Module 3: Brahe and Kepler's 3 Laws of Planetary Motion

• a danish astronomer, and considered as the "last great naked-eye astronomer"

  tycho brahe
• brahe's first astronomical and alchemical laboratory

  uraniborg
• instruments of brahe

  • brass azimuthal quadrant

  • great globe

  • armillary sphere

  • triangular sextant
• one of the first instruments built at ven and was used for observation of the 1577 comet 

  brass azimuthal quadrant
• has two scientific uses: it is use as a computational device and is also used to record the position of stars

  great globe
• is a model of objects in the sky consisting of a spherical framework of ring centered on earth

  armillary sphere
• used to measure the angular position of celestial bodies relative to the horizon

  triangular sextant
• the sun, moon, and stars revolve around the earth, and the other planets in our all solar system revolve around the sun

  geoheliocentric model
• a german astronomer who was credited with the discovery of the three laws of planetary motion

  johannes kepler
• the three laws of planetary motion


  • law of ellipses

  • law of equal areas

  • law of periods
• states that the orbit of each planet is an ellipse

  law of ellipses
• the point in the orbit where the planet is nearest to the sun

  perihelion
• the point in the orbit where the planet is farthest from the sun

  aphelion
• states that a planet sweeps out equal areas of the ellipse over equal time intervals

  law of equal areas
• states that the square of the period of revolution of a planet is proportional to the cube of the semi-major axis of its orbit

  law of periods