Final

Question 1

Explain the Doppler Wobble Method (how it works and what it tells us)

Answer 1

The Doppler Wobble is an effect used to identify exoplanets and find the minimum mass of a planet (we cannot know the exact mass of EP w/ just Doppler Wobble method because we don’t know inclination of orbit). To use it we observe the reflex motion of the stars they orbit which shows the star’s red or blueshift. This color shift gives us an idea of the orbit period/speed which helps us gain knowledge of the planet’s minimum mass.

Question 2

Explain the Transit Method (how it works and what it tells us)

Answer 2

The Transit Method is used to identify exoplanets and find their volume. When a planet is edge-on to our line of sight, we can find the volume by measuring the percentage by which the star’s light dims to find the radius then eventually the volume of the exoplanet.

Question 3

What are the components of comets, tell me about their orbits.

Answer 3

Comets are icy, dirtballs that evaporate as they near the sun. Their tails consist of dust and gasses that are pushed away from their bodies from the sun’s radiation/solar wind. Some comets are periodic (although most are not) and operate on elliptical orbits where they spend most of their time away from the sun. Additionally, comets come from the Kuiper Belt.

Question 4

What is the difference between asteroids, meteoroids and meteorites

Answer 4

1. Asteroids= “space rocks” found in belt between Jupiter and Mars
2. Meteoroids= small bodies coming mostly from asteroid belt that enter our atmosphere and often vaporize
3. Meteorites= meteoroids if they reach earth’s surface

Question 5

What would happen if a >10 km comet/asteroid hit earth?

Answer 5

The impact would cause mass extinction of life on earth. After impact, there would be global extreme heat followed by an impact winter where dust would cover the sun and nothing would grow.

Question 6

What’s going on when there’s a meteor shower?

Answer 6

When there’s a meteor shower earth in its orbit is passing through a disintegrating/disintegrated comet (this will happen at the same time each year)

Question 7

Why was Pluto demoted to dwarf planet?

Answer 7

1. Discovery of Kuiper Belt Objects that were comparable in size to Pluto
2. It’s gravity did not clear it’s neighborhood of other objects

Question 8

What are properties of terrestrial and jovian planets respectively?

Answer 8

Terrestrial: Highly dense, rocky, topological features like valleys/craters, liquid/heavy metal core
Jovian: Low density (lighter than water), made of gas/liquid/ice, have rings, cold, farther from the sun, rocky cores, many moons
classifications of planets divided by frost line/asteroid belt

Question 9

What is the greenhouse effect and how does it happen?

Answer 9

The greenhouse effect is when visible light enters the atmosphere and heats up the surface of a planet which then emits infrared light which is absorbed by the atmosphere and creates a bubble of heat in the atmosphere.

Question 10

How do we think the moon formed, what indicates this?

Answer 10

We think the moon formed from debris after a collision earth had early in it’s formation. Astronomers believe this because the moon has similar chemical/physical components as the earth.

Question 11

How do tides and the moon relate?

Answer 11

They are intrinsically linked. The moon is tidally locked in its rate of spin so from Earth we always see the same side of the moon. The moon also affects the tides by pulling the tides on one side of the Earth towards itself while the tides on the other side of the Earth pull away from the moon which creates a low tide in the center of the earth (low/high tide always changing because of Earth’s revolution)

Question 12

Who had the Geocentric theory and who had the Heliocentric theory? Why was the Geocentric theory disproved?

Answer 12

Ptolemy formulated the Geocentric Theory while Copernicus formulated the Heliocentric Theory. The GT was disproved because of Galileo’s observations of Venus’ phases. –> Venus is really close to the sun in the sky (as seen from Earth) which means it would have to go through all of its phases but only 2 of those phases would line up with Ptolemy’s system.

Question 13

What are Kepler’s Three Laws?

Answer 13

1. Planetary orbits are ellipses
2. Line between planet and sun sweeps equal areas in equal time
3. Planet’s orbital period squared is equal to cube of semi-major axis (P^2=kR^3)

Question 14

What are Newton’s Three Laws?

Answer 14

If no forces act on a body its speed/direction of motion stay constant
force= mass x acceleration (F=ma)
When two bodies interact they exert equal and opposite forces on each other

Question 15

How is gravity produced?

Answer 15

gravity produces orbit by taking its straight line motion at constant speed (motion is perpendicular to direction of gravity that is in straight line from sun to planet) and pulls it toward to star. However bc it straight line motion (perpendicular velocity) exists it ends up being carried around the star

Question 16

Explain how seasons occur.

Answer 16

Seasons occur because of the tilt of the Earth’s axis. When the Earth’s axis is tilted away from the Sun, the sun’s heat has to travel farther to heat up the surface of the Earth/is hitting the earth for a shorter amount of time and vice versa. Additionally, during summer the sun’s rays are coming in more vertically while in the winter the rays are coming in more horizontally.

Question 17

How does the “movement” of the celestial sphere work?

Answer 17

The Celestial Sphere is a distant, fixed sphere in the sky that appears to move when our Earth rotates. At any given point on earth (save for the north and south poles’ celestial poles) you can see half the celestial sphere. Each night a given constellation (ex: Orion) will be rising/seen overhead 4 min earlier than the previous night

Question 18

What is a lunar eclipse?

Answer 18

When the moon aligns behind the earth relative to the sun.
Lunar eclipses can be seen from the entire dark hemisphere.

Question 19

What is a solar eclipse?

Answer 19

A solar eclipse is when the moon aligns in front of the sun the block it out. Solar eclipses occur in phases and you can only look directly at total solar eclipses. (eclipses provided first proof of Einstein’s GR Theory)

Question 20

Why does the moon look red during a lunar eclipse?

Answer 20

The moon looks reddish because the atmosphere scatters blue/green wavelengths but refracts red wavelengths onto the moon (sun has to travel farther across atmosphere, produces red W).

Question 21

Whats the difference between a reflector and refractor telescope?

Answer 21

Reflecting telescopes use mirrors to harness light (can suffer spherical aberration) while refracting telescopes use lenses to harness light (can suffer chromatic aberration).

Question 22

Explain how telescopes work.

Answer 22

Telescopes collect light/wavelengths. The larger their diameter the lower theta the better the resolution and vice versa

Question 23

What is redshift vs. blueshift?

Answer 23

Redshift is the red wavelength (longer wavelength) given off when an object is moving away from the observer and Blueshift is the blue wavelength (shorter wavelength) given off when an object is moving toward the observer.

Question 24

What is emission and absorption respectively? What do they tell us?

Answer 24

Emission (excess energy) → when photons randomly go down energy levels and emit emission lines (emission lines=random directions). Emission lines show excess photon in continuum.
Absorption –> when photons w/ right amount of energy level passes through electrons which absorb the energy and jump up energy levels
Absorption lines show deficit photons in continuum

Question 25

How does ionization happen?

Answer 25

When photons are absorbed and an electron is freed from a bound atom

Question 26

What are photons?

Answer 26

particles that come in form of wave or energy packets that make up light

Question 27

What do the wavelength, color, brightness, and temperature of a star have to do with each other?

Answer 27

The wavelength at which the spectrum peaks (the color of the star) is a measure of its surface temperature
Thermal continuum wavelength will peak in certain color in accordance with the brightness

Question 28

What are the three components of the sun’s surface?

Answer 28

Photosphere= visible surface of the sun
Chromosphere= thin layer above photosphere that makes up atmosphere & produces emission lines
Corona= large, low density envelope structured by magnetic fields

Question 29

What are some functions of the Sun’s surface?

Answer 29

Coronal Mass Ejections= big outburst of energy that often affects radio/magnetic waves on Earth
Prominence= gentle eruption on the Earth’s surface
Solar Flare= violent release of energy
Solar Wind= E and positive I blowing from sun (interacts with comets+ planet mag. fields)
Sunspots= regions of strong magnetic field that inhibit the rise of heat to the photosphere (also used to track rotation of the Sun)

Question 30

What does the peak wavelength (color of star) of a star’s spectrum tell us?

Answer 30

The star’s surface temperature

Question 31

What do color, absorption lines & shape of stars tell us?

Answer 31

They tell us about the surface temperature and the chemical composition.

Question 32

O, B, A, F, G, K, M, L

Answer 32

Obviously Bill Always Felt Good Kissing Monica Lewinsky

Question 33

What is parallax and what is it used for?

Answer 33

Parallax is the perpendicular inclination angle measured across two different points 1 AU adjacent to each other (from one point of Earth’s orbit around the sun to the opposite point). It is used to find how far away a nearby star is.

Question 34

What is the inverse square law of light?

Answer 34

That the farther the star the lower it’s luminosity will appear to the observer. (apparent luminosity decreases with distance)

Question 35

What are the different relationships that different types of stars have between temperature and luminosity?

Answer 35

White Dwarfs= high temp, low luminosity
MS Stars= the higher the temp, the higher the luminosity
Red Giants/Supergiants= low temp, high luminosity

Question 36

How does the Stefan Boltzmann Law determine the size of stars?

Answer 36

First, you measure Temperature from the star’s spectrum. Then you find the Luminosity from the Brightness and Distance and with that you find the radius.

Question 37

What is the primary use of binary stars and how?

Answer 37

The primary use of binary star systems is to find the stellar mass of stars. We do this by knowledge that higher mass stars are always closer to the center of mass than lower mass stars.

Question 38

What’s the difference between globular clusters and open clusters?

Answer 38

An open cluster has a sparse amount of stars that are majority young and usually reside in the spiral arms of galaxies. A globular cluster is densely packed with old stars and is usually found in the halo of a galaxy. Additionally, all stars in the cluster have the same distance, age, and initial chem. Composition

Question 39

Compare O type star’s lifetimes with M type star’s lifetimes.

Answer 39

O type stars have shorter lifetimes because they have higher mass but also higher luminosity which means they burn out (die) faster than M type stars which have longer lifetimes because they have lower mass and lower luminosity

Question 40

How do pre-MS stars form and what differentiates them from MS stars?

Answer 40

Pre-MS stars form when a cloud of gas and dust collapses from it’s own gravity and as the density between particles grows, so does the heat and the pressure and the following contraction of the cloud. Pre-MS stars are different from MS stars though because there is no nuclear fusion going on in the core

Question 41

Tell me about Main Sequence Stars.

Answer 41

Main Sequence star’s energy source comes from nuclear fusion in the core where the fusion in the core is pushing outwards but the gravity from the outside is pushing in. In MS stars, Helium and Hydrogen are the elements being fused and once the fusion in the core runs out, the star moves off the MS and the Helium core expands.

Question 42

What’s the energy source difference for Red Giants vs. Red Supergiants?

Answer 42

For Red Giants, the He core heats up and creates a carbon and oxygen core. For Red Supergiants, the carbon and oxygen core contracts and the He & H shell expands

Question 43

What are the lifetime stages for a red giant after it’s red giant stage and how does it get there?

Answer 43

After the red giant stage, a star will turn into a planetary nebula and a white dwarf. Once the red giant becomes unstable the planetary nebula (which is just ionized gas expanding) will slowly expand. Eventually, the central star will become a white dwarf but over time the ions loose energy which causes the white dwarf to cool down until it eventually fades.
(both PB and WD are held up by electron degeneracy pressure.)

Question 44

What are the lifetime stages for a red supergiant after it’s red supergiant stage and how does it get there?

Answer 44

After the red supergiant stage, a star will go supernova and turn into either a Black Hole or a Neutron Star. Supernovas happen when the Fe core in a supergiant stops fusing, collapses in on itself, and releases a ton of energy. Depending on the mass of the supergiant, following the supernova, the star will either collapse into a Neutron Star or a Black Hole. (black holes can also be formed when neutron stars are too massive to be supported by neutron degeneracy pressure)

Question 45

What are Pulsars?

Answer 45

Pulsars are neutron stars with highly magnetized fields nearly perpendicular to the rotation axis that look like they’re blinking at us when they rotate.

Question 46

What are the two types of Supernovae?

Answer 46

Type 1: White Dwarf in binary system gains mass when more massive star passes
The roche limit → when WD gains mass past the Chandrasekhar limit nuclear chain reactions
Occur and the star blows up
2 white dwarfs merging can have same result
Type 2: Red Supergiant stops having reactions in Fe core
Fe core collapses, releases tons of energy and forms a neutron star

Question 47

Tell me about Black Holes.

Answer 47

Black Holes are regions in space that are so dense that not even light can escape once beyond the Schwarzschild radius/event horizon. Light and all other matter are trapped inside due to relativity/warping and once inside are said to be collapsed into singularity (only been described mathematically). However, outside the EH in the ergosphere energy can still be extracted at speeds less than the speed of light (still hella high speeds) therefore, light can orbit BH in ergosphere.

Question 48

What happens to people/objects inside and near Black Holes/when observing people/objects near Black Holes.

Answer 48

Black Holes don’t have “hair” when in equilibrium, meaning you would have to get significantly close to it to be affected by it. For low-mass Black Holes, the tidal forces are stronger which means that if you got too close you would be spaghettified. If you were to observe someone getting sucked in a BH, you would never see them fall in all the way because at the EH light is redshifted to zero energy. But if they got out before the EH they would be aged less than you. They would feel themselves fall in from their perspectives tho

Question 49

How are Black Holes detected if we cannot see the light in them?

Answer 49

Black Holes are detected by their massive gravity, by orbital speed of star if in binary system, by orbital speed of gas getting sucked into BH and through LIGO which is a new tool that detects gravitational waves.

Question 50

When do Gamma Ray Bursts occur?

Answer 50

When massive stars collapse to form Black Holes, when Neutron Stars merge to form Black Holes and when Neutron Stars and Black Holes merge to form Black Holes (birth/growth cry of BHs)

Question 51

What are the different types of Nebulae in Spiral Arms of Galaxies?

Answer 51

1. Emission nebula: gas is ionized by UV light from hot stars, and glows when electrons recombine
2. Reflection nebula: dust in a cloud of gas reflects light from stars
3. Dark absorption nebula: a large amount of dust in a cloud of gas blocks light
   all three are often associated with each other

Question 52

What are Cepheids, why are they important and how are they used?

Answer 52

Cepheids are supergiant, pulsating star variables that brighten and dim with size. They are important because they allow astronomers to make reliable measurements of distant galaxies. They are able to do this by merely finding a cepheid variable star in another galaxy and then comparing it’s apparent brightness with it’s intrinsic brightness.

Question 53

What are the 2 Hubble Type Galaxies and what are their properties?

Answer 53

1. Spiral Galaxies= new stars forming in arms, old stars formed in the disk
2. Elliptical Galaxies= no disk, no arms but consists of old stars –> means it has little gas and dust

Question 54

What does a flat rotation curve of a spiral galaxy imply?

Answer 54

The flat rotation curve of a spiral galaxy implies the existence of dark matter.

Question 55

What is gravitational lensing and how does it apply to dark matter?

Answer 55

Gravitational lensing occurs when the light from a distant object is bent by the gravity of intervening galaxies. This serves as further evidence for dark matter because the distribution of gravitational lensing arcs depends on the total mass of the galaxy which tells us that clusters are dominated by dark matter.

Question 56

How did Hubble discover the universe was expanding? What knowledge did science gain from this discovery?

Answer 56

Hubble discovered the universe was expanding by observing that spiral galaxies have large redshifts. Upon further observation, it was discovered that radial velocity increased with distance (farther galaxies were moving away at greater speeds), the redshift was caused by the expansion of the universe itself not the increased speed of galaxies and since there was now a greater lookback time we could learn more about the early formation of galaxies.

Question 57

What are quasars?

Answer 57

They are hypothesized to be black holes that inhabit the centers of galaxies. They are much smaller than but often much brighter than the galaxies that inhabit due to the massive amount of matter they are accreting. They also have “jets” perpendicular to their accretion disk due to a magnetic field

Question 58

What is Olber’s Paradox and its solution?

Answer 58

Olber’s Paradox is the question of if the universe is infinite in size and age and is uniformly filled with stars, then why doesn’t every line of sight intersect a star?
The solution: The universe has a finite age and light from the most distant stars has not reached us yet!

Question 59

What is the Cosmological Principle?

Answer 59

The CP is the idea that the universe is uniform aka both homogenous (same average density) and isotropic (looks the same in all directions)

Question 60

How does measuring the angular size of variations in temp in CMBR indicate that the universe is flat?

Answer 60

We know from physics of early universe how the density variations grew with time
All happened so early that all variations behaved same way (doesnt matter about finite universe)
We know how big physically the fluctuations shoudlve become and we’re looking at them from 13.8 billion lyrs away → if universe is flat then the angle will satisfy the angles and measurements of a euclidean triangle
But if universe is positively/negatively curved the angles will travel/look differently than euclidean triangle (measuring theta)
What we measure are temp variations that correspond with density variations and you can calculate how the density variations will have grown in size

Question 61

Why were photons in the early universe not able to travel very far?

Answer 61

The universe in those early times was incredibly hot and opaque, filled with a miasma of free electrons that blocked the path of any photon, or particle of light, that was trying to travel