Celestial Sphere
• A celestial sphere is an imaginary sphere centered on the Earth upon
which all the celestial bodies can be projected
Concept of a celestial sphere
• It was a tool used by early astronomers to visualize celestial bodies surrounding our Earth
• It was believed that stars were firmly attached to a celestial sphere surrounding Earth.
• Early astronomers assumed that the celestial sphere along with the stars rotate around a fixed,
unmoving Earth because they believed that the Earth is the center of all things.
• This assumption was made because early astronomers observed that the constellations were
moving across the sky from east to west while the relative locations of the stars remained
unchanged.
• Although the concept is proven to be false centuries ago, it is still a very important tool for
astronomers.
A useful tool
to visualize
positions of
stars in the sky
To apply
coordinate
system to
locate celestial
objects
Helpful in
navigation
Provides a
clearer picture
to understand
constellations