Astro 150 Fall 2004: Lecture 1 page 1
Welcome to Astro 150:
Stars, Galaxies and Cosmology
Prof. Steve Kawaler
TAs: Mr. Kim Arvidsson
Mr. Asif Imran
Mr. Qian Wang
Recitations begin this Wednesday
Please take a syllabus from the front table
also available at: http://www.public.iastate.edu/~f2004.astro.150
Textbook
(required)
Bennett et al: Stars, Galaxies, & Cosmology
(Part 2 of The Cosmic Perspective)
Bennett et al: The Cosmic Perspective
(for those in Astro 120 also)
2
Astro 150 Fall 2004: Lecture 1 page
•Astronomy concerns things that are
•too large to imagine
•too far to fathom
•too old to comprehend, and
•too small to see
“There are only two worthwhile professions: medicine
and astronomy. Medicine, because you are sure to help
someone, and astronomy, because you are sure you
won’t hurt anyone.”
-Aldous Huxley
Astro 150 Fall 2004: Lecture 1 page 3
Astronomical Distance Units:
• an “a.u.” = mean distance between Earth and Sun
• a light-year = distance light travels in 1 year (=67,000 a.u.)
1 l.y. = 10,000,000,000,000 km = 1013 km = 10 trillion km
The Universe is a BIG Place
Nearest
star to the
Sun
One Way Travel Time
Object
Distance
[km]
55 mph
100,000
mph
LIGHT*
Moon
384,000
174 d
2.4 hr
1.25 s
Venus
42,000,000
54.5 yr
11 d
2.33 min
Sun
150,000,000
193 yr
2 months
8.33 min
Pluto
6,000,000,000
7,800 yr
4.25 yr
5.25 hr
! Centauri
40,000,000,000,000
30,000 yr
4.25 yr
*speed of light = 300,000 km/s
677,000,000 mph
6.77 x 108 mph
One Way Travel Time
Object
Distance
[km]
55 mph
100,000
mph
LIGHT*
Astro 150 Fall 2004: Lecture 1 page 4
A Scale Model: Solar System Distances
1 a.u. = 10 meters
the Sun = a softball
Jupiter = a grape
Earth = a poppyseed
each step you take - 10 million miles!
