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
