a1 f2015 review copy - los angeles mission college f2015 review copy.pdfkepler’s 3 laws of...

Astronomy 1 — Elementary Astronomy LA Mission College

Spring F2015

Review

Astronomy 1 - Elementary Astronomy LA Mission College Levine F2015

Quotes & Cartoon of the Day“One may wonder, What came before? If space-time did not exist then, how could everything appear from nothing? . . . Explaining this initial singularity—where and when it all began—still remains the most intractable problem of modern cosmology.

— Andrei Linde

“But who shall dwell in these worlds if they be inhabited? ... Are we or they Lords of the World? ... And how are all things made for man?”

— Johannes Kepler

“Our sun is one of 100 billion stars in our galaxy. Our galaxy is one of billions of galaxies populating the universe. It would be the height of presumption to think that we are the only living things in that enormous immensity.”

— Wernher von Braun


Announcements

• Observing Project & Extra Credit Due

• Midterm graded & gradebook updated to drop lowest

• remainder of grading (hopefully) updated this weekend

• Final 12/15 at 10-12 AM!


Last Class

• Debrief Midterm

• Debrief LT

• Cosmology & Fate of the Universe

• Exoplanets (time permitting)


This Class

• Review/Debrief Midterm

• Exoplanets (time permitting)


Spring F2015

About the Final


About the Final

• Similar format to Midterms

• Similar length

• a little longer, some choice of questions

• Little new material, mostly cumulative

• Study the stuff on the midterms!

• But don’t memorize the questions themselves, you probably won’t see many that are identical

• You may bring a full sheet of notes

• both sides

• handwritten


About the Final

• Don’t leave stuff blank!

• Can you remember ANYTHING about the topic?

• Apply logic!

• Comprehension before Computation -- Big Picture before Details

• State units with numbers (except magnitude)


Spring F2015

Topics

TOUR OF UNIVERSE


Our “Cosmic Address”

• LAMC

• Sylmar

• Los Angeles County

• CA

• US

• Earth

• Solar System

• Milky Way Galaxy

• Local Group

• Virgo Supercluster

• The Universe

SCIENCE


Science

• Definition

• Method

• KEY: Hypothesis, Test, Revision

• Nomenclature -- Hypothesis, Theory

• Characteristics of Science & Belief System

• Be able to recognize science and not-science

• Be able to recognize a scientific hypothesis

• Be able to describe the scientific method

THE NIGHT SKY


Diurnal Motion

• Daily

• Everything Rises in East, sets in West

• Moves in circles around the NCP (and SCP)

• Earth is rotating

• Be able to answer questions using diagrams from the Position LT


Lunar Phases

• Cause of phases

• ID of phases

• Timing of rise/set/transit


Eclipses

• Solar and Lunar

• Cause

• Geometry

• Timing

• Why not every full/new moon


Zodiac & Apparent Solar Motion

• Ecliptic

• Zodiac

• Meaning of “The Sun is in Taurus etc.”

• Takes a year to cycle through

Name:____________________! ! Date:__________ICE 2! ASTRO 110/120! Levine Spring 2013


Seasons

• It’s the axial tilt

• It’s about energy transfer

• Be able to discuss observable consequences

• when is the Sun high in the sky, day length etc.

OLD DEAD GUYS


Greeks to Kepler

• Greek ideas

• Copernican Revolution

• Tycho Brahe

• Kepler the dude


Kepler’s 3 laws of Planetary Motion

1. The orbits of the planets are ellipses, with the Sun at one focus.

2. A line from a planet to the Sun sweeps out equal areas in equal periods of time

• Planets move fastest when physically closest to the Sun, and slowest when farthest.

3. A planet’s orbital period squared, is proportional to it’s farthest distance from the Sun cubed:

• P2 = a3

• Be able to recognize these

• Work with ellipses and eccentricity

• Recognize examples of 2nd and 3rd law (faster/slower longer period/shorter period)

• Possible calculation with 3rd law


Kepler to Sir Issac

• Galileo

• Sir Issac

• Contributions and fields of study

• Law of Universal Gravity


Law of Universal Gravity

• Be able to explain how the force varies (larger or smaller) with mass of either object, both objects and distance

• Be able to work the inverse square relationship -- how does force change if distance doubles....

LIGHT, OPTICS, TELESCOPES


Nature of Light

• Why this is important for Astronomy

• electromagnetic radiation

• waves, particles, duality

• all light, from radio to gamma ray is same thing

• all light travels at the same speed in vacuum

• c=3x108 m/s


Properties of Light

• Waves

• Relationship of wavelength and frequency

• λ = c/f

• Interference

• Particles

• Photoelectric effect

• E = h f = hc/λ

• h = 6.6 x 10-34 Js = 6.6 x 10-34 J/Hz

• Know what these relationships mean

• Know how the ranking task worked

• Possibility of seeing a a simple calculation


Electromagnetic Spectrum

• difference between red and blue light

• Basic bands of EMR (e.g. radio, visible, IR etc.)

• Relationship between band, wavelength & Energy


Telescopes and Observatories

• Refractors and Reflectors

• Size (of primary) matters

• Atmospheric Transmission & Seeing

• Multiwavelength Astronomy

• What are IR and Radio good for?

• Cameras & Spectroscopes

SOLAR SYSTEM


Solar System Properties

• Overall “bulk” properties

• Disk shape

• two types of planets

• Space “debris”

• common age


Solar System Properties

• “Anatomy” What and Where

• Sun

• Inner SS & terrestrial planets

• Asteroid Belt

• Outer SS & Jovian planets

• Kuiper Belt

• Heliopause

• Oort cloud

• Size/Distance Scales


Solar System Formation

• Raw materials -- big bang, role of supernovae

• Theories of Formation

• Solar Nebula Theory

• Differentiation

• Frost line

• Planet formation -- both types

• Disk clearing

• Cratering & Craters


Solar System Bodies

• Terrestrial Planets

• common properties

• dynamo effect

• What went wrong for Venus and Mars

• Greenhouse effect

• Jovian Planets

• common properties

• Why are Titan and Enceladus interesting

• Why isn’t Pluto a “planet” and what it is

STARS & GALAXIES


Stellar Properties

• Luminosity

• Magnitude system

• Apparent vs. Absolute magnitude

• review the ranking tasks

• Distance ladder & difficulty of distances

• Stellar parallax

• know how angle & distance relate

• Standard Candle

• how does a standard candle work


Color and Temperature & Size

• stars are (mostly) like blackbodies

• temperature and peak wavelength

• temperature and size & luminosity


Spectral Type

• Color ~ temperature ~ spectral class

• be able to answer questions based on the blackbody LT

• Harvard computers & Harvard classification scheme

• OBAFGKM

• Brightness and temperature and size (Giants)


HR Diagram

• What is it?

• What can be plotted on it?

• Main sequence

• Red giants

• Supergiants

• White Dwarfs

• Evolution


Stellar Lifecycles

• Star formation

• Main Sequence lifetime

• End states and what determines them

• Mass is everything!!!!!

• More mass means shorter life

© NASA


Main Sequence & Red Giant phase

• Main Sequence

• Hydrostatic Equilibrium

• H to He nuclear fusion

• Most of a star’s life

• Sun is on MS

• Red Giant

• New hydrostatic equilibrium

• H to He fusion in shell

• He fusion in core

• 1/10th the duration of MS lifetime


Endgame Scenarios

• Giant stars

• Planetary nebulae

• White dwarfs

• Type II supernovae

• neutron stars & pulsars

• black holes

• type Ia supernovae


The Milky Way

• Barred Spiral

• General structure

• disk, bulge, halo

• General Content

• Where are we?


Galaxy Classification

NASA/ESA


Characteristics of types

• Describe spirals, barred spirals, ellipticals, irregulars

• Which are most common?

• What are their overall properties?

• Which tend to have older or younger stars

• Which tend to have black holes (all)

COSMOLOGY


Telescopes are Time machines

• Lookback time

• Concept of the Observable Universe


Expanding Universe

• Space is expanding, not stuff

• Raisin bread & balloons

• Role of gravity in holding structures together

• Cosmological principle


Big Bang

• NOT an explosion

• Universe was infinite immediately

• How long ago was it?

• The whole universe was in a hot, dense state

• energy became matter became stars and galaxies

• Evidence for Big Bang

• Expansion

• H,He,Li abundance in early universe

• Cosmic Microwave Background


Cosmic Microwave Background

• Penzias & Wilson

• 2.7 K

• Very smooth but somewhat bumpy

• Not the very beginning, 380,000 years after BB


Fate of Universe

• 3 fates: Open, Closed, Critical or Big Crunch, Big Chill/Big Rip

• Dark Matter & Dark Energy

• Most of universe is dark

• Dark Matter

• Dark energy dominates universe

• Dark energy is unknown cause of local expansion

EXOPLANETS


Exoplanets

• If we get to them today…

IN SUMMARY…


The Galaxy Song


So Long and Thanks for All the Fish!


Spring F2015

Other Worlds

Extrasolar planets and systems


There are a lot of planets out there!

• 1879-1935 extrasolar planets around 1225 stars

• 471-484 multiple planet systems

• http://exoplanet.eu/catalog/

• Simple flat-table list

• 4696 Kepler candidates!

http://exoplanet.eu/catalog/


There are a lot of planets out there!

• 298 are very large

• Radius larger than 6x Earth

• 150 are small

• Radius less than 1.25 x Earth

DETECTION METHODS


How do we find them?

• Direct imaging

• Rare

• Radial Velocity (RV)

• Planet induces doppler shift in parent star

• Transit photometry

• Planet blocks light from parent star

• Gravitational microlensing

• Planet causes background object to brighten

• Astrometry

• Planet causes parent star to shift position periodically


Exoplanet Image

• Beta Pictoris about 63.5 light years from Earth

• Beta Pic b (planet)

• dist from Beta Pic about 9x dist Earth from Sun

• VERY large, ~ 1.6x radius of Jupiter

Beta Pictoris b (bright spot) orbiting its star (center) Credit: Bruce Macintosh et al.


RV Animation


Transit Method Animation

KEPLER


Kepler

• Capable of finding earth-sized planets in the habitable zone of nearby stars

• Transit method

• 962 confirmed planets to date

• Now in modified extended mission K2 (has lost 2 reaction wheels)


Kepler Overview

MOST EARTHLIKE PLANET “EARTH 2.0” KEPLER 452B


Transit Graph


Artist’s Concept


Kepler 452b


Kepler 186-f came first

• Kepler 186f discovered April 2014 was first Earth-size planet in Habitable zone.

• Composition not as clearly confirmed as rocky

• Orbits very close to a dim M-type Star

• about 500 ly distant


“Earth 2.0” Kepler 452b

• Discovered July 2015 (press con 7/23)

• Orbits G-type Star

• about 1400 ly distant

a1 f2015 review copy - los angeles mission college f2015 review copy.pdfkepler’s 3 laws of...

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