{
 "source": "https://peabody.kids/flashcards/space-stars-universe",
 "id": "space-stars-universe",
 "title": "Stars, Galaxies and the Universe",
 "category": "science",
 "subject": "Space",
 "levels": [
  "6-8",
  "9-12",
  "college"
 ],
 "description": "Star life cycles, galaxy types, and cosmology words.",
 "tags": [
  "stars",
  "galaxies",
  "universe"
 ],
 "frontLabel": "Term",
 "backLabel": "Meaning",
 "cards": [
  [
   "Star",
   "A huge ball of hot gas that makes its own light by fusion"
  ],
  [
   "Nebula",
   "A cloud of gas and dust in space"
  ],
  [
   "Protostar",
   "A young star still forming inside a nebula"
  ],
  [
   "Main sequence",
   "The long stage when a star fuses hydrogen into helium"
  ],
  [
   "Red giant",
   "A swollen, cool star near the end of its life"
  ],
  [
   "White dwarf",
   "The small hot core left after a medium star ends"
  ],
  [
   "Planetary nebula",
   "A glowing shell of gas thrown off by a dying star"
  ],
  [
   "Supernova",
   "The explosion of a massive star at the end of its life"
  ],
  [
   "Neutron star",
   "The super-dense core left by some supernovae"
  ],
  [
   "Pulsar",
   "A spinning neutron star that sends out beams of radiation"
  ],
  [
   "Black hole",
   "A region where gravity is so strong that not even light can escape"
  ],
  [
   "Event horizon",
   "The boundary around a black hole beyond which nothing returns"
  ],
  [
   "Red dwarf",
   "A small, cool, long-lived star"
  ],
  [
   "Supergiant",
   "A very large, luminous star"
  ],
  [
   "Binary star",
   "Two stars orbiting each other"
  ],
  [
   "Variable star",
   "A star whose brightness changes"
  ],
  [
   "Nova",
   "A white dwarf suddenly brightening by pulling in gas"
  ],
  [
   "Star color and temperature",
   "Blue stars are hottest; red stars are coolest"
  ],
  [
   "Spectral classes from hot to cool",
   "O, B, A, F, G, K, M"
  ],
  [
   "Spectral class of the Sun",
   "G"
  ],
  [
   "Luminosity",
   "The total amount of light a star gives off"
  ],
  [
   "Apparent magnitude",
   "How bright a star looks from Earth"
  ],
  [
   "Absolute magnitude",
   "How bright a star would look from a standard distance"
  ],
  [
   "Hertzsprung-Russell diagram",
   "A graph plotting star brightness against temperature"
  ],
  [
   "Light-year",
   "The distance light travels in one year, about 9.5 trillion kilometers"
  ],
  [
   "Parallax",
   "The apparent shift of a nearby star against the background as Earth moves"
  ],
  [
   "Galaxy",
   "A huge collection of stars, gas and dust held together by gravity"
  ],
  [
   "Milky Way",
   "Our home galaxy, a spiral with a central bar"
  ],
  [
   "Spiral galaxy",
   "A galaxy with arms curling out from the center"
  ],
  [
   "Elliptical galaxy",
   "A smooth oval-shaped galaxy"
  ],
  [
   "Irregular galaxy",
   "A galaxy with no regular shape"
  ],
  [
   "Galaxy cluster",
   "A group of many galaxies bound by gravity"
  ],
  [
   "Local Group",
   "The cluster of galaxies that includes the Milky Way"
  ],
  [
   "Large Magellanic Cloud",
   "A small galaxy that orbits the Milky Way"
  ],
  [
   "Quasar",
   "An extremely bright center of a distant galaxy powered by a black hole"
  ],
  [
   "Dark matter",
   "Unseen matter that adds gravity to galaxies"
  ],
  [
   "Dark energy",
   "A mysterious force that speeds up the expansion of the universe"
  ],
  [
   "Big Bang theory",
   "The universe began extremely hot and dense about 13.8 billion years ago"
  ],
  [
   "Expanding universe",
   "Space is stretching, carrying galaxies apart"
  ],
  [
   "Redshift",
   "Light from receding objects stretches toward red"
  ],
  [
   "Who found that galaxies move away from us in 1929?",
   "Edwin Hubble"
  ],
  [
   "Cosmic microwave background",
   "The faint glow left from the early universe"
  ],
  [
   "Observable universe",
   "The part of the universe we can see from Earth"
  ],
  [
   "Exoplanet",
   "A planet orbiting a star other than the Sun"
  ],
  [
   "Habitable zone",
   "The region around a star where liquid water could exist on a planet"
  ],
  [
   "Telescope",
   "An instrument that gathers light to see faraway objects"
  ],
  [
   "Refracting telescope",
   "A telescope that uses lenses"
  ],
  [
   "Reflecting telescope",
   "A telescope that uses mirrors"
  ],
  [
   "Radio telescope",
   "A dish that collects radio waves from space"
  ],
  [
   "Spectrum of starlight",
   "Shows what elements a star contains"
  ],
  [
   "Astronomy",
   "The study of space and everything in it"
  ],
  [
   "Astrophysics",
   "The branch of astronomy using physics to explain objects in space"
  ],
  [
   "Cosmology",
   "The study of the origin and structure of the universe"
  ],
  [
   "Who proposed the Sun-centered solar system in 1543?",
   "Nicolaus Copernicus"
  ],
  [
   "Who first used a telescope to study the sky in 1609?",
   "Galileo Galilei"
  ],
  [
   "Who described the laws of planetary motion?",
   "Johannes Kepler"
  ],
  [
   "Which star is closest to Earth?",
   "The Sun"
  ],
  [
   "Which star is the closest after the Sun?",
   "Proxima Centauri"
  ],
  [
   "Star formation location",
   "Inside dense nebulae"
  ],
  [
   "Chandrasekhar limit",
   "The maximum mass of a white dwarf, about 1.4 solar masses"
  ],
  [
   "Solar mass",
   "A unit equal to the mass of the Sun"
  ],
  [
   "Gravitational waves",
   "Ripples in space-time first detected in 2015"
  ],
  [
   "First image of a black hole shadow, released",
   "2019, in the galaxy M87"
  ]
 ]
}