Question

hydrogen gas and a dust cloud form new stars.
explanation
be sure to discuss the role of the force of gravity and/or fusion force in your explanation for why new stars form from a hydrogen and dust cloud. dont forget to include evidence to support your claim.
stars change very little while they are in the main - sequence stage.
explanation
be sure to discuss the role of the force of gravity and/or fusion force in your explanation for why stars change very little while they are in the main sequence stage. dont forget to include the evidence to support your claim.

Explanation:

1. Hydrogen gas and dust - star formation: Gravity causes the hydrogen gas and dust cloud to collapse inwards. As the cloud collapses, the density and temperature in the core increase. Eventually, the conditions become right for nuclear fusion to start, forming a new star. Evidence for this comes from observations of star - forming regions like the Orion Nebula, where we can see young stars emerging from dense clouds of gas and dust.
2. Main - sequence stability: During the main - sequence stage, a star is in hydrostatic equilibrium. The inward force of gravity is balanced by the outward force of the fusion pressure. In the core of a main - sequence star, hydrogen is fusing into helium, releasing energy. This energy creates an outward pressure that counteracts the inward pull of gravity. We know this because the vast majority of stars in the universe are on the main sequence, and their stable luminosities and sizes over long periods of time (billions of years for some stars) support the idea of this equilibrium.

Answer:

1. New stars form from hydrogen gas and dust clouds due to gravitational collapse, which leads to conditions for nuclear fusion. Evidence: star - forming regions like the Orion Nebula.
2. Stars change very little in the main - sequence stage because of hydrostatic equilibrium between gravitational and fusion forces. Evidence: long - term stability of main - sequence stars' luminosities and sizes.