ASt201
If observers in all reference frames must agree about the speed of light, then they cannot always agree about ______ and/or _____?
Distance and/or time
In space, speed and movement of an object is always ______ to another object
Relative
Is the speed of light additive?
NO, the speed of light is ALWAYS the same
Moving clocks run ______
Slow
Postulate that states the law of physics are the same in all reference frames that are moving at constant speeds
The first postulate of special relativity
Space and time are bound together in a single entity called _______
Spacetime
Speed is always ____ to something else
Relative
The first postulate of special relativity...
Postulate that states the laws of physics are the same in all reference frames that are moving at constant speeds.
The postulate that states the speed of light (in a vacuum) is the same for all observers, regardless of relative motion or source of observer
The second postulate of special relativity
The second postulate of special relativity
The postulate that states the speed of light (in a vacuum) is the same for all observers, regardless of relative motion or source of observer
The speed of light is ______
Invariant
The speed of light is the _______ thing known, and only _______ can achieve this speed.
Fastest, light
Theory of relativity
Theory that states motion can only ever be measured in a relative sense
Theory that states motion can only be measured in a relative sense
Theory of relativity
What did Vera Rubin actually find?
She found that stars further away from the galaxy orbitted faster than those closer to the galaxy
What did Vera Rubin expect to see in her analysis of stars orbiting our galaxy
She expected to see that stars closer to the galaxy orbited faster than those further away
What is time dilation?
The idea that time runs slower when you are moving
What is true speed?
True speed is speed relative to the ground
What percent of the universe is dark energy?
68%
What percent of the universe is dark matter?
27%
What percent of the universe is ordinary matter?
5%
A galaxy composed of a random blob of stars, dust, and gas...
Irregular Galaxy
A type of galaxy composed of two galaxies that have merged to become one, causing a massive burst of stars
Antenna galaxy/Starburst merger
Cepheid variable stars
Stars that "pulse"
Cluster of very large galaxies, mostly elliptical, have very little star formation
Galaxy clusters
Elliptical galaxies
Type of galaxy with very little gas, dust, and star formation, very old and very large
Galaxy Clusters
Cluster of very large galaxies, mostly elliptical, have very little star formation
How are cepheid variable stars standard candles?
We can measure pulse time, which is correlated to luminosity
How are elliptical galaxies thought to be formed?
From a starburst/merging spiral galaxies. Use up all gas and dust to create lots of stars around a black hole
How do spirals in disk galaxies form?
They form by interactions/colliding with other galaxies
If we know the temperature and distance of a star, we can determine its...
luminosity
Irregular galaxy
A galaxy composed of a random blob of stars, dust, and gas
Lenticular galaxies
Disk galaxies with no spirals
Less luminous cepheid variable stars take _____ to pulse
Shorter
More luminous cepheid variables stars take _____ to pulse
Longer
Nodes of the cosmic web cause extreme _______ in spacetime
Dips
Objects whose luminosity is known...
Standard candles
Objects whose physical size is known...
Standard rulers
Starburst...
When galaxies collide and result in a massive burst of stars
Supernovae are all the same luminosity, therefore they can be used as...
Standard candles
Things close to us will have a ______ parallax angle
Large
Things far away from us will have a _______ parallax angle
Small
Three main components of a spiral galaxy
Disk, bulge and halo
We can use ______ to determine the size of the Earth's orbit
Radar
We can use ______ to determine the distance to objects in the Milky Way
Parallax
We can use ______ to determine distance to distant galaxies
Supernovae
We can use ______ to compare the distance from nearby star clusters to distant ones
Main sequence fitting
We can use ______ to determine from nearby star clusters to distant ones
Cepheid variables
What are nodes?
Galaxy clusters that show up on the cosmic web as being very dense
What does a disk galaxy with no spirals indicate?
That the galaxy has not been disturbed by any other galaxies in the universe
What is the "period" of a cepheid variable star?
The time between the pulses of a star
What three big galaxies are part of the local group?
Milky Way, Andromeda, and Triangulum
When galaxies collide and result in a massive bust of stars...
Starburst
Why are galaxies in the centre of a cluster elliptical and those on the edge are spiral?
There are more galaxies in the centre, so higher chance they will collide, starburst, and form elliptical galaxies. Less galaxies on the edge to collide with no spiral galaxies remain
Why might an elliptical galaxy show a blue stripe jetting from its center?
Energy and light produced when something falls into the black hole at its center
______ do not expand, only the space between them
Galaxies
At the end of the era of nucleosynthesis, how much of the mass is hydrogen and how much is helium?
1/4 helium and 3/4 hydrogen
Era of atoms
Era when universe gets very cold, converting all plasma to hydrogen and helium gas and dark matter
Era of nuclei
Era where the universe is filled with hydrogen and helium plasma
Era of nucleosynthesis
Universe era where protons collide to form and break atoms. Temperature of nuclear fusion
Era when the universe gets very cold, converting all plasma to hydrogen and helium gas and dark matter
Era of atoms
Era where the universe is filled with hydrogen and helium plasma
Era of nuclei
How do neutrons remain after nucleosynthesis?
They get stuck in atoms and make stable helium and deuterium nuclei
Hubble's Law equation...
v = Hd speed of object is proportional to distance
If a galaxy 1000 light years away explode, when will we see it?
We will see it 1000 years after its explosion, because the light takes 1000 years to travel to us
In what era is helium and dueterium formed?
Nucleosynthesis era
Name the three pieces of evidence for the Big Bang.
- Ratio of hydrogen to helium
- Uniform microwave glow in all direction
- Hubble's Law (Redshift, blueshift)
Oblers Paradox
If the Universe is infinite and unchanging, you should be able to see a star eventually, no matter where you are. The whole sky should be filled with stars
Particle Era
Universe era with equal numbers of protons, neutrons, electrons, and neutrinos all colliding at high rates
Peculiar Velocity
The movement and speed of an object NOT caused by the expansion of the Universe
The further away we look in space, the further back we look in _______
Time
The plasma of CMB should produce almost a perfect...
Blackbody
Universe era where protons collide to form and break atoms. Temperature of nuclear fusion
Era of nucleosynthesis
Universe era with equal number of protons, neutrons, electrons, and neutrinos all colliding at high rates
Particle Era
What causes small irregularities in the CMB?
Variations in temperature and density in the plasma
What does Hubble's Law prove?
The expansion of the Universe. It proves that everything is moving away. Objects further away are moving away faster and objects closer are moving away slower
What era does CMB light come from?
The transformation from the era of nuclei to the era of atoms
What is the cosmic microwave background?
Marks the moment in space and time when the plasma of the Universe cooled. It emits microwave that is invisible to the eye
What must occur for and object to come towards Earth?
The peculiar velocity must be greater than the rate of expansion of the Universe
When did the Universe start?
14 billion years ago
Where is the center of the Universe?
Nowhere! There isn't one
Why are there limited neutrons in nucleosynthesis?
Neutrons are unstable and decay into a proton and electron
Why is the cosmic microwave background different levels of red-shifted?
The Earth has a peculiar velocity of 170km/s. The CMB in the direction that we are moving in will be less redshifted. The CMB in the direction that we are moving away from is more redshifted
Why isn't the cosmic microwave visible?
Because it has been redshifted by a factor of 1100, so it is now microwave light to us
Any two spots on the CMB have the same...
Temperature
Data tells us that distant galaxies are moving slower, therefore, expansion is...
speeding up
Gravity should slow expansion down, so we expect distant galaxies to move ______
Faster
If the energy density is high, and the Universe is sphere, distant objects look ______
Bigger than expected
If the energy density is low, and the Universe is saddle, distant objects look _______
Smaller than expected
If the energy density is right, and the Universe is flat, distant objects look _______
The expected size
If the mass density of the Universe is _______, the expansion of the Universe will continue forever without slowing down
Zero
If the mass density of the Universe is ______ than the critical density, the expansion of the Universe will slow down, but never stop
Smaller
If the mass density of the Universe is "________", then the expansion will keep slowing down to a stop
Exactly right
If the Universe has high density, it will be shaped like a _____
Sphere
If the Universe has low energy density, it will be shaped like a _______
Saddle
If the Universe is a sphere, then straight lines...
Converge
If the Universe is flat, straight lines...
are flat
If the Universe is a saddle, then straight line...
Diverge
If you put ______ into an expanding Universe, you get an accelerating expanding Universe
Dark Energy
The geometry of space depends on ______ of the Universe
Energy Density
The standard model and general relativity work ______ together
Poorly. They don't make sense at the same time
What are the two pillars of physics?
The standard model and general relativity
What effect does mass have on the expansion of space?
Mass causes gravity. Pulls down spacetime. So it would slow down Universe expansion
What is cosmological inflation?
The theory that the Universe was a tiny point and then rapidly expanded to the Universe. All points in the visible Universe were in contact before inflation. Inflation makes the Universe "flatter"
What is energy density?
The total amount of energy per unit volume
What is one theory that shows why two points on the CMB are the same temperature?
The Universe underwent a period of rapid expansion, from something very small to something very big. The two points were at one time touching before the expansion
What is the multiverse theory?
Infinitely many Universes with every condition possible. Including ones that don't follow our Universe's laws of physics or matter or anything
What shape is our Universe and how do we know?
Our Universe is flat. We know this because the blobs on the CMB are the exact size as we would expect
What will happen if the Universe keeps expanding at an accelerating rate?
Galaxies get far far apart from each other. Stars burn out. Matter is consumed by black holes. Black holes eventually evaporate away. EVERYTHING IS LEFT EMPTY AND DARK!
An object in motion stays in motion with constant speed and direction unless acted on by an external force.
Newtons First Law
Carrier particle for gravity...
There is no known carrier particle for gravity
Carrier particle for weak nuclear force...
W and Z bosons
What is the equivalence principle
The idea that the laws of physics work exactly the same in an accelerating frame of reference as they would in a gravitational field
For every applied force, there is an equal but opposite reaction force
Newtons Third Law
Function of electromagnetism
Forces in everyday life
Function of gravity
Make masses attract one another
Function of strong nuclear force
Holds atomic nuclei together
Function of weak nuclear force
Involved in radioactive decay
General relativity
Gravitational effects on masses is a result of the warping of spacetime
What is gravitational lensing?
Massive objects bend the space around them, forcing light to follow its curved contours
What is gravitational time dilation?
The idea that time runs slower the deeper you are in a gravitational well
How do you get acceleration in general relativity?
When things try to travel in a straight path through bent space
In a spacetime diagram, a light ray travels one light year every year, so light rays are always lines at a ____ degree angle
45
In a spacetime diagram, physical objects must always move _______ than the speed of light, so their paths will have ______ slopes
Slower, steeper
In a spacetime diagram, the x-axis is the ____ and the y-axis is the _____.
X-axis: distance in light years
Y-axis: time in years
In general relativity, both light and matter follow the ______ _______ path through curved spacetime
Straightest possible
In the twin paradox, each twin expects that the other should be ____ than the other twin when they reunite
Younger
In the twin paradox, why are more messages received on the way back than on the way out?
On the way out, the messages and the twin are both travelling in the same direction, but the time the message reached the traveller, they have gone further away from Earth than when the message was sent. On the way back, the twin and the message are going towards each other, so they receive the message closer to Earth than when it was sent.
What is length contraction?
Moving objects lengths are shorter
What is a lightyear?
The distance light travels in a year
Massive objects bend the space around them, forcing light to follow its curved contours
Gravitational Lensing
Newtons First Law of Gravity
Objects in motion stay in motion, unless acted on by an external force
Newtons Law of Gravity
F = G(m1m2)/R2
Newtons Second Law
The change in speed (acceleration) is equal to the applied force, divided by the mass. F=ma
Newtons Third Law
For every applied force, there is an equal but opposite reaction force
Objects with mass produce ______ ______ which are always attractive
Gravitational fields
Rank the four fundamental forces in order of strength
1. Strong nuclear force
2. Electromagnetism
3. Weak nuclear force
4. Gravity
The carrier particle for electromagnetism
Photons (light)
The carrier particle for strong nuclear force
Gluons
the change in speed (acceleration) is equal to the applied force, divided by the mass, F=ma
Newtons Second Law
The distant light travels in a year
Lightyear
The idea that moving objects length is measured to be shorter than its actual length
Length contraction
The idea that gravity is a consequence of spacetime curvature (matter causes space to curve, creating gravity)
General relativity
The idea that the laws of physics work exactly the same in an accelerating frame of reference as they would in a gravitational field
Equivalence Principle
The idea that time runs slower the deeper you are in a gravitational well
Gravitational time dilation
What is relativistic speed?
A speed that is a significant fraction of the speed of light
A clock falling into a black hole would tick ____. It would ____ when it crosses the event horizon
Slower, stop
A region of space where matter is compacted so densely that you'd have to move faster than the speed of light to escape its gravity
Black hole
Are microscopic black holes real?
No, they are only hypothetical
Binary star/system
Pair of stars that orbit one another
Black hole?
A region of space where matter is compacted so densely that you'd have to move faster than the speed of light to escape its gravity
Difference in the force of gravity between two points
Tidal force
Equation for Scwarzschild Radius
g = 2GM/c 2
What is escape speed?
Speed required for a projectile to break free from an objects gravity
Event horizon
Where escape speed equals speed of light
How are intermediate black holes formed?
From collisions of smaller objects/the birth of the Universe
How are microscopic black holes formed?
Energetic particle collisions
How are stellar black holes formed?
When stars die explosively in supernovae
How might the schwarzschild radius increase?
When the black hole consumes other objects it gains mass
How much impact does a supermassive black hole have on the galaxy and why?
They have very little impact because their mass in only a tiny fraction of the mass of the galaxy
If two massive objects orbit one another, the continual change in spacetime curvature propagates outwards as a _____ ______
Gravitational wave
In a binary system, one star may _____ matter from the other, forming an _______ ____
Steal, accretion disk
In general relativity, mass ______ spacetime. This means that objects must follow the _______ possible path through curved spacetime
Bends/curves/wraps, straightest
Name the four categories of black holes
1. Microscopic
2. Stellar Mass
3. Supermassive
4. Intermediate
Name the four ways to confirm/study the existence of black holes
1. X-rays
2. Event horizon telescope
3. Gravitational wave measurements
4. Motion of stars around Sagittarius A*
Pair of stars that orbit one another
Binary star system
Schwarzschild Radius
The distance from the singularity to the event horizon
Speed required for a projectile to break free from an objects gravity
Escape speed
The distance from the singularity to the event horizon
Schwarzschild Radius
The Schwarzschild Radius is dependent on the _____ of the black hole
Mass
The singularity of a black hole
Where the density goes to infinity (center most part of the black hole)
Tidal Force
Difference in the force of gravity between two points
What determines the amount of gravity of a black hole?
It will have the same amount of gravity as whatever it formed from
What do gravitational wave detectors do?
Measures the size of ripples in space due to converging black holes, by measuring the difference in time taken for a laser to make a round trip down the arm
What does compressed mass do to gravity?
It increases gravity
What is the shape of the event horizon in 3D space?
Its a sphere and the singularity is the center of the sphere
What moves faster than the speed of light?
Nothing
When escape speed = speed of light, the object becomes a _____ ______
Black hole
Where do some of the earliest evidence for black holes come from?
X-ray binaries
Where escape speed equals the speed of light
Event horizon
Where the density goes to infinity
Singularity of a black hole
Why is the accretion disk very hot?
Because of matter colliding as it orbits
Why might a black hole emit x-rays?
When an object falls into it, it shreds and gets very hot, producing an x-ray
A _____ amount of mass yields a lot of energy
Small
An idealized object that absorbs all wavelengths of light that strike it
Blackbody
Anything that is very ____ may function as a blackbody
Dense
Binding energy
The energy needed to dissociate two particles from one another
Blackbody
An idealized object that absorbs all wavelengths of light that strike it
Describe how we can determine the makeup of a star from its spectral lines
The spectral lines represent light waves absorbed by atoms in the outer layers of the star. Each atom has a specific absorption based on their electron shells. Can observe which energies align to spectral lines
Do photons take a long/short time to leave a star?
Long, because it has many interactions
Energy of a particle at rest
E = mc²
Instrument that separates light into a perfectly continuous radius of colour
Spectograph
Mass and energy are _____
Equivalent
Masses of individual protons must be _____ when they are bound together
Lower
Neutrinos only interact by gravity and _____ nuclear force
Weak
Neutrinos take a long/short time to leave a star
Short, they have no interactions
Nuclear fusion reaction
4 hydrogen = 1 helium + 2 positrons + 2 neutrinos + 2 gamma rays
Roughly how long does it take for a photon to escape the core of a star
Thousands of years
The energy differences between shells correspond to _____ of light absorbed or emitted when electrons transfer between them
Colours
The nuclear fusion reaction releases some of the _____ of the original protons in the form of energy and particles
Mass
Warmer blackbodies/stars have _____ light intensity
Higher
Warmer blackbodies peak in light intensity at ______ wavelengths
Shorter
What colour is high energy and high frequency wavelengths
Blue
What colour is low energy and low frequency wavelengths?
Red
What colour is produced in high energy jumps
Blue
What colour is produced in small energy jumps?
Red
What colours are hot and cold stars?
Hot: blue
Cold: red
What observatory concluded the theory of solar nuclear fusion by detecting solar neutrinos?
Sudbury Neutrino Observatory
When do objects appear white?
When you receive equal wavelengths of red, green and blue
Who discovered that the Sun is mostly made up of hydrogen and helium?
Cecelia Payne
What is apparent brightness?
Appeared brightness of a light source
Appeared brightness of a light source
Apparent brightness
What is the Balmer Series?
The series of absorption and emission lines of hydrogen
Does a close star have a large/small parallax angle?
Large
Does a far star have a large/small parallax angle?
Small
What is luminosity?
The intrinsic brightness of a light source (unchanging)
Equation for distance of a star with parallax angle
d = 1/p
Method of measuring the distance to nearby stars
OBAFGKM
What is parallax?
Method of measuring the distance to nearby stars
The series of absorption and emission lines of hydrogen
The Balmer Series
To measure the distance to a star using parallax, we measure its position when Earth is at _____ positions in orbit
Two
What are the two reasons a star is made of hydrogen may not show Balmer lines?
1. It may be too cool, so the electrons are in the ground state and can't absorb or emit energy
2. the star is too hot and have already absorbed the max amount of energy (the electrons are at n=5)
What spectral class is the Sun?
G class
What value do we need to convert between apparent brightness and luminosity?
Distance
Who created the stellar spectral types/classes?
Annie Jump Cannon
Why do M and K stars (cool stars) have lots of spectral lines?
They are cool enough that other molecules/atoms can survive in their atmospheres
A group of stars that are born together will die together
Globular cluster
A group of stars that are born together, but may drift apart over time
Open cluster
A large proportion of the stars in the sky you see are unaided are ______ and _______
Giants and supergiants
About 0.4 % of stars are ____ stars
O
About 20% of stars are ____ and ____ stars
F and G
About 4% of stars are ____ and ____ stars
B and A
About 75% of stars are ____ and ____ stars
M and K
Are white dwarf stars dead or dying?
Dead
Are red giant/supergiant stars dead or dying?
Dying
How can we determine the age of a star cluster on an HR diagram?
The age can be told by the lifespan of the shortest lived star that is still on the main sequence
Lifespan equation
Lifespan = mass/luminosity life = 1/M to the power of 2.5
Lifetime vs age
Their age depends on life time. Ratio
List the luminosity classes
1. Supergiants
2. Bright Giants
3. Giants
4. Subgiants
5. Main Sequence
Main sequence turn off age
Age of a star cluster
Of stars in the same spectral class, what factor increases luminosity
Size
On the main sequence, all M stars will be (size) and (colour), while O stars will be (size) and (colour)
M stars will be small and red
O stars will be big and blue
What is an open cluster?
A group of stars born together, but may drift apart over time
What are black dwarfs?
They are future stars
What are G-class main sequence stars called?
Yellow dwarfs
What are M-class main sequence stars called?
Red dwarfs
What is the x-axis of an HR diagram?
Surface temperature, colour, spectral class
What is the y-axis of an HR diagram?
Luminosity
What must be occurring in stars for them to be alive and on the main sequence?
Fusing hydrogen
What must occur for a star to fall of the main sequence/die?
They stop fusing hydrogen in their cores
Why do M stars live longer than O stars?
Since they are cooler with less luminosity, they burn the hydrogen in their cores slower. This allows them to live longer. While O stars are hot and luminous, they burn through their hydrogen quickly
As the inert core grows in mass and accumulates more shells, the star...
Expands
Breaking apart nuclei is called...
Fission
Combining nuclei is called...
Fusion
Contraction of a star due to its own gravity
Gravitational collapse
Convection of a star
The outer zone of a star where hot plasma rises, bringing heat to the surface
Core
The inner zone of a star that is very dense and allows for fusion to occur
Describe hydrostatic equilibrium
A density that is above equilibrium occurs, the rate of fusion increases, temperature increases, pressure increases, the core expands, which causes the density to drop back down to equilibrium
How is the iron core held up? (i.e doesn't collapse)
Degeneracy pressure
If the final product has a higher binding energy than the initial product, energy is _____
Releasing
If the final product has a lower binding energy than the initial product, energy is ______
Consumed?
Increasing energy of fusing shells eventually blows off hydrogen and helium envelopes leaving the inert carbon core
Planetary nebula
Point in molecular could that are more ______ will attract more matter because of gravity
Dense
Radiative zone of a star
The middle zone of a star what is hot and calm, but not dense enough to start fusion
The energy produced in a hydrogen burning shell is _____ than the energy produced fro a hydrogen burning core, what does that cause?
Much larger, It causes the star to puff up
The inner zone of a star that is very dense and allows for fusion to occur
Core
The iron core grows as....
Each layer completes its chain of fusion
What are molecular clouds made of?
3/4 hydrogen and 1/4 helium trace amounts of other elements and carbon dust
What causes the temperature of the core to become hot enough for fusion?
Gravitational collapse
What element cannot release energy from fusion?
Iron
What happens to electrons and protons at extremely high pressures?
The combine to form neutrons and neutrinos
What happens to extremely massive stars after a supernovae?
They collapse into a black hole
What happens to the core of a protostar as gravity is pulling in gas?
The core gets denser and hotter
What happens to the electrons of of the helium nucleus at high temperatures?
They get stripped away into the electron cloud surrounding the nucleus
What happens to the iron core after the supernovae?
It collapses into a neutron star
What is a white dwarf?
A carbon core that has been cooling for years
What two factors are needed for protons to collide, and why?
1. protons need to be moving at very high speeds (existing in very high temperatures) Because protons are both positively charged, so they will repel as they get closer
2. Protons need to be at a high density in one space, otherwise the chance of collision is too low. Without collision, they high temperature won't be able to be maintained
With electrons gone there is no more electron _____ pressur
Degeneracy
Without electron degeneracy pressure, what happens to the iron core?
It collapses onto itself and releases huge amounts of energy (supernovae)
Describe how white dwarfs explode
Two stars in a binary system, one ages and dies into a white dwarf. As the second star ages, the white dwarf collects its mass. If a white dwarf collects mass it can undergo fusion into iron and then eventually explodes
Describe the impacts of a neutron star merger
Two neutron stars in a binary system begin to merge. The closer they get together, the faster they orbit each other. Right as they are about to merge they are spinning so fast that they spray neutron star material into space. This spray decays into heavy elements
How can we tell neutrinos are being made in the Sun?
Measure the amount of neutrinos coming out of the core
How do we know the structure of the Sun if we can't see inside it?
The Sun vibrates like a bell, the observations show the structure of the intrerior
In globular clusters, all the stars are formed at...
the same time
What elements were created in the Big Bang?
Hydrogen and Helium
What is a type 1a supernovae?
An exploding white dwarf
Bulge
Center of the galaxy
Center of the galaxy
Bulge
Diameter of the Milky Way
100,000 light years
Disk
Gas and dust orbiting the center of the galaxy on a galactic plane
Force is ________ ________ to distance squared
inversely proportional
Force is _______ ________ to the masses of the object
Directly proportional
Gas and dust orbiting the center of the galaxy on a galactic plane
Disk
Globular clusters are the _______ things in the Universe
Oldest
Glow of globular clusters around the center of the galaxy that don't lie in the galactic plane
Halo
How do bulge stars orbit?
Orbit with random orientations around the center
How do disk stars orbit?
in circles with the same orientations (on a plane) around the center
How do halo stars orbit?
Around the center above and below the disk in random orientations
How many stars are in the Milky Way?
200 billion stars
How long does it take the Sun to orbit the Milky Way?
230 million years
If you double the mass of an object, the force between in and another object ________
doubles
In a globular cluster, what colour are the brightest and dimmest stars?
They are red
The doppler effect states that as you are moving towards something, it will be _______-shifted, and as you are moving away from something it will be ______-shifted
blue, red
There is ______ star formation in the bulge
Low
Under what light does cold dust glow?
Under mm/microwave light
What are dark matter particles?
We don't know, some sort of undetected particle that is table with no electric charge, but has mass
What are the three main points of evidence for dark matter?
1. speed of stars on the rim of our galaxy move faster than they should
2. gravitational lensing
3. mass of star cluster is much greater than the combined mass of only the stars
What does the Sun orbit?
The center of the Milky Way
What happens to the remnants when stars supernovae?
They cool down and form new molecular clouds which contribute to new star formation
What is at the center of our galaxy?
A black hole
What is the width of our galaxy?
1000 light years
What type of stars are location in the disk?
O stars or short lived stars
Where does most star formation occur?
In the disk
Where would O stars be located compared to the location of M stars within our galaxy?
O stars are short lived, so they can't travel far from the disk in their lifetime. M stars are long lived, so they could travel very far from the disk within their life time.