ESSC 102 Final - SELU - Welch

our only sources of information for distant objects (the broader universe)

Light

an electromagnetic wave that behaves like a particle

light

wavelength

repeat distance

frequency

number of repeated occurrences / time

speed of light

wavelength x frequency

300,000 km/s

visible light that makes up a small fraction of all light

the electromagnetic spectrum

types of light that vary by wavelength

x-rays

gama rays

radio wave

ways light interacts with matter

emission

absorption

transmission

reflection / scattering

emission

object emits light

absorption

light gets absorbed

transmission

light moves through matter

reflection / scattering

what we see

wave properties

wavelength

frequency

wavelength

what determines the appearance of everything around us

the way light interacts with matter

scatters visible light

our atmosphere

scatters light with shorter wavelengths most effectively

gases in our atmosphere

color of light with shorter wave lengths

blue

the light from an object passed through a prism to separate light into all various wavelengths, some are visible

spectrum

information that can be determined by light

chemical composition

temperature

doppler motion

light year

telescopes

chemical composition

each element has a unique spectral fingerprint which is expressed as emission and absorption lines in an objects spectrum

temperature

as an objects temperature increase, the object radiates light more strongly at shorter wavelengths

doppler motion

shifts in the wavelength of spectral lines

redshift

longer wavelengths of visible light and the object is moving away from you

blueshift

shorter wavelengths of visible light and the object is moving towards you

only tells us about the part of an object's motion toward or away from us

doppler shift

the distance that light can travel in one year

light year

how far can we look back in time bases on the universe

14 billion years

angular resolution

see more detail than our eyes

light collecting area

collects more light than our eyes

refracting

lenses uses to concentrate light

reflecting

mirrors uses concentrate light

why telescopes are in space

1. light pollution

2. turbulence of the atmosphere causing 'twinkling stars'

3. our atmosphere absorbs most of electromagnetic spectrum, including all UV and X ray and most infrared

energy provided by fusion maintains the outwards pressure that stops the star from collapsing in on itself

gravitational equilibrium

suns structure from outside in

solar wind

corona

chromosphere

photosphere

convection zone

radiation zone

core

solar wind

a flow of charged particles from the surface of the sun

outermost layer of solar atmosphere

corona

chromosphere

middle layers of the solar atmosphere

visible surface of the sun ~ 5800 K

photosphere

convection zone

energy transported upward by rising hot gas

energy transported upward by photons

radiation zone

core

energy generated by nuclear fusion ~ 15mil K

related to magnetic fields in the sun and can impact climate on earth

solar activity

types of solar activity

sunspots

solar flares

solar prominences

coronal mass ejections

sends burst of energetic charged particles out through the solar system

coronal mass ejection

stellar classification

we primarily classify stars by their luminosity and temperature but the most important property of stars is mass

amount of power a star radiates

luminosity

apparent brightness

amount of starlight that reaches earth

calculating distance

the relationship between apparent brightness and luminosity depends on distance

how we estimate star temperature

by the color and spectral type

spectral types

(hottest) O B A F G K M (coolest)

star temperature range

3000 K - 50,000 K

how we measure mass

with keplers 3rd law as long as there are two objects

Hertzsprung - Russell Diagrams

plot the luminosities against the spectral types of stars

what percentage of stars fall along the main sequences of HR diagrams

90

Life stages of stars step 1

gravitational collapse of nebula

protostar jet formation

(collapse stops) Fusion starts

stars that are too small to start fusion

brown dwarfs

Life stage of stars step 2

1. high mass vs low mass uses core hydrogen

2. fusion

3. Proton proton chain vs CNO cycle

main-sequence stars

fuses hydrogen to helium in their core like the sun

life span of high mass stars

5 million years

life span of low mass stars

10 billion years

what is a star's lifespan dependent on

mass because mass determines core temperature

fusion

small nuclei stick together to make a bigger one

enable nuclear fusion to happen in the core

high temperatures enable nuclear fusion to happen in the core by overpowering the repulsion of atoms

proton - proton chain

the release of energy by fussing four hydrogen nuclei (4 protons) into one helium nucleus in a process called the proton-proton chain

cycle that high mass stars use

CNO ( carbon nitrogen oxygen)

life stages of low a low mass star

First Red Giant Phase

Second Red Giant Phase

Instability and Collapse

protostar jet formation

rotation also causes jets of matter to shoot out along the rotation axis

When does the collapse of the nebula stop

when fusion starts

what happens with fusion that stops the collapse of the nebula

a protostar contracts and heats until the core temperature is sufficient for hydrogen fusion

what collapses a nebula

it heats up as gravity causes it to contract due to conservation of energy

following the start of hydrogen fusion what happens

new star archives long-lasting state of balance because the outwards force of fusion matches the inwards collapse of gravity

fuses their core hydrogen slowly

low mass stars

fuses their core hydrogen quickly

high mass stars

how do high mass star fuse

by using the CNO cycle: using a higher rate of carbon, nitrogen, and oxygen

how long does a star stay on the main sequence

as long as it can fuse hydrogen into helium in its core

first red giant phase

after the core hydrogen is used up, the core contracts and Helium begins fussing into a shell around the core in the first giant phase

what happens to a star after its time on the main sequence is over

it becomes larger redder and more luminous

second red giant phase

while the shell is fusing hydrogen the inner core starts to fuse helium in the second giant phase.

helium fusion

3 helium atoms make 1 carbon atom

what causes instability and collapse in a low-mass star

the lack of a low-mass star's ability to undergo advance fusion of heavier elements so carbon builds up in the core and star can never stabilize again

planetary nebula

fusion ends with a pulse that ejects the H and He into space as planetary nebula

what is a white dwarf

the core of carbon that is left behind

difference between main sequence and supergiant in high-mass stars

main: hydrogen core fusion

super: helium core fusion

what makes the elements necessary for life

high-mass stars

heavier element progression

high core temperatures allow helium to fuse with heavier elements

what allows for advance fusion reactions

core temperature in high mass stars

multiple shell fusion

high temperature nuclear fusion proceeds in a series of shells around the core

what causes instability and collapse in a high-mass star

iron is the dead end for fusion because reactions involving iron do not release energy. Iron builds up in the core until pressure can no longer resist gravity. then the core collapses creating a supernova explosion

supernova explosion and remnant

energy released by the collapse of the core drives outer layers into space and forms elements heavier than iron, such as gold and uranium

what forms blackholes and neutron stars

heavy interiors inside the remnant

neutrons that collapse in the center of a supernova explosion

a neutron star or black hole

degeneracy pressure

particles cant be in the same state in same place according to the laws of quantum physics

neutron star

the ball of neutrons left behind by a massive star supernova and is about to same size as a small city and has the mass of a large star

who discovered pulsars

Jocelyn Bell

what is a pulsar

a spinning neutron star that emits wave in the direction of its magnetic axis

what is a black hole

an object whose gravity is so powerful that not even light can escape it

how is a blackhole formed from a supernova

if the degeneracy pressure is exceeded

singularity

what gravity crushes all the matter into

what is the event horizon

the radius at which the escape velocity equals the speed of light

how big is a blackhole

the size of a small city