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Stellar Evolution

Stellar evolution is the life cycle of a star. Stars start out as clouds of gas and dust. The composition of the gas and dust will determine the stages that the star may go through.

482 Questions
Stellar Evolution

What is a star life cycle that is accurate?

See related question.

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Space Travel and Exploration
Astrophysics
Stellar Evolution

How is a protostar made?

A star begins its life as a ball of gas and dust. Gravity pulls the gas and dust into a spere. As the sphere becomes denser, it gets hotter and eventually reaches temperature of about 10,000,000 Celsius in its center. As hydrogen combines into helium, energy is released in a precess called neclear fusion.

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Galaxies
Stars
Stellar Evolution
Supernovae

What would stars be like if carbon had the smallest mass per nuclear particle?

Supernovae would be more common

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Science
Stellar Evolution

Do stars blow up?

yes. stars are aged like us and eventully they will blow up. But more stars are formed.

Some stars blow up, some don't. It depends on their mass. Stars having more than 3 times the mass of our sun will blow up when they die, stars having less than 3 times the mass of our sun will not blow up when they die instead they will just shrink and cool.

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Physics
Astronomy
Stars
Stellar Evolution

What makes a star become a red giant?

The short answer is ''running out of hydrogen''.

Most stars (like our Sun) are in the "hydrogen burning" phase of their life.

That is to say they are converting hydrogen into helium by nuclear fusion.

This releases a lot of energy.

The heat released by this reaction keeps the core (centre) of the Sun extremely hot.

This heat energy stops the Sun collapsing in on itself under gravity. It is the longest period of an active stars life.

When the star runs out of hydrogen to "burn" it stops generating heat. The core is no longer supported by the release of heat at its centre. It starts to collapse. This causes the core to get hotter. When it gets hot enough it will reaches a point where it is hot enough to "burn" helium to create heavier elements.

The core becomes stable again but at a much hotter temperature than during the hydrogen burning phase.

The rate of energy release is also slower than during the hydrogen burning phase. One of the effects of this change is that the outside of the star gets bigger and cooler. This is why we call it a Red Giant. Red because the surface is cooler so releases light predominantly in the red part of the spectrum, giant because its big.

It happens like this: Nebula-->Protostar-->Main Sequence Star-->Red Giant.

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Astronomy
Planet Earth
Stellar Evolution

When the earth gone destroyed?

The earth will be destroyed in roughly 6 billion years when the sun begins burning helium to make carbon in its core and becomes a red giant.

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The Moon
Stellar Evolution

Why is the explosion in stellar space is not audible on the surface of the earth?

Sound travels through air. Between the Earth and any star, there are long stretches of distances with hardly any particles--not nearly enough to carry sound.

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Nuclear Fusion
Stellar Evolution

Does nuclear fusion converts hydrogen to helium?

yes

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Constellations
Stellar Evolution

What stage is sigma librea in?

Sigma Librae (Brachium) is a star in the constellation Libra.

It has a spectral class of M3 so it is a red giant and in it's final stage of evolution.

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Stellar Evolution

What stage of stellar evolution marks the end of helium fusion?

In G-type stars, this would be the white dwarf stage. More massive stars could continue to fuse ever heavier elements, until the fusion products consist mainly of iron, and the stellar core collapses into a neutron star or a black hole.

567
Astronomy
Stars
Stellar Evolution

What is the range of star sizes?

Depending on the classification of a star to include stellar remnants. Sizes are approximate and are for comparison purposes only .

  • Black hole = 0.
  • Neutron Star = A city
  • White Dwarf = The Earth
  • Black Dwarf = The Earth
  • Brown Dwarf = About the same size as Jupiter.
  • Red Dwarf = About 2 times the size of the Earth up to 1/2 the Sun
  • Yellow Dwarf = Our Sun
  • Blue giant = Twice the size of the Sun
  • Red Giant = Ten to a hundred times larger than our Sun
  • Red Supergiant = 200 to 800 times larger than our Sun
  • Red Hypergiant = Greater than 800 times larger than our Sun.

See related link for a pictorial of the different sizes.

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Stellar Evolution

Which burning stage in stellar evolution is most durable?

Helium burning is most durable stage in stellar evolution.

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Science
Temperature
Stellar Evolution

How does a star's temperature change as the star ages from a main sequence star to a star to a red giant and from a red giant to a white dwarf?

Well i really think its quite obvious. The fact that you asked this question in the first place must be an indication of your level intelligence. Obviously the stars internal temperature must rise at least 1200 Kalvin's before any sort of classifcation can be changed. The number of Kalvin's increased is a direct indicator as to how said star can be properly classified. So because of this a star's temperature must increase and exponential amount before anything should be changed.

OK, you explained the answer well, but might I say, you shouldn't be questioning anybodies intelligence! I am in AIG at my school, but hey I didn't know the answer to this! Anyway its intelligence level, not level intelligence, and your questioning their intelligence, really! Your atrociously bad spelling and grammar is also unbelievable!

567
Astronomy
Stellar Evolution

What happens to a star when it ends its life?

What happens at the "end" of a star's life depends almost entirely on the original mass of the star. It will become a white dwarf star, a neutron star or a black hole.

Small red dwarf stars will fade into white dwarf and (eventually) black dwarf stars. They fuse hydrogen into helium, but don't have enough mass to ever fuse helium into heavier elements, so as their fuel is exhausted, they will shine more and more dimly. Of course, red dwarf stars aren't very bright to begin with; the closest star to our Sun is the red dwarf Proxima Centauri, at 4.2 light years distance, and it is so dim that it cannot be seen without a telescope. Some Red dwarf stars could, for all practical purposes, last forever. Some will become become white dwarfs.

Stars like our Sun burn hydrogen, but in another 4 billion years or so, the hydrogen will be substantially depleted, and an "ash" of helium will impede the hydrogen fusion. The Sun will shine less brightly, and there won't be enough heat to keep the star from collapsing, so it will begin to collapse. This will increase the heat and pressure in the core, and at some point the Sun will begin to fuse helium into heavier elements, GREATLY increasing its energy supply. The Sun will expand into a red giant, which will certainly consume the planets Mercury and Venus, and probably the Earth itself (if we haven't moved it elsewhere for safely). But the Sun doesn't have enough mass to go "supernova" and explode, so it will settle into a long decline into, probably, a whitedwarf star.

Stars of mass greater than about 8 times the Sun's mass will eventually go supernova and explode, throwing some of their mass back into space and contributing to the next generation of stars and planets. (Our solar system is probably third generation; some of our mass has already been through a supernova.) The end result of a supernova would probably be a neutronstar or a blackhole.

It's also important to know that the more massive the star, the faster it burns and the more quickly it will die. Our Sun will likely be about 10 billion years old when it expands into a red giant. A red dwarf would probably last 100 billion years or more. And a massive star will explode quickly. For example, the giant star Betelgeuse, at the shoulder of the constellation Orion, is only a few hundred million years old - and will probably go supernova within the next 50,000 years.

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Stellar Evolution

What two things balance to maintain the shape of a star?

Pressure and gravity

456
Astronomy
Stellar Evolution

What are the three factors that scientists use to classify stars?

  1. Mass
  2. Size.
  3. Temperature.
456
Astronomy
Stellar Evolution

How long do blue giants live?

All stars are different but a blue giant will only "live" for about a couple of million years. Our Sun will "live" for about 10 billion years.

456
Stellar Evolution

Are stars made of rocks?

No.

They're mainly burning gasses, just like our sun.

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Gravity
Milky Way Galaxy
Stellar Evolution

How does gravity act in the galaxy?

Various ways. Gravity of stars act on planets and cause them to rotate around them, as well as asteroids that get caught in gravity fields and fall to the plant's surface.

345
Periodic Table
Nuclear Fusion
Stellar Evolution

Why is it harder for stars to start Helium fusion than other types of fusion?

Helium fusion, or the triple alpha process produces very unstable isotopes of beryllium which then form stable carbon, however the latter does not happen as much.

This means that the star can barely maintain itself, as the beryllium's rate of decay now approximately equals the rate of fusion of helium.

The stable carbon can then rarely form oxygen, and as the production of carbon is already low, the amounts of carbon and oxygen are fairly low, and beyond that, a fairly small amount of any further elements occur.

Obviously, this doesn't necessarily mean that it would less likely occur, but philosophical arguments for the anthropic principle state that the Universe may somehow make it so that there are high amounts of carbon and oxygen in the Universe, so as to progenate life.

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Stellar Evolution

How does stardust leave a star?

You'll have to give us some idea of what you mean by stardust - this isn't an actual astronomical term!

Stars have stellar winds that broadcast atomic particles into space (giving us aurorae by the way) - is that what you mean?

Also, when stars such as the Sun evolve and turn into red giants they can become unstable (red variable stars like Mira) and can pump large amounts of material into space.

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Big Dipper
Orion
Stellar Evolution

What is a radio object?

A radio object is something in the Cosmos that emits relatively strong radio waves.

These include pulsars, quasars, and radio galaxies that all emit very intense radio waves.

Weaker objects include more local bodies, such as the Sun, Jupiter, and our own Milky Way galaxies' center.

Others include remnants of supernovae and the cosmic background radiation of the Universe.

345
Earth Sciences
Stellar Evolution

Why can't we see the very lowest mass stars?

we cant see lower mass stars because were blind.... :)

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Stellar Evolution

Why do white dwarfs have high surface temperatures?

Good question. Three part answer.

First, all stars convert gravitational potential energy into radiative energy. White dwarfs have a mass that's in the same order of magnitude as the stars that became them, but with a much higher density and a much smaller surface area. So the amount of energy radiated per inch would be higher, resulting in higher surface temperatures.

Second, the degenerate matter that makes up the bulk of a white dwarf has a very low opacity, because any absorption of a photon requires an electron transition to a higher empty state, which may not be available given the energy of the photon.

Third, since the heat-generating capacity of the white dwarf is not replenished by nuclear fusion - and IF there is no companion star present from which the dwarf gains new mass - the star will slowly cool; the high surface temperatures do not last.

345
Planetary Science
Stellar Evolution

Why will a star with a large mass radiate more energy into space and appear hotter and brighter than a star with a smaller mass?

Because the larger mass means more core pressure, making fuel (hydrogen turning into helium) burn faster and more frequently, resulting in a hotter, brigher star. A small mass star has less fuel and internal pressure, so it generates less light and is red in color. A medium star like our sun burns moderately, and is yellow.

The H-R Diagram places these stars in spectral classes, from biggest and hottest to smallest and dimmest, and the orders are O, B, A, F, G, K and M. We are a type G star.

Think of a fire; the more fuel you put on it, the hotter and brighter it blazes and it can become white-hot if it is a very intense fire. As the ashes burn down, the fire is smaller, dimmer and the coals appear red, which is cooler.

The principle is the same with stars; the bigger and hotter they are, the brighter they burn but they have shorter lives than do moderate and small stars.

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