Transcript The Sun

THE SUN
THE SUN
• The Sun is the most prominent
feature in the solar system
• It contains about 98% of the total
mass of the solar system
• The interior of the Sun can hold
over 1.3 million Earths
THE SUN
Birth of the Sun
An artists image of a
protoplanetary disc
• The Sun was formed
around 4.6 billion
years ago within a
protoplanetary disc
of gas and dust
• The central regions
of the disc began to
coalesce and
collapse
• When the Sun had
contracted enough,
nuclear reactions
began at the core,
causing the Sun to
shine as a star
THE SUN
• The Sun has been
active for 4.6 billion
years and has enough
fuel at its core to burn
for another 5 billion
years
• The Sun rotates every
25 days at the equator
to every 36 days at the
poles
• Deep down everything
appears to rotate
every 27 days
THE SUN
The vast majority of stars
lie in the main sequence
• The Sun is called a
main sequence star
• Stars in the main
sequence spend most
of their active lives in a
stable state fusing
hydrogen to helium
• Bigger stars fuse
hydrogen to helium at
a faster rate and live
shorter lives
• Smaller stars fuse
hydrogen to helium at
a slower rate and live
longer lives
THE SUN
• The Sun orbits the
center of the Milky
Way Galaxy in the
same way as the
Earth orbits the Sun
• It takes about 250,000
million years to
complete one orbit
traveling at
approximately 250
kilometers/second
THE SUN
• The Sun’s outer
layer is called the
photosphere
• It has a temperature
of 6000oC
(11,000oF)
• It’s mottled
appearance is due
to turbulent
eruptions at the
surface
• Sunspots appear in
the area of the
photosphere
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Sunspots
• Sunspots are dark
depressions on the
photosphere with a
temperature of 4000oC
(7000oF) which is cooler
than the surrounding
area
• Sunspots change over a
period of days and move
across the Sun as it
rotates
• They have a strong
magnetic field associated
with them and last from a
few days to a few weeks
THE SUN
Faculae
• Faculae are bright
luminous hydrogen
clouds which form
in the photosphere
near sunspots
• They put out more
radiation than
normal and
increase the solar
irradiance
• While sunspots
make the Sun look
darker, faculae
make it look
brighter
THE SUN
• Solar energy is
created deep within
the core
• Here the temperature
is 15,000,000oC
(27,000,000oF)
• The pressure is so
intense that nuclear
reactions take place
• Energy is carried to
the surface by both
radiation and
convection
THE SUN
Nuclear Reactions
In the Core
• The pressure at the
Sun’s core is so intense
that it causes hydrogen
nuclei to fuse together
to form one helium nucleus
• The difference in mass is
expelled as energy
• It is carried to the Sun’s
surface by radiation and
convection and is released
primarily in the form of
electromagnetic radiation
(i.e. light)
• Energy produced in the core
takes a million years to reach
the surface
THE SUN
Convection
granulation cells
• Convection occurs because
heated fluids, due to their lower
density, rise and the cooled fluids
fall
• The heated fluid will rise to the
top of a column, radiate heat
away, then fall to be reheated,
rise and so on
• A convection cell forms when a
packet of fluid becomes trapped
in this cycle
• Very large convection cells on
the Sun show a pattern that
looks like rice grains, called
granulation
THE SUN
• The chromosphere is
above the
photosphere where
temperature is
between 6000°C and
20,000 °C
• Solar energy passes
through this region
on its way from the
core
• Spicules and solar
flares arise in the
chromosphere
THE SUN
Spicules
• The chromosphere
contains spikes of
superheated gas called
spicules that rise through it
• Spicules are short-lived
phenomena corresponding
to rising jets of gas that
move upward at high
speed usually lasting only
10 minutes
• More than 100,000
spicules “tickle” the solar
atmosphere at any time
THE SUN
Solar Flares
• Solar flares are eruptions in
the chromosphere
• High energy particles and
gasses are emitted lasting
minutes to hours
• Flares produce sunquakes
similar to an 11.3 magnitude
earthquake on Earth and
release 40,000 times more
energy than the 1906 San
Francisco earthquake
Image taken by SOHO in 1999
THE SUN
Corona
• The corona is the
outer part of the Sun’s
atmosphere with
extremely high
temperatures around
1,000,000°C
(1,800,000°F)
• The outer region of the
corona stretches far
into space and
consists of particles
traveling away from
the Sun
• The corona can only
be seen during a total
solar eclipse
THE SUN
Solar Eclipse
• A solar eclipse happens
when the moon passes
between the Sun and the
Earth
• The corona is a million
times fainter than the
surface of the Sun so the
only time it can be seen is
during a total exlipse
• Ancient people often
thought that eclipses
were signs from angry
gods or omens of doom
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Prominences
Prominences on the Sun, with the
Earth shown to scale
Prominences
• A solar prominence, or
filament, is an arc of gas
that erupts from the sun
• They can loop thousands
of miles into space
• They are held above the
Sun’s surface by strong
magnetic fields and can
last many months
• Prominences are larger
than the Earth, which
would easily fit under it
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Coronal Mass
Ejections
• Coronal Mass Ejections
(CME’s) are huge bubbles of
plasma ejected from the Sun
• Solar plasma is heated to
tens of millions of degrees
and electrons, protons, and
heavy nuclei are accelerated
to near the speed of light
• The CME’s disrupt the solar
wind and can strike the Earth
disrupting communication
and navigation systems,
satellites and power grids,
sometimes with catastrophic
results
THE SUN
Solar Wind
• Solar winds are streams
of highly ionized gas that
blow continuously outward
through the Solar System
• The temperature of the
corona is so high that the
Sun cannot hold on to it and
the solar winds stream from
the Sun at one million miles
per hour
• This distorts the Earth’s
magnetosphere
THE SUN
Solar Wind
• Flares and CME’s are the
most powerful particle
accelerators in the solar
system
• A CME can erupt with the
energy of 200 billion
Hiroshima bombs
• Radiation from a flare
could kill a spacewalking
astronaut
• The Earth’s
magnetosphere shields
us from these energetic
particles
THE SUN
The Aurora Borealis
• The aurora “dances” in the polar regions as the solar
wind interacts with the Earth’s magnetic field and
energizes electrons and ions in the Earth’s upper
atmosphere
• The energized molecules and atoms in the thin polar
atmosphere then glow at different colors
THE SUN
The Future
of the Sun
• The Sun has enough
fuel to last for another 5
billion years
• At the end of it’s life it
will have used up all its
hydrogen
• When there is no longer
any source of heat to
balance gravity its core
will then collapse
THE SUN
The Future
of the Sun
• This collapsed core will
become compressed and
heated causing it to
produce a new surge of
power (from the burning of
helium into carbon at the
core and hydrogen into
helium in shells around the
core) and begin to swell
• This phase is called a red
giant and it will ultimately
grow so large it will swallow
the Earth
THE SUN
The Future
of the Sun
This is the Helix Nebula—an example
of a planetary nebula
• After about a billion
years as a red giant it
will shed its outer
layers forming a
planetary nebula
(which, by the way,
has nothing to do with
planets)
• The planetary nebula
phase is fleeting and
lasts only about
10,000 years
THE SUN
The Future
of the Sun
• Having run out of fuel the
core of the Sun will shrink
to a hot (~30,000°C)
white dwarf only a few
thousand miles in
diameter
• A white dwarf is a stable
star held up by electron
degeneracy pressure, an
exotic state of matter
• It will radiate left-over
heat for billions of years
until it cools to a black
dwarf
• A black dwarf is a cold
dark mass that has no
internal source of energy
THE SUN
SOHO
• SOHO (The Solar &
Heliospheric
Observatory) was
launched on December
2, 1995 by NASA and
the European Space
Agency (ESA)
• It became operational
in March 1996 and was
meant to operate until
1998 but has been so
successful that its
mission has been
approved until 2007
THE SUN
SOHO
• SOHO is designed to study the
internal structure of the Sun, its
outer atmosphere, and the
origin of the solar wind
• It helps us understand the
interactions between the Sun’s
and the Earth’s environment
better than ever
• It provides uninterrupted views
of the Sun and may help solve
some puzzling riddles of our
closest star
THE SUN
Mankind will not remain on
Earth forever, but in its
quest for light and space
will at first timidly
penetrate beyond the
confines of the
atmosphere, and later will
conquer for itself all the
space near the Sun. Konstantin E. Tsiolkovsky