Transcript The Sun

The Sun
Unit 6: Astronomy
First…we have to discuss light
 Information about universe
 Light emitted from stars and other bodies
in space
 Electromagnetic spectrum =
arrangement of waves according to
their wavelengths and frequencies
 We see visible part of spectrum
Visible Light
 A range of waves
with various
wavelengths
 Passed through a
prism
 Violet bent more
than blue
 Blue bent more than
green
 Etc.
Spectroscopy
 Study of the
properties of light
that depend on
wavelength
 absorption spectrum
= visible light is
passed through a
cool gas under low
pressure
Absorption Spectrum
 Each element or
compound in
gaseous form
produces unique set
of spectral lines
 Studying a star
 Lines indicate which
elements --> star’s
chemical
composition
Remember the Doppler
Effect?
 Light from a source
moving away from you
appears redder
 Waves are lengthened
 Moving toward you
appears bluer
 Waves are shortened
 Determine whether a
star or other body in
space is moving away
from or toward Earth
 Measured from the dark
lines in spectra and
comparing them with a
standard spectrum
Intro to the Sun
 “Average” star
 Earth’s primary source
of energy
 Only star whose surface
we can study
 Diameter = 109 Earths
 Mass = 332,000 times of
Earth
Our Sun is a Star
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Sorenson Video 3 decompressor
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Structure of the Sun
 Sun is made of gas
 No clear boundaries
between layers
 4 parts




Solar interior
Photosphere
Chromosphere
corona
Photosphere
 Visible surface
 Radiates most of the
sunlight we see
 Layer of gas
 Grainy texture -->
granules
 Composition = 90%
hydrogen, almost 10%
helium
 Dark lines of absorption
spectrum
Chromosphere
 Above the photosphere
 Thin layer of hot gases
 Can see during a total
solar eclipse (red rim)
 Light from photosphere
is blocked out
Corona
 Outermost portion
of the solar
atmosphere
 Weak
 Envelope of gases
--> extend a million
kilometers from sun
Corona

Solar wind = streams
of protons and
electrons ejected at
high speed from the
corona
 Travel through solar
system and are lost to
space
 Alters appearance of
bodies in the solar
system
 Earth’s magnetic field
doesn’t allow them to
reach our surface --> do
affect our atmosphere
Solar Wind
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Sunspots
 Dark spots on the
surface of the sun
 Temperature is less than
the surrounding solar
surface
 Number of sunspots
observable vary in an
11-year cycle
 Increases to maximum
(100) --> then decrease
to minimum
 Motion of sunspots -->
sun rotates about once
a month
 Not all parts rotate at
the same speed
Sunspots
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The Solar Cycle
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Prominences
 Concentration of
gases often
appearing as arches
extending beyond
corona
 Sometimes can
erupt  matter
escapes Sun’s
atmosphere
Solar Flares
 Sudden eruption
 Above sunspot cluster
 Release lots of energy
(UV, radio, X-ray)
 Atomic particles
released --> reach Earth
day later (affect longdistance radio
communications)
 Auroras = bright display
of light caused by solar
radiation interacting
with the upper
atmosphere at the
poles
 Following strong solar
flare
How Solar Activity Affects the
Earth
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Solar Interior
 Source of energy = nuclear fusion
 Combining of the nuclei of lighter
elements to form a heavier element
 Energy released because some matter is
converted to energy
Introduction to Nuclear
Energy
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Process of nuclear fusion
 Converts four hydrogen nuclei into the
nucleus of a helium atom
 Lots of energy released!
 4 hydrogens = 4.032 amu; 1 helium = 4.003
amu
 Missing mass! (.029 amu)
 Animation
Process of nuclear fusion
 E = mc2
 c = speed of light
 Speed of light is very high (300,000
km/sec) --> amount of energy released
from small mass is very high
 One pinhead of hydrogen to helium > burning
thousands of tons of coal
Nuclear Fusion in the Sun
 Small percentage of hydrogen is
converted to energy
 Helium forms the solar core --> grows
Future of the Sun
 Will the sun run out of hydrogen fuel?
 Last another 100 billion years
 Sun will grow
 Engulf Earth
 Sun can exist in its stable state for 10
billion years
 Already 4.5 billion years old