Astronomy Exam 2 Study Guide

Wavelength

(upside down y) distance between crests

Frequency

number of cycles per second

Speed ( c)

= wavelength x frequency

Color

visible light

Electromagnetic spectrum (most energy to low energy)

Gamma, x-ray, ultra violet, colors, infrared, microwave, radio (light)

Electromagnetic spectrum NOT absorbed by atmosphere (penetrates atmosphere)

visible light (color) and radio waves

Wavelength range of visible light

400-700 nm or 4000-7000 A

Emission spectrum

Hot low density gas (lines on black background), wavelength of lines tell us about chemical composition

Absorption spectrum

compact object with cooler gas in front (continuous spectrum with dark lines), dark lines (absorption lines) tell us about chemical composition

Continuous spectrum (thermal blackbody radiation)

Compact object (depends only on temp… due to two laws??)

Absorption of a photon

kicks an electron to a higher level

Photon emitted

Electron falls to lower level

Energy difference between 2 electron levels

determines wavelength

Doppler Effect

spectrum of an object can tell you if the object is moving away or towards you and how fast

Red shift

objects moving away, light coming from it shifts to longer wavelengths (red color)

Blue shift

objects moving towards you and light coming from It shifts to shorter wavelengths

No shift

object moving sideways, same wavelengths

Photon

1 particle of light

1 hertz

1 wave per second

How to find color of object on spectrum

where spectrum peaks, hotter objects peak at shorter wavelengths

Hotter object emits more light at

all colors

Chemical Fingerprint

each atom produces a distinct set of emission and absorption lines

Ground State

Lowest energy an electron can have

Excited state

electron has higher energy than ground state

Why build telescopes

1) collect more light than our eyes (sharper images, longer exposures) 2) can see more details than our eyes (resolution) 3) can detect light that is invisible to our eyes (infrared, ultraviolet, etc)

Reflecting telescope

has curved mirrors to make images less blurred, focuses colors to a single point, made by Issac Newton

Refracting telescope

Uses 2 lenses to get rays of light to become parallel, used by Galileo

Resolution

Measure of how close two things can be and be seen as separate objects

Lens

used to bend light and bring to focus at a point, each color focused to slightly different point

Objective Lens

Big lens on refracting telescope that collects light

Primary mirror

big mirror on reflecting telescope

Eye Piece

Small lens you look through

Viewfinder

scope like thing on telescope to find object in sky

Why was the Hubble space telescope better than a 5 meter ground based telescope built at the same time?

Telescopes in space reduced atmospheric turbulence, there was so adaptive optics

Why do we not need another Hubble space telescope?

We have adaptive optics now that removes the image distortion due to atmospheric turbulence

Best location for today’s optical telescopes?

in high altitude, low artificial light places?

Adaptive Optics

deformed mirror which compensates for distortion by atmosphere, removes effects of atmospheric turbulence

What type of light make it through atmosphere

optical light and radio waves

Why build non-optical telescopes?

To capture other types of light that we are unable to see with our eyes

Radio telescopes

type of telescope that captures radio waves

Radio telescope advantages

1) cheaper to build, can make larger 2) sky is dark in radio even during the day, operates 24 hours 3) can observe through clouds and possibly rain

Radio telescope ideal location

in valleys to block other radio signals or somewhere remote probably

Interferometry

Multiple radio dishes linked together (capture radio waves and combine signal)

All large telescopes today are

reflectors

Segmented primary mirrors

many hexagonal mirrors put together to form primary mirror of reflecting telescope

Survey telescopes

capture image of big part of sky

Baseline (radio telescope)

spacing between two radio dishes, longer baselines = higher resolutions

Atmospheric turbulence

Blurs images of telescopes

Largest telescope in space

James Webb Space Telescope (infrared)

Sun is a big ball of…

gas, hydrogen and helium

Solar telescopes

Looks at just sun, need long focal length, solar telescopes in space receive UV X-ray light

Hydrogen

most abundant element in the universe

6 layers of the sun (outside to inside)

corona, chromosphere, photosphere, convection zone, radiative zone, core

Corona and Chromosphere

outside the photosphere and can only see during total solar eclipse

Photosphere

layer of sun we see with eyes

convection zone

in photosphere where hot stuff rises and cool stuff sinks

Radiation zone

where light (from core) constantly bounces off hot gas particles

core

hottest densest part of sun, where nuclear fusion happens (energy of sun produced)

Distance from the Earth

93 million miles

Age of sun

4.5 billion years

Granulation

texture on sun surface, bubbles appear on sun (proof of convection)

Temperature of the sun

27 million degrees Fahrenheit approx

equilibrium

inward force of gravity is balanced by outward force of pressure (in future, equilibrium breaks, sun dies)

convection

hot stuff rises, cool stuff sinks

nuclear fusion

two light nuclei combine to a heavier nucleus (review steps)

sunspots

dark spots on the sun, due to gas being cooler than surrounding below photosphere (gas rises and falls due to sun’s magnetic field)

prominences

loops of gas rising from photosphere and falling down, same as sunspots but from different angle

Solar flares

more energy, velocity than prominences, gas escapes sun with escape velocity

Sun rotation

sun rotates faster at equator (25 days) than at poles (30 days), cause magnetic field lines to get twisted

Sun’s magnetic cycle

11 year period

Solar maximum

many spots/prominences, some flares

Solar minimum

few sunspots/prominences, no flares

Chromosphere and corona emit what type of light

X-ray and UV

Hottest part of sun

Corona then chromosphere then photosphere

Solar winds

steady stream of charged particles escaping through holes in the corona

Coronal mass ejection

sudden ejection of coronal material due to prominences and flares

solar particles

bursts of fast charged moving particles? from coronal mass ejection or solar flare?

auroras

Solar winds trapped in Earth’s magnetic field which interact w/ atmospheric particles, also from flares and coronal mass ejection. maybe solar storms too?

Fission

heavy nucleus splits apart (nuclear power plants)

Proton Proton Chain

Fusion process that takes place in the sun, process that turns hydrogen into helium

Atomic Mass Number

Number of protons plus neutrons

Neutrino

little neutron, neutral particle

Positron

Example of antimatter, anti electron that has positive charge

Sun born with how much hydrogen?

90%

Process in Radiative zone

Photons are absorbed and scattered by hot gas in sun until they lose energy ( how continuous spectrum is produced

Solar Oscillations

sun’s vibrations tells us about sun’s interior (sun is pulsating)

Proton proton chain step 1

H-1 + H1 = H-2 + neutrino + positron

Proton proton chain step 2

H-2 + H-1 = He-3 (helium) + gamma ray

Proton proton chain step 3

He-3 + He-3 = H-1 + He-4 + H-1

Apparent magnitude

How bright an object appears to us

Absolute magnitude

How bright a star actually is when placed at same distance (10 parsec)

Luminosity

Total amount of energy at all wavelengths it emits per second

Parallax

apparent shift of an object due to change in your perspective, smaller shift, further away it is, need to look at object from 2 different vantage points (or take a picture and wait six months and take another one)

Baseline (stellar Properties)

Distance between 2 vantage points

Magnitude

Unit of measurement for brightness (smaller number = brighter)

Smaller magnitude =

Brighter

Proper motion

neutral motion of a star (stars move and orbit center of gravity in different speeds and directions)

How to tell if parallax shift or proper motion?

Wait a year and look, no parallax shift after a year

Spectral type from hottest to coolest

O, B, A, F, G, K, M (oh be a fine girl kiss me)

Spectral type

classification of stars according to temperature (and color?)