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Unformatted text preview: Chapter 16/Chapter17
Chapter Questions of the Day
Questions What are stars? What are their properties? Who was Annie Jump Cannon? Why was she
important to the study of stars?
important What is stellar spectroscopy? What does it tell us
about a star?
about What is the Sun? Why is it important to study this
particular Parallax of a Star
Distance (parsec) =
Parallax Angle (" ) Parallax of a Star
Parallax = 0.2"
= 5 parsecs
0.2" Differential Magnitude
− . 5 log 2 2
log 2 =2 f
log 1 f
m =2 2.5 =
10 m2 − 1
2.5 = . 5m2
m Differential Magnitude
Differential Two stars have a magnitude of 7 and 3. How
much brighter is the star with a magnitude of 3
than the star with a magnitude of 7?
f2 2 =
2 . 5m2
2 . 57
3 Distance Modulus
m m1 =
f1 Luminosity (L)
(10 parsec ) 2 2
− . 5 log 2 f
1 = 2 − 1
m Distance Modulus L 2
− . 5 log
2 L 4
(10 ) 2 π
M 10 − . 5 log 2
d 10 − log 5
M d d 5 log =
M 10 d M + log 5
m 10 Distance Modulus
Distance A star has a absolute magnitude of -5 and a
distance of 1000 parsecs.
What is the
magnitude of the star as view from Earth?
M + log 5 10 pc =
m 1000 pc − + log 5
m 10 pc − + log( 100 )
Fig.16.09 Annie Jump Cannon
Annie 1863 – 1941 A.D. Born in Delaware,
grew up in Dover,
Delaware. Entered Wellsley
College http://astro.wsu.edu/worthey/astro/html/imwomen/04cannon.jpg Annie Jump Cannon’s Work
Annie Worked under Edward C. Pickering at
Harvard University to classify spectra of
stars 1911 - 1914: Created the Henry Draper
Catalogue 1918: Doctorate Degree 1914: Honorary in the Royal Astronomical
Society Spectral Types
Spectral http://blueox.uoregon.edu/~courses/BrauImages/Chap17/FG17_010.jpg Fig.16.18
Fig.16.19 Mass – Luminosity A star has a mass of 5M, how much brighter is
this star than the Sun?
M = L Θ Θ
M 3.5 5MΘ
L = LΘ Θ
LΘ What is the Sun?
What Our nearest star. The center of our solar system. The main engine for all the heat produced in
the solar system.
the http://spaceflightnow.com/news/n0211/04soho/sun.jpg What are the properties of the sun?
What Distance: 1.49 X 108 km = 1 A.U.
km Size: 1.4 X 106 meter = 0.5° Mass: 2 X 1030 kg Density: 1.4 g/cm3 Distance to the Sun
Distance Aristotle was the first person to consider the
problem. But Kepler was the first to obtain a
precise measurement. Recent measurements use radar bouncing
off other planets to obtain more precise
measurements. Size of the Sun
Size Aristarchus was the first to consider the size of the
Sun. The modern method involves the angle of the light
rays. If the Earth were the size of a penny, 150 Earths
would fit across the face of the sun.
would The Mass of the Sun
The Newton was the first person to find
accurately the mass of the sun with his
theory of gravitation.
theory 30,000X more massive than the Earth. The Density of the Sun
The The density is simple calculation of the
mass over the volume.
mass The density is only 40 percent higher than
water suggesting a gaseous composition.
water The Layers of a Star
Corona http://www.conceptdraw.com/samples/samplestour/Proton/Proton.gif Proton-Proton Chain
Proton-Proton Sun Prominence
Sun http://www.uniba.sk/~ago/pics/sun/1907anim.gif Sun Flare
Sun http://msowww.anu.edu.au/msovc/displays/images/sunflare.jpg Sunspot Cycle
Sunspot http://www.hao.ucar.edu/public/education/sp/images/sunspotn.2.jpg Homework 8
Homework What is the luminosity of the Sun? What is the luminosity
of a O type star? And what the luminosity of the K type
star? How do they compare to the luminosity of the Sun?
And how much heavier is the O than the K type star?
And Two stars have magnitudes of 4 and 9 respectively. How
much brighter is the star with magnitude 4 than the star
with magnitude 9? If these two star were the same
absolute magnitude (-4), how much further is the star with
apparent magnitude of 9 than the star with the apparent
magnitude of 4?
magnitude Page 391, CQ 3, 12 Describe the different layers of the Sun via their respective
temperatures and pressures. ...
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This note was uploaded on 12/04/2011 for the course AST 1004 taught by Professor Howard during the Fall '09 term at Broward College.
- Fall '09