SCI-103 Introductory Astronomy
Day 01: Introduction and Unit 1: Our Planetary Neighborhood
1. Introduction
a. Personal Introduction
b. Course Description
i. Run through the course description
ii. Text
iii. Calculators
c. Daily Schedule
i. Distribute and point to on the course web page
d. Course Web Page
i. Review contents
ii. Hot Tips
e. Attendance
f. Questions
2. Unit 1: Our Planetary Neighborhood
a. Earth
i. Characteristics
ii. Radius
iii. Mass
b. Moon
i. Characteristics
ii. Radius
iii. Distance from Earth: Proportion Problem “If the Earth were 1 foot in
diameter, how far away would the Moon be at this scale?”
Model Distance to Moon Actual Distance to Moon

Model Diameter of Earth Actual Diameter of Earth
Actual Distance to Moon
Model Distance to Moon  Model Diameter of Earth 
Actual Diameter of Earth
384,400 km
Model Distance to Moon  1 ft  
2  6,378 km 
 30.1 ft
iv. Mass
Announcement: Seating is for registered students. Want-to-be’s must wait for a free seat.
c. The Planets
i. Planets
ii. Dwarf Planets
iii. Meteoroids, Asteroids, Comets, Dust
iv. Total Mass:
v. NSSDC Planetary Fact Sheet
d. The Sun
i. SOHO web page
ii. Radius
iii. Volume: Ratio Problem “How much larger in volume is the Sun compared
to the Earth?”
4 3
RSun
Volume of Sun
 3
Volume of Earth 4 R 3
Earth
3
 R 
R3
 3Sun   Sun 
REarth  REarth 
3
 6.96  108 m 

 
6
 6.378  10 m 
3
 109 
3
 1.3  106
 1.3 Million
iv. Mass: Mass Distribution in the Solar System
e. The Astronomical Unit
i. Definition: See Wikipedia
ii. Velocity, distance time problems: “How long would light take to travel
from the Earth to the Moon?”
1. v=d/t problems: light travel time from Earth to Moon,
d
v
t
d 384,400 km 3.84  105 km 3.84  108 m
t 


 1.28 s
v
8 m
8 m
8 m
3  10
3  10
3  10
s
s
s
2. v=d/t problems: Earth to Sun
d
t
d
1 AU
1.5  1011 m
t 

 500 s  8.33 minutes
v 3  108 m
8 m
3  10
s
s
3. v=d/t problems: Sun to Pluto
v
d
t
d
t
v
39.48 AU

m
3  108
s
39.48  1.5  1011 m

m
3  108
s


 1.5  1011 m 

 39.48  
 3  108 m 


s 

 39.48  500 s 
v


 39.48  8.33 minutes

 5.48 hours
3. Summary
a. Hierarchy of structures
i. http://www.youtube.com/watch?v=HEheh1BH34Q
b. Special Units: The AU
c. Types of Mathematical Problems
i. Ratio
ii. Proportion
iii. V=d/t
d. Distribute HW #1
Unit 02: Beyond the Solar System
1) Stellar Evolution
A) http://antwrp.gsfc.nasa.gov/apod/image/0808/ngc290_hst_big.jpg
B) By the naked eye, almost all stars appear to be white – physiological issue
C) Stars will change their properties in a complex way over time. See Fig 59.1 & 2
D) Timescale of change is far longer than a human lifetime, leading to the belief that stars
are “eternally unchanging”.
E) How do we know stars change if we have never see one change because they change so
slowly? (Note exception in Supernova)
2) The Milky Way Galaxy
A) Define the Milky Way
i) http://antwrp.gsfc.nasa.gov/apod/image/0705/deathvalleysky_nps_big.jpg
ii) http://antwrp.gsfc.nasa.gov/apod/image/0905/m51deep_christensen_big.jpg
iii) http://antwrp.gsfc.nasa.gov/apod/image/1003/NGC4565_hager.jpg
iv) http://antwrp.gsfc.nasa.gov/apod/image/0807/MWspitzer_lab_2048.jpg
(1) Dimensions
(a) Diameter about 100,000 ly
(b) Thickness about 3,000 ly
(c) Aspect Ratio = .03
(d) Standard compact disk is 12 cm in diameter and 0.14 cm thick, aspect ratio
.01
(e) If the Earth were 1 foot in diameter the Moon would be 30 feet away, the solar
system would be 89 miles in diameter (?), and the nearest star beyond the Sun
would be 600,000 miles away (slightly longer than a round trip journey to the
Moon!
(f) If the Sun were 1 foot in diameter, the Milky Way would be 129 million miles
in diameter, (more than the distance to the Sun 93 million miles)
(2) Content
(a) Stars, star clusters, stellar remnants
(b) Loose gas and “dust” (raw material for making new stars), (GMC’s)
(c) Super massive (3 million MSun) black hole at the galactic center
3) The Light Year
A) Define it.
B) How fast is light? 0.133 sec to circle the Earth.
C) Write it. 9.46 x 1015 m, 9.46 x 1012 km, 63.240 AU
4) Galaxy Clusters and Beyond
A) The Local Group
i) M31, Andromeda galaxy is approaching the Milky Way at 59 km/s. How long until
the collision occurs?
d
v
t
d 2.54  106 ly 2.54  106  9.46  1012 km
t 

 7.98  1016 s  2.53  109 yr
km
km
v
301
301
s
s
B) Poor Galaxy Clusters
C) Rich Galaxy Clusters
5) The Still Unknown Universe
Unit 03: Astronomical Numbers
1) The Metric System
A) You must be competent with using the metric system. It’s the first obstacle in this course
for the non-science major.
B) See course web page for a pretty good tutorial
C) See me for further assistance
D) Content Tutoring Center
E)
2) Scientific Notation
A) You must be competent with using scientific notation. It’s the second obstacle in this
course for the non-science major.
B) See course web page for a pretty good tutorial
C) See me for further assistance
D) Content Tutoring Center
3) Special Units
A) Examine Table 3.3
4) Approximation
A) The numbers we deal with are not the precise abstract conceptual numbers of a math
course (e.g. 2 = 2.0000…), but are estimates of measured properties that have some
limited accuracy.
B) Examine the distances to the twenty Brightest stars (Appendix Table 9)
i) Which stars in this list have distances that are most precisely known?
ii) What can be said of the distances to the most distant stars in this list?
iii) What is the true distance to Deneb?
C) For our purposes, three significant figures are sufficient.
i) e.g.
5) Summary
1.50 108 m
 500 s  8.33 min
8 m
3.00 10
s