Shape of solar-system

Why the shape of all planets and the Sun is sphere?
ANSWER: In simple words

Because the gravity planets and the Sun is equal in all parts and it exerts equal gravity on all objects, that's why the shape of planets and the Sun is sphere.

The gravitational force of a planet is depend on the mass of that planet. Our earth have mass of 5.974e24 kg and radius is 6371.01 km. The gravitational attraction of earth is 9.8m/s. Which is enough for make it sphere in shape. There many celestial body in space which is not sphere in shape.
For example :
[Example 1]-Metis- A moon of planet Jupiter. The mass of Metis is 1.25e17 kg and radius is about 20.0 km which is really a very small moon.

More about Metis - Metish is the moon of Jupiter which discovered by Stephen Synnott in the year 1979. In the year 1983 the name Metis is given to this moon.

[Example 2]- Neptune have 14 moon in which only one moon is sphere in shape.
Name - Triton which have mass of 2.147e22 kg and radius 1353.4 km.

PHENOMENA :

As we know that the gravity of an object/body depends on it's own mass.
If the mass of a body is very much then it's gravitational force is also very much. And as we know that the gravity is equal for every object which is in contact of that planet/object.

So we can say that the sphere shape of a planet is depend on increasment of its mass and volume. Increasment in shape of a planet cause for even surface of that planet.

EXAMPLES :

1. A huge rock is on a planet. Every time it is under effect of gravity of that planet. Day by day It is becoming weak and weak one day it will becomes very weak and fall on the surface of that planet, this will continously happen because the gravitational force is continuosly exerting on it. And small partical of rock make a even surface on that planet. In this way that planet becomes sphere in shape.

2. On the Earth breaking of rock is very fast because on earth different types of forces are exerting on the rock.

Why the shape of all planets and the Sun is sphere?

There are four forces and conditions for breaking of rock:-

A) Gravitational attraction of the Earth.

B) Weathering of rock due to sunlight, rain, snow.

C)Atmospheric pressure of Earth.
iv)Force applied by any living organism.

1. On Sun, this process is too fast because the temprature of the sun is too much. So, the ojects/body present on the sun is in plasma state and plasma have not its definite shape it spreads evenly on the surface of sun.