astronomy final Flashcards
(55 cards)
What is nuclear fusion?
The process where two light atomic nuclei combine to form a heavier nucleus, releasing energy
What is lost in nuclear fusion?
Mass, which becomes a large amount of energy (E = mc^2)
What element is fused in stars like the Sun?
Hydrogen is fused into helium
What does nuclear fusion do in stars?
It powers the star and produces light and heat
Where does fusion take place?
In the core of stars
It can take energy a long time to escape a star;
True, since energy created in the core must make its way to the outside/surface of a star to radiate into space, which can take hundreds of thousands of years
What is the Big Bang theory?
The idea that the universe began from a tiny, hot dense point (singularity) that suddenly expanded violently and started cooling and has been expanding for 13.8 billion years
What are the three key pieces of evidence for the Big Bang theory?
Nucleosynthesis, the redshift of galaxies, and the cosmic microwave background radiation
What is cosmic microwave background radiation?
Leftover heat from the Big Bang. Would have started as visible light, but has been redshifted into microwave lengths. Discovered as a signal-like background noise discovered by radio astronomers in satellite.
What is the redshift of galaxies (besides Andromeda)
Since wavelengths are longer on the red end of the visible light spectrum (shorter on the blue end), when distance galaxies were noticed as red in color, they are moving away from each other.
The farther away a galaxy is…
the faster it was moving away from us
How is nucleosynthesis evidence of the Big Bang?
Once nucleosynthesis was possible in the cooled singularity, isotopes (sane element with same protons but different neutrons) being colliding to form elements. Since the Big Bang only created helium and hydrogen, the light elements, the process stabilized to get a ration of 75% hydrogen and 25% helium in the universe - now,, in the milky way 75% is still hydrogen and 35% is helium. (oxygen, carbon, came overtime in smallest amounts)
spectrum
a band of colors produced by separating the components of light
Each element produces a unique and different
spectrum
we can determine the composition of stars by inspecting
their spectra
What is the first stage in a star’s life cycle?
Protostar- spinning cloud of dust and hydrogen contracted by gravity to become very hot, allowing nuclei to collide and fuse (meaning a star is formed)
What is second stage of star’s life?
The main sequence - when hydrogen fuses to create helium and energy and the pull of gravity and outward push of fusion create an equilibrium
What is third stage of all stars
When hydrogen is almost gone heliumbegins to fuse, getting much larger and brighter as a Red Giant (outer layers expand and cool, core gets hotter, causing an imbalnce)
What determines the lifespan of a star?
Mass (high mass live for longer time)
After being red giants low mass stars will
experience a nebula when gravity cannot hold the layers (they expand into space)
What is leftover from a nebula?
A white dwarf, which is the carbon core left behind. It as a low mass with no fusing elements and is smaller, dimmer, but still hot.
After a white dwarf planets become
black dwarfs - none exist now but will be when white dwarf cools and no longer gloss from heat. end of low-mass star’s life
Instead of experiencing a nebula, high mass stars will
curse carbon to create other elements working from out it (iron in the center) - the Many different fusion reactions create the super giant stage, where the star is very bright and large .
After becoming a super giant, stars will
enter the supernova once the iron tries to fuse and the core of the star collapses, causing layers to explode into space
