Is it possible for a star to skip the main sequence and immediately begin burning helium in its core? Explain your answer.

Stars begin their life cycle in large clouds of dust and gas known as molecular clouds or stellar nurseries. These regions are rich in hydrogen, helium, and other elements. Due to gravitational forces, these clouds start to condense, collapse, and form denser regions. As the cloud collapses, the material at the center warms up, eventually forming a protostar, the earliest stage of star development.
Stars can vary in size, temperature, and brightness, depending on the amount of material available in the molecular cloud. Initially, this collapsing process can take several millions of years.

As the cloud continues collapsing under gravity, it heats up and forms a protostar, which is essentially a young star in its formative stages. The protostar phase is characterized by intense activity as the material continues to fall into the core and the temperature increases.
When the core temperature reaches around 10 million Kelvin, nuclear fusion begins. Hydrogen atoms start to fuse into helium, generating energy that pushes back against gravitational forces. This point marks the transition of the protostar into a main sequence star. The pressure from the energy released by fusion balances the force of gravity pulling the star inward.

The main sequence phase is the longest period in a star's life cycle. During this phase, a star burns hydrogen into helium in its core. This balanced state is known as hydrostatic equilibrium. The properties of a main sequence star, such as size, brightness, and lifespan, primarily depend on its mass. More massive stars burn hotter and faster, shortening their time on the main sequence, while less massive stars, like our Sun, can remain in this phase for billions of years.
This phase is crucial for determining the star's future evolution and eventual death. The energy produced during this phase creates the light and heat emitted by the star.

Helium fusion begins only after a star has exhausted its hydrogen supply in the core, which occurs during the main sequence phase. Once the hydrogen is depleted, the core begins to contract under gravity, and temperatures rise again. When the temperature in the core exceeds around 100 million Kelvin, helium atoms start fusing into heavier elements like carbon and oxygen. This process is also known as the triple-alpha process.
Helium fusion generates less energy than hydrogen fusion, but it is more difficult to initiate due to the higher temperatures required. Some stars may go through periods of instability and changes in size as they approach and enter the helium fusion phase.

After a star completes its main sequence phase, it enters the red giant stage. This stage occurs when the core is depleted of hydrogen, causing the core to contract and the outer layers to expand and cool. As a result, the star becomes significantly larger and redder.
During this stage, the core's temperature increases enough to start helium fusion. The expanded outer layers are cooler and can stretch several times the star's original size. Depending on the initial mass of the star, it will either lose its outer layers and form a planetary nebula with a white dwarf at its core or explode in a supernova, leaving behind a neutron star or black hole.
The red giant stage is a relatively short part of a star's lifecycle compared to the main sequence phase but is crucial in its end-of-life evolution.