Astronomy

Astronomy

1. Topic 1

   • Earth
     • earth
     • solstices
       • summer
         • jun 21st
       • winter
         • dec 21st
     • equinoxes
       • vernal
         • march 20th
       • autumnal
     • equation of time
       • days are sometimes longer or shorter than others due to non circular orbit of earth
     • types of day
       • sidereal: 23 hrs 56mins                  time to rotate 360 degrees
       • solar: 24 hrs             time for sun to get to same position in sky
     • aurorae
       • spectacular light shows near north and south poles
       • caused by particles in solar wind interacting with earth's magnetic field
     • Eratosthenes
       • On summer solstice in Syene, sun was at zenith
       • also, at same time in Alexandria, sun was 1/50th of a circle south of zenith
       • as Alexandria was due north of Syene, the arc from Alexandria to Syene must be 1/50th circumference of earth
       • distance from alexandria to syene was about 790km so circumference of earth must have been about 39500km
   • Sun
     • diameter
       • 1.4 million km
     • distance to earth
       • 150 million km
     • orbital period
       • at poles
         • 36 days
       • at equator
         • 25 days
     • photosphere
       • 5,800K
     • Atmosphere
       • Chromosphere + corona
       • 2 million K
     • Nuclear fusion
       • Hydrogen nuclei fuse
         • into helium
       • reaction
         • tritium + deuterium --> helium + a neutron (+ energy)
       • Heavier elements are formed in supernovae
     • Solar wind
       • charged particles ejected from upper atmosphere
       • enough energy to escape sun's gravity
       • reaches heliosphere at edge of solar system
       • partially deflected by earth's magnetic field
       • can damage satellites and electrical transformers
       • causes aurorae
   • Moon
     • Features
       • Seas
         • Sea of Crises
         • Sea of Tranquility
         • Ocean of storms
         • Formed by large craters that filled with lava and solidified
       • Highlands
         • Apennine Mountain range
       • Craters
         • Tycho
         • Copernicus
         • Kepler
     • Rotational period
       • 27.3 days
     • Orbital period
       • "
     • Diameter
       • 3500km
     • Distance from earth
       • 380,000km
     • Far side
       • more craters
       • more highlands
       • fewer seas
     • Giant Impact Hypothesis (GIH)
       • Theia collided with young earth
       • Evidence
         • relative abundances of oxygen isotopes are almost identical to earth's
         • it was once molten
         • moon has iron core like earth
         • observed similar collisions in other systems
         • computer simulations support hypothesis

2. Topic 2

3. Topic 3

4. Topic 4