Astronomy Exam #3 Review – Flashcards

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light
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electromagnetic radiation
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light and matter interact through
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emission, absorption, transmission, reflection/scattering
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light as a particle
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individual components of light (photons) carry energy
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light as a wave
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produces interference patterns (double slit experiment)
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speed equation
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wavelength x frequency = speed
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energy equation
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Planck's constant x speed of light % wavelength = energy
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wavelength
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distance between peaks and troughs (in meters)
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frequency
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how many peaks pass by every second (in Hertz)
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correlation between wavelength, frequency, and energy
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- larger wavelength = lower energy - larger frequency = higher energy
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electromagnetic spectrum
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- shortest wavelength photons: gamma rays - longest wavelength photons: radio - all have same speed
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protons
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positive charge
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neutrons
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neutral charge and have slightly larger mass than proton
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quarks
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components that make up protons and neutrons; are divisible as they are elementary particles
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electrons
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negatively charged and are also elementary particles; in a cloud
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equal and opposite fundamental charge
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describes how much an object will interact with electromagnetic fields
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quantized
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charge only comes in multiples of fundamental charge
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elements
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atoms with differing numbers of protons
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isotopes
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variations on elements with different number of neutrons
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deuterium
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hydrogen with a neutron alongside the proton in the nucleus (D or 2H)
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ions
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variations of elements with more or fewer electrons, making them negatively or positively charged
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how is energy stored in atoms?
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electrons in atoms only have specific energies; not all energies are possible
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energy levels
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specific allowed energies in atoms; to move from one to another, electrons require photon with an exact amount of energy
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absorption
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atoms can absorb light, moving electrons into higher energy levels
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emission
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atoms can emit light moving electrons to lower energy levels
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spectrum
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tells us how bright a particular object is at each wavelength; we can see a spectrum by passing object's light through prism
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continuous light
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white light; hot dense energy source through a prism
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emission lines
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light emitted directly from hot low density cloud through a prism
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absorption lines
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hot dense energy source shines light through cool low density cloud and through a prism
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chemical fingerprints
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different elements have different energy levels, which leave specific chemical fingerprints in spectra
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Law 1 (the Stefan-Boltzmann law)
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a hotter object's surface emits more light (per unit area) at all wavelengths
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Law 2 (Wien's law)
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a hotter object emits photons with a higher average energy
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telescope's collecting area
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area of the mirror = π (d/2)^2 ; if a mirror doubles in size, the collecting area increases by 4x
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angular resolution
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smallest angular size we can distinguish; how close can two stars be together before we can't tell them apart (ex: eye - 1 arcminute; hubble - 0.05 arcseconds)
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limit of angular resolution
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depends on wavelength; at longer wavelengths, you need a larger telescope to get the same angular solution
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refracting telescope
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lens is the primary optic; have much greater diameters; most modern telescopes
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reflecting telescope
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mirror is the primary optic
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telescope
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work by gathering light over a large area, and focusing it onto a small area
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best ground based sites for astronomical observing
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calm, high, dark, dry
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transmission in atmosphere
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only radio and visible light pass easily through the atmosphere; we need telescopes in space to observe other forms
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ancient beliefs of the sun
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thought that sun was burning wood or a lump of coal; didn't understand scale of the sun so they didn't realize that energy output by burning wood was unfeasible
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gravitational contraction
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as the Sun contracts, gravitational potential energy is converted into thermal energy; could only powered the sun for 25 million years
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nuclear fusion
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nuclear reaction where two (or more) atomic nuclei collide and stick together to form a new nucleus; some of the mass is converted into energy
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how mass plays into nuclear fusion
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for any nucleus with lower masses than iron, this process will release energy. if you want to fuse two nuclei heavier than iron, you need to inject energy
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proton-proton chain
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4 H protons make a 4He nucleus and energy in form of gamma rays
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crucial point of p-p chain
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total mass of 4He nucleus is 0.7% lower than the mass of 4 protons
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Sun's interior layers
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core, radiative zone, convective zone
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Sun's atmosphere layers
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- photosphere: layer we see, 5800 K - chromosphere: red layer observed using hydrogen filter, 10 000 K - corona: incredibly thin outer atmosphere, 1 000 000 K
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brightness of star appearance depends on
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how much light it releases and how far away it is
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relationships between star properties
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- luminosity = emitted flux x surface area (L = 4πr^2 x σT^4 or L = r^2 x t^4)
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spectral types
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hottest to coolest: OBAFGKM strongest absorption lines: A weakest: O
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Hertzsprung-Russell Diagram
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- size increases diagonally to the upper right - mass increases diagonally to the upper left - lifetime increases to lower right
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pages in Lecture Tutorials to review
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pg 47-49, 59-61, 63-66, 117-120
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