Stellar Evolution

stars are formed in a stellar nebula. clouds smash together making a protostar.

more and more clouds spiral in the protostar making the clouds into hydrogen then a huge explosion finally makes the main sequence of a star. when a star is young it burns fast and hot and bright, and the light is blue when it is young. when 4 hydrogen atoms smash together it forms 1 helium atom. Hydrogen is blue and helium is red so when a lot of hydrogen is converted in shines yellow then orange and red then die. the stars size depends on how it dies out. all stars lice in the same way but die in a diffrent way

How a small star lives

a small star lives for 7 trillion years when it runs out of hydrogen then runs out of heluim it just fades away

how medium/sun like stars live

sunlike stars begin as Blue Dwarfs

Red giant

a sun like star lives for 12 billion years, when it runs out of hydrogen the core at the center collapses and shrinks down. Because the pressure is less the star gets orange and cools down and Expands 250 times its original size becoming a red giant. Some inner planets may get swallowed as the stars swells up. when it gets big enough and stops expanding it becomes red and cooler.

Planetary Nebula

when the star runs out of helium the core once again shrinks down to the size of the earth then it tries to expand but this time it would never be hot enough to make a larger star. the outer layers get pushed of into space and exploding becoming a planetary nebula. the planetary nebula becomes a stellar nebula after a few million years.

White dwarf

the left over is a small dense core, although a white dwarf it is also very small

(the size of the earth) so the light will be much less than it used to be.

Any planets that survive the red giant stage will become very cold and never impossible for 1 planet to be in the goldilocks zone.

A white dwarf is very dense and it has strong gravity when a star passes the white dwarf steals the star's energy but a lot of energy escapes.

a white dwarf might fullyu cool down becoming a black dwarf

How Massive stars live

massive stars begin as Blue Supergiants or Blue hypergiants

Red Supergiant/Red hypergiant

Massive stars swell up in the same way as sunlike stars with the same results, however they are far much larger than red giants and explode in a diffrent way if the star has extremley high masses it becomes a Red Hypergiant but hypergiants are rare. mostly massive stars become super giants

Supernova

A supernova is very violent it can even destroy a black hole.

It even out shines the whole galaxy for a short time, at night when there is a supernova u cant see any stars unless u go very close to them like on a planet orbiting a star is the only way to see one while there is a supernova.

A supernova can be up to 10 light years the largest supernova known is the crab nebula

black hole/neutron star

if the star has a very high mass it becomes a neutron star far more denser than a white dwarf. One star bit the size of a tea spoon weighs more than a cruise ship packed with people on earth's gravity a black hole has much stronger gravity light cant escape it

These are names for some of the stages of stellar evolution.

• molecular cloud, a stellar nursery where cool clouds of molecular gasses begin collapsing at various point to form protostars.
• stellar nebula, a nebular region of collapsing gas in the process of collapse star formation.
• average star, a star of mass not exceeding 3 solar masses that is on the main sequence of the H&R diagram.
• massive star, a star of 3 solar masses or greater.
• red giant, a star beginning to die, it has run out of hydrogen to burn collapsed enough to ignite helium burning, the resulting large increase in energy release has made its outer shell expand enormously.
• red super giant, a very very large red giant.
• planetary nebula, the cloud of hot gasses surrounding an average star in the process of dieing or that has died. they were initially called planetary nebula because astronomers frequently mistook them for planets before realizing they were really nebular clouds of gas.
• supernova, a massive explosion of a dieing massive star (many times larger than a nova) that completely disrupts a dead star. it is driven by a rebound effect as inwardly collapsing matter of the dead star collides with the surface of the newly formed neutron star. the rebound shockwave blows away most of the infalling gas and drives formation of all elements more massive than nickle and iron. if the supernova is powerful enough it causes the neutron star to implode, becoming a black hole.
• white dwarf, the final visible stage of an average star that has died, after this it cools until it becomes an invisible black dwarf.
• neutron star, one of the final stages of a massive star following a supernova. if the massive star was able to eject enough mass as it died so that the mass of the neutron star formed in the supernova does not exceed 3 solar masses the neutron star is stable. neutron stars consist of nothing but neutrons bound by gravity (not the strong force that holds them together in atomic nuclei).
• black hole, the other of the final stages of a massive star following a supernova. this star failed to eject enough mass as it died to be able to form a stable neutron star. it continues collapsing until its escape velocity exceeds the speed of light. as now even light cannot leave the resulting object is called a black hole. however unlike the cold undetectable black dwarf, black holes because of their enormous mass can be detected by their effects on visible matter surrounding them.