How long does nebula stage last

Stage 7 - The core is hot enough for the helium to fuse to form carbon. The outer layers begin to expand, cool and shine less brightly. The expanding star is now called a Red Giant. Stage 8 - The helium core runs out, and the outer layers drift of away from the core as a gaseous shell, this gas that surrounds the core is called a Planetary Nebula. The core becomes a W hite Dwarf the star eventually cools and dims. When it stops shining, the now dead star is called a Black Dwarf.

Massive stars have a mass 3x times that of the Sun. Some are 50x that of the Sun. Stage 1 - Massive stars evolve in a simlar way to a small stars until it reaces its main sequence stage see small stars, stages The stars shine steadily until the hydrogen has fused to form helium it takes billions of years in a small star, but only millions in a massive star.

Stage 2 - The massive star then becomes a Red Supergiant and starts of with a helium core surrounded by a shell of cooling, expanding gas. Stage 3 - In the next million years a series of nuclear reactions occur forming different elements in shells around the iron core. Stage 4 - The core collapses in less than a second, causing an explosion called a Supernova , in which a shock wave blows of the outer layers of the star.

It is very poetic to say that we are made from the dust of the stars. Amazingly, it's also true! Much of our bodies, and our planet, are made of elements that were created in the explosions of massive stars. Let's examine exactly how this can be. Life Cycles of Stars A star's life cycle is determined by its mass. The larger its mass, the shorter its life cycle. A star's mass is determined by the amount of matter that is available in its nebula , the giant cloud of gas and dust from which it was born.

Over time, the hydrogen gas in the nebula is pulled together by gravity and it begins to spin. As the gas spins faster, it heats up and becomes as a protostar. Eventually the temperature reaches 15,, degrees and nuclear fusion occurs in the cloud's core.

The cloud begins to glow brightly, contracts a little, and becomes stable. It is now a main sequence star and will remain in this stage, shining for millions to billions of years to come. This is the stage our Sun is at right now. As the main sequence star glows, hydrogen in its core is converted into helium by nuclear fusion. When the hydrogen supply in the core begins to run out, and the star is no longer generating heat by nuclear fusion, the core becomes unstable and contracts.

The outer shell of the star, which is still mostly hydrogen, starts to expand. As it expands, it cools and glows red. The star has now reached the red giant phase. It is red because it is cooler than it was in the main sequence star stage and it is a giant because the outer shell has expanded outward.

In the core of the red giant, helium fuses into carbon. Eventually, fusion moved to the vast shell of expanding gas that surrounds the core. The star expanded, and as the outer shell cooled, it dimmed to a reddish-orange glow. This star spent about a billion years as a red giant, and once that phase of its life ended, it shed its outer layers in a last exhalation, which astronomers call a stellar wind. Then it turns into a white dwarf.

The image at the top captures the star when it shed its outer layers, forming a planetary nebula and leaving a white dwarf behind. Planetary nebula is a misnomer from history. In the earlier days of astronomy, when telescopes were not so powerful as today, these shells of expanding gas resembled planets.

We now know that they have nothing to do with planets, and everything to do with stars, but the name has stuck. As for the star at the center of the image, its fate is sealed.