The process of star formation begins with the contraction of dense regions within giant molecular clouds. These clouds are vast, cold reservoirs of gas and dust that exist in the interstellar medium. As the cloud contracts, its gravity causes it to collapse in on itself. As the cloud collapses, it begins to heat up due to the conversion of gravitational potential energy into thermal energy.

How stars are being formed?

As the cloud continues to collapse, it becomes denser and hotter, and eventually, the temperature and pressure at its center become sufficient to initiate nuclear fusion. This is the process by which hydrogen atoms are fused together to form helium, releasing vast amounts of energy in the form of light and heat. This marks the birth of a new star.

As the cloud continues to collapse, it forms a dense, hot core known as a protostar. The protostar continues to contract and heat up, becoming hotter and denser until the conditions are right for nuclear fusion to begin. This marks the transition from a protostar to a main-sequence star, like the Sun.

As the star begins to shine, it starts to push back against the surrounding cloud material, creating a "stellar wind" that can be seen as a "photoionization" region at the border of the cloud. The photoionization region is a region where the radiation from the newly formed star causes the surrounding gas to become ionized, creating a bright HII region.

The process of star formation is not always a smooth one, and many stars form in clusters. The interaction between these stars can be intense, leading to the formation of binary and multiple-star systems. Additionally, stars can form in the presence of other, pre-existing stars, leading to the formation of complex systems of stars.

It is also common for stars to form in association with clouds of gas and dust known as nebulae. These clouds of gas and dust can provide the raw materials needed for the formation of new stars, as well as play a role in shaping the final characteristics of the stars that form within them.

Star formation can also be triggered by external factors, such as the collision of molecular clouds or the compression of a cloud by the shock wave from a nearby supernova explosion.

The process of star formation is not well understood, and many questions about the process remain unanswered. For example, it is not clear why some molecular clouds collapse to form stars while others do not, or why some regions of a molecular cloud form many stars while others form only a few. Additionally, it is not clear how the properties of a star are determined by the conditions in which it forms, or how these conditions vary from one star-forming region to another.

The study of star formation is an active area of research, and many new discoveries are being made as technology continues to improve. Astronomers are using a variety of observational techniques, including infrared and submillimeter telescopes, to study the early stages of star formation. Computer simulations are also being used to model the collapse of molecular clouds and the formation of stars within them.

Overall, the process of star formation is a complex and dynamic one that is still not fully understood. It involves the collapse of giant molecular clouds, the formation of protostars, and the ignition of nuclear fusion. Many other factors, including the presence of other stars and nebulae, can also play a role in shaping the final characteristics of a new star. The study of star formation is an active field of research that continues to yield new discoveries and insights into the origins of stars and the universe.

In summary, Star formation happens in dense regions within giant molecular clouds, the cloud contracts and collapses under its own gravity. As the cloud contracts, it heats up, and as it reaches the center it gets hotter and hotter.