Key Concepts:

1. Course Introduction
2. Math tools: power of 10 and scientific notation
3. Scales of the Universe and Units
4. Pale Blue Dot

Introduction: astronomy is "science of the heavenly bodies"

• Course Information
• Syllabus
• Student Contract
• Grading: Your final grade will be computed for a 100 total point system
• 70 points from 3 midterms + final exam
• 10 points from pre-lecture reading quizes (using OWL)
• 10 points from HWs (using OWL)
• 10 points from in-class activities
• Extra-credit opportunities exist.
• OWL

Quiz 1

Power of Ten and Scientific Notation

Scales of the Universe and Units

• Distance
• meter: unit of length equal to 1,650,763.73 wavelengths in vacuum of the radiation corresponding to the transition between the levels 2p(10) and 5d(5) of the krypton-86 atom


• km: 1000 meters (10³ m)


• AU: astronomical unit (150 million km or 1.5 x 10⁸ km)


• Lyr: light year (distance traveled by light in 1 year)


• c = 300,000 km per second (3 x 10⁵ km/s)
• 1 yr = 32 million seconds (3.2 x 10⁷ s)
• 1 Lyr = (3 x 10⁵ km/s) x (3.2 x 10⁷ s) = 10 x 10¹² km
• Size
• Earth radius: 6,378 km (or 6.4 x 10³ km)


• Sun's radius: 700,000 km (or 7 x 10⁵ km)


• Solar system: about 100 AU or about 10 light hour


• nearest star: about 1 light year


• Milky Way Galaxy: 50,000 lyr


• Local Group: 1.5 million lyr


• Visible Universe: 15 billion lyr




• Mass
• Earth mass: mass of Earth = 6 x 10²⁷ gram


• Solar mass: mass of Sun = 2 x 10³³ gram




• Luminosity = energy output per second
• Solar luminosity: 4 x 10²⁶ watts

A Pale Blue Dot

NEXT READING ASSIGNMENT: Units 5 & 13 (Schneider & Arny)