Almost half.
The celestial sphere is a theoretical imaginary sphere surrounding the Earth, on which all celestial objects are considered to be located. It is often thought of as a giant dome in the sky where the stars, planets, and Sun appear to be positioned.
Since the Earth is a Spheroid shape, (not a true sphere) 50% of its surface is illuminated by the Sun, at any given moment.
From the South Pole, 50% of the sky is always visible, while the remaining 50% is obstructed by the Earth. This is because as the Earth rotates, half of the celestial sphere is always blocked from view at any given time.
To determine the angular distance between two points in a celestial sphere, one can use spherical trigonometry or coordinate systems such as right ascension and declination. By calculating the difference in these coordinates for the two points, the angular distance can be found.
Portion
No a sphere doesn't even have any angles
any two points on the sphere ;)
Any view of a sphere will be a circle.
No sun doesn't revolve to any celestial body, but the celestial body revolve around the sun.
A sphere does NOT have any edges
At 40 degrees north latitude, you would not be able to see any particular star directly overhead as the celestial sphere rotates throughout the night. Instead, you would see a variety of different stars and constellations depending on the time of year and time of night.
Sphere