What is the role of gravity in the formation of a star?

Gravity plays a crucial role in the formation of a star, as it causes the collapse of a cloud of gas and dust.

Stars form from clouds of gas and dust, known as nebulae. These clouds are held together by their own gravity, but they are also in a state of equilibrium, with the pressure from the gas pushing outwards balancing the force of gravity pulling inwards. However, if the cloud is disturbed, for example by a nearby supernova explosion, the balance is upset and gravity becomes the dominant force.

As the cloud collapses under its own gravity, it becomes denser and hotter. At the centre of the cloud, the temperature and pressure become high enough for nuclear fusion to begin, which releases a huge amount of energy and causes the star to shine. The energy produced by fusion also creates an outward pressure, which balances the force of gravity and prevents the star from collapsing further.

The size and mass of the star that forms depends on the initial conditions of the cloud, such as its size, density and temperature. If the cloud is too small, it may not have enough mass to sustain fusion and will become a brown dwarf. If it is too large, the gravitational forces will be too strong and the star will become a black hole.

In summary, gravity is the driving force behind the formation of a star, causing the collapse of a cloud of gas and dust and leading to the ignition of nuclear fusion. Understanding the role of gravity in star formation is crucial for our understanding of the universe and the processes that shape it.