Transcript dtu7ech01 - Fort Thomas Independent Schools

CHAPTER 1:
Discovering
the Night
Sky—
Constellations,
Asterisms and
the Celestial
Sphere
WHAT DO YOU THINK?
Is the North Star—Polaris—the brightest
star in the night sky?
 Do astronomers regard constellations as
the familiar patterns of stars in the sky?
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Describe the Nature and Use of
Constellations
Constellations make star locating easy.
 Constellation : a region and a group of
stars
 Night sky is divided into 88 regions
(constellations)
 Astronomers, requiring more accuracy,
now use a coordinate system as well (right
ascension and declination: see the
celestial sphere)
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In order to more easily locate objects in the sky, we
divide the sky into regions named after familiar
patterns of stars called constellations.
Ancient constellations were
imaginary pictures outlined
by familiar patterns of stars.
Modern astronomers divide the sky into
88 official constellations or regions of
space, many of which contain the
ancient star patterns.
Some Common Guides to Finding Constellations
Using the “Big Dipper” as a guide
The “Summer Triangle”
The “Winter Triangle”
Starry Night Exercise
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Chapter 1
Stars and Constellations
Locating your position on Earth
Earth’s coordinate system uses a series of
grid lines that circle the globe N-S and
E-W and that intersect at right
angles…These grid lines are called
 longitude (north-south)
 latitude (east-west)
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Labeling one hemisphere
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Latitude
Longitude
Zenith
Horizon
Meridians and parallels
Prime meridian
Equator
Label your plastic hemisphere
Latitude vs. Longitude
http://www.hammondmap.com/sites/hammond/geography/latlong1.html
http://www.nasa.gov/
What is the approximate latitude
and longitude for Fort Thomas, KY?
The latitude of Fort Thomas is 39.075N. The
longitude is 84.447W.
Locating your position in the sky
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Rise and run above the Earth’s surface
are called…
– Altitude (0-90o) starts at the horizon, ends at
zenith
– Azimuth (0-360o) starts at due north
http://meteorites.pdx.ed
u/measurements.htm
http://geology.isu.edu/geostac/Field_E
xercise/topomaps/bearing.htm
Starry Night Exercise
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Chapter 2
Changing Latitude
…to envision the
night sky rotating
eastward like the
outer shell of a
hollow sphere...
Celestial Sphere
The celestial sphere aids in navigating the
sky
 Earth-based view
 A coordinate system (it works on the
principle of latitude-longitude and altitudeazimuth)
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– Declination
– Right ascension
Relationships between the three
coordinate systems
Declination is related to altitude and
latitude
 Right ascension is related to longitude and
azimuth
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Astronomers describe the universe as an imaginary
sphere surrounding the earth on which all objects in the
sky can be located, called the CELESTIAL SPHERE.
 As viewed from Earth, the
celestial sphere appears to rotate
around two axis points, the north
and south celestial poles, which
are located directly above the
Earth’s poles.
Between these is the celestial
equator, which divides the
celestial sphere into northern and
southern hemispheres.
We define the position of an
object on the celestial sphere
using two coordinates, right
ascension and declination.
See animation 1.1 and
interactive exercise 1.1
Starry Night Demo
Turn on celestial grid, turn off horizon
 Note the coordinates listed for each grid
line
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Angular Diameter and Distance
Used to describe the apparent size of or
distance between astronomical objects.
 Uses degrees, arcminutes and arcseconds.
 Example of a measurement : 60o 30’ 3’’
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Usage of Angular Diameter
Size of an object (Sun and Moon have
very similar angular diameters—0.5o
degrees or 30’ arcminutes)
 Distance between objects
 Distance object traveles
 True diameter (calculated)
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Ecliptic Plane on the Celestial
Sphere
The annual path of the Sun as it appears
on the celestial sphere.
 The ecliptic and the celestial equator are
tilted at a 23 ½-degree angle
 Earth orbits the Sun while tilted at a 23
½- degree angle.
 Starry Night Demo: the celestial sphere
and the ecliptic plane
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Starry Night Celestial Sphere
Open Starry Night program
 Go to Options/Guides/celestial grid, pole,
meridian, zenith
 Go to observing/diurnal/diurnal a
 Go to earth’s orbit/orbit a
 Go to seasons/view over south pole
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One effect of this motion is to change the location in the Earth’s orbit
at which summer and winter occur, and thus change the time of year
when the Sun appears in certain constellations.
Astrology Table
Pisces - February 20- March 20
Aries - March 21 - April 20
 Taurus - April 21 - May 21
 Gemini - May 22 - June 21
 Cancer - June 22 - July 22
 Leo - July 23 -August 21
 Virgo - August 22 - September 23
 Libra - September 24 - October 23
 Scorpio - October 24 - November 22
 Sagittarius - November 23 - December 22
 Capricorn - December 23 - January 20
 Aquarius - January 21 - February 19
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We can see how different stars appear at different times of day by looking at
the position of the Sun against the backdrop of stars. The side of the Earth
facing the Sun is experiencing “day,” while the side of the Earth turned away
from the Sun is experiencing “night.”
SEPTEMBER
(The Sun is in Virgo)
MARCH
(The Sun is in Pisces)
Zodiac Activity
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Select one of 13 zodiac constellations.
Use the Starry Night Program to find your zodiac
constellation
Draw your zodiac constellation to scale.
Label the stars in your constellation.
Classroom demonstration using lamp as the Sun
Questions
– Explain what it means for the Sun to be in your
zodiac constellation.
– When is your zodiac constellation visible?
Stars in 3-D
Activity F-8 Three-Dimensional
Constellations
 How far away from the Earth are these
stars?
 Is the brightness of stars an indicator of
distance? Explain.
 How would these constellations appear in
different places in space?
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Student Activities
Chapter 1
Stars and Constellations
 Chapter 2
Changing Latitude
 Starry Night Demos
 Zodiac activity
 3-d stars
 Observing project
 Questions
 Research option
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http://www.whfreeman.com/dtu7e