answersLogoWhite

0

Stars are born from clouds of gas and then they enter a stable period of about 5 billion years. Their brightness is due to fusion reactions fuelled by hydrogen. As a star's supply of hydrogen runs out, the high radiation pressure produced by the fusion reactions decreases. Without this outwards pressure, the force of gravity causes the star's core to contract. This increases the temperature of the core, making it hotter than it was during the stable period. The core is now mainly helium. Eventually, the core temperature becomes high enough for further more complex nuclear fusion reactions to occur. The new fusion reactions cause a higher outward radiation pressure than before. At this point the inward gravitational forces are unable to balance the radiation pressure and the star expands. It expands so much that the outer layers cool to about 3000 °C. Because the surface is cooler it looks red (only red-hot, not white-hot), so this type of star called a red giant. When our Sun reaches this stage it will be so large that the Earth will be inside it! :O But this won't happen for at least another 2 million years...

User Avatar

Wiki User

16y ago

What else can I help you with?

Continue Learning about Astronomy

What happens to the suns energy when it hits earth on a pie graph?

When the sun's energy hits the Earth, approximately 30% is reflected back into space, 20% is absorbed by the atmosphere, and the remaining 50% reaches the Earth's surface where it is absorbed and used for various processes like heating the planet and powering the water cycle.


Why liquid hydrogen cannot be used as a fuel?

Liquid hydrogen IS used as a fuel. It's used in rockets - and some cars.


In the fusion reaction on the sun what happens to hydrogen that does not convert into helium?

It just stays there waiting to be used-the sun has enough to last many billions of years and luckily for us the rate of burning has stayed fairly constant so far, but eventually it will run out of hydrogen and die.


Why sun have hydrogen and helium?

Hydrogen is the fuel used by the sun, helium is the waste produced by hydrogen use in the fusion process


A large bright star whose hot core has used most of its hydrogen is a?

Red giant. The word "most" in the question isn't quite accurate. There is still a lot of hydrogen remaining in a star when the amount of helium becomes a problem. Hydrogen in the star is fused into helium, and the helium is at least roughly analogous to the ash in a wood fire; it is what's left over from the hydrogen fusion, and too much gets in the way. When the proportion of helium gets too high - above about 50% is enough - the helium begins to interfere with the hydrogen fusion process. Without enough new heat generated by fusion, the star begins to collapse under the influence of gravity. The compression increases the temperature, and when the pressure and temperature gets high enough, the helium "ash" in the core becomes helium "fuel" for the Red Giant phase.

Related Questions

Source of the suns energy?

Elements used to create: Hydrogen, Helium, Time. Things the Sun contains: Neutrinos, Heat, Atoms, Photons, Hydrogen, Helium.


What happens to the hydrogen produced from the splitting of water?

Hydrogen is released in the atmosphere.


What happens to Windex when it is used up?

it gets recycled


What happens to energy used by machines?

it gets broken


Does shaquille o Neal play for the phoenix suns?

He used to play for the Suns.


Where does the body get hydrogen from?

The body gets hydrogen primarily from the food and beverages we consume. Hydrogen is a component of many molecules found in foods, and as we digest these molecules, hydrogen is absorbed into the bloodstream and used in various metabolic processes throughout the body.


What happens to the energy as it is passed from the producer to a series of consumers?

It gets used up on the way.


What happens to the reaction rate as reactant gets used up?

The rate goes down.


Is hydrogen gas a compound?

Yes, hydrogen gas is a compound. It is made up of molecules which consist of two atoms of hydrogen, an element. It just happens that the same name is used for the gas as for the element.


What happens when a used dry cell graphite rod is heated?

Nothing except that it gets hot


What happens to petrol after it is used?

It gets used up. Turns into heat, carbon monoxide and some other polluting stuff.


What happens to a battery when it is used in an appliance?

it gets eaten by a tiny monster inside the battery which gives energy to the appliance