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108 Cards in this Set
- Front
- Back
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How does electromagnetic radiation travel |
Travels the same speed through a vacuum and is given the symbol c (Latin=celeritas or swift) -changes with the medium in which light is moving |
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What is the c for water and glass |
Water (226,000,000 m/s) Glass (200,000,000 m/s) |
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Speed of light |
Is constant and unchangeable -space and time will change to accommodate this limit |
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History of speed of light |
Was measured in 1670 Predicted by Maxwells electromagnetism equations 200 years later |
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What is the consequence of speed of light |
See the object in the amount of time it takes to get to it |
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Speed of light traveling |
Light travel times are measurable in common units if time Ex. Moon is 1 light second distant so we see it as it was 1 second ago Ex. Sun is 8 mins Ex. Neptune is about 4 light hours away |
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What is the most distant object detectable to the human eye |
Neighbor galaxy if Andromeda -about 2.5 million light years away |
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What are galaxy clusters |
Groups of galaxies that are held together by the long range force of gravity from each galaxy (influencing each other) |
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What is the galaxy cluster we are in |
Milky way, andromeda, large magellanic cloud, small magellanic cloud and triangular galaxy |
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How far is the fornax galaxy cluster and abell 2218 |
Fornax (60 million light years from milky way) Abell (2 billion light years from milky way) |
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What is the cosmic microwave background |
Grayish glow in the sky like a featureless wall (Cant see any further than this point) -observable universe stretches to 13.77 billion light years |
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What is scientific notation |
Look at that book Ex. 9.5×10 power 15 |
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What is astronomic unit |
Distance unit 1 au is 1 earth sun distance (mean) 1au=1.5×10°4 |
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What are parsec |
Standard formal unit of distance - 1 pc= 3.26 light years 206265au in 1 parsec |
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Short wavelengths |
New orbiting observatories high above the opaque atmosphere now show the universe in short wavelengths such as uv and x Ray's |
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Long wavelengths |
New technology allows us to survey the universe at long wavelengths in Infrared radio |
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What are the 3 steps to a scientific approach |
1) process of observation of nature 2) construction of a model or some explanation (hypothesis) 3) testing b against a and revising b to better predict a (If cant be tested against nature it's a philosophy) |
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What is a law |
A well test theory. It has been proven many times |
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What is iterative |
Revising |
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What is the scientific theory |
The testing of your theory and revising it retesting it and revising it to converge towards a more complete model that predicts most aspect of observed phenomenon |
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What was the function of Stonehenge |
-3000BC to 2000BC -used as an astronomical observatory to allow an observer to predict eclipses, solstices, and equinoxes |
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What were the earliest recorded measurements of the sky motions |
From the ancient babylonian cities about 1800BC |
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What did the babylonians believe |
-heavenly motions told human fate ( 12 zodiac signs) -measured thr length of a year to be 360 which corresponded to thr 360 degree circle -charted planets (wanderers) |
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What did the cree and ininew atchakosuk people believe |
Through atchakos iskwew (star women) people came to earth to learn and teach then return to misewa - Mars was Kitom pampaniw (circles back) -also mooswa acak (moose spirit) because it circles back |
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What is the story of mista muskwa |
The big dipper-large aggressive bear that was a bully -2 birds sent it into the sky |
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Ancient Greek |
Was influenced by babylonian Astotelian thinking was motivated by observation Aristotle created model of universe -earth fixed in the center -sun, moon, planets are fixated to spheres centered on the earth -each sphere rotated around its center making it rotate around the earth |
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What us the stellar magnitude system |
Created by hipparchus (127BC) -catalogued stars into 6 classes of brightness called magnitudes -fainter stars correspond to higher magnitude numbers -magnitude scale is a logarithmic scale |
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Stellar magnitude system |
-A 5 magnitude difference corresponds to a factor of 100 in brightness -1 magnitude difference is a factor of 2 5 brightness -lowee magnitude= brighter stars |
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What did ptolemy do |
-created model of heavens motions based on circles upon circles idea -added a minor circle to each planets motion called epicycle motion -explained Mars circle back motion known as retrograde motion |
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What was eratosthenes |
-director of library in Alexandria -he set out to measure the eaths circumference -by placing a pole -dawn of quantitative measure in astronomy |
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What did pyyhagoreans suggest |
That the earth was round |
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What did nicholas copernicus do |
- advanced a heliocentric view (sun centered) in 1543 -switched the sun and earth in ptolemys model |
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Who was Johannes Kepler |
-1600 Kepler mathematically analyzed planetary motion trying to predict positions -if her restricted the planets to orbiting the sun in circles her could not predict - led to kepler 3 laws of planetary motion 1) planets follow elliptical patches |
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What are keplers 3 laws of planetary motion |
1) planets follow elliptical patches around the sun, which is located at one of 2 focus points of ellipse 2) planets orbital speed changes with its distance from the sun so that an equal area is swept out by the planets movement in a given time 3) the square of the period of revolution is proportional to the cube of the semi-major axis of the orbit |
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Look at law 3 |
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Who was Galileo galilei
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Was the first to use a telescope to the sky 1609-10 - observes many more stars and resolved the milky ways hazy glow into countless individual stars - moon was not perfectly round or smooth but had mountains, craters and maria( seas) -Jupiter had moons revolving it not the earth -sun was center of motion |
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What were Galileo's 3 key ideas that came from his experiments with falling bodies |
1) distance travellsd by a falling object is equal to the square of the time it has been falling 2) 2 objects of different masses fall to the ground at the same time 3) objects natural state is not at rest buy is to keep doing what it is doing |
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What did newton do |
-univerisal law of gravity -planets are held in orbit around the sun by the invisible string of gravity re-created astrophysics (applying physics and astronomical observations) |
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What are newton's 3 laws |
1) an object in motion will always stay in motion in a straight line unless acted upon by a force 2) force is the product of a mass and an acceleration 3) forces always come in pairs, a force acting on a body is always accompanied by an equal but opposite reactive force |
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What are the 5 ways we receive astrophysical info (1) |
Electromagnetic radiation -gives most extensive information -every waveland is observed |
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(2) |
Neutrinos |
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3 |
Gravitational radiation -gravity waves I-a disturbance in space and time by massive objects in non uniform motion |
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4 |
Cosmic Ray's -highly energetic charged particles continuously bombarding the earth -change direction from magnetic fields so their source cant be identified |
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5 |
Matter infall -interplanetary dust and meteorites from within the solar system and from mars and moon - no interstellar matter has been collected |
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What are the 3 things waves need |
1) source ( something accelerating or changing speed and disturbing its surroundings) 2) medium ( something to carry the message of disturbance) 3) energy ( waves carry energy away from the source and give it to the observer) |
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Know |
Speed of wave is only determined by the properties of the medium not the source or energy |
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What is an electromagnetic wave |
Light that is a wave of combined ele and magnetism -changing electric and magnetic fields create a self sustaining electromagnetic wave |
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What is a wavelength |
Length between wave crests |
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What is period |
The times it takes for the wave to complete one full un and down cycle |
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What is frequency |
Number of full up down up cycles the wave completes each second |
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Radiation ( term for light) |
Radiation we receive come in waves -wavelengths of visible light (uv, x ray, gamma ray) are measurable in nanometers |
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Atmosphere absorption |
-earthe atmosphere is selective -blockd wavelengths of radiation especially short wavelengths |
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What is a spectrum in spectroscopy |
The separating of light into component wavelengths called colors creates a spectrum of wavelengths -prism is used for visible light -digital electronics are used to so this in the radio domain |
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What are continuum spectra |
When stars emit continuous radiation meaning their spectra contains all wavelengths |
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What is an absorption spectra |
When we see the continuum of the star minus the lines that the nebula emits (Observing a hot star through a warm gas cloud) |
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What is bright line spectra |
Nebulae (clouds of warm interstellar gas) emit only discrete radiation that is only certain lines of radiation are emitted |
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Continuous spectra clors |
Stars range from blue-white to red. -realizee this is an indication of their temp -white is hotter than yellow which is hotter than red |
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What is wiens law |
The relationship between a stars surface temp and the brightest wavelength (colour) it radiates |
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What causes the lines in the emission line spectra |
Single atoms of each chemical element when heated radiates light with a different set of spectral lines |
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What did niels bohr do |
Constructed a model of the hydrogen atom where electrons orbit the proton (Hydrogen lamp emote a fuchsia light) A combination of 3 main lines |
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What are the 3 main lines to create the fuchsia colour |
Red (,hydrogen line) Turquoise (HB line) Blue violet (gamma line) |
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What is emission |
An electromagnetic emits a photon and drops to a lower energy state losing energy -photind energy is equal to the energy difference between 2 levels |
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What is absorption |
An electron absorbs the energy of a photon to go to a higher energy level |
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Know |
-absorption spectrum always shoes the same lines in the same relative positions so-so whether we see emission or absorption we can always identify hydrogen gas in astronomical objects like stars |
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Read |
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What is the doppler effect |
An object emits line and continuum radiation according to whatever elements are found in that object However if the object is in motion these line will appear at different wavelengths than they do when the object is at rest |
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What is the inverse square law of brightness |
-brightness is the amount of light arriving at a particular place -decreases as the distance from a light source increases -light obeyd an inverse square law |
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What is refraction (important for telescopes with lenses need this process to form an image) |
When light enters a material like water it moves slower and changes direction, the change in velocity and direction is refraction (bending) |
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What is a refraction telescope |
Uses the retractions of light in a glass lens to create and image of an object -has 2 lens 1) objective lens (large lens) 2) eyepiece (small lens) |
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What is the largest reflecting telescope |
Never exceeded 1 meter in diameter -a lens bigger than 1 meter would shatter under the stress of it's own weight |
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What is the path of light reflection |
(Ray of light can be changed by reflection) 1) a concave surface mirror will bring light into focus and form an image 2) secondary mirror can redirect the converging beam to focus in an accessible place for the eye lens or instruments |
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The reflection of radio radiation |
Path of Radio waves can also be changed through reflection off a metal surface and bundles of radio waves brought to a focus at a radio receiver |
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What type is the BUAO telescope |
Reflecting design called the ritchey chretien cassegrain 16 inches or 0.41 meters mirror Focal length of 3414mm |
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What are the 3 important measures of a telescope's power |
1) Light gathering power (Numbrr of photons a telescope can collect simultaneously) - related to the diameter of telescope (larger mirros=brighter images) -most important |
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What are the largest optial telescopes |
10m -twin keck telescopes -gran telescopio canarias |
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2 |
Resolving power (Smallest angular size the telescope can separate and image distinctly) -limiting angular resolution of any telescope is a function of its primary mirror diameter and the wavelength of light it collects |
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Angular separation |
Depends on distance -2 stars separated by a particular distance will have a larger angular resolution of they are nearby than if they are far away from the observer |
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What are the typical telescope resolutions |
- optical telescopes (0.5-2 arc seconds) -Hubble space telescope (larger than 0.1) - single dish radio telescope (1-30 arcminutes) |
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3 |
Magnifying power (Abolity to increase the apparent angular size of object) -magnification is related to social length of telescope -usefulness of magnification is limited by the light gathering power and resolving power of the telescopeb |
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What was the start of radio astronomy |
Karl jansky -hired by bell to look for man made radio interference -built a directional 20.5 MHz antenna turntable -noticed faint hiss every 23bhours and 56 mins |
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Who was grote reber |
-built a steerable parabolic reflector antenna ( prototype of modern radio telescopes) -center of our gravity was a source of radio emission |
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An interferometer is sensitive to sky structure inversely proportional to the spacing of antenna pairs |
Short spacing- big structures= low spatial frequencies Long spacing- small structures = high spatial frequencies |
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Interferometer telescopes |
Act as a natural low pass or high pass filters when imaging the sky depending on their antenna configuration and the time they spend on the object |
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What is the difference between science and philosophy and y are the no 100% accepted facts |
Testing and proving -because they r always being questioned and can be reversed |
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What did native American stories of the sky show |
That the stories connected to the sky may have been based on historic fact |
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What is the one ingredient did the Greek add to modern scientific method that was missing from cultures before |
Observation of nature |
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How did the greek and pythagorean see the universe |
Saw the earth as the center rather than the sun being the center |
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How did eratosthenes measure the earth's circumference |
His method was a geometric one based on the observation of the sun - sunlight struck the bottom vertical well at noon in syene meaning the sun was directly over. At the same time and date in Alexandria shaw that the shadow column saw that the sun was not directly over - the curvature of the earth means that straight up isnt the same in 2 placed - used the angle in Alexandria to measure the earth's circumference |
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What is the aridtotlean model of the universe |
The earth was the center |
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Why didn't the heliocentric model not catch on |
-lacked equants, epicycles and elements of the ptomelmic model -it still didn't predict planetary positions a y better than ptolemys geocentric model |
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What did Tycho Branhe offer kepler |
Kepler used and helped branhe in making observations of Mars and other planets movements from his observatory (Uraniborg) -this started Keplers start if mathematically analyzing planetary motion -discovered plansents dont move in a perfect circle |
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What are the two necessary ingredients for a planet to orbit the sun |
Gravity from the sun and forward motion of the planet |
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What did newton concluded about gravity |
-magnitude of gravity must decrease with increasing distance between two objects in proportion to inverse square of their operation -gravitational attraction between two bodies must be proportion to their masses (more mass the stronger pull) ⁸ |
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What first measured the speed of light |
Romer in 1670 when observing Jupiters moons |
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What is the equation relating lights wav and frequency together |
Wavelength × frequency= speed |
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Examples of short and long wavelengths |
Short (x ray and uv and optical) Long (ir and radio) |
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What are the main wavelengths of optical light in the visible spectrum |
700- red 600-yellow 500- green 400- blue 350-purple |
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What is recombination |
When an electron recombined with an atom |
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What happens I'd an atom is ionized |
Its electron is ejected called ionization |
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What are the approximate surface temp of red yellow and blue stars |
Red-4500k Yellow-5800k Blue-12000k |
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What are the 2 basic designs of telescopes |
Refractor Reflector |
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What 2 telescope properties determine the instruments angular resolution |
Diameter and wavelength of observation |
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What are the 4 reasons why getting about the air important |
1) weather conditions (weather is clear as much as 75% of the time) 2) prefer dry high sites ad atmosphere filters out certain starlight where the absorption is due to water vapor 3) near cities provide illumination 4) bad seeing. Images are distorted by the instant twisting and bending of light Ray's by turbulent air |
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What is Canada's radio observatory called |
The dominion radio astrophysical observatory -in pentiction BC |
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What is base line for interferometer |
The distance between two antennas in a pair |
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What us maximum baseline in interferometer |
Essentially the width of interferometer |
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What is interference |
The property observer between a pair of antennas that give us spatial information on the sky |
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What is interferometer |
2 or more telescopes linked together Sharpen images by electronically linking two or more radio telescopes |
