What is formed form nebulae? A. Planets B. Galaxies C. Moons D. Stars

D. Stars

The correct answer is D. Stars.

To understand why stars are formed from nebulae, let's break down the process.

First, what is a nebula? A nebula is a vast cloud of gas and dust found in outer space. These clouds often result from the remnants of old stars or are the birthplaces of new ones.

Stars are formed in nebulae through a process called stellar nucleosynthesis, which involves the gravitational collapse of the gas and dust within the cloud. Here are the general steps:

1. Gravitational Collapse: Due to various factors such as the influence of nearby stars or a shockwave from a supernova, a nebula can begin to collapse under its own gravity. As the cloud contracts, it starts to spin and flatten into a rotating disk shape.

2. Protostar Formation: As the collapsing cloud continues to shrink, the central region becomes denser and hotter, forming what is known as a protostar. This protostar is not yet a full-fledged star but is on its way to becoming one.

3. Nuclear Fusion: As the protostar continues to contract, its core becomes hot and dense enough for nuclear fusion to occur. Nuclear fusion is the process where hydrogen atoms combine to form helium, releasing a tremendous amount of energy in the form of light and heat. This marks the birth of a star.

4. Main Sequence Star: Once nuclear fusion begins, the gravitational force pulling the star inward is balanced by the outward force generated by the fusion reactions. This equilibrium creates a stable phase called the main sequence, which is where stars spend most of their lives.

So, to recap, stars are formed from nebulae through the process of gravitational collapse and subsequent nuclear fusion. This process results in the conversion of hydrogen into helium, releasing energy and giving birth to a new star.