Stars and the Universe flashcards

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What is meant by “Electromagnetic spectrum” in this lesson?Starlight: The spectrum includes radiation from radio waves through gamma rays, differing in wavelength and frequency.
What is meant by “Spectral line” in this lesson?Starlight: A spectral line occurs at a wavelength associated with particular atomic or molecular transitions.
What is meant by “Color and temperature” in this lesson?Starlight: For approximately thermal emitters, hotter surfaces peak at shorter wavelengths.
What is meant by “Luminosity” in this lesson?Starlight: Luminosity is a source's total energy output per unit time.
What is meant by “Apparent brightness” in this lesson?Starlight: Apparent brightness is received light intensity and depends on luminosity, distance, and intervening material.
What is meant by “Parallax” in this lesson?Starlight: Parallax is an apparent positional shift used to estimate distances to nearby stars.
What is meant by “Nebula” in this lesson?Stellar life cycles: A nebula is a cloud of gas and dust that can include regions of star formation.
What is meant by “Protostar” in this lesson?Stellar life cycles: A protostar is a contracting young stellar object before stable main-sequence hydrogen fusion.
What is meant by “Main sequence” in this lesson?Stellar life cycles: A main-sequence star sustains hydrogen fusion in its core with approximate balance between gravity and pressure.
What is meant by “Red giant” in this lesson?Stellar life cycles: A red giant is an expanded later stage reached by many stars as their internal fuel conditions change.
What is meant by “White dwarf” in this lesson?Stellar life cycles: A white dwarf is a compact stellar remnant supported largely by electron degeneracy pressure.
What is meant by “Massive-star fate” in this lesson?Stellar life cycles: Many massive stars undergo core collapse and may leave neutron stars or black holes, with outcomes depending on their properties.
What is meant by “Galaxy” in this lesson?Galaxies and the expanding universe: A galaxy is a gravitationally bound system of stars, gas, dust, and dark matter.
What is meant by “Milky Way” in this lesson?Galaxies and the expanding universe: The Milky Way is the galaxy containing the Solar System.
What is meant by “Redshift” in this lesson?Galaxies and the expanding universe: Redshift shifts spectral features toward longer wavelengths and can arise through motion or cosmological expansion.
What is meant by “Cosmic expansion” in this lesson?Galaxies and the expanding universe: On large scales, distant unbound galaxies generally recede as space expands.
What is meant by “Cosmic microwave background” in this lesson?Galaxies and the expanding universe: The cosmic microwave background is relic radiation from the early hot universe.
What is meant by “Light-travel time” in this lesson?Galaxies and the expanding universe: Finite light speed means distant objects are observed as they were when the received light was emitted.