Download Sun Lecture

Sun Lecture
1. Bulk Properties
 Fill in Vital Statistics, except Luminosity
 Show the TRACE Photographs
 Read the description of the Sun from Warren’s Recreations in Astronomy, 1879
 Define Luminosity
2. Maintenance of Solar Heat
 Read “On the Maintenance of Solar Heat” from Young’s Lesson’s in Astronomy,
1903
3. Energy Source of the Sun
 Nuclear Fusion: The Proton-Proton Chain
i. 4p1He + 2 +7
ii. 7 are “thermalized” by the time they reach the surface
 Energy generated from Mass Loss
Initial Mass of 4p:
6.6943x10-27 kg
Final Mass of 1He:
6.6466x10-27 kg
Mass Lost =
0.0477x10-27 kg
 Mass is converted into Energy through Einstein’s E=mc2
 How much mass must be converted into Energy each second?
E/t = mc2/t =L
m/t =L /c2 = 4,3 x 109 kg/sec
= 4.3 Million metric tons per second!
4. Two Layer Model of the Sun (See Interior of Sun Handout)
 Core
 Envelope
 Weight lifter Analogy
5. The Lifetime of the Sun
 How long can the Sun continue to lose mass at this rate?
 Personal Weight Loss Analogy
 Estimated Lifetime of the Sun = M/(m/t)
T = 1.99x1030 kg/4.3x109 kg/sec
= 4.62x1020 sec
= 15 Trillion years
 The more correct answer is 10 Billion year lifetime, with about 5 Billion to go
The Sun
Vital Statistics
Radius_______________
Volume______________
Mass _______________
Density _____________
Surface Temperature _________
Core Temperature ___________
Luminosity ________________
Definition of luminosity: ______________________________________
_____________________________________________________________
Source of the Sun’s Luminosity is _______________________________
Implications of the Sun’s Luminosity:
 The Sun produces energy by converting mass into energy.
 The luminosity of the Sun thus represents a continual mass loss.
 The Sun is currently converting 4.3 million metric tones of mass into energy each
second.
 How long can the Sun maintain this rate of mass loss?
Simple answer: ____________________________
More accurate answer: 10 Billion years.
The moral of the story: The Sun has a limited lifetime because it is
producing energy at the expense of its own mass. It will eventually run out of
mass to convert into energy. Thus, all stars have limited lifetimes because
they operate in a manner similar to the Sun. Further, the more luminous a
star is the faster it converts mass into energy and the shorter its lifetime.
High luminosity stars have relatively short lifetimes. Low luminosity stars
have relatively long lifetimes.
Earth
Two Layer Model of the Sun
Envelope
Core
Thermal
Forces
Gravitational
Forces
Property
Radius
Volume
Mass
Density
Temperature
Core
~Inner 20%
~1% of Solar Volume
~1/3rd of Total Mass
~100 gm/cm3
15 Million K
Envelope
~Outer 80%
~99% of Solar Volume
~2/3rds of Total Mass
~1 gm/cm3
5,800 K
The function of the core is to produce energy and support the envelope.
The envelope’s function is to contain the core and maintain core
conditions so energy can continue to be produced.