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230 Cards in this Set

  • Front
  • Back
Celestial Sphere
the illusion that stars lie on a sphere surrounding the earth


-illusion bc lack depth perception when look into space (bc stars so far away)

-helps us map the sky
Celestial Equator
projection of Earth's equator into space
(complete circle around celestial sphere)
Celestial Poles
point directly above earth's N pole

point directly above earth's S pole
path the sun appears to follow when circling around the celestial sphere

-crosses celestial equator at 23.5* bc thats the TILT of earth's AXIS!
imaginary halr circle from S horizon through the zenith to N horizon

(zenith = direct pt overhead)

-used as reference for locating objects
spinning of object around axis

(earth rotates once on axis a day)
(axis = imaginary line from N pole to S pole thru center of earth)
orbital motion of one object around another

(earth orbits sun once each year)
slowly / gradually changes orientation of earth's axis
-direction axis is pointing changes

-bc axis now points to Polaris thats the north star (so N star will change over time)

-does NOT affect amt of axis tilt (or season pattern)
-causes constellations that correspond to the solstices & equinoxes to change (bc that depends on the direction earth's axis pts in space)

--caused by gravity's effect on tilted, rotating object thats NOT a perfect sphere
-stays upright bc rotating objects tend to keep spinning around same axis [law of conservation of angular momentum]-- prevents gravity from pulling top over
Solar System
the sun and all the objects that orbit it

[planets moons, asteroids (rock chunks), comets (ice balls), & particles of interplanetary dust]
an island of stars in space

-a few hundred million to > a trillion stars

(Milky Way = large: >100billion stars
--our solar system = halway from center to edge of disk)

**individual galaxies do not expand while universe continues to (due to gravity)
Galaxy Clusters
groups of galaxies

(we're in the LOCAL GROUP)
areas where galaxy clusters are tightly packed


-between these galaxy groupings is huge empty space
sum total of all matter and energy

-including all superclusters and all voids between them
"cosmic address"
--Solar System
---Milky Way Galaxy
----Local Group
-----Local Supercluster
Big Bang

(age of universe?)
when universe expansion began

-produced only 2 elements:

(14 billion years ago)

-first / simplest atoms created
-more complex atoms created in stars
-when stars dies atoms expelled into space to make new stars / planets *we're starstuff*
Scale of the Universe
-10 Billion Light Years across

-~10^22 stars in the universe
Universe when Sun = grapefruit?
Earth = ballpoint

Jupiter = marble
Life of Stars
Birth = in clouds of gas / dust

shine due to NUCLEAR FUSION:
-atomic nuclei smash together and stick to make heavier nuclei (happens thruout life)

DIE: when it exhausts all usable fuel for fusion

---->splits off & can eventually form new stars / planets
all elements besides
Hydrogen & Helium
were made by:


age of solar system?
~ 4.6 bya
speed of light
300,000 km/s

(light takes 8 min from sun to earth)
10 trillion km / yr

---- measures how long it takes stars to reach us (bc so far away)

*unit of DISTANCE not time*

*the farther we look in the distance the further we look back in time*
"observable universe"
portion of the entire universe that we can potentially observe

(beyond that - 15 bill light years would be looking to before the universe existed -- nothing to see)
nearest star?

(other than our sun)
Alpha Centauri

(4.4 light years away)
-3 star system
Earth rotates what direction

Sun & Stars appear to rise/set what direction?
(counterclockwise from above N pole)

--why Sun / Stars APPEAR to
Ecliptic Plane
a flat plane defined by earth's orbital path

(1 AU = line from earth to sun on plane)
Earth orbits sun what direction?

(same direction it rotates)
*the entire milky way galaxy is rotating*
*also!**most of he mas of galaxy is located outside the visible disk in the galaxy's "halo"
--no light coming from it so termed "DARK MATTER"

*some galaxies orbit the milky way*

*milky way is moving toward the Andromeda Galaxy*
Hubble Telescope

(date & 2 facts)
1920s by Edward Hubble

1)virtually ever galaxy outside our Local Group is moving AWAY from us

2)the more distant the galaxy the faster it appears to be moving away

*due to the fact the ENTIRE universe is expanding
Think about universe in 4 dimensions
1) length
2) width
3) depth
1 km =

__ miles
1 km = .62 miles
1 AU =

__ miles
1 AU = 93,000,000 miles
1 Light-Year =

___ AU
1 Light-Year = 63,000 AU
1 Parsec =

___ Light-Years
1 Parsec = 3.26 light-years
the distance to an object with an angle of ONE ARCSECOND
is 1 parsec

(parsec is equiv to 3.26 light years)
region of the sky with well-defined borders

(set by IAU [international atronomical union])

--divided sky into 88 constellations
"angular size"
the angle it appears to span your field of view

*each degree is
divided into 60 arcminutes
divided into 60 arcseconds*
"angular distance"
angle appearing to seperate 2 objects

*each degree is
divided into 60 arcminutes
divided into 60 arcseconds*
circumpolar stars
near north celestial pole

-never rise or set
-ALWAYS above horizon

-make daily counterclockwise circles

-degrees N or S of the equator
degrees East of the
Prime Meridian

(prime meridian is 0* longitude)
how long is ONE revolution
of earth?
365 1/4 days
when in N hemisphere
all stars appear to rotate

(the N star)
at Equator all stars appear to move
vertically up & down
Summer Solstice
when sun is @ farthest pt North on Celestial Sphere

-moment when N hemisphere receives most direct sunlight
Winter Solstice
when sun is @ farthest pt South on Celestial Sphere

-moment when N hemisphere receives least direct sunlight
Vernal Equinox
day when sun is directly above celestial equator


-moment when N hemisphere goes from tipped away from the sun to tipped toward the sun
Autumnal Equinox
when sun is directly above celestial equator


-moment when N hemisphere goes from tipped toward the sun to tipped away from the sun
in winter we are NOT farther from the sun
our part of the globe is simply tilted away from the sun,
causing us to receive less energy

(longer shadows)
one complete precession (wobble)

-how long?
every 26,000 years
Lunar Eclipse
-moon passes thru earth's shadow

(earth between moon & sun)

*red moon*
Solar Eclipse
-moon's shadow moves across earth

(moon between sun and earth)

*ring of sunlight*
near objects appear in different places when viewed from different locations

-used by astronomers to determine distance
the constellations along the ecliptic

(the ecliptic is the path the sun takes on the celestial sphere)
during summer sunlight strikes at a steeper angle
the steeper angle makes sunlight more concentrated

-in summer the sun follows a longer and higher path thru the sky
--->days longer w/ short midday shadows
Qualities of the Equinoxes
-only 2 days of year that sun rises exactly due east and sets exactly due west

-2 days when sunlight falls EQUALLY on both hemispheres

-(summer solstice = 1st day of summer)

-reflect Northern seasons
(equator gets most direct sunlight on 2 equinoxes and least on the solstices)
N Hemisphere's seasons are more extreme than the S hemisphere's
-most of earth's land lies in N hemisphere
--ocean resists temp changes

-earth moves faster in orbit when closer to sun and slower when farther (moves slower during N hemisphere's summer -- when earth's farther from sun)(& N hemisphere's summer lasts couple days longer due to this)
length of

Moon's orbit
27 1/3 days

*moon's ~380,000 km from earth
"lunar phases"
the cycle of the moon as it moves thru the sky

-thru cycle appearance & times of rising and setting change

-phase depends on moon's position relative to sun as it orbits earth
phases of moon result from 2 qualities
1) half the moon always faces the sun while other half faces away

2) as you look at the ball at different positions in orbit you see different combinations of bright & dark faces

*different phases reach their highest pts @ different times
waxing phases
phases from new to full
waning phases
phases from full to new

(waning = decreasing)
moon phases listed
-new moon

-waxing crescent

-1st Quarter

-Waxing Gibbous

-Full Moon

-Waning Gibbous

-3rd Quarter

-Waning Crescent
"synchronous rotation"
the fact that the moon rotates once on its axis in the same amt of time it makes 1 orbit around earth

**CAUSES US TO ALWAYS SEE THE SAME FACE OF THE MOON**(though see different phases)
New moon occurs ....
when moon is between sun & earth

*if on moon you see full earth when its a new moon*
{*always the OPPOSITE phase! if u were on moon*}
moon passes thru ecliptic plane
only twice each orbit
the 2 pts in each orbit @ which moon crosses the ecliptic plane
2 conditions for an eclipse to occur:
1) phase of moon must be
full (for lunar)
or new (for solar
-bc these are the only phases in which earth moon & sun lie in a straight line)

2)the new or full moon must occur when the nodes of the moon's orbit are aligned w/sun and earth (because thats the only time new and full moons are on the ecliptic plane)
where sunlight is completely blocked (central)
where sunlight is only partially blocked

(lighter than umbra)
lunar eclipse

when happens
when total / when partial
begins the moment moon's orbit carries it into earth's penumbra

(passes thru earth's umbra when perfectly alligned [total lunar eclipse])

Partial Lunar Eclipse:
-only part of full moon passes thru the umbra

Penumbral Lunar Eclipse:
-moon passes thru earth's penumbra only
time when moon is entirely engulfed in the umbra in

dark and red (due to earth's atmosphere scattering some sunlight)
Solar Eclipse
Total Solar Eclipse:
-anyone in the area where moon's umbra touches earth's surface

Partial Solar Eclipse:
-anyone w/i the moon's penumbral shadow (only part of the sun blocked from view)

Annular Eclipse:
-when moon's far away from earth & umbral shadow doesn't reach earth
"eclipse seasons"
2 periods each year when nodes of moon's orbit are aligned w/ sun
"saros cycle"
eclipses recur in cycle of ~ 18 yrs & 11 days
5 planets to see w/ naked eye

-early evening / early morning

-reddish color

-2nd brightest when visible

"apparent retrograde motion"

of the planets
planets usually move eastward relative to stars but occasionally reverse course & move westward
"steller parallax"
apparent shifting of stationary object when looking from different locations (or different eyes)

*why greeks rejected a sun-centered model*

-stars are so far away that stellar parallax is undetectable to naked eye
[nearby stars should appear to shift back and forth against distant stars bc we view stars from different places in our orbit at different times]
ancient astronomy

how old?
17,000 BC
benefits of keeping track of astronomy
social / religious needs

agriculture (when to plant / harvest)

religion (gods control heavenly events)
ancient egyption astronomy
-used diurnal motions as a clock

-developed 365 day calandar

-some pyramids associated w/ important celestial events

ancient astronomy
-developed 60 based counting system
(still used for min, sec, angles)

-tables of planetary motion

-prediction of eclipses
&heliachal rising (first appearance after being too close to sun)


ancient astronomy
-records well preserved -- date back 3000 years

-oldest records of comets / eclipses / sunspots

-**Recorded supernovae**

-astronomy was tied to gov't

-astr declined in imp after 1200 AD

ancient astr
-defined modern constelations & many star names

-developed mythological stories about constellations
mayans of central america

ancient astr
-complicated, highly accurate calandar system

-precise tables for motions of moon & venus

-timed some wars on positions of venus & jupiter

-predicted eclipses

-milky way was "origin of all life" "world tree"

-built many observatories correlated w celestial allignment
Incas of S america

ancient astr
Cuzco (capital) laid out to mimic sky &
point to specific horizon risings

--sun's movement thru pillars marked time to plant at different altitudes

--nearly every temple had astrological allignments

ancient astr
-stonehenge 2000 bc
--->prob not associated w/ astr calendar
native N americans

ancient astr
-tracked stars to predict season change
----indicated when time to relocate
heliocentric universe

-planets revolve around sun
geocentric universe
developed by ancient greeks
-advocated by church

-didn't explain varying motion of the planets
-heliocentric universe

-determined mercury & venus closer to the sun than earth

-estimated rotation periods and distances between planets & sun

-oversaw building of first modern observatory

-first to record detailed motions of planets

-recorded magnitude / brightness of supernovae (exploding star)

----disproved greek notiont that stars are close to earth and never change

worked w/ brahe

developed 3 laws of planetary motion:
1)a planet's orbit is an ellipse w/ the sun at one focus

2)planets speed up when near the sun

3) P^2 = a^3
(P = orbital period (yrs)
a = length of semi-major axis)
---plants closer to sun have shorter year than those farther away
discovered jupiter's moons
(not only earth has satellites)

-telescope observations supported heliocentric view

-church put him under house arrest
first to decribe
-physical motion
-concept of gravity
-unified physical view of the universe

-invented calculus

-until him no one understood why planets moved

-developed model that showed gravity was responsible in keeping planets in orbit

-mathematically proved kepler's 3 laws of planetary motion
Newton's laws of motion
1) Law Of Inertia:
-obj at rest will remain at rest -obj in motion will remain in motion
-unless acted upon by an outside force

2)F = (m)(a)
-force = (mass) (acceleration)

-force causes accelleration (change in velocity)
-force causes change in momentum
-weight = (mass)(g)

3)for every force there is an equal and opposite reaction force
because of newton we now know....
earth has an equatorial bulge (from moon pulling on us)

-led us to discover neptune
ealiest known astronomical records?

-predicted weather from moon

-Carved Lunar Calendar
Seven days a week from?
seven naked-eye objects that appeared to move among constellations:

Sun, Moon, & 5 planets recognized
[mars, mercury, jupiter, venus, saturn]
obelisks determined time of day

-divided day & night into 12 parts ---> varied in length bc amt of daylight varies during the year

-eventually built water-clocks (like hourglass)
determining time of day at night

(ancient people)
-by position and phase of moon
[first quarter moon sets ~ midnight]

-positions of the stars
[different constellations rise at different times during different months]
the study of ancient structure in search of astronomical connections?

-evaluates structures to see any particular astronomical allignments

--oriented with cardinal directions
developed arithmetic for later astronomical calculations?

-adopted model that allowed him to calculate a planet's orbital period & distance from sun

-beleived orbits must be perfect circles STILL
observed a supernova (explosion of a distant star) -thought it was a nova (new star)
-proved it was farther away from the moon by measuring its parallax

*Best set of naked-eye observations ever made

-couldn't detect steller parallax --> concluded earth was stationary w/ sun orbiting it while other planets orbit the sun
-hired by brahe


-orbits are Ellipses

-3 laws of planetary motion
Keplers 1st
law of planetary motion
the orbit of each planet is an ellipse with the sun at one focus

{tells us planet's distance from sun varies during orbit
--closest @ perihelion
--farthest @ aphelion}
Keplers 2nd
law of planetary motion
as a planet moves around orbit it sweeps out equal areas in equal times

{planets travel faster when they're closer to the sun
-moves the greater distance @ perihelion
& shorter distance @ aphelion
in same amt of time}
Kepler's 3rd
law of planetary motion
more distant planets orbit the sun at slower speeds
obeying mathematical relationship
p^2 = a^3
(p = planet's orbital period, a = avg distance in astronomical units)

--suggested planetary motiomn might be the result of a force from the sun
answered the 3 objections to a sun based model:::

-demonstrated moving objects remain in motion unless a force acts upon it
[birds & such should stay w/ moving earth, not be left behind]

-built a telscope - saw sunspots w/imperfections
[heavens aren't perfect]

-provided strong evidence that stars were far enough away to be unable to detect steller parallax
Ancient Aristotle
model of the universe
-all spheres responsible for celestial motion transparent & interconnected

-earth @ center explained by gravity

-gravity pulled heavy things toward center of universe & allowed lighter things to float to heavens
the apparent positions of the sun moon and planets among the stars influence human events

-predictions far less reliable than astronomical ones

-we know now that patterns of the stars in constellations are accidents
-and constellations are only the apparent associations of the stars
sidereal day
how long it takes for a star to go from its highest point one day to its highest point the next

(23 hrs 56 min)

represents 360* rotation of earth
solar day
our 24 hour day

-the time it takes the sun to make one circuit around the local sky
(from its highest point one day to its highest point the next)

*4 min longer than the sidereal

*represent ~361* rotation of earth (makes the 4 min)
synodic month
month comes from the moon's 29.5 day cycle

-the time required for each cycle of phases

-not moon's true orbital period
sidereal month
moon's true orbital period

-only ~ 27.33 days

(how long it takes moon to complete orbit relative to position of distant stars)
sidereal year
time it takes for earth to complete one orbit relative to stars
tropical year
20 min shorter than sidereal year

-in sync w/seasons
-time from spring equinox to spring equinox

(bc each year location of equinoxes and solstices shifts amoung the stars ~ 20 min worth)
a planet's
"sidereal period"
time planet takes to orbit sun

measured relative to stars
"synodic period"
time between when it's lined up with Sun one time and the next time its similar in alignment
when planet is opposite the sun of earth

(planets closer to sun can experience this as "superior conjunction)
when earth is between the sun and the planet

(planets closer to sun can experience this as "inferior conjunction"---they never have an opposition)
apparent solar time
base time of sun's actual position in local sky (sundials)

-noon = precise moment when sun's highest in sky
Newton's first law of Motion
objects in motion stay in motion
objects in rest stay at rest
-unless acted upon by an outside force
Newton's 2nd law
Force = (mass)(accelleration)
Newton's 3rd law
for every action there's an equal and opposite reaction

-explained why planets move

-developed model that gravity is keeping planets in their orbits

-mathematically proved kepler's 3 laws

-can now determine mass of objects, their orbits, how much force they exert on eachother

-earth has an equatorial bulge (from moon pulling)

-discovery of planet neptune

-applications of calculus

1905 & 1915

(special & general relativity theories)
2 observations for relativity
1)your description of reality is the same regardless of the constant velocity you're moving

2)speed of light is constant
and nothing is faster
3 results of special relativity
1) length of object decreases as speed increases

2)clocks passing by you move more slowly than clocks at rest {time dilation}
---time and space cannot be seperated & equal the single entity of "spacetime"

3)mass of an object increases as it moves faster
E = mc^2
newton was wrong!
newton's physics of gravity can describe small objects but don't work when applied to massive bodies or really fast speed
einstein says objects warp the space around them
gravity doesn't attract objects the curvature of space draws them together
even things without mass would be attracted toward a massive body

(says einstein)
like light

-black holes
Types of Energy
-Kinetic (energy of motion)

-Potential (stored)

-thermal (heat)

-radiative (light)

-mass-energy (e = mc^2)
E = mc^2
laws of energy
1)can't be created or destroyed

2)can be converted from one form to another
"phase changes"
occur when thermal (heat) energy is added to matter

-increasing thermal energy causes bonds to break

-decreasing thermal energy produces stronger bonds
plasma phase
extreme heat

-free electrons move amoung + ions

-molecular dissasociation
gas phase
atoms / molecules essentially unconstrained
liquid phase
atoms / molecules remain together but move freely
solid phase
atoms / molecules held tightly in place
electromagnetic radiation
speed of light?
300,000 km /sec
light properties?
both a Partical
and a Wave
light's wave-like properties
-shadow edges aren't crisp

-different colors of light have different wavelengths
light's partical-like properties
-can knock electrons of a surface
(photoelectric effect)
visual light

(optical spectrum)
-blue = shorter wavelengths

-red = longer wavelengths

-white light = all the colors

-water & ice act as prisms seperating colors
UV rays
waves short of our detection
(shorter than blue)
IR (infrared) rays
waves long of our detection
(longer than red)
Telescope types:

refractor telescope
uses lenses to produce image

-good for close bright objects (planets, moon)

-lense causes distortion
-different light wavelengths focus on different points
-size limitations
reflector telescope
uses mirrors to produce images

-better for distant dim fuzzy objects

-blocked light from secondary mirror
-light focuses on different distances
purposes of telescope

resolve (sharpness)

problems observing atmosphere from earth
atmosphere of dust/gas/h2o/ice causes stars to twinkle

-spherical atmosphere causes distortion of shape/position/color

-light pollution
hubble space telescope
-orbiting earth since 1993

-gathers UV, IR, & visible light

(clear images of planets)
Charge Coupled Devices

photographic film for astronomers

-silicon square divided into light sensitive cells (pixels)

-viewed/processed on computers
radio astronomy

(radio telescopes)
telescopes can look @ radiowaves

-radio dishes can be combined to form better image

-useful in detecting features like black holes
metonic cycle
by ancient greek astronomer

-19 year cycle

--bc takes 19 years for the lunar phases to repeat on the same dates
18-year saros cycle
--predicted eclipses
sacred round
mayan cycle

260 days

-eclipse prediction
first proposed sun-centered modeL?

how did greeks explain "apparent retrograde motion"

for their geocentric modeL?
"Ptolemaic Model"

-each planet moves around earth on a small circle that turns around a larger circle
celestial coordinates
coordinates are

[similar to latitude]
-parallal to celestial equator
-celestial equator = 0*
-labeled POSITIVE or NEGATIVE (not N/S)

[similar to longitude]
-0 = line that runs thru spring equinox (same as longitude)
-measures in HOURS (not E/W)
---full circle = 24 hrs
----each hr represents 15*
stars w/
declination of:
0*: lie on celestial equator
-rise due east - set due west

>0*: rise N of due east
-set N of due west

<0*:rise S of due east
-set S of due west

spacecraft goes past planet & continues

orbits planet its studying

-longer term study
lander / probe

lands on surface
probes atmosphere

designed to return a sample
how far it'll go in a certain amt of time
tell us speed AND direction
if its velocity is changing

-a change in speed or direction or both
you don't feel any effect of moving when
acceleration of gravity

earth: increases by 10 m/s
how do u change an object's momentum?
only by applying a FORCE
falling without any resistence

-whenever there's nothing to prevent you from falling

-astronauts weightless when orbiting earth bc in constant state of free fall
(there is gravity in space)
newton's third law

for every force there's an equal and opposite force

-much greater acceleration for you than earth (bc you're so much smaller)
white light
black light
white :
all colors mixed in equal proportion

black light
absence of color
how light & matter interact
-emits light (turn on bulb)

-hand near a light -- hand absorbs light -- energy warms hand

-glass / air - allow light to pass thru

-light bounces off matter
-reflection = bouncing in same direction
-scattering = random bouncing
distance from one peak to the next
number of peaks passing by a pt each second
frequency can also be reffered as
cycles per second

speed of wave?
(wavelength)(frequency) = speed
strength of force any particle would exerience @ a pt in space

-earth's gravitational field depends on earth's mass and the distance pt is from earth
light's "field"
light waves are vibrate electric AND magnetic fields

-vibrations of electric field - electron goes up and down
wavelength & frequency related
longer the wavelength
the lower the frequency
light's individual particles

-can be counted individually
-each have a wavelength & frequency

-shorter the wavelength, the higher the frequency == THE HIGHER THE ENERGY OF ITS PHOTONS
electromagnetic spectrum
the complete spectrum of light

visible = 400-700nm

gamma --- xrays --- UV --- visible --- IR --- (microwaves) --- radiowaves
-longest(smallest amt of energy)
matter is composed of
-different types = different elements
atomic #
atomic mass
atomic number = # of protons in nucleus

atomic mass = protons + neutrons
(can vary -- isotopes)
atoms combine to form molecules

(O2 molecule = two O atoms)

-molecules w 2+ types of atoms = compounds (H2O)
phase changes occur..
when one chemical bond is broken & replaced by another
the process that molecules escape from a solid
(some gas always present with solid ice / liquid water)
process by which molecucles escape from a liquid

[high temps = higher sublimation & evaporation]
molecular dissociation
at high enough temps collisions between molecules so violent they break chemical bonds holding individual h2o molecules together

molecules split into peices
@ temps HIGHER than molecular dissociation

collisions break bonds holding electrons around nuclei of an atom
allowing electron to go free

-leaves remaining atom w + charge

(the process of stripping electrons from atoms)
hot gas in which atoms have been ionized
(can be reffered to as gas or plasma... ex. the SUN!)

at temps HIGHER? than ionization

whats left becomes a hot gas of freely moving electrons & + charged ions of H &O
force / unit area
pressure's effect on state changes
higher pressure = needs higher temps to change state

(stay solid longer... & such
what particles can interact w light?
how can atoms contain energy?\

1) bc of their mass they posses mass-energy (mc^2)

2)kinetic energy bc of their motion

3)electrical potential energy
-depends on the arrangement of electrons around nuclei
energy stored by electrons in atoms
-electrons can have only particular amts of energy & not energy in between!!!
"energy levels" of an atom
the possible energies of electrons
lowest possible energy level for electron?
level 1
"excited state"
all possible energy levels other than ground state

(though they will quickly "calm" & return to ground state)
"energy level transitions"
only occur when electron gains or loses specif amt of energy seperating 2 levels
(any other amt and nothing will happen)

-the electron can gain enough energy to reach ionization level and will then escape the atom completely (ionizing the atom)

*energy levels differ from element to element*
process of obtaining a spectrum and reading info

(look like rainbows)
"intensity" (light)
the amount of radiation

-proportional to (number of photons @ that wavelength)x(energy of those photons)

-lot of light = high intensity
"continuous spectrum"
-common bulb
=spans a broad range of wavelengths w/o interruption
"emission line spectrum"
low density cloud
-emits light only @ specific wavelengths

-spectrum consists of bright emission lines against black background
"absorbtion line spectrum"
cloud between us and bulb

-cloud absorbs specific wavelengths but we still see most of the continuous light of bulb

--spectrum = dark absorption lines against background rainbow
when electrons go back to ground state...
they emid a photon of light (when they release that energy)

-the photon released has the same energy the electron lost
=== specific Wavelength & frequency
"chemical fingerprints"
hydrogen emits and absorbs light at specific WL's = can detect its presence in distant objects (only H produces a certain set of lines)

-molecules can vibrate and rotate and also produce spec. spectra (molecular bands)
thermal radiation
the temperature dependence of light
-photon energies depend only on objects temp (not what obj made of)
hotter object emit photons....
hotter = emits more light

hotter = emits photons w higher energy (shorter wavelengths)

-first turning on light glows red ... hotter gets blue

-cool star = red light

-hotter stars = blueish
doppler effect
moving toward you - higher pitch
-each pulse a lil closer
-waves get bunched
--gives them shorter WL
--higher frequency

moving away from you - lower pitch
-each pulse from farther away
-stretches out WLs
---giving them lower frequency
doppler effect applied to light
-moving toward us
-light waves bunch
-shorter WLs

-moving away
-longer WLs
"rest wavelengths" applied to light
the wavelengths of hydrogen lines in stationary clouds

-if lines appear longer = REDSHIFT

-lines seem shorter = BLUESHIFT

(can also tell if rotating)
how lens' work
light hits lens
-slows down
-causes light to bend
(farther from center = bent more)
-converge to pt - FOCUS
-forms image of original obj
-image appears on "focal plane"
"charge coupled devices"
-chip of silicon VERY sensitive to photons
-divided into grid (pixels)
-when photon strikes pixel == electric charge accumulates

-more sensitive to light than normal film
-accurately records 90% of photons that strike them
-can records BOTH DIM & BRIGHT light @ same time
telescope's "light collecting area"
how much total light telescope can collect at a time

-by diameter of lca
telescope's angular resolution
smallest angle over which we can tell 2 dots are distinct

-depends on their actual seperation & their distance from us

-larger = higher angular resolution
-earth's atmosphere limits angular resolution
telescope's "diffraction limit"
the angular resolution a telescope could acheive if it were limited only by light wave interference

-depends on diameter of telescops mirror & WL being observed

-larger telescops = smaller diffraction limit
use diffraction grating to seperate various colors of light into spectra -- then recorded w CCD

-can reveal chemical comp, temp, & rotation rate from spectrum BUT depends on SPECTRAL RESOLUTION
(higher = more detail)
--depends on how much spectrograph spreads out light...spreads out light too much = dim
"light curves"
graphs that show how objects intensity varies w time
arctic circle
antarctic circle
arctic = N

antarctic = S
difference between
"special" & general relativity
special - shows that space and time are intertwined - IGNORES gravity

general - offers new view of gravity --explains expansion of universe & black holes
-applies WITH OR WITHOUT gravity
theory of relativity leads to....
-no info can travel faster than speed of light

-moving faster = time moves slower

-moving faster = length is shorter

-faster = mass is greater
(E = mc^2)
2 absolutes of relativity
-motion is relative NOT everything

1)laws of nature same for everyone

2)speed of light same for everyone