In order what are the six stages of a star?

Answer 1

supernova explosion

they hurt red giant supernova nebula black dwarf black hole

O.o What In The World? how Can It Start As A Red Giant? Start With This:

All through the long main sequence stage, the relentless compression of gravity is balanced by the outward pressure from the nuclear fusion reactions in the core. Eventually the hydrogen in the core is all converted to helium and the nuclear reactions stop. Gravity takes over and the core shrinks. The layers outside the core collapse too, the ones closer to the center collapse quicker than the ones near the surface. As the layers collapses, the gas compresses and heats up.

Eventually, the layer just outside the core called the ``shell layer'' gets hot and dense enough for fusion to start. The fusion in the layer just outside the core is called shell burning. This fusion is very rapid because the shell layer is still compressing and increasing in temperature. The luminosity of the star increases from its main sequence value. The gas envelope surrounding the core puffs outward under the action of the extra outward pressure. As the star begins to expand it becomes a subgiant and then a red giant.

At the bloated out surface, the increased amount of energy is spread out over a larger area so each square centimeter will be cooler. The surface will have a red color because it is so cool and will be much further from the center than during the main sequence. Despite its cooler surface temperature, the red giant is very luminous because of its huge surface area. When the Sun becomes a red giant, Mercury and Venus will be swallowed up by the Sun and perhaps the Earth will too. Even if the Earth is not swallowed up, conditions on its surface will become impossible for life to exist. The Sun's increased luminosity will heat the Earth's surface so much that the water oceans and atmosphere will evaporate away. Massive main sequence stars will expand much further to become supergiants. Betelgeuse, the bright red star in the top left corner of the Orion constellation, is an example of a supergiant star. If placed at the center of our solar system, all of the planets out to Jupiter would be inside Betelgeuse. A few supergiants are even larger than Betelgeuse!

HST image

Red giants can have strong ``winds'' that dispel more mass than all of the stellar winds that occurred during the long main sequence stage. However, most of the star's mass will be lost in the ``last gasp'' stage (planetary nebula or supernova) described below. All through the star's life after it first started nuclear reactions, it has been losing mass as it converted some mass to energy and other mass was lost in the winds. This means that even though a red giant is large in terms of linear size, it is less massive than the main sequence star it came from. A red giant has the extremes in temperature and density: its surface is cold and very low density, while its core is very hot and extremely dense.

Stage 6: Core fusionIf the star is massive enough, gravity can compress the core enough to create high enough temperatures to start fusing helium (or heavier elements if it is repeating this stage). In low mass stars (like the Sun), the onset of helium fusion can be veryrapid, producing a burst of energy called a helium flash. Eventually the reaction rate settles down. Fusion in the core during this stage releases more energy/second than the core fusion of the main sequence stage, so the star is bigger, but stable! Hydrostatic equilibrium is restored until the core fuel runs out.

Stars entering and leaving this stage can create conditions in their interiors that trap their radiated energy in their outer layers. The outward thermal pressure increases enough to expand the outer layers of the star. The trapped energy is able to escape when the outer layers are expanded and the thermal pressure drops. Gravity takes over and the star shrinks, but it shrinks beyond the equilibrium point. The energy becomes trapped again and the cycle continues.

In ordinary stars hydrostatic equilibrium works to dampen (diminish) the pulsations. But stars entering and leaving stage 6 can briefly (in terms of star lifetimes!) create conditions where the pressure and gravity are out of sync and the pulsations continue for a time. The larger, more luminous stars will pulsate with longer periods than the smaller, fainter stars because gravity takes longer to pull the more extended outer layers of the larger stars back. The period-luminosity relation can be used to determine the distances of these luminous stars from the inverse square law of light brightness. This is explored further in the Milky Way chapter.

This picture of NGC 3603 from the Hubble Space Telescope (courtesy of Space Telescope Science Institute) captures the life cycle of stars in a single view. From lower right to upper left you see: dark clouds and a giant gaseous pillar with embryo stars at the tip to circumstellar disks around young stars to main sequence stars in a cluster at center to a supergiant with a ring and bipolar outflow at upper left of center near the end of the life cycle.

Stage 7: Red Giant or SupergiantWhen the core fuel runs out again, the core resumes its collapse. If the star is massive enough, it will repeat stage 5. The number of times a star can cycle through stages 5 to 7 depends on the mass of the star. Each time through the cycle, the star creates new heavier elements from the ash of fusion reactions in the previous cycle. This creation of heavier elements from lighter elements is called stellar nucleosynthesis. For the most massive stars, this continues up to the production of iron in the core. Stars like our Sun will synthesize elements only up to carbon and oxygen in their cores. Each repeat of stages 5 to 7 occurs over a shorter time period than the previous repeat.

Up to the production of iron in the most massive stars, the nuclear fusion process is able to create extra energy from the fusion of lighter nuclei. But the fusion of iron nuclei absorbs energy. The core of the massive stars implodes and the density gets so great that protons and electrons are combined to form neutrons + neutrinos and the outer layers are ejected in a huge supernova explosion. The more common low-mass stars will have a gentler death, forming a planetary nebula

Answer 2

1. Stellar nebula: a cloud of gas and dust from which stars form.
2. Protostar: a hot, dense core forming within the nebula.
3. Main sequence star: stable phase where a star fuses hydrogen into helium in its core.
4. Red giant or supergiant: phase when a star runs out of hydrogen in its core and expands.
5. Supernova: explosive death of a massive star, resulting in a bright burst of light.
6. White dwarf or black hole: end stage where the core either collapses into a dense white dwarf or a black hole.

Answer 3

Highly simplified, the stages are as follows:

Low mass stars:

nebula -> protostar -> main sequence star -> red giant (not always red, but most stars of this size and category are) -> white dwarf, then finally black dwarf.

(A red dwarf is a low mass star which does not go through the red giant stage.)

High mass stars:

nebula, protostar, main sequence star, supergiant, supernova. Finally they end as neutron stars or as black holes.

Answer 4

It depends on the type of star. If the star has a high enough mass (from 5 to 10 times our sun) it will live for a few billion of years (not as much as smaller stars) and then it will swell. The result: a giant explosion that could alter or interfere with changes nearby. A star like our sun will eventually swell, vaporizing all life and water off Earth and maybe enveloping Earth as well as Mercury and Venus (have no fear this wont happen for 5 billion more years). Then when all the hydrogen and helium are gone, the star will collapse on its core, and the result a white dwarf.

Answer 5

A star starts as a blue giant, then becomes a yellow dwarf. It will then swell into a red giant. Then, at the end of it's life, it becomes a super giant and explodes. The remains are usually a red dwarf, which brightens and becomes a white dwarf. The white dwarf fades and becomes a black dwarf which turns to dust. Sometimes after a supernova it turns into a pulsar, which rotates 300-1,000 times a minute and makes giant rhythmic pulses that stretch for light years.

Answer 6

1)protostars2)main-sequence stars3)giants & supergiants4)white dwarfs

Answer 7

The life a star begins in nebulae. Clouds of dust and gas collapse upon themselves to form protostars. Further collapse from gravitational forces causes protostars to become main sequence stars. As time goes by, stars expand. Eventually, the star will collapse and explode. Depending on the original mass of the star, this explosion may result in a black dwarf, ,neutron star, or a black hole.

Answer 8

The details are a bit complicated, and vary depending on the star's mass, mainly. I recommend you read the Wikipedia article on "stellar evolution" to get a general overview; then ask back here if you have any additional questions.

Answer 9

>>>>average star > red giant > planetary nebula > white dwarf

nebula

> black hole

>>>>massive star > red supergiant > supernova > neutron star

Answer 10

The answer is specific.

A main sequence star starts it's life when the temperature of the core reaches 10 million degrees kelvin. Nuclear fusion occurs and the star is "on the main sequence". It will continue nuclear fusion until all of the hydrogen in the core has been fused into hydrogen. At that point, the star is no longer "on the main sequence" and it's cycle is over.