Astronomy Midterm 1

Front 1

star trails

Back 1

type of photograph that utilizes long-exposure times to capture the apparent motion of stars in the night sky due to the rotation of the Earth.

Front 2

where are star trails straight?

Back 2

the equator

Front 3

at middle latitudes, star trails ___.

Back 3

trace slanted lines relative to horizon as they rise and set.

Front 4

cirumpolar constellations (2)

Back 4

those that never rise or set in the sky; always visible from your location; depending on where you are, circumpolar constellations will be different

Front 5

Where are there no circumpolar constellations? Where are there the most?

Back 5

None at the equator; many at either the north or south poles.

Front 6

celestial pole (2)

Back 6

the point on the celestial sphere directly above either of the earth's geographic poles, around which the stars and planets appear to rotate during the course of the night. The north celestial pole is currently within one degree of the star Polaris

Front 7

Where would one have to be to see both celestial poles?

Back 7

the equator; because it is right in the middle, each celestial pole would be at either side of the horizon, at opposite ends of your FOV.

Front 8

earth's diameter

Back 8

13000 km

Front 9

our solar system consists of ___.

Back 9

our sun, its family of planets, and some smaller bodies like moons and comets.

Front 10

planets

Back 10

small, spherical, nonluminous bodies that orbit a star and shine by reflected light.

Front 11

star

Back 11

self-luminous ball of hot gas that generates its own energy

Front 12

astronomical unit

Back 12

1.5 x 10 to the 8th

Front 13

how to remember planets from the Sun outwards:

Back 13

My Very Educated Mother Just Served Us Noodles: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

Front 14

lightyear

Back 14

the distance that light travels in one year; approx. 10 to the 13th kms or 63,000 AU

Front 15

What is the closest star to the sun? How far away from Earth is it?

Back 15

Alpha Centauri; 4.2 ly

Front 16

galaxy

Back 16

a great cloud of stars, gas, and dust held together by the combined gravity of all of its matter

Front 17

galaxies range from ___ to over ____ ly in diameter and can contain ___ stars.

Back 17

1000; 300,000; biggest ones contain more than a trillion stars

Front 18

the Earth's galaxy is called

Back 18

the Milky Way galaxy.

Front 19

the solar system is ___, our galaxy contains ___, and the universe is ____.

Back 19

our planets, sun, local area; contains solar system and billions of stars and whatever planets orbit them; everything altogether.

Front 20

groups of galaxies connected in a vast network

Back 20

clusters

Front 21

clusters of clusters

Back 21

superclusters

Front 22

superclusters form __.

Back 22

filaments and walls

Front 23

the largest structures in our universe

Back 23

filaments and walls

Front 24

how old is the universe?

Back 24

14 billion years old

Front 25

beginning of the universe

Back 25

the big bang

Front 26

when was our solar system created?

Back 26

4.6 billion years ago

Front 27

when did life on earth begin?

Back 27

3.4 billion years ago

Front 28

when did life on land emerge?

Back 28

0.4 billion years ago

Front 29

constellations

Back 29

groups of stars and a certain area of the sky

Front 30

the International Astronomical Union officially recognized ___ constellations

Back 30

88

Front 31

asterism

Back 31

less formally defined groupings, ex. The Big Dipper that is part of the constellation Ursa Major

Front 32

how do astronomers assign Greek letters to stars?

Back 32

in order from brightest to least brightest (alpha, beta, and so on)

Front 33

the scale used to describe brightness of stars

Back 33

magnitude scale

Front 34

brightest star in the sky (and its magnitude)

Back 34

Sirius; -1.47.

Front 35

faintest stars you can see with the human eye are __ magnitude.

Back 35

sixth

Front 36

apparent visual magnitudes (m subscript v)

Back 36

describe how the stars look to human eyes observing from earth

Front 37

the 'v' in mv stands for __. It helps remind you that __.

Back 37

visual; reminds you that only visible light is included

Front 38

flux

Back 38

a measure of the light energy from a star that hits one square meter in one second

Front 39

wavelength (2)

Back 39

difference between crests; represented by lambda

Front 40

frequency (f)

Back 40

the number of crests passing a given spot each second

Front 41

all EM radiation travels at ___

Back 41

300,000 km/s (speed of light, c)

Front 42

if something is particle-like, then it ___

Back 42

also behaves as if it's made up of particles called photons

Front 43

photon

Back 43

a particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency but has zero rest mass

Front 44

1 nm = ___ m

Back 44

one billionth of a meter

Front 45

most energetic waves are ___

Back 45

gamma

Front 46

first person to point simple telescope to the sky in 1609:

Back 46

Galileo

Front 47

refraction

Back 47

the bending of a ray of light as it travels through a lens and back out into air

Front 48

reflection

Back 48

light is deflected when it hits a shiny surface like a mirror

Front 49

refracting telescopes use __ to gather light, while reflecting telescopes use ___

Back 49

lens; mirror

Front 50

one big issue with refracting telescopes (what is it, what it looks like, what causes it, how to minimize)

Back 50

chromatic aberration: when light passes through a lens, different wavelengths are refracted different amounts as they pass thru the lens. Shorter wavelengths are bent more. Occurs with all lenses, some worse than others. use of another lens only way to minimize. appearance of image will show halos of colour around focused part.

Front 51

why are really large lenses impractical? (4)

Back 51

very heavy, would need a long tube (long focal length of lens; issues with general observatory construction as it would need to be very big), glass needs to be very pure, both sides of lens need to be shaped perfectly

Front 52

what type of telescopes are preferred and why? (6)

Back 52

reflecting telescopes:

- they can be made larger and don't face same issues with refraction

- no problem with chromatic aberration b/c no refraction

- can change # of mirrors to alter the path of the light, so a shorter tube can be used

- since light reflects off mirror:

- don't need to worry about flaws inside of glass

- only have to shape one side

- can support mirror on back as well as edges

Front 53

light-gathering power

Back 53

ability of a telescope to collect light

Front 54

light-gathering power depends on ___

Back 54

the area of the primary lens or mirror

Front 55

if telescope A can collect 100x more light than telescope B, then the same star will ___

Back 55

look brighter in telescope A

Front 56

resolving power

Back 56

ability of a telescope to reveal fine detail/ the ability to resolve (detect separately) closely-spaced objects in the sky

Front 57

in regards to resolving power, alpha is proportional to __.

Back 57

lambda (wavelength) over size of scope (D, or diameter)

Front 58

in regards to resolving power, we want alpha (resolving power) to be as __ as possible because ___.

Back 58

small; a small number for resolving power means the telescope can resolve or tell apart closely spaced objects

Front 59

seeing

Back 59

amount of blurring due to earth's atmosphere (good seeing - clear, non-turbulent atmosphere)

Front 60

magnifying power

Back 60

ability of a telescope to make things look bettter

Front 61

magnifying power: M =

Back 61

focal length of primary lens/mirror over focal length of eyepiece; therefore, can change M by changing eyepiece

Front 62

light pollution and how to prevent it

Back 62

brightening of night sky by city lights, etc. Can avoid it by playing observatories on top of mountains

Front 63

characteristics of a good observatory site ()

Back 63

- high elevation > lower density atmosphere

- secluded, dark, quiet (remote)

- dry air is better (less condensation on scope parts, less wear on metal, etc.)

- cooler and constant temp, less localized air turbulence

- consistently good weather > more efficient use of observatory

Front 64

all modern optical telescopes are __ telescopes

Back 64

reflecting

Front 65

three types of reflecting telescopes

Back 65

primary focus, cassegrain focus, and Newtonian focus

Front 66

all modern optical telescopes utilize 3 things:

Back 66

- reflective telescopes

- siderial (w/ respect to stars) drive to track stars

- use active optics

Front 67

active optics

Back 67

controls shape of telescope's mirror; rods on underside of mirror can move up and down as required to ensure that a mirror's shape stays a perfect 'shallow bowl' (parabola), means mirror can be very thin for its size (less heavy, less material, can cool down more rapidly)

Front 68

three different kinds of detectors

Back 68

photographic plates, photonomers, and charge-couple devices (CCDs)

Front 69

photographic plates

Back 69

light-sensitive emulsion on glass or film to get picture; used on older telescopes

Front 70

photonomers

Back 70

instruments that count photons from star > no picture

Front 71

charge-couple devices (CCDs)

Back 71

electronic (digital detector) made of silicon

- chip made up of individual pixels and as photons land on pixels, they kick out electrons out of the silicon atoms

- electrons are stored in pixels until exposure is over

- when exposure over, chip is 'read out' > electrons are transferred to neighbouring pixels in specific way, by manipulating a voltage on the chip

- reconstructs image in computer

Front 72

advantages of CCDs

Back 72

- high efficiency > eg for every 100 photons that hit the chip, > 90 of them will kick out an electron (will go towards making a picture)

- images are digital so storage, image manipulation and sharing are much easier than with photographic plates

Front 73

spectronomer

Back 73

break up light into spectrum; a separate piece of equipment attached to telescope. Record spectrum with a CCD

Front 74

nucleus

Back 74

contains positively charged protons and neutrally charged neutrons

Front 75

electrons

Back 75

negatively charged particles orbiting nucleus

Front 76

atoms are mostly __

Back 76

empty space

Front 77

atoms can be either ___ , __ or ___s.

Back 77

isotopes; ionized (ions), molecules

Front 78

isotope atoms

Back 78

same # of protons as other atoms in that family, but different number of neutrons (eg carbon-12: 6 protons, 7 neutrons [stable]; carbon-14: 6 protons, 8 neutrons [unstable]

Front 79

ionized atom (ion)

Back 79

an ion is an atom that's lost one or more electrons

Front 80

molecules

Back 80

atoms bonded together

Front 81

energy levels

Back 81

regions around a nucleus having a specific energy associated with them

Front 82

simplest atom:

Back 82

hydrogen > nucleus = 1 proton, and it has 1 electron

Front 83

in regards to energy levels, electrons can reside in any level, but always want to be in the ___ energy level.

Back 83

lowest

Front 84

excited atom

Back 84

energy levels differ in their values for the energy (e.g. if a photon comes along with energy = difference between 2 levels, then the electron can absorb the photon and jump to a higher energy level

Front 85

the energy of a photon is [formula]

Back 85

E = hc over lambda; the lower the energy, the bigger lambda has to be - inverse relationship

Front 86

the ____ temp of a star determines the main type of EM radiation it emits, and what colour it appears to be

Back 86

surface

Front 87

'surface' of a star

Back 87

the outer layers of gas > the atmosphere, b/c no physical 'surface;' the layer we see

Front 88

the ___ of a star is directly related to its temperature

Back 88

colour

Front 89

thermal energy

Back 89

heat energy; molecules fly around, collide with one another

Front 90

in thermal energy, each heat collision causes ___ to emit

Back 90

electromagnetic radiation

Front 91

the hotter a star's gases, the __ the motion, the more energetic __ emitted

Back 91

faster; EM radiation

Front 92

hotter radiation has a __ wavelength

Back 92

shorter

Front 93

the Kelvin temperature scale

Back 93

T(K) = T(C) + 273

Front 94

coldest temp you can go

Back 94

absolute zero: -273 degrees K

Front 95

radiation and __ mean the same thing

Back 95

energy

Front 96

coldest things in space are around ___ degrees K

Back 96

10

Front 97

blackbody radiation

Back 97

radiation emitted by a heated object (anything above zero degrees K emits some)

Front 98

an ideal blackbody will produce a ___ dictated by the equation

Back 98

curve

Front 99

because an ideal blackbody absorbs all radiation falling on it so that its not reflecting any away, and gives off energy at the same rate so that it stays a constant tempt, ___ and ___ make good blackbodies

Back 99

anything black with a matte finish is better than a shiny surface; stars

Front 100

bbs emit energy at all wavelengths, but most of the energy is emitted ____

Back 100

at a certain wavelength depending on the temperature of the blackbody

Front 101

Wein's law

Back 101

the higher the temperature, the shorter the wavelength the peak energy emitted occurs

Front 102

Stefan Boltzmann law

Back 102

a blackbody at a higher temperature emits more radiation at all wavelengths than a cooler one

Front 103

when white light is split through a prism, it produces a __

Back 103

spectrum

Front 104

spectrums are useful to astronomy for 2 reasons

Back 104

- can use to estimate temperature

- can use to determine elements present in gas of star

Front 105

Isaac Newton first to ___

Back 105

pass light through a prism

Front 106

3 types of spectra described by Kirchoff's laws

Back 106

continuous, emission line (bright line), absorption (dark line)

Front 107

continuous spectrum

Back 107

continuous band of colors, produced by hot solid (like filament, toaster coil), hot liquid (lava), or hot, dense gas (interior of star)

Front 108

emission line (bright line) spectrum

Back 108

bright lines of colour superimposed on a dark background, produced by hot, thin gas (like streetlights not LED)

Front 109

absorption (dark line spectrum)

Back 109

dark lines superposed on a continuous spectrum

- light making up a continuous spectrum passes through a cool, thin gas (the atmosphere, outermost layers of star, etc.)

Front 110

later in time, scientists realized why spectra were like this. They realized that photons are ____ when they make a transition between energy levels, so ____.

Back 110

emitted or absorbed; bright lines or dark lines are produced in spectrum

Front 111

bright lines are emitted when an electron ___

Back 111

is in a higher energy level, emits a photon and drops to a lower level

Front 112

emission spectra are ___

Back 112

unique; like a fingerprint for gas

Front 113

the number and strength of lines in a spectra speak to the star's (2)

Back 113

temperature; composition (to a certain extent)

Front 114

motion TOWARDS the observer causes spectral lines to ___

Back 114

shift to the BLUE part of spectrum; blueshift

Front 115

motion AWAY from the observer causes spectral lines to be _____

Back 115

shifted slightly towards the red part of spectrum; redshift

Front 116

star spectrum

Back 116

used when star moving away

Front 117

'rest' spectrum

Back 117

if the star wasn't moving; where the lines would be in wavelengths relative to you

Front 118

if the star's spectrum and rest spectrum are the same, then ___

Back 118

the star is not moving

Front 119

radial velocity

Back 119

velocity along the line of sight

Front 120

the sun is comprised of

Back 120

big ball of gas, mostly hydrogen and helium; the core produces energy

Front 121

the sun's __ produces energy

Back 121

core

Front 122

___ helps the sun stay the same

Back 122

hydrostatic equilibrium

Front 123

sun and stars generate energy via

Back 123

fusion

Front 124

fusion occurs at __ (3)

Back 124

high temps > gas is ionized, which means free nuclei and free electrons moving around

Front 125

fusion

Back 125

2 nuclei fuse together, forming one larger nucleus and energy

Front 126

conservation of energy

Back 126

energy is neither destroyed nor created, just transformed from one form to another

Front 127

__ (or __) can be converted into energy

Back 127

mass or matter

Front 128

E = mc squared means that

Back 128

a little bit of matter can be converted into a lot of energy; therefore, matter and energy are 2 different manifestations of the same thing, which is what his equation is saying.

Front 129

the sun converts ___ tons of matter into energy each second

Back 129

4 million

Front 130

for each matter particle, there is a corresponding ___

Back 130

antimatter particle (e.g. for each electron there is a positron)

Front 131

positron e+

Back 131

positive energy, same mass as electron

Front 132

when matter and antimatter meet, they ____ and create ___

Back 132

mutually destruct and create energy (gamma ray photons)

Front 133

neutrinos (7)

Back 133

'the little neutral one'

- Greek letter 'nu'

- practically no mass

- zero electric charge (neutral)

- capable of carrying energy

- travels at practically the speed of light

- interact very weakly with matter

Front 134

nuclear force

Back 134

strong, short range force holding nucleus together

Front 135

to keep nucleus together, the charged particles must be ___ in the first place

Back 135

close enough together

Front 136

fusion occurs in the core but not other areas because they are not ___

Back 136

hot enough

Front 137

in the sun and stars, hydrogen fuses to helium via a series of reactions called the

Back 137

proton-proton chain

Front 138

proton-proton chain (3)

Back 138

1- 2 protons fuse to form an isotope of hydrogen, 2H (deuteron), a neutrino, and a positron.

2- 2H fuses with another 1H to form an isotope of helium (3He) and a gamma photon

3- the 2 3He fuse to form an ordinary helium, 4He, and 2 extra protons come out as well

Front 139

the energy released via proton-proton chain appears as energy in many forms (3)

Back 139

- the neutrinos carry some energy

- the positron will find and annihilate a free electron and be converted into 2 gamma photons (energy)

- gamma photon in second reaction is energy

Front 140

once energy is produced in core of sun, it works its way out through the __ and __ zones

Back 140

radiated and convective

Front 141

although neutrinos zip out of the sun in a few seconds, photons travel differently. in the radiative zone, they ___, and in the convective zone, they ___.

Back 141

photon is absorbed and re-emitted in a random direction, losing a little bit of energy ea. time; as energy rises, its absorbed by pockets of gas that rise to cooler layers, release the energy, and drop back down to pick more energy up, in a cycle

Front 142

adaptive optics (3)

Back 142

- change shape of primary mirror to account for the distortion of 'wavefronts' from object in space due to atmospheric turbulence

- monitor light from bright star near the target object to see how to deform the mirror

- high power sodium lazer 'creates' fake star and monitors light from there

Front 143

how do modern radio telescopes work? (3)

Back 143

- large dish collects radiowaves (like a primary mirror collects light)

- dish reflects signal to a focus where detector is located

- detector records radio signal; computers analyze data (no image is produced directly)

Front 144

what are two primary reasons why radio dishes in radio telescopes need to be so big?

Back 144

1- radio signals from space are naturally weak, so large collecting area is necessary to result in a stronger signal

2- resolving power: depends on both the wavelength and diameter of your collecting surface; radio wavelengths are really long compared to light, so large dish needed to compensate and produce decent RP

Front 145

contour maps

Back 145

computer puts info into images of object producing radiation

Front 146

radio galaxies

Back 146

emit gases from the center of the galaxies into space (probably hydrogen gas) that slams up against other stuff inbetween galaxies that gives off radio waves

Front 147

advantages of radio telescopes (3)

Back 147

- biggest one: you can use/observe day and night and light and weather does not affect radiowaves

- some objects only emit radio emission, so radio scopes show us things we wouldn't have known were there

- can link (electronically) several scopes together to simulate a much larger one (interferometer array) which greatly increases resolving power

Front 148

a bigger diameter does not mean you're looking at a bigger area of the sky in one exposure.. t or f?

Back 148

true