Transcript Intro Astro PP

Chapter 1
Charting the Heavens: The Foundations of Astronomy
Size of Our Universe
Sun, Earth, and Moon
Figure 1-3
Galaxy
Figure 1-4
Galaxy Cluster
This photograph shows a
typical cluster of
galaxies, roughly a
million light-years from
Earth. Each galaxy
contains hundreds of
billions of stars, probably
planets, and, possibly,
living creatures.
Figure 1-9
Orion in 3-D
Two groups of circumpolar constellations…
one we never see.
South circumpolar constellations lie
between 41ºS and 90ºS
one we always see.
North circumpolar constellations lie
between 49º N and 90ºN
Figure 1-11
Celestial Sphere
Vocab:
Celestial Equator (CE):
Projection of Earth’s equator
onto the celestial sphere
Celestial Meridian (CM):
A circle running through the
celestial poles.
Right Ascension (RA):
Measures longitude on the
celestial sphere
Declination (DEC):
Measures latitude on the
celestial sphere.
Figure 1-15
The Zodiac
Zodiacal constellations lie along the ecliptic. The ecliptic is a region of space
that the sun appears to move over one year when viewed from Earth. The stars
we can’t see when the sun is up are “eclipsed” by the sun.
Constellations Near Orion
The 88 constellations span the entire sky. A star is “in” a constellation the same
way a city or town is in a state.
Figure 1-8
Constellation Orion
The stars are connected to show the pattern visualized by the Greeks: the
outline of a hunter. You can easily find this constellation in the winter sky by
identifying the line of three bright stars in the hunter’s “belt”.
The motion of the earth in its orbit causes our view
of the nighttime background stars to be
constantly changing. We associate different
constellations with the seasons:
•
•
•
•
Gemini and Leo with spring
Scorpio and Hercules with summer
Cygnus and Lyra with fall
Orion and Taurus with winter
Star Naming
Johann Bayer designated the brighter stars in each
constellation by a Greek letter.
• Stars lettered in order of brightness
• α usually being the brightest and Ω usually the faintest
John Flamsteed numbered the stars visible to the naked
eye from west to east across the constellation.
• His systematic method was to name a star by using a
letter or number followed by the Latin name of the
constellation.
When using star charts east and west directions are opposite in the sky.
•To the right is west of the sun
•To the left is east of the sun
Star Charts
• Find the meridian in the sky using the date
and time. Draw a verticle line.
• Find the field of view. Draw a two lines for
your field of view. These are the stars that
you can see on this date.
• Note: Along the CE you will be able to see
exactly 12 h of RA from horizon to horizon.
6h to the east of your meridian and 6h to
the west.
Figure 1-18
Precession
Figure 1-19
Variations in the Solar Day
Figure 1-29
Triangulation
Figure 1-30
Geometric Scaling
Figure 1-31
Parallax
Figure 1-32
Parallax Geometry
Figure 1-33
Measuring Earth’s Radius
More Precisely 1-1
Angular Measure
More Precisely 1-2
Celestial Coordinates
More Precisely 1-3a
Measuring Distances with Geometry
More Precisely 1-3b
Measuring Distances with Geometry