LECTURE 1
2 questions
Babylonian Astronomy
Astronomers were priests
Created first star catalogues
Developed lunar calendar with 354 days
Ephemerides clay tablets of planetary positions, permanent
records
Egyptian Astronomy
Constellations on tomb walls
Developed sundial
Astronomers were priests
Sun god Ra
Sidereal star based calendar using Sirius to predict Nile
flooding
Chinese Astronomy
Knew year was 365.25 days
Recorded comets, meteors, meteorites
Predicted solar and lunar eclipses
Recorded sunspots and supernova explosion
Mayan Astronomy
Developed complicated numbering system and calendar based on
numbers 20 and 13
Some temples were observatories
Priests were asronomers
American Indian Astronomy
Knew phases of moon
Medicine Wheels circular mounds in earth
Petroglyphs, pictograms, calendar sticks
May have recorded crab supernova
Polynesian Astronomy
Could navigate by stars
VOCAB
Ephemerides clay tablets of planetary positions
Sidereal star based
Medicine wheels circular mounts in earth
LECTURE 2
2 questions
Earliest constellations were defined by Sumerians in 2000 BC
88 constellations today
Angular measure based on number 60 introduced by Babylonians
Based on pi was introduced by Greeks, 2pi radians in circle
VOCAB
Celestial Sphere huge imaginary sphere which holds all celestial
objects, pivots around celestial poles
Great circle plane passes through center of the sphere
Small circle plane does not pass through center of the
sphere
Diurnal motion rotation of earth toward the east makes the
heavens appear to be moving toward the west during each day
Constellation area of sky containing pattern of stars
Angular separation measured from observer, angle between two
lines extending toward two objects
Minute of arc 1/60 of a degree of arc
Second of arc 1/60 of minute of arc, 1/3600 of one degree
Prime Meridian great circle which runs north and south through
Greenwich
Longitude parallel to equator, LA is 118 W
Latitude south or north of equator, LA is 34 N
Right Ascension (R.A.) analogous to longitude
Declination (Dec) analogous to latitude
Azimuth angle between north point and direction to object
LECTURE 3
3 questions
1 people
Earths Revolution
Earth revolves around sun in flat surface called ecliptic
plane
Sun appears to move eastward around the sky
Earths spin axis is inclined by 23.5 degrees
Sun rises and sets farther N in summer than in winter
VOCAB
Ecliptic plane flat surface that earth revolves around the sun
in
Ecliptic apparent path of the sun in the sky
Annual motion eastward motion of the sun along the ecliptic
Equinoxes the two intersection points of the ecliptic and the
celestial equator
Zodiac band in the sky, which lies 9 degrees on either side of
the ecliptic on celestial sphere
Vernal Equinox intersection point of the ecliptic and celestial
equator at which sun is moving from s to n across celestial
equator, March 21
Summer Solstice 3 months after vernal equinox, as far north as
it can move, June 21, length of day is greatest
Autumnal equinox 3 months after summer solstice, crosses
celestial equator north to south, September 23
Winter solstice 3 months after autumnal equinox, as far south as
it can, December 21, length of day is shortest
Uniform circular motion motions in circles at constant
speeds
Foucault pendulum pendulum appears to rotate direction of swing
as time goes by, but its earth turning while pendulum swings
Coriolis effect water and clouds appear to swirl around going
down drains
Aberration of starlight telescope has to be inclined in
direction of earths orbital motion
Heliocentric model earth moving around stationary sun
PEOPLE
Pythagoreas
Saw universe as set of 8 concentric spheres with earth at
center, geocentric model
Anaxagoras
Said that sun must be a large body located far from earth
Estimated diameter of sun to be 35 miles
Described reasons for moon phases
Views at odds with religion and he was exiled from Athens
Plato
Argued for uniform circular motion motion only in circles and at
constant speeds
Aristotle
Increased number of spheres in geocentric model to 55
Said that earth could not be rotating
Wrote down reasons for phases of moon, but probably Anaxagoras
ideas
Saw difference in natural behavior of earthly objects and
heavenly objects, believed that two sets of rules existed
Earthly fall and stop
Heavenly keep moving in circles
Said that apparent motion of sun in sky could be caused by
motion of earth, but rejected this
Error due to inability to detect stellar parallax
James Bradley
Discovered aberration of starlight
Aristachmus of Samos
Argued that earth was moving around stationary sun
LECTURE 4
4 questions
3 people
Planets
5 planets visible to naked eye: Mercury, Venus, Mars, Jupiter,
Saturn
Lack simple uniform motion of sun and moon
Always stay near the ecliptic
Post-Greek Astronomy
Decimal system invented by Hindus
Some Greek documents were translated into Arabic rather than
simply being destroyed without any translation
Arabs developed trigonometry
VOCAB
Elongation angle angle relative to position of sun in the
sky
Epicycles small circles that carry the planets
Equant point within deferent about which the line connecting
that point to center of a planets epicycle would move at constant
angular rate of speed
Ockhams Razor simplest possible, not overly complicated
Synodic period times between successive configurations relative
to sun
PEOPLE
Hipparchus
Considered greatest astronomer of pre-Christian era
Created observatory on Island of Rhodes
Added epicycles
Discovered precession
Stellar magnitudes
Ptolemy
Greatest post-Christian era astronomer
Developed most comprehensive geocentric model
Book Almagest
Use of symmetrical circle to model motions of celestial
objects
Explained motion of the moon
St. Thomas Acquinas
Blended Aristotle, including Ptolematic model, with
Christianity
Central, unmoving Earth
Ibn al-Shatir
Developed a model for the motions of planets which seems to be
identical to heliocentric model developed 200 years later by
Copernicus
Copernicus
Polish monk who studied astronomy and was a contemporary of
Christopher Columbus
Developed sun centered model
De Revolutionibus, spurred scientific revolution in Europe
Planetary orbits were circles in which each planets speed
remained constant
Computed relative distances of 6 known planets using records of
configurations of planets
Eliminated epicycles as explanation for retrograde motion
LECTURE 5
3 questions
2 people
Comparing the two celestial models
Copernicus was better than Ptolemys but not accurate enough to
account for all irregularities in motions of other planets
Both based on assumption that planets move at constant speed,
Copernicus had epicycles
Both thought all stars were located at common distance from
earth
Observations of stellar parallax prove that earth moves support
Copernicus and not Ptolemy
Copernican model more aesthetic since it could explain motions
of Mercury and Venus without special rules, also simpler
explanation for retrograde motion
Keplers Laws of Planetary Motion
1st Law Each planets path around sun is ellipse, with sun at one
focus and other empty
2nd Law planet moves along elliptical path with speed that
changes so that it sweeps out equal areas in equal time
3rd Law a3/p2 = C, ratio of cube of planets average distance a
from sun to square of orbital period is same for each planet
VOCAB
Stellar parallax apparent annual shifting of nearby stars with
respect to background stars
PEOPLE
Tyson Brahe
Developed observatory on Island of Hveen
Built largest and most accurate naked eye instruments yet
constructed
Observed planetary motions for 20 years
Observer, not theorist
Hired assistant, Kepler
Kepler
First astronomer to support Copernican system in print in The
Cosmic Mystery
Astrologer and mystic
Thought planets made music as they orbited
Established orbits as ellipses
LECTURE 6
2 questions
1 people
Venus went through phases: full, gibbous, quarter, crescent
VOCAB
Galilean moons Jupiters 4 satellites
Scalar only how fast something is moving
Vector both magnitude and direction
Jerk rate of change of acceleration
Inertia property of object whereby it tends to maintain whatever
velocity it has
Newtons First Law (Law of Inertia) unless object is acted upon
by net, outside force, it will maintain constant speed in straight
line Conservation of Linear Momentum
Newtons Second Law Acceleration is inversely proportional to
mass being accelerated, acceleration = net force/mass, F = ma
Newtons Third Law when object x exerts force on y, y exerts
equal and opposite force back on x
Mass measure of amount of material in an object
Linear momentum product of mass times velocity
Centripetal (center-seeking) force force directed toward the
center of the curve along which object is moving
Angular momentum product of mass times velocity times radius of
the orbit, am = mvr
PEOPLE
Galileo
Believed in Copernican system
Built his first telescope, first person to use telescope to
study the sky
5 important observations
Mountains, valleys, craters on moon
Sunspots
More stars that can be observed with naked eye
Four largest moons of Jupiter, known as Galilean Moons
Complete cycle of phases of Venus
Belief in Copernican system got him in trouble with church,
placed under house arrest for remaining 10 years of his life
Dialogue on Two World Systems
Developed concept of inertia
Proposed that falling body would speed up at constant rate
Set the standard for studying nature through reliance on
observation and experimentation to test hypotheses
LECTURE 7
2 questions
1 person
On most days Earth there are two high tides and two low
tides
VOCAB
Law of universal gravitation between every two objects there is
an attractive force, magnitude of which is directly proportional to
the mass of each object and inversely proportional to the square of
the distance between the centers of the objects, F = Gm1m2 / d 2
where G is the Universal Constant of Gravitation, m1 and m2 are the
masses, and d is the distance between their centers.
Center of mass (CM) average location of the various masses in a
system, weighted according to how far each is from that point,
center of gravity
Barycenter center of mass of two astronomical objects revolving
around one another
Spring tide greatest difference between high and low tide during
given day, occur twice a month when lunar and solar tides
correspond, only occur at new or full moon
Syzygy when sun, moon, and earth are all located in a line
Neap tide smallest difference between high and low tide in a
single day, when solar tide most nearly cancels
Spin-orbit coupling period of rotation hats equal to orbital
period
Tidal friction torque which results from tidal pull of the moon
acting on oceans, has slowed the earths rotation rate
PEOPLE
Henry Cavendish
First person to measure the universal constant of
gravitation
LECTURE 8
1 question
No people
Earth is not a perfect sphere
Takes 25,800 years for spin axis to precess around cone once
Newtons laws laid the foundation for our modern notion of the
universe
Escape earths orbit then goes into orbit around the sun
VOCAB
Precess because the earth has an oblate shape, both the sun and
moon try to tip the spinning earth so axis is normal to ecliptic,
however, the earth responds by having its spin axis move very
slowly on the surface of a cone
Perturbation motion of each planet around the sun is disturbed
by the presence of the other planets in the solar system
Circular velocity velocity of 8km/second or more in order to
avoid return to earths surface
Escape velocity 11 km/sec to leave earths gravitational field
entirely
Theory of relativity showed that inertial mass is equivalent to
gravitational mass
Wave equation says that all light is nothing more than
electromagnetic radiation which is propagating through space, all
light will propagate in vacuum at the same speed, c
Visible spectrum set of colors or wavelengths produced when
light is dispersed, such as by a prism
LECTURE 9
1 question
No people
Speed of light c
Wavelength lambda
Circumference of earth is 1/7 of one light second
Sun is located 8 1/3 light minutes from earth
Pluto is located 5 light hours from sun
Light year is 5.9 trillion miles
Speed of propagation = wavelength x frequency
Speed of light slower anywhere than in a vacuum
Speed of light in water is of speed in vacuum
Red light fastest, violet light slowest
Order of increasing frequency radio, infrared, visible,
ultraviolet, x-ray, gamma ray
Fahrenheit scale: freezing 32F/boiling 212F.
Celsius (or Centigrade) scale: freezing 0C/boiling 100C.
Kelvin (or absolute) scale:
0 K = absolute zero (-273.15 C or -459o.6 F)
273.15 K = freezing point of water (0 C)
373.15 K = boiling point of water (100 C)
VOCAB
Photons particles or packets of energy
Plancks constant energy of a single photon is proportional to
frequency of wave, E=hv
Electromagnetic spectrum entire array of electromagnetic waves,
extends from long wavelength, low frequency radio waves to short
wavelength, high frequency gamma rays
LECTURE 10
5 questions
2 people
Kirchoffs Rules of Spectral Analysis
Summarize how three types of spectra are produced
1. Hot, dense glowing object will emit continuous, black body
type spectrum
2. Hot, low-density gas will emit light of only certain
wavelengths bright line, or emission line, spectrum
3. When light having a continuous spectrum passes through cooler
gas, dark lines appear superimposed upon the continuous
spectrum
VOCAB
Wiens Law inverse relationship between black bodys temperature
and peak wavelength of spectral energy distribution
Stefan-Boltzmann Law states how much energy a black body of a
given temperature will give off ever second from every small area
of its surface, E = sT4
Ultraviolet Catastrophe disagreement between theory and
observation
Photoelectric effect certain metals, when illuminated with beam
of light of high frequency, would emit individual electrons
Continuous spectrum contains entire range of wavelengths rather
than separate, discrete wavelengths
PEOPLE
Max Planck
Explained the reason for the ultraviolet catastrophe for the
first time
Claimed that light radiated by a black body is always emitted in
multiples of very tiny units of energy called quanta (photons)
E=hv
Albert Einstein
First explained the photoelectric effect, suggested that all the
electromagnetic radiation, not just from black bodies, travels as
quanta
Joseph von Fraunhofer
Analyzed the solar spectrum and found more than 800 dark lines
lying on top of the continuous spectrum
Called Fraunhofer lines
Robert Bunsen, Gustav Kirchoff
Observed spectra of hot, glowing gases in their lab
Did not give off continuous spectra of dark lines
Gave off spectra consisting of bright lines on dark
background
Johannes Balmer
Devised empirical formula with which he could compute the
wavelength spacings of the different lines in the spectrum of
hydrogen gas
Lord Rutherford
Proposed model for the atom in which the positive charge was
somewhere in the middle and the negative charge surrounded the
positive charge
Niels Bohr
Combined Balmers formula with Plancks quantum and with
Rutherfords simple, qualitative atomic model and developed his own
Bohr Model of the Atom
LECTURE 11
2 questions
No people
Three postulates of the Bohr atom:
1. Electron travels only in circular orbits around the nucleus,
can only have certain specific energies
2. Electron in one atom can move from one energy level to
another thereby changing the total energy of that atom
3. Energy of a photon determines the frequency (or wavelength)
of light that is associated with that photon
Photons of more than one energy are being simultaneously
absorbed in the gas
VOCAB
Photon smallest possible amount of electromagnetic energy of a
particular wavelength
Photosphere visible surface of the sun
Ionization process by which electron is removed from the
atom
Re-combination process in which protons re-capture free
electrons and make new neural atoms
Heisenberg Uncertainty Principle physicists can never know both
the position and momentum of a particle to infinitely good
accuracy
LECTURE 12
3 questions
2 people
Phases of moon caused by relative position of the earth, moon,
sun
New, waxing crescent, first quarter, waxing gibbous, full moon,
waning gibbous, third quarter, waning crescent, new moon
VOCAB
Doppler effect observed change in wavelength from source moving
toward or away from observer
Blue shift motion toward the observer, longer wavelength
Red shift motion away from observer, shorter wavelength
Radial velocity velocity component along the line of sight,
toward or away from, the observer
Tangential velocity velocity component perpendicular to line of
sight
Inverse square law of light light (or radiation) spreading from
small source decreases in intensity as the inverse square of the
distance from the source
Perigee point in the orbit of an earth satellite where it is
closest to earth, largest apparent size of the moon
Apogee point in orbit of earth satellite when it is farthest
from the earth, smallest apparent size of moon
Synodic period time interval between successive similar
alignments of a celestial object with respect to the sun
PEOPLE
Eratosthenes
Devised clever way to measure Earths size
Ptolemy
Determined distance from earth to moon to be 27.3 earth
diameters using geocentric parallax
Anaxagoras
Explained reasons for moons phases
Thought moon was closer to earth than was the sun
LECTURE 13
5 questions
No people
Earth
Composition
Crust thin, outermost layer of earth, rocky
Mantle thick, solid layer between crust and core
Outer core composed of liquid metals
Inner core centermost portion, mainly solid iron and nickel
Magnetic field originates in liquid outer core
VOCAB
Lunar eclipse eclipse in which the moon passes into the shadow
of the earth
Umbra portion of a shadow that receives no direct light from
light source
Penumbra portion of shadow that receives direct light from only
one part of the light source
Eclipse season time of the year during which eclipse is
possible
Penumbral lunar eclipse eclipse of the moon in which the moon
passes through the earths penumbra, but not through umbra
Total lunar eclipse eclipse of the moon in which the moon is
completely in the umbra of the earths shadow for portion of the
eclipse
Partial lunar eclipse only portion of the moon passes through
umbra, this is a portion of the entire eclipse
Solar eclipse eclipse of sun in which light from sun is blocked
by moon
Total solar eclipse light from normally visible portion of the
sun (photosphere) is completely blocked by the moon
Corona outer atmosphere of the sun, only visible during total
solar eclipse
Partial solar eclipse only portion of suns disk is covered by
moons disk
Annular solar eclipse moon located too far to completely cover
sun, edge of sun is seen
Differentiation sinking of denser materials toward center of the
earth
Dynamo effect explains earths and other planets magnetic fields
as being due to electric currents flowing within molten iron
cores
Van allen belts two doughnut shaped regions composed of charged
particles emitted by sun and captured by magnetic field of the
earth, located in earths magnetosphere
LECTURE 14
4 questions
No people
Interior of earth was heated by radioactive decay of uranium and
other elements
Heat resulted in interval of extensive volcanic activity
Such volcanic activity was the origin of the earths atmosphere
through the process of outgassing
1. Water vapor (steam) went into atmosphere turned to rain
2. CO2 combined with surface to carbonate minerals
3. Nitrogen
4. Argon can use it to date eart
VOCAB
Continental drift gradual motion of continents relative to one
another
Rift zone where tectonic plates are being pushed apart, normally
by molten material being forced up out of the mantle
Sea floor spreading when warm magma must stop flowing vertically
and begin to flow horizontally
Subduction zone the material in the sea floor plate dips into
the earth and slides beneath the continental plate
Convection warm magma rises, moves horizontally, then falls back
into subduction zones
Milankovich Effect idea that Ice Ages were caused by small
changes in obliquity of earths spin axis and small changes in the
eccentricity or earths orbit
Outgassing vents and volcanoes allowed heated gases to escape
from rock of the mantle and crust
Troposphere lowest level of earths atmosphere, 75% of mass,
weather occurs here
LECTURE 15
1 question
No people
Moons surface
Maria lowlands on Moon that resemble sea when viewed from earth,
darker in color
Highlands light in color
Mountains on moon are result of cratering
Formed 4.6 billion years ago
Temperatures range from 100 to -173 C
Theories
Double-planet theory earth and moon formed at the same time from
same rotating disk of material
Fission hypothesis large basin of the pacific ocean is the place
from which moon was ejected
Capture theory moon was originally solar system debris that was
captured by earths gravitational field
Large impact theory moon formed as result of glancing impact
between large mars-sized object and the earth
Planets
All planet orbits are ellipses except Mercury and Pluto
Each planet revolves around the sun eastward
All planets except Venus, Uranus, Pluto rotate counterclockwise
retrograde
Jovian
Bigger diameters
More satellites
Ring
Terrestrial
More dense
VOCAB
Meteorites interplanetary chunk of matter that has struck a
planet or moon
LECTURE 17
2 questions
No people
Mercury
Hardest to see from earth, close to sun, exhibits phases like
Venus does
Similar to moon, covered in impact craters, but less
prominent
Cooled more slowly than the moon
No permanent atmosphere
Most eccentric orbit, except for Pluto
Ice on floors of craters
Venus
Surface shrouded by heavy clouds
Retrograde rotation
Sharp edged rocks calm winds
Pioneer Venus I, Magellan
Surface covered with rolling hills
500 million years average surface age, twice as old as earth
Evidence of volcanic and tectonic activity mountains, large lava
flows, volcanoes
Evidence of sulfuric acid in clouds, landslides by tectonic
activity possibly
96% CO2
Upper atmosphere is windy
90 times atmospheric pressure of the earth
VOCAB
Mariner 10 got 4,000 photos of Mercury, 3 fly-bys
Scarps cliffs in a line
Caloris Basin bulls-eye crater
Albedo fraction of incident radiation that object reflects
LECTURE 18
1 question
No people
Venus
Thick clouds and high temperatures
Greenhouse effect
Mars
Only planet with surface features that can be seen from
earth
Best seen at opposition configuration of planet when it is
opposite the sun in our sky, occur every 2.2 years
There are seasons as on earth, but they are 6 months long
Two polar caps, made of water ice base
Possible vegetation
Extremely thin atmosphere
Populated with craters, large volcanoes, canyons
Olympus Mons largest volcano on Mars
Lacks tectonic plates
Viking landed on Mars
5 km escape velocity
LECTURE 19
3 questions
No people
Evidence of water on Mars by two Rovers Spirit and
opportunity
Moons of Mars
Phobos and Deimos
Shaped like potatoes, dark surfaces similar to asteroids
Captured asteroids
Jupiter
318 times more massive than earth
Low density
Differential rotation
Great red spot large red oval in atmosphere
Liquid molecular hydrogen deep in atmosphere
Small core, if at all
Strong magnetic field, 20,000 that of earth
Magnetosphere extends 15 million km
Emits more energy than it receives from Sun
LECTURE 20
1 question
No people
Jupiter has 4 rings
Saturn radiates more heat than it absorbs
Saturn has 62 moons
Titan Saturns moon
Has an atmosphere, thought to be colder version of earths early
atmosphere
Second largest moon in solar system
Possible lake, liquid hydrocarbon, not water
Jupiters Moons
66 moons
4 orbit close, fragmented moonlets
8 outer moons traveling in opposite directions, eccentric
orbits, dark surfaces, probably captured asteroids
4 large satellites known as Galilean moons
Ganymede, Titan, Callisto, Io, Moon, Europa, Triton
Io
Volcanic geysers that spew hot sulfur onto surface
Surrounded by halo of sodium atoms
Surface is ice, experiences tidal heating
Possibility of life in ocean
Ganymede - largest moon in solar system
Callisto least active surface, largest known impact crater
Valhalla
LECTURE 21
1 question
No people
Saturn has really thin rings
Thought to have originated from close, icy moon which shattered,
or when comet was pulled apart, or from material too close to form
a moon
Uranus
Small or no rocky core at all
Atmosphere similar to Jupiter and Saturn hydrogen and helium
with some methane
10 thin rings
Neptune
Similar to Uranus, smaller in diameter
Exhibits weather patterns in atmosphere
Winds up to 700 mph
Triton largest moon
Only one to revolve around planet in retrograde direction
Active volcanism
Most eccentric orbit
VOCAB
Cassinis division largest division between some of the rings
Roche limit minimum radius at which satellite may orbit without
being broken apart
Occultation passing of one astronomical object in front of
another
LECTURE 22
3 questions
No people
Pluto
Methane atmosphere
Charon, Hydra, Nix
5 total moons
Could be a former moon of Neptune
Debris asteroids, meteoroids, comets, dust
Asteroid minor planet
Revolve around the sun in counterclockwise direction in or near
plane of ecliptic
Probably primordial material that never formed into a planet
because of Jupiters gravitational force
Ceres first asteroid
Largest asteroid, dwarf planet
VOCAB
Apollo asteroids 50 asteroids with diameters larger than 1
km
Kirkwoods Gaps due to tugs from Jupiter
Trojan Asteroids two groups of asteroids located at Jupiters
distance from sun
LECTURE 23
3 questions
No people
Comet Halley - period of 76 years
Comet tail always points away from sun
Can die:
Gradual evaporation of nuclei
Evaporation of volatile material, leaving chunks of rock
Fall into the sun
Most comets either elliptical or parabolic
Three sizes of meteoroids
1. Smallest micro-meteorites slowed down at top of earths
atmosphere, not evaporated during passage
2. Meteor streak in the sky when dust-grain or pebble-sized
meteoroid is heated by passage through atmosphere
3. Largest can pass through earths atmosphere without being
evaporated, meteorite remains
Meteorites:
1. Irons made of 80-90% iron, some nickel
2. Stones stony, can contain iron and nickel, 90% of all
meteorites
3. Stony irons half and half
VOCAB
Head coma and nucleus, sometimes hydrogen envelope
Coma part of head made of diffuse cloud of gas and dust
Nucleus solid chunk of comet located in head
Tail gas/dust swept away from comets head
Gas (ionic) straight, always
Dust tail curved, sometimes
Oort cloud billions of comet nuclei in spherical shell
Kuiper belt band of comets and dwarf planets that exists closer
to the solar system than the Oort cloud
Meteoroid piece of interplanetary matter that is smaller than an
asteroid
LECTURE 24
6 questions
No people
Sun is a G2 star in the main sequence phase of its life
5800 Kelvin
4.6 billion years old
Red giant in 5 billion years
Heating mechanism of sun
Shock waves produced in solar interior and dump energy into
corona
Magnetic reconnection heating due to changes in coronal magnetic
field
VOCAB
Solar constant rate at which solar energy strikes the earth
Solar luminosity rate at which sun releases energy into
space
Photosphere visible surface of the sun
Chromosphere region of the solar atmosphere some 2,000 to 3,000
km thick that lies between the photosphere and the corona, only
observable during total solar eclipse
Transition zone above the chromosphere
Solar corona portion of solar atmosphere only visible during
total solar eclipse
Zeeman effect splitting of spectral lines by strong magnetic
field
LECTURE 25
4 questions
No people
Marauder Minimum few or no sunspots
Galactic Cosmic Rays High-speed nuclei that originate outside
solar system produce radioisotopes
Prominences channels of solar material above disk of sun
Leptons smallest particles, electrons and neutrinos
Fusion reactions when sub-atomic particles which comprise
different nuclei interact with each other and energy is liberated,
converting hydrogen into helium
Nuclear fusion two nuclei combine to form larger nucleus,
releasing energy in the process, occur within core of the sun
Deuterium hydrogen nucleus that contains one neutron and one
proton
LECTURE 27
2 questions
1 person
Few stars so bright that they have negative magnitudes
Stars color determined by temperature
VOCAB
Luminosity total rate at which energy is being released, power
emitted by star
Apparent magnitude measure of amount of light received from
celestial object
Parallax angle 1/2 of the max angle through which a star appears
to be displaced in 6 months due to earths motion around the sun
Parsec distance star would have if it had a parallax angle of 1
arcsecond
Absolute magnitude apparent magnitude a star would have if it
were at a distance of 10 parsecs
Proper motion angle through which star moves each year
Tangential velocity speed across line of sight
Radial velocity velocity toward or away from earth
Total space velocity stars actual motion relative to sun,
combines both other velocities
PEOPLE
Hipparchus
Created first star catalog with corresponding brightness
Aristotle
Concluded that earth was stationary because he couldnt detect
stellar parallax
Friedrich Bessel
First measurement of stellar parallax using 61 Cygni
Huggins
First stellar radial velocity measurement based on Sirius
Sir William Hershchel
First to estimate direction sun is moving, by measuring total
space velocities of stars near sun
Father Angelo Secchi
First spectral classifications, but he made them in wrong
order
Annie Jump Cannon
Developed methods for determining stars spectral
classification
Determined spectral types for 500,000 stars
OBAFGKM
LECTURE 28
2 questions
No people
Main sequence, white dwarf, red giant, supergiant
Know absolute and apparent magnitude, can compute distance
VOCAB
Hertzsprung-Russel diagram plot of absolute magnitude
(luminosity) versus surface temperature (spectral class)
Luminosity classes different groupings into which stars can be
placed based upon different widths of their spectral lines
White dwarfs hot but dim stars because they are small
Giant star great luminosity, large size
Supergiant very great luminosity and size
Optical doubles two stars that have a small angular separation
as seen from earth but are not gravitationally linked
Binary star system system of two stars gravitationally bound
together, orbit each other
Visual binary orbiting pair of stars that can be resolved with
telescope as two stars
Spectroscopic binary orbiting pair of stars that can be
determined as two because of Doppler effect
Ecliptic binary one star moves in front of another as viewed
from earth
Astrometric binary orbiting pair of stars in which wiggles in
proper motion reveals presence the other
Composite spectrum binary binary star system with stars having
spectra that are different enough to distinguish them from one
another
LECTURE 29
1 question
No people
Cepheid variable Delta Cephei, rapid brightening then
dimming
Emission nebula interstellar gas that fluoresces due to uv light
from star
Nebula dense cloud
Reflection nebula interstellar dust visible due to reflected
light from nearby star, bluish in color
LECTURE 30
2 questions
No people
Stars are born in the cold, giant molecular clouds (GMC)
GMCs collapse possibly by a shock wave
Evaporating gaseous globules (EGG) dense regions, material
collapses, sometimes become stars
Protostar star in process of formation before it reaches main
sequence
Cocoon nebula dust and gas surrounding protostar, blocks much of
radiation
Brown dwarf starlike object whose mass is too small to sustain
nuclear fusion, cannot sustain nuclear reactions
LECTURE 31
2 questions
No people
Flyweight
Stars with mass less than .4 solar masses
Convection throughout most or all the star
Hydrogen cycled throughout core
Become white dwarfs
Lightweight
Includes sun
.4-2 solar masses
Not fully convective, dont use all of their hydrogen fuel
supply
Become red giant after
Begins to contract once its depleted of hydrogen
Red giant consists of helium intermingled with electrons
Super lightweight
2-4 solar masses
Cores never become degenerate, no helium flash
Electron degeneracy state of gas in which electrons are packed
as densely as nature permits
Helium flash red giant evolves and hydrogen burning takes place
in outer layers of the star, helium ashes are dumped back onto
core, raising temperature
Planetary nebula spherical shell of gas expelled by red giant
near end of its life
White dwarf cores of red giants that remain after outer parts
have been blown away, 10% of all stars
LECTURE 32
1 person
Subrahamanyan Chandrasekhar
Leading theorist in study of white dwarf stars
Set the limit beyond which white stars cannot exist as white
dwarfs 1.4 solar masses
Ian Shelton
Discovered SN1987A
LECTURE 33
4 questions
1 person
Stages of middleweight star
Protostar
Main sequence
Red giant
Supernova
Supernova remnant nebula and pulsar
VOCAB
Neutron star middleweight star that has collapsed to the point
at which it is supported by neutron degeneracy
Pulsar celestial object of small angular size that emits pulses
of radio waves with regular period between
Lighthouse model theory that explains pulsar behavior as due to
spinning neutron star
Synchrotron radiation beam of radio-frequency radiation is
caused by this process in which electrons traveling near the speed
of light spiral around the pulsars intense magnetic field lines
Special theory of relativity predicts that observed behavior of
matter is due to its speed relative to the person who makes the
observation
General theory of relativity expands special relativity to
include accelerated systems and presents an alternative way of
explaining the phenomenon of gravitation
Principle of relativity states that all observers moving at
constant velocity relative to each other are equivalent
Michelson-Morley Experiment showed that speed of light cant
depend upon motion of the observer
Principle of equivalence effects of the force of gravity are
indistinguishable from those of acceleration
PEOPLE
Walter Baade, Fritz Zwicky
Theory of neutron stars
Jocelyn Bell
Discovered unknown source of rapidly pulsating radio waves -
pulsar
LECTURE 34
3 questions
2 people
Light bends in presence of massive object
Perihelion advance of planet Mercury
Gravitational redshift of photons leaving a star
Time delays of Viking radio signals
Neutron degeneracy cannot support neutron star whose mass is
greater than 3 solar masses
VOCAB
Heavyweights (very massive stars) core has mass greater than 3
solar masses and it swallows itself as a black hole
Schwarzschild Radius radius of a black holes event horizon, no
light can escape from it
Black hole object whose escape velocity exceeds speed of light
and radius is equal to or less than s radius
Event horizon surface of sphere around a black hole from which
nothing can escape, radius is s radius
Supermassive black hole contain mass of several hundred thousand
or more stars
Population I stars heavier elements in atmospheres, young stars,
includes sun
Population II stars contain very little material in atmpsheres
other than hydrogen and helium, old stars
PEOPLE
Daniel Popper
First measured the gravitational redshift of photons for a white
dwarf star
Joseph Taylor, Russel Hulse
Discovered binary pulsar
Karl Schwarzschild
First to point out that there was a solution to one of Einsteins
Field Equations in theory of general relativity which has a
singularity (point of infinite density and zero volume) as one
possible solution
Schwarzschild Radius radius of a black holes event horizon
Steven Hawking
Claimed that black holes might disappear or evaporate when the
particles inside them would meet anti-particles from outside
universe
Angular momentum can be removed from spinning black hole even
though no mass can escape
Claimed that entire universe might be viewed as one gigantic
black hole
John Wheeler
First to use the term black hole
Walter Baade
Used Mt. Wilson telescope, multiple stellar populations in our
galaxy
Thomas Wright
Theory of the Universe, said that sun is a disk shaped system of
stars
Immanuel Kant
Introduced Island universes
William Herschel
Counted numbers of stars in different parts of sky and came up
with grindstone model of milky way
Jacobus Kapteyn
Concluded that earth is at the center of the galaxy
LECTURE 35
6 questions
3 people
Galaxy has 5 components disk, nuclear bulge, nucleus, halo,
galactic corona
Sun takes 250 million years to complete revolution around center
of galaxy
Mass of inner galaxy estimated at 110 billion solar masses
VOCAB
Globular star cluster spherical group of up to hundreds of
thousands of stars, found primarily in the halo of the galaxy
Disk flat dense portion of a spiral galaxy that rotates in plane
around nucleus
Nuclear bulge central region of spiral galaxy
Nucleus very central part of nuclear bulge, thought to contain
supermassive black hole
Halo part of spiral galaxy on both sides of disk, spherical in
shape, comprised of stars, star clusters, and gas
Galactic corona hot, ionized gas in outer part of the halo
Galactic rotation curve graph of orbital speed of objects in
galactic disk as function of their distance from the center
Spiral galaxy disk-shaped galaxy with arms in spiral pattern
PEOPLE
Harlow Shapley
Tried to determine suns location in galaxy using globular
clusters
Used Henrietta Levitts discovery of Cepheid period luminosity
relationship
Showed that galaxy is larger than Herschel had imagined
Moved the solar system away from center of the galaxy
Considered first 20th century equivalent of Copernicus
Oort, Lindblad
Used patterns of velocities of stars to show that center of
galaxy is thousands of light years away in direction of
Sagittarius
Adriaan van Maanen
Mistakenly concluded that he could detect the rotation of
nebulae which were in fact galaxies
Shapley
Argued that milky way was large enough to contain all of the
known stars and nebulae
Curtis
Argued that milky way was not this large and there were other
galaxies in the universe
Hubble
Found Cepheid variables in 3 spiral nebulae, proving that they
were actually spiral galaxies
Demonstrated that milky way is not the only galaxy
2nd 20th century equivalent of Copernicus
LECTURE 36
10 questions
3 people
Four major galaxy types:
Elliptical
Class of galaxies that have smooth spheroidal shapes
Classified from round (E0) to very elongated (E7)
Most galaxies in existence are ellipticals, but most are smaller
than spiral galaxies
A few giant elliptical galaxies have 1013 stars and are thus
larger than any spiral galaxy
Contain primarily old, population II stars, appear to have
little gas or dust in them
Spiral
Normal spiral - S
Barred-spiral Spiral galaxy in which the spiral arms come from
the ends of a straight bar running through the nucleus rather than
from the nucleus itself , SB
Each type is further subdivided into Sa, Sb, Sc, depending on
how large the nuclear bulge is and how tightly the spiral arms are
wound around the nucleus
Sa largest nuclear bulges and the most tightly-wound arms
Sb middle-sized bulges and moderately-wound arms
Sc smallest bulges and loosely-wound spiral arms
S0 appear to have disk like spirals but have no spiral arms at
all
Most spiral galaxies are from 50,000 -200,000 light years across
and contain from 109 to 1012 stars.
4 sub-classes of barred spiral galaxies:
SB0 bar and a disk, no spiral arms
SBa bars, large bulges, tightly-wound spiral arms
SBb bars, medium-sized bulges, moderately-wound spiral arms
SBc bars, small bulges, loosely-wound spiral arms
Total of 8 different types of spiral galaxies
Contain both old (population II) and young (population I)
stars
Contain both gas and dust and have star formation going on
Irregular
Galaxy of irregular shape that cannot be classified as spiral or
elliptical
Fewer than 20% of all galaxies
All small, fewer than 25% stars in Milky Way
Galaxies exhibit no proper motion
Evidence of past collisions has to come from present
appearance
When galaxies collide gas and dust interact, but few collisions
between stars
Most important properties of a galaxy that we can measure are
its distance, mass, and motion
Summary of galaxies:
Elliptical: E0 E7 galaxies that appear circular (E0) to very
elongated (E7)
Spiral Sa Sc Sa, large nuclei and tightly wound arms, Sb small
nuclei and open arms
Barred spiral SBa SBc spirals with elongated nuclei
S0 S0 Disklike, no spiral structure
Irregular Ir do not fit into any other category
Distances measured by distance indicators:
Cepheid variables are excellent distance indicators but can be
seen in only relatively nearby galaxies, out to perhaps 20 million
light-years
Bright syars (giants, supergiants, novae) can be used as
distance indicators
Large globular clusters and supernovae are of consistent
brightness so they can be used to determine distances to more
distant galaxies
These objects allow astronomers to determine distances to about
100 MLY
VOCAB
Hubble Law law of the redshifts by Hubble and Humanson, showed
that the universe is expanding, and this work is the foundation for
todays theories of cosmology, not due to Doppler effect, v = H0d, v
radial velocity, d distance, h hubble constant
Cosmology study of the nature and evolution of the universe as a
whole
Hubble constant proportionality constant in the Hubble Law,
ration of the recessional velocities of the galaxies to their
distances
Local Group - cluster of 28 or so galaxies that includes our own
Milky way galaxy
Missing mass difference between mass of clusters of galaxies as
calculated from Keplerian motions and the amount of visible mass
seen in photos
Cold dark matter matter that is too cool to emit sufficient
radiation to allow us to detect it
PEOPLE
Edward Hubble
Divided galaxy into normal and abnormal
Developed tuning form diagram
Everything is Hubble
LECTURE 37
4 questions
No people
Methods of Measuring Masses of Galaxies:
Observing rotation periods of some parts of it using Doppler
shift data then applying keplers law
Use pair of galaxies revolving around each other, but difficult
to determine the angle of the plane of revolution to our line of
sight
Utilizing their clustering, gives mass values for clusters that
are much greater than is accounted for by the visible stars within
the galaxies in the cluster
VOCAB
Supercluster group of clusters of galaxies
Local supercluster contains the local group and the virgo
cluster. 60% of the members are contained in dislike structure
Peculiar galaxies abnormal shapes which suggest that either
explosions have occurred in them or that they are the result of a
collision between two otherwise normal galaxies
Radio galaxy galaxy having greatest luminosity at radio
wavelengths, often exhibit unusual jets in visible light
Cygnus A first radio galaxy discovered in 1951 and has a
double-loved radio source associated with the visible light
image
Active galaxy galaxy with an unusually luminous nucleus, Seyfert
galaxies and N galaxies, aka active galactic nuclei
Quasar (quasi-stellar source, QSS) small, intense celestial
source of radiation with a very large redshift
Local hypothesis proposal stating that quasars are much nearer
than a cosmological interpretation of their redshifts would
indicate
Seyfert galaxy one of a class of spiral galaxies having active
nuclei and spectra containing emission lines
N galaxies have brighter nuclei than Seyfert galaxies
BL Lac objects (blazers) especially luminous active galactic
nuclei that vary in luminosity by a factor of up to 100 in just a
few months
Gravitational lens phenomenon in which a massive body between
another object and the viewer causes the distant object to be seen
as two or more identical objects, or as an arc, or as a complete
ring
Isotropy states that the universe looks the same in all
directions
Cosmological principle the basic assumption of cosmology, which
held that on a large scale, the universe is the same everywhere
Universality says that the universe obeys the same physical laws
everywhere
LECTURE 38
7 questions
3 people
Freedmanns Models:
Three possible geometries:
Closed one in which parallel lines will eventually close back
upon themselves, will eventually stop its current expansion and
collapse back in upon itself based on Riemannian geometry
Flat one in which two parallel lines will always remain
parallel, will continue to expand but slow the rate until it almost
stops, the sum of the three angles in a triangle is exactly 180 in
this model based on Euclidean plane geometry
Open one in which parallel lines will diverge, geometry of a
saddle, the expansion of the universe will continue forever and
will not slow down as much as in the flat model based on hyperbolic
geometry
Key theoretical ideas
Extremely high density of matter could exist in the early
universe
Particles of matter could form spontaneously from quantum
fluctuations of pre-existing energy field
Virtual pair particles cannot be observed because they last for
too little time
Quarks and leptons are the most elementary of particles
Four forces of nature strong nuclear force, electromagnetic
force, weak nuclear force, gravitational force were all once
unified into single force
Phase transitions existed in which these 4 forces became
separated from one another, they liberated energy
One phase transition caused the early universe to inflate very
rapidly for a very brief moment of time in the past
Big Bang
Universe started as scalar field
Something caused the spacetime filled by this scalar field to
begin to expand
Planck Epoch force of gravity became decoupled from the other
three forces
Grand Unification Epoch - 10-43 to 10-35 second
All matter and energy were interchangeable and in equilibrium
and the remaining 3 forces were combined into one
Quarks and leptons and their anti-particles were constantly
colliding with each other and energy was liberated from
collisions
Two photons of energy could collide and generate a
particle-anti-particle pair if their total energies exceeded Mc2,
where M is their combined rest mass.
Matter, anti-matter, and photons were all thought to be in equal
amounts at that time
VOCAB
Einstein ring a complete ring
Cosmological redshift shift toward longer wavelengths that is
due to the expansion of the universe, the expansion of space
itself, the expanding space lengthens (redshifts) an already
emitted wave
Standard Model of the Big Bang developed by Robert Wagoner,
William Fowler, and Fred Hoyle, states that universe began at t=0
in a state of infinitely high temperature and density
Cosmological singularity state of infinitely high temperature
and density, we dont believe that such a singularity can exist
Planck Density - 1094 gm/cm3
Scalar field unstable, vacuum-like state of pure energy
Flatness problem inability of standard big bang model to account
for the apparent flatness of the universe
PEOPLE
Alexander Freedmann
Russian mathematician
One of first people to make use of general relativity in
cosmology
Georges Lemaitre
First to propose a model for the Big Bang
Thought that one primeval atom fragmented into many pieces and
that cosmic rays were the radiation from the Big Bang
He was wrong
George Gamow
First to suggest that universe started as fundamental particles
which were fused together into heavier elements during the Big
Bang
Robert Wagoner, William Fowler, and Fred Hoyle
Developed the standard model of the Big Bang
LECTURE 39
10 questions
5 people
Inflationary Epoch
Temperature dropped and universe underwent a phase transition in
which the strong nuclear force split off
Rapid expansion caused the energy density of the scalar field to
decrease more slowly
Exponential expansion
At the end, the rapid inflation ceased and scalar field
oscillated around minimum value of its energy density
Quark Soup
Quarks and anti-quarks combined into heavier particles called
hadrons (baryons, anti-baryons, mesons, anti-mesons)
Weak nuclear force and electromagnetic force separated during
this epoch
Era of Nucleosynthesis (Big Freeze-Out)
Almost all of our current helium, deuterium (heavy hydrogen),
and some lithium nuclei were created in a series of nuclear
reactions
Opaque Era
Between 100 seconds and 379,000 years after the big bang
Remaining free photons and helium, deuterium, and lithium nuclei
moved about in an opaque sea of photons, electrons, nuclei, and
neutrinos
Recombination Era
From 379,000 to 1,300,000 years after the big bang additional
electrons re-combined with nuclei to create even more neutral
atoms
VOCAB
Inflationary universe model modification of the standard big
bang that holds that the early universe experienced a brief period
of extremely rapid expansion
Symmetry breaking release enormous amounts of energy
Horizon problem inability of standard big bang model to account
for directional uniformity of the background radiation
Cosmic Microwave Background Radiation redshifted photons from an
apparently cold black body are the best evidence that we have today
that the Big Bang actually occurred
COBE Cosmic Background Explorer, satellite that successfully
measured the background radiation at various wavelengths
Cold Dark Matter massive particles which are traveling with
small velocities relative to the speed of light
Hot Dark Matter less-massive exotic particles which are
postulated to be traveling close to the speed of light
PEOPLE
Alan Guth
MIT, proposed the inflationary model in the early 1980s
Ralph Alpher and Robert Herman
First to suggest that radiation existed
Predicted that photons should be seen at the earth as radio
waves having a temperature only a few degrees above zero
Robert Dicke
Princeton physicist made plans to search for the radiation
Robert Wilson and Arno Penzias
Bell labs, accidentally discovered background radiation while
they were doing applied research on microwave transmission
Awarded the 1978 Nobel prize for their discovery
LECTURE 40
6 questions
No people
Will the expansion stop?
Best way is to compare the recession speeds of distant galaxies
to speeds of nearby galaxies
Determine the overall density of matter (and energy) in the
universe. If dark matter exists, the universe is barely dense
enough to lie on the boundary between open and closed
VOCAB
Hubble Time maximum possible age of the universe, equal to the
reciprocal of the Hubble constant
The oscillating universe theory big bang theory that holds the
universe goes through repeating cycles of explosion, expansion, and
contraction
Hubble Diagram plot of radial velocity versus distance
Flat universe borderline case between open and closed, the
gravity just balances its expansion so that it stops expanding only
in an infinite amount of time in the future
Critical density density of a perfectly flat universe
cD - Supergiant, ellipticals central, dominant
Dwarf ellipticals smallest ellipticals
