Quarter 1 Exam Flashcards
Elliptical Galaxies
These galaxies have little to no structure, rotation, or interstellar matter. This results in minimal star formation and dominance of the long lived, red stars. These ellipsoid-shaped collections of stars are the most common type of galaxy
Spiral Galaxies
These galaxies are disk-shaped width either a round central hub (unbarred) or a hub shaped like a bar (barred). They rotated with spiral arms that contain interstellar dust and gas, promoting star formation an an abundance of young stars
As they rotated gas and dust gets swept into nebulas, forms new stars
Irregular galaxies
These galaxies have an irregular shape and are considered to be the result of the collisions of galaxies. As a result, they generally contain a complex mix of interstellar gas and dust, young stars, and old stars
What are the two measurements of brightness for stars
apparent magnitude and intrinsic brightness (luminosity)
Apparent magnitude
how bright a star appears
Intrinsic brightness info
how bright the star actually is
Brightness compared to the Sun at a standard distance
1 = brightness of our Sun
< 1 = less bright
> 1 = more bright than sun
Distance is standardized, distance would not effect luminosity
Nuclear fusion info
a nuclear reaction in which two atoms are fused together
New elements are created and energy is released
This process is responsible for creating ALL elements found in the universe
Star defintion
Giant ball of hydrogen gas, massive enough to be hot enough in its interior for nuclear fusion to take place
Hydrostatic equilibrium
In star, gravity pulls in because mass wants to go to center, but energy in its core (gas pressure) is pushing out
If these forces are equal, it is called hydrostatic equilibrium
When star loses hydrostatic equilibrium star changes size, becomes unstable. Stars lose hydrostatic equilibrium if star runs out of hydrogen in the core to be fused
General and simplified method to determine composition based on density
We can take two substances that the planet has high percentages of, and based on the densities of those substances we canc calculate what the densities of planets would be that have certain percentages of each of those substances. Then we could make a graph where we take one of the substances and graph how much density an object would have if it had certain percentages of the substance. Then we can take the density of the planet and predict the amount of each substance the planet has based on where it falls on the graph.
Low or medium mass stars info
last about 10 million years
nebula, main sequence, red giant, “planetary” nebula, white dwarf
High mass stars info
Last about 10 million years
Main sequence, red supergiant, supernova, neutron star or if SUPER massive then become black hole
Main sequence stars
Core reaches a temp of about 15 million Kelvin
Hydrogen begins to fuse into Helium in the core
About 90% of star lifetime is present in the main sequence stage
Classified based on temperature and luminosity
On the main sequence, as temperature decreases, luminosity decreases
Red MS stars are smaller, cooler, and live longer because they burn fuel more slowly.
Blue MS stars are more massive, and therefore hotter, and therefore burn their fuel faster → shorter lives
Main sequence stars are in hydrostatic equilibrium
Red Giant stars
Stars decrease in size as all (or most) hydrogen is consumed in the core, energy output drops, gravity starts “winning and the core contracts. Core gets hotter and dense as the star contracts, increased heat ignites hydrogen fusion in envelope around core, which produces more heat because of greater area of fusion: energy output wins against gravity and star expands. Diameter increases x10, surface temp decreases as the star expands because there is more surface area.
Core is helium because there is no nuclear fusion and gravitational contraction produces energy. H ydrogen layer because of nuclear fusion. Envelope expands because of increased energy production, cools because of increased surface area. The temperature is lower while the luminosity is higher
“Planetary” Nebulae
End of red giant stage for most stars
Outer layers are only weakly gravitationally bound to the star
Exact mechanisms not well understood
The outer envelope expanding out as a shell appears as a ring in the sky.
White Dwarf
Just the core is left
SIGNIFICANT decrease in size
Mass of sun, size of Earth
DENSITY INCREASES TREMENDOUSLY
Solid, but still hot, so it is glowing
No fusion is occurring; thus no energy from fusion
No gravitational contraction is occurring, thus no energy from gravity
Star is now just an inactive core of mostly Helium
Stil l hot because the core is only left, but is the hottest and densest part, core has lost heat but is still hot
Not as bright because it is so small
Hotter and dimmer than red giants
Red Super Giants (equivalent of?)
Equivalent of red giants, high mass stars turn into super giants
A chain of reactions take place in the core producing He, C, O, Ne, Mg, Si, S, Ar, Ca, Ti, Cr, Fe
Highest temperature = Blue Super Giants
Supernova
high mass stars
Stars reach iron, which they can’t fuse to produce energy
Core collapses due to gravity
Sudden collapse and extreme temperatures can cause lots of carbon fusion to occur at once
This sudden release of massive amounts of energy blow out the outer layers of the star in a violent explosion
Neutron stars
high mass stars
Forms from supernova, iron core can no longer sustain fusion
Core grows until it is too heavy to support itself
Core collapses, density increases, neutrinos are emitted, normal iron nuclei are converted into neutrons
Core collapse stops, neutron star is formed
Rest of the star collapses in on the core, but bounces off the new neutron star (also pushed outwards by the neutrinos)
Very small ~ 30 km across
D = 2 x 1014 g/cm3
Black holes
high mass stars
Stars with a mass of greater than 25 times that of our Sun will collapse with such extreme densities they become black holes
Density = 2 quadrillion g/cc (denser than atomic nuclei!) How is mass packed in so densely?
Doppler effect
the apparent change in the frequency of a wave caused by relative motion between the source of the wave and the observer
Frequency of soundwaves changed, you hear higher pitch when something playing sound is moving toward you, lower pitch when something playing sound is moving away from you
WORKS WITH LIGHT WAVES, higher frequency means bluer light, lower frequency means redder light
Timeline of universe creation
At t=0, the universe began expanding very quickly, and rapidly cooled as it expanded; fundamental forces are created
From 1 second to about 3 minutes, subatomic particles form, but the universe is far too hot for atoms to exist
By 3 minutes, the universe cools enough for atomic nuclei to exist
By 380,000 years, electrons can finally ‘stick’ to atoms and the first light appears (so we couldn’t see anything before this time)
And by 200 million years, the first stars formed
Main evidence for Big Bang
CMBR (Cosmic microwave background radiation)
Redshift
no stars older than 13.8 billion years
CMBR
In 1964, Amo Penzias and Robert Wilson accidentally discovered CMBR while conducting diagnostic observations using a new microwave receiver owned by Bell Laboratories
CMBR = “Echo” or “Afterglow” of the Big Bang as gamma ray waves have stretched out to microwaves due to space expanding
