Astronomy Lab 2
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School
University of Nebraska, Omaha *
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Course
1354
Subject
Astronomy
Date
Feb 20, 2024
Type
docx
Pages
5
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Name: NAME_Paige Luft_____
CLASS_Astronomy Lab__
Instructions:
Go to web site http://astro.unl.edu
. Click on the Nebraska astronomy applet project and then go to NAAP Modules(at top of screen) and pick Basic Coordinates and Seasons. Read the materials and complete the guide below and complete the exercises and complete the document below—the background materials will help you answer the questions—the flash demonstration will help you complete the rest.
NOTE: You are only doing the season’s part of this exercise.
ON LINE LAB 02
Nebraska Astronomy Applet Project
Student Guide to the
Seasons – Student Guide
Seasons and the Ecliptic
Work through the introductory material on the page entitled Orbits and Light
.
Open the
Seasons and Ecliptic Simulator
.
Note that there are three main panels (left, upper right, and lower right) each of
which have two different views. Controls run along the bottom of the simulation
that affect more than one panel. Click animate and then move through the six
views to get an overview this simulator’s capabilities. We will address each of
these six views separately.
Experiment with the various methods to advance time in the simulator. You may
click the start animate/stop animation button, drag the yearly time slider, or drag
either the sun or the earth in the left panel to advance time.
Note that this animation does not illustrate the rotation of the earth. Because the
timescales of rotation and revolution are so different, it isn’t possible to
effectively show both simultaneously. NAAP – Basic Coordinates & Motions 1/5
Tip:
Once the stick figure
is selected you can gain
greater precision over its
motion by
moving the
mouse a distance away
from the figure.
Left Panel – Orbit View
Practice clicking and dragging in this panel to change the
perspective. Change the perspective so that you are
looking directly down onto the plane of the Earth’s orbit
Click labels. Note that you can see how the direct rays of
the sun hit at different latitudes throughout the year.
Experiment with this view until you can quickly create the two views shown
below. Note that these images explain the shape of the elliptic on the celestial
sphere. In the image on the left (summer solstice) an observer on the Earth sees
the sun above the celestial equator. In the image on the right (winter solstice) an
observer on the Earth sees the sun below the celestial equator. Left Panel – Celestial Sphere
This view shows the earth at the center of the celestial sphere.
The celestial equator and the ecliptic with the sun’s location
are shown. Note that you may click on the sun and drag it and
read out its coordinates.
Experiment with this view until you can quickly create the
image to the right – the direct rays of the sun hitting the earth
on the summer solstice. Upper Right Panel – View from Sun
This view shows the earth as seen from the sun. It gives the
best view of the subsolar point – the location on the earth
where the direct rays of the sun are hitting. The noon
observer’s location on the Earth is indicated by a red parallel
of latitude which can be dragged to new latitudes (this affects
the appearance of the lower right panel). It is possible for the
red parallel to be at an inaccessible location in this view.
Create the image shown to the right – an observer at latitude
80°N on the summer solstice.
Upper Right Panel – View from Side
NAAP – Basic Coordinates & Motions 2/5
Tip:
Note that if you
click and drag the
Earth,
you
will
change the date and
location rather than
the perspective.
This view shows the earth as seen from a location in the plane of the ecliptic
along a line tangent to the Earth’s orbit. It allows one to easily see the regions of
the Earth that are in daylight and those that are in shadow.
Dragging the stick figure allows one to very conveniently change latitude.
Dragging the stick figure on top of the subsolar point
effectively puts the observer at the latitude where the
direct rays of the sun are hitting.
Although rotation is suppressed in this simulation,
keep in mind that the stick figure is on a planet that is
rotating with a period of 24 hours about an axis
connecting the north and south poles. Thus, 12 hours
later it will be on the other side of the earth.
Set up the simulator for the image at right – the winter solstice for an observer at
80
N. Since this observer’s parallel of latitude is located entirely in the shaded
region, this observer will not see the sun on this day. Lower Right Panel – Sunbeam Spread
This view shows a “cylinder” of light coming from the sun. It is projected on a
grid to convey the area over which the light is spread. As this light is spread over
a larger area, its intensity decreases. Lower Right Panel – Sunlight
Angle
This view shows the angle
with which rays of sunlight
are striking the Earth. It lists
the noon sun’s angle with
respect to the horizon (its
altitude).
Verify that when the noon
observer is at the latitude
where the most direct rays of
the sun are hitting, the sun is
directly overhead making an
angle of 90
with the ground.
Verify that when the noon
observer is at the latitude where the least direct rays of the sun are hitting, the sun
is on the horizon.
Question 1: The table below contains entries for the coordinates for the sun on the ecliptic as well as the latitude at which the most direct and least direct rays of the sun are hitting. Use the simulation to complete the table. NAAP – Basic Coordinates & Motions 3/5
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Date
RA
DEC
Latitude of
Most Direct Latitude of Least
Direct Ray
February 5
21.3h
-15.8°
15.8°
74.1° N
March 21
23.9h
0.0°
0.0°
90° N
May 5
2.9 h
+16.5°
16.5° N
73.5° S
June 21
6.1h
23.4°
23.2° N
66.5° S
August 5
9.2h
16.3°
16.2° N
73.9° S
September 21
12.1h
-0.6°
0°
90° N
November 5
14.9h
-16.6°
16.6° S
73.6° N
December 21
18.1h
-23.4°
23.5° S
66.4° N
Question 2: Using the data in the table above, formulate general rules relating the
declination of the sun to the latitude where the most direct and least direct rays of the sun
are hitting. The most direct rays are during the summer, which is about May to
August. The least direct rays of the sun are during the wintertime, which is September to
March.
Question 3: The region between the Tropic of Cancer and the Tropic of Capricorn is
commonly known as the tropics. Using the sunlight data table from question 1, define the
significance of this region. The significance of this region is that it has the most direct
rays of sun through the entire year and it stays warm in those specific areas.
Question 4: Using the sunlight data table from question 1, define the significance of the
region north of the Arctic Circle commonly referred to simply as the Arctic. The
Arctic is colder because it has the least direct rays of sun throughout the year.
NAAP – Basic Coordinates & Motions 4/5
Question 5: Use the simulator to complete the table below. For each latitude write a short
paragraph which describes the variations in sunlight (seasons) that are experienced at this
latitude throughout the year. Latitude
Description of Yearly Pattern of Sunlight
0°
The noon sun’s angular height above the horizon ranges from 90° on the
vernal equinox, to 66.5° on the summer solstice, to 90° on the autumnal
equinox, and back to 66.5° on the winter solstice. Thus, the equator always
receives very direct intense sunlight throughout the year which accounts for
the very high temperatures. 23.5° N
The noon sun's angular height above the horizon rages from 66.5° on the
vernal equinox, to 90° on the summer solstice, to 66.5° on the autumnal
equinox, and back to 43° on the winter solstice. Therefore, it never goes
below 43° creating the topical weather.
41° N
The noon sun's angular height above the horizon goes from 48° on the
vernal equinox, to 72° on the summer solstice, to 48° on the autumnal and
back to 25° on the winter solstice. Therefore, the temperatures do get hot
but on the moderate side.
66.5° N
The noon sun's angular height above the horizon ranges from 23.5° on the
vernal equinox, to 0° on the summer solstice to 23.5° on the autumnal
equinox, and back to 0° on the winter solstice therefore it is very cold
climate due to the low angles.
90° N
The noon sun's angular height above the horizon ranges from 0° on the
vernal equinox, to 23.4° on the summer solstice to 23.5° on the autumnal
equinox and back to -23.4° on the winter solstice. Therefore, at times there
is no sunlight for days and causes extremely cold temperatures.
NAAP – Basic Coordinates & Motions 5/5