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46 Cards in this Set
- Front
- Back
absolute magnitude
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a star's true energy output, its luminosity; the absolute magnitude of a star equals the apparent magnitude of a star at a distance of 10 parsecs
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apparent brightness
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brightness, amount of energy that passes each second through a square meter of the sphere's surface
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apparent magnitude
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how bright an object appears to an Earth-based observer, directly related to apparent brightness; scale goes backwards
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hertzsprung-russell diagram
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a diagram where the luminosities (absolute magnitudes) of stars are plotted against their spectral types (or surface temperatures)
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parallax
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apparent displacement of an object because of a change in the viewer's point of view
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parsec
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the distance at which a star has a parallax of one second; the word is a contraction of the phrase "the distance at which a star has a PARallax of one arcSECond" ; star with a parallax angle of 1 arcsec (second of arc) is at a distance of 1 parsec
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radial velocity
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the component of a star's motion parallel to our line of sight; either towards us or away from us
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tangential velocity
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the component of space velocity perpendicular to our line of sight; across the plane of the sky
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spectroscopic parallax
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the luminosity of a star if found using spectroscopy
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spectral types
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the added integer of 0 - 9 to the original letter from OBAFGAKM
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photometry
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measuring a star's apparent brightness
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spectral classes
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a star could be assigned a letter from A to O according to the strength or weakness of the hydrogen Balmer lines in the star's spectrum
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hydrogen fusion
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the process of converting hydrogen into helium, also called hydrogen burning
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thermonuclear fusion
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the fusing together of hydrogen nuclei, only takes place at extremely high temperatures because all nuclei are positively charged and repel each other, but at high temperatures, they are moving so fast that they overcome electric repulsion and touch one another, leading to thermonuclear fusion
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proton-proton chain
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a sequence of several separate reactions during which two of four protons (hydrogen nuclei) are turned into neutrons and eventually combine with the other protons to produce a helium nucleus
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hydrostatic equilibrium
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a balance between the weight of a layer in a star and the pressure that supports it
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thermal equilibrium
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the principle that the temperature in a star is different at different depths, but the temperature at each depth remains constant
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radiative diffusion
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protons created in the thermonuclear inferno at a star's center diffuse outward toward the star's surface; result: migration from hot core to cooler surface where they escape into space
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neutrino (solar neutrino)
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particles that have no electric charge, a solar neutrino is a neutrino from the sun
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photosphere
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a thin layer of gas from which all of the sun's visible light emanates
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stellar evolution
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how stars are born, live their lives, and finally die. Examples:
1) contracting clouds give birth to a clump called a protostar that becomes a main-sequence star 2) Protostar contracts and increases in surface temperature over time, not hot enough for thermonuclear fusion, glows b/c of heat form contraction 3)Accretion disks - starts adding mass to selves because accretion disk in nebula with protostar at center spins and particles in disk collide with each other and spiral in to the protostar 4) Cocoon nebulae - luminous starts emit UV radiation which makes dark nebula evaporate and leave pillars with a cocoon nebula containing a star at tip |
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interstellar medium
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the combination of gas and dust between stars in space
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nebula
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an interstellar cloud
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accretion
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a process when particles orbiting the protostar within the disk collide with each other, causing them to lose energy, spiral inward onto the protostar, and then add to the protostar's mass
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protostar
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a star in its earliest stages of formation
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main-sequence lifetime
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the total time that a star will spend as a main-sequence star
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helium fusion
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the thermonuclear fusion of helium nuclei to form carbon and oxygen, releases energy
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Pauli exclusion principle
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a principle first stated in 1925 that states that two electrons cannot simultaneously occupy the same quantum state
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degeneracy
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a phenomenon where closely packed particles resist compression as a consequence of the Pauli exclusion principle
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star colors
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red stars - cold; blue stars - hot
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brown dwarf
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a substar too small of thermonuclear fusion, glows by heat
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white dwarf
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a small, but hot star with a low luminosity; frequently stars become white dwarfs after their time on the main sequence
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optical double stars
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two stars that are in the same line of sight but at different distances
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binaries
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a pair of stars that orbit each other
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dark nebulae
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nebulae that block all light because they have a dense concentration of dust; many stars form here
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reflection nebulae
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nebulae with a lower concentration of dust than dark nebulae, the dust scatters short wavelength blue light better than longer wavelength red light giving the nebulae a blue color
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interstellar extinction
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intensity of light is reduced as it passes through material in interstellar space
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interstellar reddening
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an effect where the light from remote stars appears redder because as it passes through the interstellar medium, blue light is scattered and abosrbed, while long wavelength red light passes through
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best formation places for stars
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1) stars will most easily form in places where the interstellar material is relatively dense because gravity must overcome the internal pressure pushing particles apart to form a star.
2) the pressure of the interstellar medium should be low 3) temperature should be as low as possible, pressure goes down as gas temperature decreases All of this equals - Dark Nebulae |
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Earth's 3 main energy sources
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solar energy, tidal forces from sun and moon power ocean, internal heat creates geologic activity
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plate tectonics
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movement of the plates, driven by convection within the asthenosphere
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Earth's 3 main energy sources
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solar energy, tidal forces from sun and moon power ocean, internal heat creates geologic activity
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plate tectonics
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movement of the plates, driven by convection within the asthenosphere
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Earth's 3 main energy sources
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solar energy, tidal forces from sun and moon power ocean, internal heat creates geologic activity
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plate tectonics
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movement of the plates, driven by convection within the asthenosphere
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Theories of the moon's origin
1) Fission Theory 2) Capture Theory 3) Co-Creation Theory 4) Collisional Ejection Theory |
1) Early Earth was spinning so fast that a chunk of its mass tore away and became the Moon.
2) the Moon was formed elsewhere in the solar system but but was drawn to the earth by gravitational forces 3) Earth and Moon were formed at the same time, but separately. 4) Proto-Earth was struck off-center by a Mars-sized object and this collision ejected debris from which the moon was formed. CORRECT ONE! |