The life cycle of a star
This causes the outer layers of the star to expand outward, increasing the size of the star many times. O- and B-Class Stars O- and B-class stars are some of the largest ones you will see in the night sky.
Life cycle of a star for kids
Mid-sized stars are red giants during two different phases of their post-main-sequence evolution: red-giant-branch stars, with inert cores made of helium and hydrogen-burning shells, and asymptotic-giant-branch stars, with inert cores made of carbon and helium-burning shells inside the hydrogen-burning shells. The massive star is much bigger in its expanding stage. Because the core-collapse mechanism of a supernova is, at present, only partially understood, it is still not known whether it is possible for a star to collapse directly to a black hole without producing a visible supernova, or whether some supernovae initially form unstable neutron stars which then collapse into black holes; the exact relation between the initial mass of the star and the final remnant is also not completely certain. Stars are formed in clouds of gas and dust, known as nebulae. Main article: Subgiant When a star exhausts the hydrogen in its core, it leaves the main sequence and begins to fuse hydrogen in a shell outside the core. With the high infrared energy input from the central star, ideal conditions are formed in these circumstellar envelopes for maser excitation. Stars somewhat less massive may partially ignite carbon, but are unable to fully fuse the carbon before electron degeneracy sets in, and these stars will eventually leave a oxygen-neon-magnesium white dwarf. For all but the lowest-mass stars, the fused material has remained deep in the stellar interior prior to this point, so the convecting envelope makes fusion products visible at the star's surface for the first time.
The two supernovae, one reddish yellow and one blue, form a close pair just below the image center to the right of the galaxy nucleus Image Credit: C. As it expands, it first becomes a sub-giant star, then a red giant.
It will start to expand into a red giant — and will likely swallow our planet when that happens — and then eventually diffuse into a planetary nebula, leaving a white dwarf behind.
In more-massive stars the stars become more luminous and the pulsation period is longer, leading to enhanced mass loss, and the stars become heavily obscured at visual wavelengths. Nebulae are dense clouds of dust and gas that can give rise to hundreds of stars.
They vary in size, mass and temperature, diameters ranging from x smaller to over x larger than that of the Sun. The central star then cools to a white dwarf. On the right of the illustration is the life cycle of a massive star 10 times or more the size of our Sun.
Life cycle of a star nasa
The massive star is much bigger in its expanding stage. Eventually either the core becomes degenerate, in stars around the mass of the sun, or the outer layers cool sufficiently to become opaque, in more massive stars. At this stage of evolution, the results are subtle, with the largest effects, alterations to the isotopes of hydrogen and helium, being unobservable. Smaller stars like the sun contract peacefully into white dwarfs while their outer shells radiate away as planetary nebulae. Ordinarily, atoms are mostly electron clouds by volume, with very compact nuclei at the center proportionally, if atoms were the size of a football stadium, their nuclei would be the size of dust mites. When it stops shining, the now dead star is called a Black Dwarf. The star will eject its outer layers into space, and then contract down, eventually becoming a white dwarf. The larger its mass, the shorter its life cycle. The star has now reached the red giant phase. Stars can exist in this stage for billions of years. It will spend 90 percent of its life in this stage, fusing hydrogen molecules and forming helium in its core. The extremely energetic neutrinos fragment some nuclei; some of their energy is consumed in releasing nucleons , including neutrons , and some of their energy is transformed into heat and kinetic energy , thus augmenting the shock wave started by rebound of some of the infalling material from the collapse of the core. Many of these helium-fusing stars cluster towards the cool end of the horizontal branch as K-type giants and are referred to as red clump giants. Models[ edit ] A stellar evolutionary model is a mathematical model that can be used to compute the evolutionary phases of a star from its formation until it becomes a remnant. Where a star goes from this point depends on its size.
A Neutron Star — Small but scary. 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.
How do we know the life cycle of a star
At the end of helium fusion, the core of a star consists primarily of carbon and oxygen. White dwarfs are stable because the inward pull of gravity is balanced by the degeneracy pressure of the star's electrons, a consequence of the Pauli exclusion principle. Life Cycle of a Star Credit: NASA Eventually, however, the hydrogen fuel that powers the nuclear reactions within stars will begin to run out, and they will enter the final phases of their lifetime. A massive star will undergo a supernova explosion. A protostar turns into a main sequence star which eventually runs out of fuel and collapses more or less violently, depending on its mass. Reference URLs:. Its remaining core of carbon will continue to cool and decrease in luminosity over billions of years until it becomes a white dwarf. Although lower-mass stars normally do not burn off their outer layers so rapidly, they can likewise avoid becoming red giants or red supergiants if they are in binary systems close enough so that the companion star strips off the envelope as it expands, or if they rotate rapidly enough so that convection extends all the way from the core to the surface, resulting in the absence of a separate core and envelope due to thorough mixing. Such an explosion is termed a nova. All stars evolve the same way up to the red giant phase. Electron degeneracy pressure provides a rather soft limit against further compression; therefore, for a given chemical composition, white dwarfs of higher mass have a smaller volume. These mysterious and frightening objects can slow down time and rip you apart and nothing can escape the grasp of a black hole when it reaches its event horizon.
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