The Solar System and The Universe

• Your journey starts by looking closely at how the Earth and the Sun are connected, especially how the Sun's position in the sky decides the different seasons

  
• Seasons


  1. Earth leaning and moving around the Sun

  2. Earth's tilt makes days shorter or longer as the year goes by

  3. Tilt changes where the Sun sits in the sky, which changes how much sunlight you get

  
• You will learn about constellations – those captivating patterns of stars that have guided civilizations for centuries

  
• Types of constellations

  • Circumpolar
  • Seasonal
  • Zodiacal

  
• Constellations


  Captivating patterns of stars that have guided civilizations for centuries

  
• Constellations


  • Help you determine directions
  • Mark the changing of seasons

  
• Motions of the Earth and the Constellations

  Observe which constellations grace our skies at different times of the year

  
• Another effect of Earth's rotation is that we have a cycle of daylight and darkness approximately every 24 hours

  
• When the North Pole is tilted towards the Sun

  The length of daytime will be longer than nighttime in the Northern Hemisphere
• When the North Pole is tilted away from the Sun


  Nighttime will then be longer than daytime in the Northern Hemisphere
• Direct rays


  Light rays that hit the earth at 90 degrees
• Indirect rays


  Light rays that hit the earth at an angle

  
• Areas of the Earth that are hit by direct rays are warmer than areas that are hit by indirect rays
• The equator is always hit by direct rays of the sun, which is why it is always warm there
• The poles are always being hit by indirect rays, that is why it is cold there
• Seasons

  Short periods of climate change caused by changes in the amount of solar radiation (sunlight) an area receives
• Earth is tilted from the vertical by 23.5 degrees
• Direct rays


  Rays of the Sun that hit the ground at 90°

  
• Oblique rays


  Rays of the Sun that hit the ground at an angle

  
• When the Sun's rays strike the ground at a high angle, the ground receives a greater amount of solar energy than when the rays are inclined
• When the Sun's rays come in at an oblique angle, the ground will receive a lesser amount of solar energy
• Earth's axis is tilted about 23.5 degrees relative to our plane of orbit (the ecliptic) around the Sun

  
• Our northern axis points almost directly toward Polaris, the North Star

  
• What causes our seasons?

  1. Earth's axis is tilted

  2. As we orbit our Sun, our axis always points to the same fixed location in space

  3. The distribution of the Sun's rays changes throughout the year

  
• In June, in the northern hemisphere summer, the Sun's rays reach the north pole and beyond, enveloping the Arctic circle

  
• In December, in the northern hemisphere winter, the north pole is tilted away from the incoming sunshine
• During summer in the northern hemisphere, the northern half of Earth is tilted toward the Sun

  
• During winter in the northern hemisphere, the northern hemisphere points away from our Sun
• During fall and spring, Earth's axis is more or less perpendicular to the incoming rays of the Sun

  
• At the summer solstice, June 21 or 22, the Sun's rays hit the Earth most directly along the Tropic of Cancer (23.5 degrees N)

  
• Winter solstice for the Northern Hemisphere happens on December 21 or 22

  
• The autumnal equinox happens on September 22 or 23 and the vernal or spring equinox happens March 21 or 22 in the Northern Hemisphere

  
• Constellation


  A group of stars that looks like a particular shape in the sky and has been given a name

  
• Today, there are 88 officially recognized constellations

  
• The constellations you can see at night depend on the time of year and your location on Earth

  
• Circumpolar constellations


  Constellations that appear to circle around the celestial poles

  
• The northern constellations rotate around Polaris, or the North Star, the closest star to the North celestial pole

  
• The southern constellations rotate the South celestial pole, which is not marked by any bright star

  
• The number of the circumpolar constellations you can see depends on your latitude

  
• Northern circumpolar constellations

  • Ursa Major
  • Ursa Minor
  • Cepheus
  • Cassiopeia
  • Draco
  • Camelopardalis
  • Lacerta
  • Lynx