful enough that they can cause a CME.
The ______, the outermost part of the Sun’s
atmosphere, is characterized by its high
temperature and low density
The Sun also
ejects a stream
of charged
particles into
space known
as the solar
wind
www.mreclipse.com/Special/SEprimer.html
Total Solar
Eclipse
Solar magnetic fields also create
other atmospheric phenomena
• prominences
• solar flares
• coronal mass
ejections
(CMEs)
The most powerful solar flare in 14 years, ..
erupted from sunspot 486 in late October of
2003. The explosion hurled a coronal mass
ejection almost directly toward Earth, which
triggered bright auroras when it arrived on
Earth.
The Earth’s magnetic field is caused by
movement of material in Earth’s interior
The Earth’s magnetic field produces a
magnetosphere that deflects and traps
particles from the solar wind protecting Earth
Relevance of Earth’s protective
magnetosphere
• Protects against Solar Flares - violent explosions
on the Sun releasing large burst of charged
particles into the solar system
• Protects against Solar Wind - dangerous stream
of charged particles constantly coming from the
Sun
• Gives us Northern Lights (Aurora Borealis)
Northern Lights (Aurora Borealis)
As the charged particles from the Sun interact
with the magnetic field around Earth, the
particles collide with the nitrogen and oxygen
atoms in the atmosphere and excite those
atoms to emit light
Aurora as seen from space
Collisions dominated the early solar system
• dust collects together into planetesimals
• planetesimals collect together into
protoplanets
• Protoplanets gather up left over debris and
became planets
The solar system formed from a giant cloud of
rotating, cold gas and dust called the solar
nebula about 4.6 billion years ago
The planets formed by the accretion of
planetesimals and the accumulation of gases
in the solar nebula
Which planet formed
at the furthest location
from the Sun where it
was hot enough to boil
water ?
A. Mercury
B. Mars
C. Jupiter
D. Neptune
E. None of the above