Celestial bodies:A natural object out in space. Includes:
planets cometsmoons starsasteroids
Stars: give off light and heat but are very far away. Ex. The Sun
Planets: moving stars.
Patterns made up of stars.
Celestial bodies move in cyclic paths called orbits.These orbits result from
gravitational forces.Planets, suns and moons
revolve on a central axis.
Stars generally move from east to west.The point around which the
stars rotate is the North Star… Polaris.Ursa Major and Minor, and
Cassiopeia never go below the horizon.
See pages 360(1)
Aristotle (383-322 B.C.E.)Visualized the universe as
being geocentric. This means the Earth is the centre of the universe and everything else revolves around it.
He believed that the Earth was a sphere due to the curved edges observed during a lunar eclipse.
Ptolemy (83-168 C.E.)Based his model on his
observations of Mars.Mars orbital path creates a
loop or s-shape in the sky.His model showed each planet
attached to a crystal sphere with its centre at Earth.
Each planet was not attached directly to its sphere but to an off-centre wheel (epicycle).Accepted for
nearly 15oo years.
Used to locate and predict the position of the Sun, Moon and stars.
Along with a compass, it could be used to describe the position of any celestial body in relation to the direction North and to the horizon.Allowed for more accurate
observations to be made.
Copernicus (1473-1543)Believed in a heliocentric
universe (Sun at the centre).The Earth rotated on its axis
once daily and revolved around the Sun once a year.
Galileo (1564-1642)First person to view the
“heavens” through a telescope.Allowed him to see objects
about 20x closer.
He observed: Craters on the
Moon Spots on the Sun Four “stars” orbiting Jupiter
(called the Galilean Moons)
Now that the Sun was placed at the centre of our solar system, other astronomers could work to understand the motion of the planets.
Improvements in the telescope would show new and strange objects never imagined!
Johannes Kepler (1571-1630)Developed 3 Laws of
Planetary Motion1. All planets move in ellipses
with the Sun at one focus.2.Planets sweep out at equal
areas of their elliptical orbit in equal times.
3. The time a planet takes to revolve around the Sun is directly related to how far away it is from the Sun.
Sir Isaac Newton (1643-1727)Developed the three laws of
motion.First to show that the force of
gravity affects allcelestial bodies, causing them to stay in orbit.
Invented the reflecting telescope which uses a curved mirror to focus the light to a point at an eyepiece.
Inner PlanetsMercuryVenusEarthMars
Jovian PlanetsJupiterSaturnUranusNeptune