Stages of nebula
Stage 1- Stars are born in a region of high density Nebula, and condenses into a huge globule of gas and dust and contracts under its own gravity.
This image shows the Orion Nebula or M42 .
Stage 2 - A region of condensing matter will begin to heat up and start to glow forming Protostars. If a protostar contains enough matter the central temperature reaches 15 million degrees centigrade.
This image is the outflow (colored red)and protostar.
Stage 3 - At this temperature, nuclear reactions in which hydrogen fuses to form helium can start.
Stage 4 - The star begins to release energy, stopping it from contracting even more and causes it to shine. It is now a Main Sequence Star.
The nearest main sequence star to Earth, the Sun
Stage 5 - A star of one solar mass remains in main sequence for about 10 billion years, until all of the hydrogen has fused to form helium.
Stage 6 - The helium core now starts to contract further and reactions begin to occur in a shell around the core.
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.
The star expands to a Red Giant, below
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.
A Planetary Nebula
Stage 9 - The remaining core (thats 80% of the original star) is now in its final stages. The core becomes a White Dwarf the star eventually cools and dims. When it stops shining, the now dead star is called a Black Dwarf.