ASTR exam #3

• earth rotation

  rotates on its axis once every 24 hours. different stars become visible in the night sky while others disappear below the horizon

  
• earths orbit around the sun


  the earth orbits around the sun once every year. an observer from earth will see different stars at different times because of this motion

  
• observer location


  stars visible in the northern hemisphere may not be visible in southern hemisphere
• circumpolar stars


  rotate around the celestial poles without rising or setting
• seasonal stars


  rise and set in the sky due to earths rotation and its orbit
• seasonal stars visibility


  the tilt of the earths axis and orbit creates changing seasons which affects visibility of stars
• why summers are hotter than winters


  the earth is tilted toward the sun and is higher in the sky causing the days to be longer and warmer
• why the earth exhibits seasons


  the earths orbit around the sun and the tilt of its axis causes the sunlight to vary

  
• why the moon exhibits phases


  the moons position relative to the earth and the sun causes varying amounts of sunlight to illuminate its surface as seen from earth

  
• Keplers first law


  each planet moves around the sun in an elliptical orbit and the sun is at one focus. this applies to the motion of planets in the galaxy

  
• Keplers second law


  each planet always sweeps out the same amount of area from from it to the sun. planets move faster the closer they are to the sun

  
• Keplers third law


  the length of a planets year is proportional to the size of its orbit. the further a planets average distance from the sun the longer its year is
• what does the force of gravity depend on?


  the mass of the two objects and their distance from each other
• retrograde motion


  refers to the apparent backward motion of a planet against the backdrop of stars as observed from earth
• geocentric model


  earth is considered to be at the center of the universe, and the sun and planets orbit around it.

  
• heliocentric model


  the sun is at the center of the solar system and the planets orbit around it.

  
• neutrinos (how we know fusion is occurring in the suns core)


  nuclear fusion in the suns core can be detected on earth
• Helioseismology (how we know fusion is occurring in the suns core)


  uses vibrations of the suns surface to map its interior
• basic feature of a sunspot


  About half the heat of the rest of the sun (55,000 degrees). They last from days to weeks, then fragment and spread out.
• solar cycle and how it affects earth


  The solar cycle is a natural phenomenon that influences solar actively levels over a 11-year period, with effects on earth's space environment, technology, and climate
• Photosphere (of the Sun)


  surface of the sun, part we see, has sunspots

  
• chromosphere (of the sun)


  above the photosphere, reflects the suns magnetic field

  
• corona (of the sun)


  outer atmosphere, millions of degrees

  
• differences and similarities between terrestrial planets and earth


  Earth:

  - Atmosphere mostly nitrogen and oxygen

  -water vapor

  - One moon

  -Plenty of geological activity

  Terrestrial Planets:

  -Mostly Rocky Surfaces

  -mars has a moon

  usually has some kind of water (mars Venus)

  -Venus is geologically active while the others are not
• jovian planets and Jupiter


  -composed of gasses

  -have solid cores

  -multiple moon

  - extensive storms
• compare Jovian and terrestrial planets


  both orbit the sun, both are composed of solid and gaseous materials
• contrast Jovian and terrestrial planets


  Jovian planets are larger, further from the sun, rotate faster, have more moons, more rings
• terrestrial planets


  Mercury, Venus, Earth, Mars

  
• Jovian planets


  Jupiter, Saturn, Uranus, Neptune

  
• roles our atmosphere plays


  filters radiation, sculpts the surface, traps heat, weather
• what evidence do we have for human caused climate change

  glaciers are melting/disappearing, temperature of the planet is going up
• Jupiter major moons


  Io: most geologically active

  Mimas: looks like a Death Star

  Ganymede: largest moon

  Europa: liquid water

  
• Saturn major moons


  Titan: biggest moon

  Mimas

  Enceladus: liquid water vapor
• why terrestrial planets formed closer to the sun and Jovian planets further from the sun


  because the Jovian planets are made of gasses and it doesn't work for them to be close to the sun
• how can we explore inside our solar system


  space probes, satellites, rovers, telescopes
• how can we explore outside out solar system


  telescopes, detection methods, interstellar probes, radio astronomy
• difficulties associated with human space travel

  time, cost, risk
• what is required for life to exist

  Atmosphere, differentiated (geological activity), magnetic field (proximity to sun, presence of the moon), water, climate
• ways to find other life in the universe


  go there, send out signals, listen
• attributes of the most easily found extra-solar planets


  large size, orbital period, high stellar activity, proximity to earth