ASTR 170B2- Midterm Exam Guide - Comprehensive Notes for the exam ( 28 pages long!)
6 Oct 2017
School
Department
Course
Professor
U of A
ASTR 170B2
MIDTERM EXAM
STUDY GUIDE
Intro: PTYS 170B 8/28/17
Age of the universe- 14 billion years
Lifetimes of stars (millions to many billions of years)
Age of the Earth 4.5 billion years
How is earth moving through space?
What if earth suddenly stopped spinning?
Earth Orbits the sun every year
"the right handed" sense of rotation and orbit
Earth rotates around its axis every day
The sun is orbiting the center of the milky way every 230 million years
Expansion of the universe:
More distant the galaxy the faster the velocity
Galaxies outside the local group are moving away from us
"Local group" galactic motion is determined by mutual gravitational pull
Speed = distance traveled in a given amount of time
!
Night Sky
Patterns
-Apparent motion across the sky:
-East to west circles
-Lunar phases (month)
-Seasonal changes (year)
-Earth Precession
!
88 official constellations
Patterns have no physical meaning simply projections onto the
"celestial sphere"
Today they are used as convenient "landmarks" for observing! and
cataloging
!
When we look along the ecliptic we are looking through the plane of the
solar system
Ecliptic is the apparent path of the sun over a year (moving through
certain constellations)
!
find more resources at oneclass.com
find more resources at oneclass.com
The bright stars in a constellation
Can be quite far from each other
!If Earths
Angles, not distances, are used to measure the separation and
positions of objects on the sky
!
Circumference of a circle = 2 pi x radius
Angular size= fraction of the circumference occupied by the object
Angular size= 360 degrees x 9physical size) / (2 pi x distance)
An object's angular size (or separation of two objects) is smaller when
the object is farther away
!
Angular size of textbook at arms length
. 2 degrees
find more resources at oneclass.com
find more resources at oneclass.com
