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THE SUN

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From the Sun, we base our understanding of all stars in the Universe. No solid ... Surface of the Sun is ringing' ... Same for the Sun. 7. Solar Cross-Section ... – PowerPoint PPT presentation

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Title: THE SUN


1
THE SUN
  • The star we see by day

2
Goals
  • Summarize the overall properties of the Sun.
  • What are the different parts of the Sun?
  • Where does the light we see come from?
  • The scientific method solar neutrinos.

3
The Sun, Our Star
  • The Sun is an average star.
  • From the Sun, we base our understanding of all
    stars in the Universe.
  • No solid surface.

4
Vital Statistics
  • Radius 100 x Earth (696,000 km)
  • Mass 300,000 x Earth (1.99 x 1030 kg)
  • Surface temp 5,800 K
  • Core temp 15,000,000 K
  • Luminosity 4 x 1026 Watts
  • Solar Day
  • 24.9 Earth days (equator)
  • 29.8 Earth days (poles)

5
Interior Properties
  • Core 20 x density of iron
  • Surface 10,000 x less dense than air
  • Average density Jupiter
  • Core 15,000,000 K
  • Surface 5800 K

6
Scientific Method
  • How do we know this stuff?
  • Three examples
  • Fusion in the core (core temperature).
  • Different zones in interior.
  • Solar activity and Earth

7
1. The Core
  • Scientific Method
  • Observations
  • Make hypothesis (a model)
  • Models make predictions
  • Test predictions
  • Compare results of predictions with observations
  • Revise model if necessary.

8
Testing the Core
  • Observe Suns
  • Mass (how?)
  • Composition (how?)
  • Radius
  • Use physics to make a model Sun.
  • Predict
  • Surface temp/density (how do you test?)
  • Surface Luminosity (how do you test?)
  • Core temp/density ? Fusion Rate ? neutrino rate
    (test?)

9
In The Core
  • Density 20 x density of Iron
  • Temperature 15,000,000 K
  • Hydrogen atoms fuse together.
  • Create Helium atoms.

10
Nuclear Fusion
  • 4H ? He
  • The mass of 4 H nuclei (4 protons)
  • 4 x (1.6726 x10-27 kg) 6.690 x 10-27 kg
  • The mass of He nuclei 6.643 x 10-27 kg
  • Where does the extra 4.7 x 10-29 kg go?
  • ENERGY! ? E mc2
  • E (4.7 x 10-29 kg ) x (3.0 x 108 m/s)2
  • E hc/l ? l 4.6 x 10-14 m (gamma rays)
  • So 4H ? He light!

11
2. Helioseismology
  • Continuous monitoring of Sun.
  • Ground based observatories
  • One spacecraft (SOHO)
  • Surface of the Sun is ringing
  • Sound waves cross the the solar interior and
    reflect off of the surface (photosphere).

12
Solar Interior
  • Core
  • Only place with fusion
  • Radiation Zone
  • Transparent
  • Convections Zone
  • Boiling hot

13
Convection
  • A pot of boiling water
  • Hot material rises.
  • Cooler material sinks.
  • The energy from the pots hot bottom is
    physically carried by the convection cells in the
    water to the surface.
  • Same for the Sun.

14
Solar Cross-Section
  • Progressively smaller convection cells carry the
    energy towards surface.
  • See tops of these cells as granules.

15
The Photosphere
  • This is the origin of the 5,800 K thermal
    radiation we see.
  • l k/T k/(5800 K) ? l 480 nm (visible
    light)
  • This is the light we see.
  • Thats why we see this as the surface.

16
3. Solar Activity and Earth
  • Is there a connection between Solar Activity and
    Earths Climate?
  • Observation
  • Little Ice Age
  • Maunder Minimum

17
What is Solar Activity?
  • Sunspots
  • Magnetic Fields
  • Coronal Mass Ejections
  • Solar Wind
  • Magnetic Storms
  • Aurora
  • Other effects?

18
Sunspots
  • 11-year sunspot cycle.
  • Center Umbra 4500 K
  • Edge Penumbra 5500 K
  • Photosphere 5800 K

19
Magnetic fields and Sunspots
  • At kinks, disruption in convection cells.
  • Sunspots form.

20
Magnetic fields and Sunspots
  • Where magnetic fields pop out of Sun, form
    sunspots.
  • Sunspots come in pairs.

21
Prominences
Hot low density gas emission lines
22
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23
Corona and Solar Wind
  • Hot, low density, gas emits the radiation we see
    as the Corona 1,000,000 K
  • Solar Wind Like steam above our boiling pot of
    water, the gas evaporates.
  • Carries away a million tons of Suns mass each
    second!
  • Only 0.1 of total Suns mass in last 4.6 billion
    years.

24
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25
Solar Cycle
  • Increase in solar wind activity
  • - Coronal Mass Ejections
  • Increase in Auroral displays on Earth
  • Increase in disruptions on and around Earth.

Courtesy of SOHO/LASCO/EIT consortium.
26
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27
Aurora
  • The solar wind
  • passes out
  • through the
  • Solar System.
  • Consists of electrons, protons and other charged
    particles stripped from the Suns surface.
  • Magnetic fields herd charged particles into
    atmosphere at poles.
  • Charged particles excite electrons in atoms. ?
    Light!

28
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29
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30
2003 CME
Oklahoma 10/29/2003
Credit E. Woldt
31
Homework 7
  • Due Monday 30-Jan, Read Exoplanet articles plus
    the website
  • http//www.howstuffworks.com/planet-hunting2.htm
  • Why do we believe there are planets around other
    stars? How have we detected them?
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