Sun is full of gases. Then how could we see a boundary in it? i.e., when we see it, we could see a sphere..?

Question

If sun is made up of gases, then the gases should decrease in density gradually with height. But, since we are able to see some boundary, it means that there is a sudden decrease in density at that part of the sun..? Why is it so..?

Answer 1

I want you to light a match or a candle or some other kind of flame. Do you see a precise boundary between the flame and the rest of the air? I do. It is the exact spot where the gases of the flame cease to give off light and are then transparent. The sun has a similar boundary, and that is what we perceive as the "edge". In Actuality, the sun has no exact edge, it just gets more vacuuous with distance, just as the Earth does, and any other body that has an atmosphere. The only bodies with a true edge are things like asteroids and maybe the moon, where there is a clear boundary between space and the body itself.

Answer 2

Gases do have mass -- and the sun has gravity and rotation. From Wikipedia:

The Sun does not have a definite boundary as rocky planets do; the density of its gases drops approximately exponentially with increasing distance from the center of the Sun. Nevertheless, the Sun has a well-defined interior structure, described below. The Sun's radius is measured from its center to the edge of the photosphere. This is simply the layer below which the gases are thick enough to be opaque but above which they are transparent; the photosphere is the surface most readily visible to the naked eye. Most of the Sun's mass lies within about 0.7 radii of the center.

Also, check out the second link below for a wonderful view of the sun and its not-so-spherical boundary!!

Answer 3

sun is not made up of gases... it consists gases... it has a surface ful of gases...

Answer 4

the gravity keeps it together

Answer 5

it's full of plasma actually