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Warm Up 6/3/08
1) A refracting telescope produces an image using a(n)
____.
a. spectroscope
c. mirror
b. prism
d. objective lens
2) A reflecting telescope produces an image using a(n)
____.
a. lens
c. prism
b. antenna
d. concave mirror
3) Which property of an optical telescope is associated
with sharper images?
a. light-gathering power c. magnifying power
b. resolving power
d. chromatic aberration
Answers: 1) d. 2) d. 3) b.
The Sun
Chapter 24, Section 3
Sun Facts
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An “Average” Star
Diameter = 109 x Earth
Volume = 1.25 x Earth
Mass = 332,000 x Earth
Density = ¼ x Earth
Structure of the Sun
• The sun is made of gas, no sharp
boundaries exist
• We can divide the sun into four parts: the
solar interior; the visible surface, or
photosphere; and two atmospheric layers,
the chromosphere and corona
• The interior makes up all but a tiny
fraction of the sun’s mass
Solar Structure
Concept Check
• What is the structure of the sun?
• The solar interior, the photosphere, the
chromosphere, and the corona
Photosphere
• Photosphere – radiates most of the light we
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see and can be thought of as the visible
“surface” of the sun
The photosphere consists of a layer of gas less
than 500 km thick
It has a grainy texture resulting from numerous
relatively small (the size of Texas), bright
markings called granules
They owe their brightness to hotter gases rising
from the interior, it spreads and cools, eventually
sinking back into the interior
The combined motion of the hotter material
replacing the cooler material is called
convection
Photosphere
Chromosphere
• Chromosphere – A relatively thin layer
of hot gases a few km thick above the
photosphere
• Only observable for a few moments during
a total solar eclipse or with special
instruments that block out the light from
the photosphere
Chromosphere
Corona and Solar Wind
• Corona – outer most portion of the solar
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atmosphere, very weak and is visible only when
the photosphere is covered
Envelope of ionized gases normally extend
millions of kilometers from the sun
Solar Wind – Streams of protons and electrons
that boil from the corona
The wind travels outward through the solar
system at speeds up to 800 km/s
During this journey, the solar wind interacts with
different bodies in the solar system, including
our Earth’s magnetosphere
Corona and Solar Wind
Concept Check
• Which layer of the sun can be thought of
as its surface?
• The photosphere
Sunspots
• Sunspots – dark regions on the surface of the
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photosphere, an individual spot contains a black
center rimmed by a lighter region
Sunspots appear dark because of their
temperature, about 1500 K less than that of the
surrounding solar surface
During the 1800s, people believed that a tiny
planet named Vulcan was orbiting between
Mercury and the Sun
The number of sunspots varies on an 11-year
cycle
Sunspots
Mean Annual Sunspot Numbers
Concept Check
• Are the same number of sunspots always
present on the sun? Explain.
• No, because the number of sunspots
varies in an 11-year cycle.
Prominences
• Prominences – huge cloudlike structures
consisting of chromospheric gases
• They appear as great arches that extend
into the corona
• Others rise explosively away from the sun
• Prominences are ionized gases trapped by
magnetic fields that extend from regions
of intense solar activity
Prominences
Solar Flares
• Solar Flares – brief outbursts that normally last
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about an hour and appear as a sudden
brightening of the region above a sunspot
cluster
During their existence, solar flares release
enormous amounts of energy, much of it in the
form of ultraviolet, radio, and x-ray radiation
Fast moving particles are ejected, causing the
solar wind to intensify
Auroras – following solar flares, Earth’s upper
atmosphere near the magnetic poles is set
alight; also called the northern and southern
lights
Solar Flares and the Aurora
The Solar Interior
• Nuclear Fusion – The process by which the
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sun produces energy; this nuclear reaction
converts four hydrogen nuclei into the nucleus of
a helium atom and tremendous energy is
released
Only a small percentage of the hydrogen in the
nuclear reaction is actually converted to energy
As Hydrogen is consumed, the product of the
reaction – helium – forms the solar core
It is believed that a star our size can exist in its
stable state for ~10 Billion years, making our
sun middle-aged at ~4.5 Billion years old
Nuclear Fusion
Concept Check
• How does the sun produce energy?
• Deep in its interior, the sun produces
energy by a process known as nuclear
fusion, wherein four hydrogen nuclei are
converted into the nucleus of a helium
atom and tremendous energy is released.
Assignment
• Read Chapter 24, Section 3 (pg. 684-690)
• Do Chapter 24 Assessment #1-34 (pg. 695696)
• Study for the Chapter 24 Quiz!!!