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The Sun

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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 ... – PowerPoint PPT presentation

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Title: The Sun


1
The Sun
  • Unit 6 Astronomy

2
Firstwe 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

3
Visible Light
  • A range of waves with various wavelengths
  • Passed through a prism
  • Violet bent more than blue
  • Blue bent more than green
  • Etc.

4
Spectroscopy
  • Study of the properties of light that depend on
    wavelength
  • absorption spectrum visible light is passed
    through a cool gas under low pressure

5
Absorption Spectrum
  • Each element or compound in gaseous form produces
    unique set of spectral lines
  • Studying a star
  • Lines indicate which elements --gt stars chemical
    composition

6
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

7
Intro to the Sun
  • Average star
  • Earths primary source of energy
  • Only star whose surface we can study
  • Diameter 109 Earths
  • Mass 332,000 times of Earth

8
Our Sun is a Star
9
Structure of the Sun
  • Sun is made of gas
  • No clear boundaries between layers
  • 4 parts
  • Solar interior
  • Photosphere
  • Chromosphere
  • corona

10
Photosphere
  • Visible surface
  • Radiates most of the sunlight we see
  • Layer of gas
  • Grainy texture --gt granules
  • Composition 90 hydrogen, almost 10 helium
  • Dark lines of absorption spectrum

11
Chromosphere
  • Above the photosphere
  • Thin layer of hot gases
  • Can see during a total solar eclipse (red rim)
  • Light from photosphere is blocked out

12
Corona
  • Outermost portion of the solar atmosphere
  • Weak
  • Envelope of gases --gt extend a million
    kilometers from sun

13
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
  • Earths magnetic field doesnt allow them to
    reach our surface --gt do affect our atmosphere

14
Solar Wind
15
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) --gt then decrease to
    minimum
  • Motion of sunspots --gt sun rotates about once a
    month
  • Not all parts rotate at the same speed (gaseous)

16
Sunspots
17
The Solar Cycle
18
Prominences
  • Concentration of gases often appearing as arches
    extending beyond corona
  • Sometimes can erupt ? matter escapes Suns
    atmosphere

19
Solar Flares
  • Sudden eruption
  • Above sunspot cluster
  • Release lots of energy (UV, radio, X-ray)
  • Atomic particles released --gt reach Earth day
    later (affect long-distance radio communications)
  • Auroras bright display of light caused by solar
    radiation interacting with the upper atmosphere
    at the poles
  • Following strong solar flare

20
How Solar Activity Affects the Earth
21
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

22
Introduction to Nuclear Energy
23
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

24
Process of nuclear fusion
  • E mc2
  • c speed of light
  • Speed of light is very high (300,000 km/sec) --gt
    amount of energy released from small mass is very
    high
  • One pinhead of hydrogen to helium gt burning
    thousands of tons of coal

25
Nuclear Fusion in the Sun
  • Small percentage of hydrogen is converted to
    energy
  • Helium forms the solar core --gt grows

26
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
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