flashcards astronomy final - concepts and terms

stellar classification

1. OBAFGKM

2. hot to cold

3. least to most common

parallax

The apparent shift in position of a nearby star against the background of distant stars, used to measure distances to stars. The observed displacement of an object caused by the change of the observer's point of view.

magnitude system

measure of the brightness of a star or other celestial body. the brighter the object, the lower the number assigned. based off apparent and absolute values

metallicity

proportion of a star’s composition that is not hydrogen or hellium

binary star systems

1. two stars that orbit around a common center of mass.

2. types are detached, semi-detached, and contact

3. they can transfer mass which affects their evolutions

4. they can create unique nebulae

mass/luminosity/radius relationship

1. luminosity is proportional to mass

2. L ∝ M^3.9

3. small increase in mass results in a lot more luminosity

4. if a star has more surface area, then it has more ability to emit light (luminosity

HR diagram

1. vertical axis = luminosity

2. horizontal axis = temp in k

3. luminosity increase as you go up

4. temp increase as you go left (suprising)

5. 90% main sequence

6. 10% giants and supergiants

7. 10% dwarves

8. shows the evolution of stars

9. sun in the middle

beyer designation for stars

1. stars assigned greek letters

2. brightest stars to least

3. starts from alpha, beta…

4. genitive form of the constellation, like alpha andromedae

types of nebulae

1. types: H II regions, planetary, supernova remnants, cold neutral hydrogen clouds, giant molecular clouds

2. H II regions are big cloud of gas (plasma, ionized hydrogen) heated up by nearby stars

3. planetary ones are when when a star goes from giant to white dwarf and experiences mass loss in slow motion faux-explosion, leaves a huge cloud of gas behind, nothing to do with a planet, too hot for star birthing

4. supernova remnants are what is left behind when a star explodes, can contain a neutron star or a black hole, too hot for star birthing

5. cold neutral hydrogen clouds (H1) contain atomic hydrogen that are very cold but not bonded together

6. giant molecular clouds are the type that yield stars, in a state of hydrostatic equilibrium until something triggers overdensity, contain molecular hydrogen (bonded)

star formation

1. they come from giant molecular clouds

2. stellar nurseries have the right size, temperature, density

3. triggered by cloud collision or star explosion shockwaves that pushes gas into itself

4. happens in bursts, self-perpetuating

5. first stars would have been huge and lived short, creating supernovas that made the periodic table

hayashi track

1. Path a protostar follows on HR diagram before becoming a star

2. Shows journey as gas cloud collapses, heats up, gets denser

3. Mass determines which track, how long it takes, and final position

4. More massive stars evolve faster along tracks

6. Ends when star reaches main sequence/zero age main sequence

7. Mass is THE most important property determining everything about the track

main sequence lifetimes

1. More massive stars live shorter lives despite more fuel (higher luminosity burns fuel faster)

2. Sun: ~10 billion years; O-stars: ~1 million years; M-stars: hundreds of billions

3. Stars spend 90% of life on main sequence fusing hydrogen

4. Mass determines entire stellar evolution path and ultimate fate

5. In binary systems, more massive star evolves off main sequence first

evolution steps

1. RGB: H-shell fusion, core contracts, star expands

2. Helium Flash: Sudden He ignition in degenerate core

3. Horizontal Branch: Core He fusion + H-shell burning

4. AGB: Alternating He/H shell burning

5. Mass Loss: Strong winds eject outer layers

6. Planetary Nebula: Ejected material + exposed hot coreted material forms colorful nebula, exposing hot core (future white dwarf)

white dwarf

1. Leftover cores of low/medium-mass stars

2. No longer generating fusion energy

3. Supported by degenerate electron gas pressure

4. Prevented from collapse by Pauli exclusion principle

5. Final evolutionary stage for most stars including our Sun

degenerate gas

1. Special quantum state of matter

2. Found in white dwarfs after mass loss

3. Electrons forced into higher energy states

4. Creates pressure that resists gravity

5. Prevents collapse despite no fusion

methods of distance measurement

1. Parallax: Measuring apparent shift of nearby stars from different Earth positions

2. Variable stars: Period-luminosity relationship helps determine distance to galaxies

3. Main sequence fitting: Temperature-luminosity relationship of stars estimates distance

4. Type I supernovae: Standard candles with known luminosity reveal galaxy distances

5. Redshift: Measures how much light stretches due to universe expansion (doppler)

variable stars

1. Stars that change brightness over time

2. Period of brightness variation directly relates to luminosity

3. Critical for measuring distances to galaxies

4. Stars in evolutionary transition phases

5. Helped discover other galaxies exist beyond Milky Way

components of milky way

1. Barred spiral galaxy with central bulge and spiral arms

2. Supermassive black hole at center

3. Population I stars (young, high metallicity) in spiral arms

4. Population II stars (older, lower metallicity) in central region

5. Dark matter halo surrounding and holding galaxy together

6. Interstellar medium of gas and dust between stars

population I stars

1. Youngest generation of stars

2. Found in spiral arms and disk of Milky Way

3. Include our Sun

4. Have higher metallicity than older stars

5. Formed from recycled gas of dead Population II stars

6. Can have wide range of masses

7. Still have gas available for making new stars

population II stars

1. Older generation of stars (10-13 billion years old)

2. Found in central region/bulge of Milky Way

3. Lower metallicity than Population I stars

4. Redder and smaller than Population I stars

5. Largest Population II stars died long ago

6. Recycled gas from their deaths formed Population I stars

7. Comparable to "grandparents" in stellar generations

galaxy classification

1. Hubble's tuning fork diagram: elliptical, spiral, or irregular

2. Elliptical galaxies are older, larger, and have stopped forming stars

3. Spiral galaxies (like Milky Way) have active star formation in their arms

4. Barred spirals have central regions stretched in bar-like shape

5. Irregular galaxies don't fit other categories, often result from mergers

6. Galaxy color indicates star population - blue for young stars, red/orange for older stars

7. Milky Way is a barred spiral galaxy with population I stars in arms, population II in center

8. Galaxies evolve from spirals to ellipticals through mergers

spiral galaxy

1. Have spiral arms where active star formation occurs

2. Contain supermassive black holes at their centers

3. Younger than elliptical galaxies, still forming stars

4. Milky Way is a barred spiral galaxy

5. Eventually evolve into elliptical galaxies through mergers

6. Appear bluer due to younger, hotter stars

elliptical galaxy

1. Older than spiral galaxies

2. Little to no active star formation

3. Appear redder due to older stars

4. Form through galaxy mergers

5. Contain mostly Population II stars (lower metallicity)

6. Minimal gas and dust content

hubble’s law/cosmological redshift

1. Galaxies are moving away from us at speeds proportional to their distance

2. Light from distant galaxies is redshifted due to universe expansion

3. Allows measurement of cosmic distances and expansion rate

4. Supports Big Bang theory

5. Hubble constant (H₀) quantifies the expansion rate

quasars

1. Now known as Active Galactic Nuclei

2. Extremely bright objects powered by supermassive black holes

3. Appear star-like but are actually distant galaxies

4. Represent earliest stages of galaxy evolution

5. Black holes at centers have huge accretion disks giving off tremendous light

6. Found at very high redshifts, showing they're from early universe

galaxy evolution

1. Galaxies started small and merged into bigger ones

2. Early galaxies were spirals with active star formation

3. Mergers transform spirals into elliptical galaxies

4. Star formation occurs in bursts, triggered by mergers

5. Supermassive black holes form at centers, creating AGNs

6. Universe had peak star formation ~10 billion years ago ("cosmic high noon")

star-bursting

1. Intense period of rapid star formation

2. Typically occurs after galaxy mergers

3. Self-perpetuating process - new stars explode, triggering more star formation

4. Creates irregular galaxy appearance

5. Milky Way currently forms ~1 sun-worth of stars per year, not in bursting phase

6. Eventually galaxies use up gas reserves and become quiescent

quiescent galaxies

1. No longer making new stars

2. Final stage of galaxy evolution

3. Typically elliptical galaxies

4. Have used up all available gas for star formation

5. Contain mostly older, redder stars

6. Result after mergers and star-bursting phases end

evidence of dark matter

1. Galaxy rotation curves - stars orbit too fast at edges (newton says stars farther from the galactic center should orbit more slowly)

2. Gravitational lensing - light bends around invisible mass

3. Galaxy formation simulations match observations only with dark matter

4. Galaxy clusters held together by more mass than visible

properties of dark matter

1. Massive - has mass to explain gravitational effects

2. Neutral - not positively or negatively charged

3. Dark - doesn't interact with light (doesn't absorb or emit)

4. Stable - existed since beginning of universe

5. Cold - not moving at speed of light

6. Makes up about 27% of universe

dark energy and evidence

the mysterious force of empty space itself that is causing the universe to expand at an accelerating rate

1. Accelerating expansion of the universe - we think gravity would slow expansion, but it’s not

2. Distant supernovae appear dimmer than expected, space is expanding faster than expected, pushing them farther away

3. Universe is transitioning from matter-dominated to dark energy-dominated

vacuum energy

1. Proposed explanation for dark energy

2. Energy inherent in empty space itself

3. Could explain why universe's expansion is accelerating

4. Lab measurements predict expansion rate soo much faster than observed

what is universe made of

1. 5% ordinary matter (stars, planets, etc.)

2. 25% dark matter (5 times more than ordinary matter)

3. 70% dark energy

4. Dark matter provides gravitational effects but doesn't interact with light

5. Dark energy causes accelerating expansion of universe

binary evolution

1. Stars in can transfer mass to each other

2. Mass transfer can dramatically alter stellar life paths

3. Can lead to various phenomena like novae and supernovae

4. Close ones may eventually merge, creating unique astronomical event

roche lobe

1. Boundary determining if matter is gravitationally bound to a star

2. If gas crosses outside Roche lobe, it's no longer bound to that star

3. In binary systems, matter outside one star's Roche lobe can fall onto companion star

4. Size depends on star's mass and object's velocity

5. Semi-detached binary: one star overflows its Roche lobe

6. Contact binary: both stars overflow their Roche lobes

high mass evolution

1. Stars with mass greater than 8 times the Sun's mass

2. Fuse elements up to iron in core (enough heat and pressure to continue nuclear fusion beyond hydrogen and helium, creating progressively heavier elements through fusion reactions)

3. Core collapses rapidly when iron fusion begins (fusing iron requires energy rather than releasing it - net negative energy wise)

4. Collapse triggers Type II supernova explosion

5. End as neutron stars or black holes

6. Have convective core with radiative outer zone (In high-mass stars, the core is convective (material physically moves up and down, transferring heat through motion), while the outer zone transfers energy through radiation. This is the opposite arrangement from low-mass stars, which have radiative cores and convective outer zones)

neutron stars

1. Formed when electron capture turns protons into neutrons (When a massive star's core collapses, the pressure becomes so intense that electrons are forced into atomic nuclei. These electrons combine with protons to form neutrons)

2. Incredibly dense - 100 trillion times Earth's density

3. Spin extremely fast with strong magnetic fields

4. Radiation beams shoot from poles (they have extremely strong magnetic fields that aren't aligned with their rotation axis. when the stars spin rapidly, charged particles are accelerated along magnetic field lines, producing intense beams of radiation that shoot out from the magnetic poles)

5. Result from core collapse of stars too massive for white dwarfs (the outer layers are blown off in a supernova explosion, while the core compresses into a neutron star)

spacetime

1. Space and time are linked together as one thing

2. Mass/energy curves and warps it, causing gravity

3. We all move through it at the same rate

4. Moving faster through space means moving slower through time

5. its curvature causes light to bend near massive objects

6. Extreme warping creates black holes

curvature of space

1. Mass/energy causes space to bend and curve

2. More mass in smaller space creates steeper curvature

3. affects light's path, making it bend

4. Extreme cases create "holes" light cannot escape from

5. Jupiter's mass creates gentle bend over large area; same mass compressed would create steeper curve

6. Black holes form when it becomes so steep nothing escapes

characteristics of black holes

1. Region where gravity is so strong nothing can escape, not even light

2. Created when massive stars collapse under their own gravity

3. Defined by event horizon - point of no return for matter and light

4. Singularity at center where spacetime curvature becomes infinite

5. Warp spacetime extremely around them

6. Can be detected by effects on nearby stars and gas

7. Emit Hawking radiation

evolution of black holes

1. Formation from collapse of massive star core after supernova

2. Initial stellar-mass black hole (~10 times sun's mass, ~30km size)

3. Growth through accretion of surrounding matter

4. Possible merger with other black holes to increase mass

5. May become active galactic nucleus (quasar) when consuming large amounts of matter

6. Eventually may grow to supermassive black hole at galaxy center

7. Very slow shrinkage through Hawking radiation if not fed

solar activity

1. Follows 11-year cycle of high and low activity

2. Driven by sun's magnetic field twisting and untwisting

3. Sunspots appear darker because they're cooler than surrounding areas (because magnetic field lines entering/exiting the photosphere block energy from rising, making these areas cooler)

4. Prominences are huge arcs of charged particles flowing along twisted magnetic field lines

5. Solar flares and coronal mass ejections release energy when magnetic fields unwind

6. Can cause Northern Lights and disrupt Earth's communications/satellites

layers of sun

1. Core: Central region where nuclear fusion occurs, converting hydrogen to helium

2. Radiative Zone: Light carries energy outward from core

3. Convective Zone: Energy transferred by rising and falling gas

4. Photosphere: Visible surface of sun

5. Chromosphere: Denser portion of sun's atmosphere

6. Corona: Less dense, much hotter outer atmosphere

7. Solar Wind: Constant stream of particles and energy flowing from sun

nuclear fusion

1. Converts hydrogen into helium in sun's core

2. Releases energy according to E=MC² (einsteins theory of relativity). a little mass = a shit ton of energy. (matter converted to energy)

3. Requires extremely high temperature and density to overcome proton repulsion

4. Proton-proton chain is main fusion process in sun

5. Produces neutrinos that can be detected on Earth

6. Powers stars throughout their main sequence lifetime

proton-proton chain

1. Main process by which the sun generates energy

2. Converts hydrogen into helium in the sun's core

3. Produces energy, high-energy light, neutrinos, and positrons

4. Requires extremely hot and dense conditions to occur

5. Created most of the helium in the early universe

hydrostatic equilibrium

1. Balance between gravity pulling inward and gas pressure pushing outward

2. When balanced, stars remain stable on main sequence

3. When imbalanced, stars evolve and change

4. Required for stars to maintain fusion in their cores

5. When gravity wins, it leads to stellar collapse

big bang event

1. A moment when universe was extremely hot and dense

2. Happened everywhere, not at a specific location

3. Not necessarily the beginning of universe, just when our physics breaks down

4. Evidence includes cosmic microwave background radiation

5. Led to symmetry breaking of the four forces

cosmic microwave background radiation

1. Leftover light from the Big Bang

2. Discovered accidentally

3. Comes from all directions and is nearly uniform

4. Temperature helps determine the age of universe

5. Comes from recombination era of early universe

6. Originally high energy, now detected as microwaves due to universe's expansion

symmetry breaking

1. At 10^32 Kelvin, perfect symmetry existed between all forces

2. As universe cooled, symmetries broke down

3. Forces became distinguishable from each other

4. Gravity broke free first, followed by strong force

5. Happened during the Planck Epoch, very early in universe's history

time periods of early universe

1. the beginning: time = at 0, temp= really hot

2. The Planck Epoch: time = at a fraction of a second, temp = absolute hot (cooled enough for gravity and the strong force to become independent)

3. Neutrons, Protons and Electrons: time = at 1 second, temp = way less hot, size = ten times bigger (10 cyr across) (now all the fundamental forces Neutrons, protons and electrons are freely moving about but it is still too hot for atoms to form)

4. Nucleosynthesis: time = at 100 seconds, temp = slightly less hot, size = 30 times bigger (Hydrogen nuclei fuse (PP CHAIN!) to form helium but very little else.)

5. Recombination: time = at almost 400,000 years, temp = wayyyy cooler, size = more than 100000 times bigger, cool enough for atoms to form, now sufficiently spread out so that light can spread. where the CMB light comes from

6. dark ages: time = at 150 million years, temp = reduced by a few thousand kelvins, not a lot, cool down so much that the Universe becomes neutral. No new light is being created. The light that exists doesn’t have enough energy to excite the electrons in atoms

7. Reionization: time = at 1 billion years, temp = 10s of ks, stars and galaxies form, first stars were huge population III stars making supernovas

big bang problems

1. every theory we have about the early Universe contains monopoles, we havent found any

2. flatness = The Universe appears to be flat. model predicts that the universe's curvature should either grow or shrink significantly over time, but observations show it's remarkably flat. This flatness requires an incredibly specific initial density in the very early universe, which is an improbable coincidence

inflation

1. solution to the flatness problem to back up the big bang theory

2. another force (like dark energy) that existed when the Universe was hot but due to the same concept as symmetry breaking it lost energy once the Universe expanded

3. The Universe would double in size about 100 times in a fraction of a second