Star History

Main sequence star types include,red dwarves,yellow dwarves,blue giants,red giants,red supergiants.Stars spend most of their lives

After its core hydrogen is depleted, a red main sequence star will go supernova after its red giant phase.

The Low mass stars spend there main life as a fusion machine which turns hydrogen into helium and a very slow and methodical pace. When the energy released by this fusion reaches the surface it is released into space and this is the star luminosity. Over a long, long time sometimes billions of years a low mass star consumes the hydrogen in its core and converts it to helium, at which point the core starts to contract and shrink. Once all of the hydrogen inside the stars core begins to become totally exhausted, the core pressure gives way to the crush of gravity because it has no more fusion occurring in its core at that time. As the core shrinks rapidly and the outer layers start to expand the stars shape begins to grow in size and its luminosity becomes extraordinary brighter due to the outer shell starting to produce fusion more rapidly then the core did during the main sequence life of the star. As this situation grows more rapidly and extreme the core starts to rapidly burn again and fuse its core helium into carbon. Then just before its final death the star ejects its outer layers into space. This leaves only the degenerate carbon core and since this core is still very hot it emits intensely powerful ultraviolet radiation and glows brightly in what is known as a planetary nebula. The nebula fades and cools over around a million or so years and we are left with a white dwarf cooling indefinitely till

Red Giant- Expending hydrogen in their cores, these stars extend their outer layers and can grow to > 100 times their main sequence size. 99% of original mass. 10% of lifespan.

A carbon-rich inner core is now occurring at this point and helium becomes depleted again. Fusion also eventually restores it once again. The core shrinks in size but the stars mass increases. Hydrogen and helium usage rates increase. Any non-burning layers are beginning to expand and at this stage, the star is a Red Giant, once again. This is a true repeat of events. But if it is a solar-mass star, the temperature will never reach the needed level for the next round of nuclear reactions to take place. Fortunately for Sun-like mass stars, they will reach the correct temperature.

There are four maybe five stages in a Suns lifetime. The first stage is the birth of the sun. According to the Nebular Theory, the Sun and all the other planets of our Solar System began as a giant cloud of gas and dust. Around 4.57 billion years something happened to cause the cloud to collapse, the end result was a gravitational collapse at the center of the cloud. There were pockets of dust collecting matter and turned into a big ball we would eventually call our sun. Our Sun is currently 5,778 K, or 27 million degrees F, which is pretty hot.

Stars begin their life cycle as molecular clouds. Some event, such as a shockwave or collision of a galaxy, causes the cloud to collapse and form smaller pieces, which collapse inward on itself, and form a protostar. As the star collapses, gravitational energy creates heat, resulting in the rotation of the particles. During this phase of formation,

The Sun’s expected lifespan is 10 billion years. The lifespan of all other stars is relative to the mass of the Sun. If the mass of a star is less than the Sun then its lifespan will be longer than 10 billion years and if the mass of a star is more than the Sun then its lifespan will be shorter than 10 billion years.

Stars are born of gas and dust and have a life cycle based on their original mass. The sun produces energy and turns it into hydrogen into helium. Our sun is a bright yellow star and is made of mostly of hydrogen and helium. The size of the sun is a medium size star in the main sequence. The life cycle of a star is the low-mass (main sequence), medium-mass (giant,and white dwarf) , and High-mass ( supergiant, supernova, and black hole. There are three types of galaxies which are elliptical galaxies, spiral galaxies, and irregular galaxies. We classify stars by their size, color, temperature, and their luminosity. When a star dies it becomes a black hole until millions of years. The hottest star is the blue star the coldest star is the red star.

Once its 10 billion years of burning comes to an end, the hydrogen that it has been using as a fuel source has, for the most part, depleted. The center of the star begins to increase in size as the production of helium increases and an inner core of helium starts to grow. The helium does not burn at these temperatures so the burning is moved out to higher layers. This inner core begins to shrink under the force of gravity and while the star is extremely hot, it is still too cool to fuse helium. The burning of hydrogen in the outer layers, however, increases and the radius of the star increases nearly three times, bringing the star out of Main Sequence section and into the category of subgiant.

There are many stages in the life-cycle of a star. Stars are formed in clouds of gas and dust, also referred to as a nebulae. The lifetime of a star depends on its size; if the star is massive, perhaps like the sun, it will have a shorter life-span. A star like a dwarf star, an extremely small star, will have a longer life-span. Stars begin as protostars, then go into main sequence stars, supergiants, and last but not least, the stars will become old and turn into either a white dwarf or a black hole. You may not be able to see every star in the night sky, but don’t be fooled, space is filled with gas and dust too thin to be seen by the naked eye; this gas and dust is called interstellar medium.

Stars spend approximately eighty percent of their lives on the main sequence before evolving into something else. A star leaves the Main Sequence when it has exhausted most of the hydrogen in its core, which causes it to lose equilibrium. It begins to contract again as radiation and thermal pressure decrease, and gravity dominates. Even though core hydrogen fusion ceases, energy is still generated in the core because of gravitational contraction. While the Main Sequence is the hydrogen core fusion stage, the first stage after the Main Sequence is the hydrogen shell fusion stage of a star’s life. During the hydrogen shell fusion stage, the nuclear fusion rate is considerably greater than during the Main Sequence. Changes in the outer layers of a star occur as the internal changes are happening. Increased pressure causes enormous expansion in the outer layers of the star, which leads to them cooling because they are farther away from the core. Visible

The life (and, sometimes, death) cycle of a star begins when gravity triumphs over heat. This results in a cloud, composed of gasses and minerals, losing balance, and beginning to contract. Balance for the cloud is not restored, until several radical changes have been experienced by the cloud, and have, subsequently, altered the cloud.

These two masses go through a similar process. High Mass Stars are born from the Stellar Nebula,(just like the Low Mass stars), and become a star although they are a lot bigger than them. They too become Red Giants, but as Red Supergiants. After becoming a Red Supergiant, there is a distinction. High Mass stars go through a phase called Supernova. A Supernova happens when a star runs out of nuclear fuel, making its mass seep through into it’s core. Soon enough, the core gets too heavy it can’t withstand its own gravitational pull so it collapses. This results in an enormous explosion. After the Supernova, there are two things a High Mass star ends up as. A Black Hole or a Neutron Star. A Black hole is like a gravitational vacuum. It sucks up matter, radiation, and even light. So much matter clumped in a tiny space makes the Black hole extremely powerful. A Neutron star is formed after the explosion, when the stars outer layer blows apart in a spectacular display. It leaves a small, dense core that continues to diminish. Protons and electrons are packed tightly by gravity, producing the

The Sun appears to have been active for 4.6 billion years and has enough fuel to go on for another five billion years or so. At the end of its life, the Sun will start to fuse helium into heavier elements and begin to swell up, ultimately growing so large that it will swallow the Earth. After a billion years as a red giant, it will suddenly collapse into a white dwarf -- the final end product of a star like ours. It may take a trillion years to cool off completely.