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Physics 320: Astronomy and
Astrophysics – Lecture X
Carsten Denker
Physics Department
Center for Solar–Terrestrial Research
NJIT
Problem 9.9
Electron is initially at rest in reference frame.

  me v

2
2


m
vc


m
c

m
c
c

e
e
e
Ephoton  me c 2   me c 2 
v  1
 
if v  0    1  Ephoton  0!
c

Ephoton
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Problem 9.12
s
2
2
        ds 
0
3
3
At wavelength where the opacity is greatest, the value of s
is smallest. If the temperature of the star’s atmosphere
increases outward, than a smaller value of s corresponds
to looking at a higher temperature and a brighter gas. At
wavelength where the opacity is greatest, you would
therefore emission lines.
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Problem 9.13
A large hollow spherical shell of hot gas will look like a
ring if you can see straight through the middle of the
shell. That is, the shell must be optically thin, and an
optically thin hot gas produces emission lines. Near the
edges of the shell, where your line of sight passes through
more gas, the shell appears brighter and you see in a ring.
In 1992 a tremendous explosion occurred in the
constellation of Cygnus. Dubbed Nova Cygni 1992.
Astronomers hypothesize that this system's white
dwarf had so much gas dumped onto it's surface
that conditions became ripe for nuclear fusion. The
resulting thermonuclear detonation blasted much of
the surrounding gas into an expanding shell.
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Exhibition Title Contest

Ian
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Journey to the Center of our/your
Universe
Voyage to the Center of our Solar
System
The Sun: More than a Reason to
Skip Class
Our Sun: What can it do for you?
Brick City Sun
The Key to Live on Earth: The Sun
Our Sun: The Orb of Life
The Giant Nuclear Reactor: The
Sun
NJIT Center for Solar-Terrestrial Research

John
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The Sun: Our
Closest Star
The Sun: A Look
inside our Closest
Star
Gerardo, Matthew,
& Mike
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Sunbelievable Solar
Sciene
November 5th, 2003
The Sun
 The
Solar Interior
 Mass
 Luminosity
 Radius
 Effective
Temperature
 Surface Composition
 The
Solar Atmosphere
 The Solar Cycle
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Sun – Overview
Mass (kg)
1.989e+30
Mass (Earth = 1)
332,830
Equatorial radius (km)
695,000
Equatorial radius (Earth = 1)
108.97
Mean density (gm/cm3)
1.410
Rotational period (days)
25-36
Escape velocity (km/sec)
618.02
Luminosity (ergs/sec)
Magnitude (Vo)
Mean surface temperature
Age (billion years)
3.827e33
-26.8
6,000°C
4.5
Principal chemistry
Hydrogen
Helium
Oxygen
Carbon
Nitrogen
Neon
Iron
Silicon
Magnesium
All others
NJIT Center for Solar-Terrestrial Research
92.1%
7.8%
0.061%
0.030%
0.0084%
0.0076%
0.0037%
0.0031%
0.0024%
0.0030%
November 5th, 2003
Evolution of the Sun and its Interior
Standard Solar Model:
X: 0.71  0.34
Y: 0.27  0.64
Sun–Earth Connection?
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
pp–Chain
Solar Neutrino Problem!
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November 5th, 2003
Interior Structure
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November 5th, 2003
Convection Condition
d ln P
 2.5
d ln T
The Sun is purely radiative below r/R = 0.71 and becomes
convective above that point. Physically this occurs because
the opacity in the outer layers of the Sun becomes large
enough to inhibit the transport of energy.
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Differential Rotation and
Magnetic Fields
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November 5th, 2003
Helioseismology
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November 5th, 2003
Photosphere
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November 5th, 2003
Sunspots – Umbra and Penumbra
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November 5th, 2003
Active Regions
Active region 9169 was the
host of the largest sunspot
group observed so far during
the current solar cycle. On
20 September 2000, the
sunspot area within the group
spanned 2,140 millionths of
the visible solar surface, an
area a dozen times larger than
the entire surface of the Earth!
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Spectrum of Granulation
“Wiggly” spectral lines in the
solar photosphere inside and
outside a region of activity,
reflecting rising and sinking
motions in granulation. Over
the central one third of the
spectrogram height, the slit
crossed a magnetically active
region. Here, the velocity
amplitudes are much reduced,
demonstrating how convection
is disturbed in magnetic areas.
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Model of Convection
3D animation of convection. The animation shows temperature fluctuations in a
layer of unstable, turbulent gas. (Courtesy of Andrea Malagoli, University of Chicago)
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Supergranulation
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November 5th, 2003
Photospheric Magnetic Fields
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November 5th, 2003
Sunspots – Pores & Filigree
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November 5th, 2003
Thin Flux Tube Model
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November 5th, 2003
Magnetic Carpet
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November 5th, 2003
Chromosphere
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November 5th, 2003
Mercury Transit
November 15th, 1999
The images were taken 20 seconds apart from 21:11 (first contact) to 22:10 UT
(last contact). The image were captured with a Kodak MegaPlus 4.2 CCD
camera. The spatial resolution is about 1 per pixel. Here, we show only a
small portion of the full disk images near the solar north pole. The field of
view is approximately 470  170 or 340,000 km  125,000 km on the Sun.
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Prominences
The SoHO EIT full sun image,
taken on 14 September 1999 in
the He II line at 304 Å shows
the upper chromosphere/lower
transition region at a
temperature of about 60,000 K.
The bright features are called
active regions. A huge erupting
prominence escaping the Sun
can be seen in the upper right
part of the image. Prominences
are “cool” 60,000 K plasma
embedded in the much hotter
surrounding corona, which is
typically at temperatures above
1 million K.
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Filament Evolution
Temporal evolution in Ha center line of
a sigmoidal filament in active region
NOAA 8668 during August 2000.
NJIT Center for Solar-Terrestrial Research
(a) Videomagnetogram , (b) CaI line
wing filtergram, (c) Ha – 0.6 Å
filtergram, and (d) Ha center line
filtergram.
November 5th, 2003
Filament Eruption
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November 5th, 2003
Sympathetic Flare
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November 5th, 2003
Transition Region & Corona
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November 5th, 2003
Corona – EIT 304 Å
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November 5th, 2003
Corona – EIT 171 Å
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November 5th, 2003
Corona – LASCO C2
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November 5th, 2003
Corona – LASCO C3
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November 5th, 2003
Corona and Planets
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November 5th, 2003
Coronal Mass Ejection – LASCO
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November 5th, 2003
Coronal Mass Ejection & Comet
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November 5th, 2003
Coronal Mass Ejection – TRACE
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November 5th, 2003
Space Weather
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November 5th, 2003
Space Weather –
Sun Earth Connection
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November 5th, 2003
Space Weather – Bow Shock
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November 5th, 2003
Space Weather Effects on Earth
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November 5th, 2003
Solar Cycle – Butterfly Diagram
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November 5th, 2003
Solar Cycle
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November 5th, 2003
Solar Cycle – Synoptic Map
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November 5th, 2003
Big Bear Solar Observatory
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November 5th, 2003
Telescopes and Control Room
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November 5th, 2003
BBSO – Instruments
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November 5th, 2003
Optical Lab and Parallel Computer
NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Homework Class Project
Continue improving the PPT presentation.
 Use the abstract from the previous assignment
as a starting point for a PowerPoint presentation.
 The PPT presentation should have between 5
and 10 slides.
 Bring a print-out of the draft version to the next
class as a discussion template for group work
 Homework is due Wednesday November 12th,
2003 at the beginning of the lecture!
 Exhibition name competition!

NJIT Center for Solar-Terrestrial Research
November 5th, 2003
Homework
 Homework
is due Wednesday November
12th, 2003 at the beginning of the lecture!
 Homework assignment: Problems 11.1,
11.2, and 11.8!
 Late homework receives only half the
credit!
 The homework is group homework!
 Homework should be handed in as a text
document!
NJIT Center for Solar-Terrestrial Research
November 5th, 2003