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Study Guide

# [ASTR 3] - Final Exam Guide - Everything you need to know! (35 pages long)

Department
Astronomy
Course Code
ASTR 3
Professor
Sakai S
Study Guide
Final

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UCLA
ASTR 3
FINAL EXAM
STUDY GUIDE

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Lecture 1: Intro
- Homework: All homework assignments done on
www.masteringastronomy.com, make sure to register. Class ID for
Lecture 1 is MASAKAIW17. Homework is due every Monday at 8am.
- To do well: Do readings in advance of lecture, use own notes plus
slides posted on course webpage when you review lecture.
- Lecture will cover important things, textbook covers everything in
detail.
- The “How” and “Why” are more important than rote memorization.
- Weekly online assignments are excellent source of questions for the
two midterms and final.
- If it can’t be quantified, it probably isn’t science.
- Numbers in astronomy and physic are very large or very small. Use
scientific notation for if number of digits before or after the decimal
point becomes large.
- 5100 = 5.1 x 103
- Speed of light = 300000000 meters/second or 300000
kilometers/second.
- Light year = about 6 trillion miles, is a unit of distance, not time.
- When we are looking at something 3 light years away, we are seeing
that thing as it was 3 years ago!
- The Universe is 13.7 billion years old, so we cannot see a galaxy that
is 15 billion light years away because the light there has not reached
us yet.
- There are 100 billion stars in the Milky Way.
- There are 100 billion galaxies in the observable Universe.
- Origins of science goes back to 2000 years.
- Astronomy known to ancient Greeks: Earth is Round because of
horizon effects on ship sails, curved lunar eclipse shadows,
- Eratosthenes measures Earth’s diameter: He heard sun shadows at
Noon were no the same length in the southern town of Syene. Syene
could have NO SHADOWS at same time Sun was casting 7 degree
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shadows in Alexandria. So, distance from Alexandria to Syene
corresponds to 7 of the 360 degrees of earth.
- Moon goes around earth in 29.5 days, while sun’s apparent position
changes a little.
- Phases of the Moon: Half the moon is illuminated by the Sun, we see
a combination of the light and dark faces.
- Full Moon: Rises at 6PM when sun sets, sets at 6AM when sun rises.
- New Moon: Rises at 6AM when the sun rises, sets at 6PM when the
sun sets.
- First Quarter: Rises at noon, sets at midnight.
- Solar eclipse: When our view of the Sun is blocked by the moon. THe
moon is just barely big enough to cover Sun.
- Lunar Eclipse: The moon moves into and throught the shadow cast
by the Earth. Since Earth is so much larger than the moon, the Full
moon will appear dark for about an hour.
- Eclipses don’t happen every new and full moon because moon’s
orbital plan is tilted 5 degrees out of the Sun’s ecliptic plane (defined
as Sun’s apparent path across fixed stars).
- Classical astronomy discovered that earth is spherical, moon orbits
monthly, circumference about 25000 miles, reason for rarity of
eclipse.
- Stars seemed to move on fixed paths.
- Daily rising and setting of objects: Sun time vs star time. Solar clock
set to 24 hours, but stars are a bit faster, rising every 23 hours 56
minutes.
- This is because Sun’s path is unlike fixed stars. It moves on circular
path called the Ecliptic, tilted 23 degrees out of Celestial Equator.
- Winter solsice: SHortest daylight of year in Northern Hemisphere.
Summer Solstice: Longest daylight of year in Northern Hemisphere.
- Equinox: When each hemisphere has 12 hours of sunlight and 12
hours of night.
- It is NOT hotter in sumver bcause we’re closer to sun than in winter.
The distance that our hemisphere is tilted to the sun as opposed to
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find more resources at oneclass.com