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Chapter 18: Problem 15

What happens inside a protostar to slow and eventually halt its gravitational contraction?

Short Answer

Expert verified
Gravitational contraction in a protostar is halted by the onset of nuclear fusion, where hydrogen combines to form helium. This releases a lot of energy, creating an outward pressure that counteracts the inward force of gravity, leading to a state of equilibrium.

Step by step solution

01

Understand Protostar Dynamics

Protostars are young stars - they form from the dust and gas in a interstellar molecular cloud as a result of gravitational instabilities. These instabilities cause pockets of matter to contract under their own gravity.
02

Gravitational Contraction

The initial phase in the life of any star is contraction under gravity. Gravitational energy is converted into heat, causing the temperature and pressure at the core to increase. This process continues until the core temperature is high enough (about 15 million degrees Celsius) for nuclear fusion to start.
03

Nuclear Fusion

When the core temperature is high enough, nuclear fusion begins. The most common reaction is hydrogen combining to form helium (Hydrogen fusion). This process releases an enormous amount of energy. This outgoing pressure from the energy released forms a counterbalance against the gravitational contraction.
04

Transition to Equilibrium

Once the nuclear fusion has begun, the energy released creates an outward pressure that counteracts the inward force of gravity. This halts further gravitational contraction and leads to a state of equilibrium, also known as the Main Sequence stage of a star.

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Most popular questions from this chapter

Search the World Wide Web for recent discoveries about how brown dwarfs form. Do they tend to form in the same locations as "real" stars? Do they form in relatively small or relatively large numbers compared to "real" stars? What techniques are used to make these discoveries?

What is an evolutionary track? How can evolutionary tracks help us interpret the H-R diagram?

What are giant molecular clouds? What role do these clouds play in the birth of stars?

Briefly describe four mechanisms that compress the interstellar medium and trigger star formation.

What are H II regions? Near what kinds of stars are they found? Why do only these stars give rise to H II regions?
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