Step 3: Identify the stage of life cycle being asked about.The stars in the question are less massive than the Sun, therefore it is referring to low-mass stars.Explain questions require details of how and why those processes occur.Describe questions require details of the processes occurring.The Sun has been on the main sequence for 4.6 billion years and will remain there for an estimated 6.5 billion years.Main sequence stars can vary in mass from ~10% of the mass of the Sun to 200 times the mass of the Sun.A star will spend most of its life on the main sequence.As the temperature of the star increases and its volume decreases due to gravitational collapse, the gas pressure increases.The star reaches a stable state where the inward and outward forces are in equilibrium.With more frequent collisions, the kinetic energy of the particles increases, increasing the probability that fusion will occur.The protostar’s gravitational field continues to attract more gas and dust, increasing the temperature and pressure of the core.Eventually the temperature will reach millions of degrees Kelvin and the fusion of hydrogen nuclei to helium nuclei begins.Protostars can be detected by telescopes that can observe infrared radiation.Work done on the particles of gas and dust by collisions between the particles causes an increase in their kinetic energy, resulting in an increase in temperature.The gravitational collapse causes the gas to heat up and glow, forming a protostar.This inward movement of matter is called gravitational collapse.Gravitational attraction between individual atoms forms denser clumps of matter.All stars form from a giant cloud of hydrogen gas and dust called a nebula.Low mass: stars with a mass less than about 1.4 times the mass of the Sun ( 1.4 M Sun).After these stages, the life-cycle branches depending on the whether the star is:.The first four stages in the life cycle of stars are the same for stars of all masses.The exact route a star's development takes depends on its initial mass.The life cycle of stars go in predictable stages.This time in the life of a Red Giant is very short compared to the main sequence lifetime, only a few million years.
The helium produced falls onto the core where it can be used as fuel. A shell around the core will rise to such a temperature as to ignite further hydrogen fusion in that region of the star. Within the core temperatures will rise to begin fusion of helium into carbon. To counter the core's collapse the outer envelope expands causing the temperature to drop at the surface but also increasing surface area and thereby the luminosity of the star. When the star has run out of hydrogen fuel to fuse into helium within its core the core will begin to collapse and heat some more. See the referenced page also for the chart and other descriptions.
Once the dust clears, the only thing remaining will be a rapidly spinning neutron stars, or possibly even a black hole. Massive stars, on the other hand, will experience a most energetic and violent end, which will see their remains scattered about the cosmos in a enormous explosion, called a supernova. Small stars, like the Sun, will undergo a relatively peaceful and beautiful death that sees them pass through a planetary nebula phase to become a white dwarf.
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