Astronomy Final Flashcards
radial velocity
- technique used to detect exoplanets by observing the “wobble” of a star caused by the gravitational influence of orbiting planets
- measuring the star’s spectral lines for signs of movement towards and away from Earth, which is detected as blue or red shifts in the star’s light spectrum
- star moving toward earth - light = blue shifted
- away from earth - light = redshifted
Formation of the solar system
- protoplanetary disk
- higher temperatures around the star therefore inner regions ( Only heavy, rocky materials could condense) and outer regions (Cooler temperatures allowed lighter elements and ices to condense, leading to the formation of gas giants)
types of stars (Letter characterization)
O-type: Blue stars, extremely hot (>30,000 K)
B-type: Blue-white stars (10,000-30,000 K)
A-type: White stars (7,500-10,000 K)
F-type: Yellow-white stars (6,000-7,500 K)
G-type: Yellow stars (5,200-6,000 K)
K-type: Orange stars (3,700-5,200 K)
M-type: Red stars (2,400-3,700 K)
main sequence stars
- stable hydrogen fusion in their cores
- longest phase in a star’s life
- position on main sequence is primarily determined by mass
- Main sequence stars, including our Sun, spend the majority of their lives in this stable state, fusing hydrogen in their cores and maintaining a balance between gravitational collapse and thermal pressure
HR diagrams
- Hertzsprung-Russell (HR) diagram
- plots the luminosity of stars against their temperature or color
- categorize stars based on their properties
- shows different phases of stellar life cycles
How to read them:
Temperature: Hotter stars on the left, cooler on the right
Luminosity: Brighter stars at the top, fainter at the bottom
Size: Larger stars towards the top-right, smaller towards the bottom-left
Mass (for main sequence): More massive stars top-left, less massive bottom-right
degenerate electron pressure
- in super dense matter, electrons are squeezed really tightly together (don’t have room to move around) so they start piling up into higher energy levels (stacking creates a pressure that pushes outwards)
- the pressure is special because doesn’t depend on temperature, gets stronger as matter gets dense,
keeps white dwarf stars from collapsing under their own gravity.
Nucleosynthesis
protons and neutrons combined to form the first light elements, primarily hydrogen and helium
Stellar Nucleosynthesis:
Takes place in the cores of stars during their lifetimes.
Stars fuse hydrogen into helium through nuclear fusion, releasing energy that powers them.
virial theorem
- As the protostar contracts under its own gravity, the gravitational potential energy is converted into kinetic energy of the falling material, which then heats up the protostar
- as it heats up effects particles of gas
- ionization (creates plasma of ions and electrons)
- nuclear fusion
- creation of magnetic field as it starts to spin faster and collapse
Type 1 vs type 2 supernovas
Type 1 - no hydrogen lines in spectra
white dwarfs
thermonuclear explosion
brighter - more consistent
Type 2 - strong hydrogen lines in spectra
massive stars
core collapse
variation in peak brightness
kinetic molecular theory
- gas molecules in container creates pressure
1 solar mass star vs 100 solar mass star
1 solar mass (same size as our sun, lifespace 10 b years on the main sequence, fusion of hydrogen into helium)
- will eventually become a red giant and end as a white dwarf
100 solar mass ( 100 times mass than our sun)
- very bright
burns through fuel quickle living only a few million years
much hotter than our sun
end life in supernova explosion and may form black hole after death
neutron star
very dense formed when massive star explodes as supernova
composed of neutrons - since dense high gravity and magnetic fields
ex: pulsar (rapidly rotating neutron stars emitting beams of radiation)
pulsar
type of neutron star
emits beams of electromagnetic radiation from magnetic poles
expremely dense
(emits across multiple wavelengths)
parallax measurement
- method used to determine distance to celestial objects (usually nearby stars) (indirect visual observation)
Observe a star from two points in Earth’s orbit, six months apart.
Measure the star’s apparent shift against background stars (parallax angle).
formula: Distance (in parsecs) = 1 / parallax angle (in arcseconds)
more effective on nearby stars
radar method
radar sends out radio waves which travel at the speed of light –> bounce off objects then come back
- measure time took for echoes to return
immediate results, limited to objects within solar system
direct measurement
nuclear fusion
hydrogen atoms combining to form helium (extremely high temperature and pressure)
p-p chain releases energy and occurs in stars core
Distance modulus formula
μ = m - M
m(apparent magnitude) - observed brightness from Earth
M(absolute magnitude) - intrinsic brightness at standard distance
calculating the distance to an object in parsecs
PARSECS
hydrostatic equilibrium
- state of balance between graviting pulling downwards and pressure pushing outward
results - object maintains shape - no net movement of material in object
ex: stars: gravity tries to collpse star while fusion pressure pushes outward
main sequence stage
- stable phase where outward pressure from nuclear fusion in cores balances inward pull of gravity
- primarily fuse hydrogen into helium (nuclear fusion)
leaves main sequence after hydrogen fuel in core runs out. -> goes to evolutionary stage
white dwarf
not as luminous (decreases over time)
initially very hot (cools over time)
Very old (billions of years)
result from stars with initial masses between 0.6 and 8 solar masses
supergiant
very luminous
wide range of temperature
relatively young (few million)
form from stars with initial masses between 10 and 40 solar masses
binding of iron
- determines final stable configuration of stars core before undergoing supernova explosion
- Fusion reactions involving elements lighter than iron release energy, while fusing iron or heavier elements requires energy input
- core producting iron grows outer layer but no further fusion occurs within core itself
chandrasekhar limit
The maximum mass a white dwarf star can have while remaining stable.
(~1.4XSun’s mass)
cannot support itself against gravity - once it exceeds this limit it will collapse further and can become neutron star, or triggers supernova explosion
in binary star system: (Mass transfer can push white dwarfs over the limit, leading to supernovae or altering evolutionary paths.)
Telescope (what are the 2 kinds)
refracting (uses lenses to focus light)\
reflecting (uses mirrors to reflect light to focus opint)
shorter eyepiece increases magnification( Magnification= Eyepiece Focal Length/Telescope Focal Length
Schwarzchild radius
- radius of sphere around mass so that if all mass were compressed within sphere, nothing can escape
(escape velocity from its surce would equal the speed of light)
radius increases with mass
how much mass would need to be compressed into tiny volume to become a black hole
evidence of dark matter?
When astronomers measure the rotation speeds of stars in galaxies, they find that these speeds do not decrease with distance from the galactic center as expected based on the visible mass. Instead, the rotation curves tend to flatten out at larger distances, indicating that there is more mass present than what can be accounted for by the visible stars and gas.
population 1 star
-younger
rich in heavy elements (metals
found in disk of spiral galaxies (ex:sun)
population 2 star
older
low percentage of heavy metals
found in halo of galaxies and in globular clusters
big bang theory and hydrogen
big bang made universe hot and dense as it expanded cooled down enough for protons and neutrons to form
Because the universe had a much higher number of protons than neutrons, hydrogen remained the most abundant element.
drake equation
mathematical formula used to estimate number of active, communicative extraterrestrial civilizations in the milky way galaxy
N=R* fpneflfifcL
N = The number of civilizations in the Milky Way galaxy with which humans could communicate.
R* = The average rate of star formation in the galaxy (number of stars formed per year).
f_p = The fraction of those stars that have planetary systems.
n_e = The average number of planets that could potentially support life for each star that has planets.
f_l = The fraction of those planets that actually develop life.
f_i = The fraction of planets with life that develop intelligent life.
f_c = The fraction of civilizations that develop technology that can communicate across interstellar distances.
L = The length of time that civilizations are able to communicate.
How galaxies have changed over time
- formation + early development ( Big bang universe filled with hot gas and dark matter which was pulled together by gravity to form first chaotic and irregular galaxies)
- mergers and collisions (transforming them into more organized shapes)
- star formation( galixies experience rapid star formation due to abundance of gas and dust)
- evolution of structure ( evolution from simple shapes into more complex structures(ex: our milky way developed arms filled with young stars)
why do galaxies change over time?
gravitational interaction (mergers or collisions)
dark matter influence (provides gravitational framework within which visible matter can accumulate)
environmental factors (dense vs less dense clusters leading to different frequencies of interactions -> different evolutionary paths
internal processes - internal processes (ex: supernova explosions can eject gas from a galaxy or heat it up preventing further star formation)
solar system life exist?
has to have:
- evidence of water
- organic compounds (ex: methane emmisions)
- geological activity
energy source (hydrothermal activity (vents)
organic chemistry -> could lead to prebiotic processes similar to earth
cosmic distance ladder
- series of methods that astronomers use to measure distances to celestial objects in the universe
- builds on each rung - (certain level of uncertainty leading scientists to cross check with different methods:
- parallax,
- standard candles(measuring brightness of stars with known relationship between luminosity and pulsation period),
- type la supernovae (consistent peak brightness)
- tully fisher relation (relates luminosity of psiral galaxies to rotation speed
Different types of galaxies
- spiral
- eliptical
- barred spiral
- irregular
astrobiology
- study life in extreme environments
- orgin and evolution of life on earth (impact of environments on life)
- habitability in the solar system
- space exploration (potential life-supporting environments)
Hubble Tuning Fork
helps scientists understand galaxy morphology - way to classify glaxies based on pbservable features
two main categories
- left side (elliptical galaxies)
- right side (spiral galaxies)
Lenticular galaxies (at fork’s junction) exhibits characteristics of both elliptical and spiral galaxies
how has the hubble tuning fork evolved
original concept (classification scheme) and was based on visual characteristics based off of photographic plates
- complexity of galaxy evolution (realization that galaxies undergo various transformations due to mergers, interactions, etc.)
- refinement of categories(advanced telescope allow for more detail observations of structures)
- recognition of irregular galaxies
Early vs current universe composition
early ( hot and dense initial conditions (bigbang)
- nucleosynthesis (75% became hydrogen 25% helium)
- ionized plasma state (high temperature could not form neutral atoms)
- formation of neutral atoms allowed photons to escape leading to release of cosmic microwave background radiation (CMB)
Current
- matter distribution 68% dark energy 27% dark matter 5% baryonic (ordinary) matter)
- star formation and heavy elements (released during supernova explosions)
- structure formation (web like arrangment of galaxy clusters and super clusters
period luminosity relationship
- (longer the period of pulsation, the more luminous the star is.) measuring distances to celestial objects using Cepheid variable stars.
M=alog(P)+b
M -absolute magnitude (intrinsic brightness).
P- pulsation period (in days).
a and b (constants determined from observational data.)
after they can ccalculate distance to star using distance modulus formula
henrietta leavitt
standard candle
object whose luminosity is well understood.
determine its distance by comparing its apparent brightness to its absolute brightness (how bright it actually is at a standard distance).
ex: Type la Supernovae (consistent peak brightness)
Cepheid variable star (pulsate over regular periods)
transit method (finding exoplanets or stars)
monitoring the brightness of a star over time. When a planet passes in front of its host star (from our perspective), it blocks a small portion of the star’s light, causing a temporary dip in brightness.
can detect planets around stars located thousands of light-years away and is highly sensitive
radial velocity method (doppler method)
measures changes in a star’s spectrum due to its motion caused by the gravitational pull of an orbiting planet. As the planet orbits, it causes the star to wobble slightly, resulting in shifts in the star’s spectral lines (toward red or blue)
used to discover 51 pegb
direct imaging
capturing images of exoplanets directly by blocking out the light from their parent stars
It allows for the study of the planet’s atmosphere and surface conditions.
magnification
makes an object look larger than its actual size, allowing us to see details that are otherwise too small to discern with the naked eye.
ratio or factor (ie 10x)
resolution
ability to distinguish between two separate points or objects that are close together. It determines how clearly and sharply an image can be seen.
independent
quantified by the minimum distance between two points that can still be
focal length
distance from lens to focal point (shorter = wider field of view and larger magnification)
