02 The Sun-online
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1402
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Astronomy
Date
Feb 20, 2024
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Astronomy 1402 - Online
The Sun
The purpose of this laboratory activity is to learn about the sun including its apparent motion, sunspots
and layers.
p. 2
Part 1: Background
Galileo was the first person to record the sunspots
and their motion and realize that this meant that the sun
was rotating on its own axis. This was a surprising and
exciting idea in the 1600s because it meant that the
Earth was not the center of all motions. When Galileo
made his first discoveries there were no cameras, and
all images had to be drawn. Each sunspot has a position
on the sun’s surface, which can be specified by latitude
and a longitude, just as places on the Earth. Because the
sun spins on its own axis, it has an equator as well as a
north pole and south pole. Since the plane of the Earth’s
orbit around the sun is almost in the same plane as the
sun’s equator, we see the sun’s equator almost in the
middle of the sun’s face.
As the sun appears to move in the daytime
sky, its height or altitude increases from sunrise
until local noon, then decreases until sunset. As
the altitude changes, so does the length of a
shadow. When the sun is low on the horizon, a
shadow can be very long (in fact, it may not even
be measured). When the sun reaches its zenith or
high point at noon, a shadow is very small. Some
people would say that there is no shadow. By
measuring the length of a shadow, the altitude of
the sun can be determined. Altitudes on the
celestial sphere are measured by angles because earthbound observers have no concept of depth beyond a
few hundred meters.
During
the
day,
the
sun’s
direction
from
North or azimuth or bearing also changes. In the
northern hemisphere above the tropics, the sun is
always in the southern sky, but travels across it
form east to west. Refraction of light by the
atmosphere causes the sun to appear to be in the
northern half of the sky at times especially close to
sunrise and sunset. By holding a compass in a
shadow, the sun’s azimuth or direction can be
measured.
The sun contains different layers that can
be divided into two categories. The inner layers
include the Inner Core, the Radiative Zone and
p. 3
Convection Zone. Photosphere, Chromosphere, and the Corona comprised the outer layers of the sun. In
the Core, the temperature is at its highest temperature, and it begins to decrease from the core to the
convection zone. Then, in the outer layers, the temperature increases from the photosphere to the corona.
Below is a diagram that illustrates the layers of the sun.
Solar Vocabulary:
Aurora
- Faint lights in the night sky caused by the sun’s emissions.
Corona
- The part of the solar atmosphere only visible to the naked eye during a solar eclipse.
Differential
Rotation
- The different speeds of rotation of the Sun’s surface. Disk
- The round appearance of the surface to the sun against the sky Penumbra
- The outside area of a sunspot made up of dark and bright features.
Photosphere
- The surface of the sun that is visible to us, where sunspots can be seen.
Plage
- A faint, large, bright area around most sunspots.
Prominence
- Dark filaments seen on the sun’s surface which stand off from the limb when viewed on edge.
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p. 4
Solar
Cycle
- The 11-year cycle in the number of sunspots and other activities of the sun.
Solar
Flare
- A release of energy and mass from the sun in a specific region.
Solar
Eclipse
- When the moon is directly between the earth and the sun, blocking he solar disk and revealing the corona.
Sunspot
- Areas on the sun, which appear darker because they are relatively cooler than the area around them.
Umbra
- The darker inner region of a sunspot with a temperature of 4,200K.
p. 5
The Best Websites about the Sun
The Sun Has Spots
Background information for middle school and high school teachers
http://magaxp1.msfc.nasa.gov/outreach/education/index.html
SpaceWeather
Up to date information about the sun and its effects on Earth including the latest 10-day movie of sun
observations
http://www.spaceweather.com/
Sunspotters Club
The Astronomical League’s program to encourage observation and drawing of the sun’s disk
http://www.astroleague.org/al/obsclubs/sunspot/sunsptcl.html
Ask the Space Scientist (about the sun)
Great answers to questions
http://image.gsfc.nasa.gov/poetry/ask/asun.html
Stanford Solar Center
Providing solar on-line activity resources for the joy of solar science exploration
http://solar-center.stanford.edu/
The Sun Today
Pictures taken from the SOHO telescope outside the Earth’s atmosphere
http://sohowww.nascom.nasa.gov/data/realtime-update.html
Galileo’s Data
See Galileo’s 35 sunspot drawings from 1613
http://galileo.rice.edu/sci/observations/sunspot_drawings.html
The Sun from Space
The detailed sun imaged in x-rays, ultraviolet, white light, and magnetic field
http://www.lmsal.com/YPOP/ProjectionRoom/latest.html
p. 6
Part 2: Activity
2.1 Textbook Review
1. Use the knowledge provided in your textbook to answer the questions.
2.2 Identification of the Layers of the Sun
1. Use the diagram and solar vocabulary provided in the background to help you label the layers of the sun.
2.3 Finding the Altitude and Shadow Length
1. Use the following formula, tan θ = (length of wedge) / (shadow length) where θ is altitude to complete the table found in section 3.4.
Length of wedge: 76mm
Record your results in the Lab Report section.
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p. 7
Name Class Part 3: Lab Report – The Sun
3.1 Textbook Review
a. What is the spectral type classification of the Sun? b. The_____ ___
is the coolest part of the Sun.
c. What helps protect us from bad rays from harming us? ________ d. When are there many sunspots on the sun? _______ e. What causes sunspots? _______ _
f. What are some of the damages that can occur with Solar Flares?
3.2 Identification of the Layers of the Sun
Using the following terms to label the layers of the sun: Corona, Inner Core, Photosphere, Convection Zone, Radiative Zone, Chromosphere , Subsurface flows
1._______ 2._______ 3._______ 4. _______ _________________
5. _______ 6. _______ 7. _______ Image Credit: NASA
p. 8
3.3 Finding the Altitude and Shadow Length
Data Taken on: August 3, 1997 Length of Wedge: 76 mm
Time
Azimuth (º from N)
Shadow length (mm)
Altitude (º)
7:30 a.m.
85
225
8:40 a.m.
90
140
9:35 a.m.
100
40.2
10:45 am
107.5
51.7
12:00 noon
120
37
13:00 p.m.
135
28
13:45 p.m.
150
29
14:30 p.m.
165
65.3
15:45 p.m.
192
53.1
17:30 p.m.
215
109
18:00 p.m.
225
143
18:45 p.m.
240
215