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- That Lucky Old Sun got nothing to do, but, roam around heaven all day.
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-. How long before the Sun expands and swallows up the Earth?
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-. Someday in the far future, 5 billion years from now, the Earth will be inside the Sun. Not that the distance of 93 million miles will shorten between the Earth and the Sun, but, the Sun will expand into a Red Giant Star. If we think of the size of the Sun as a soccer ball, when it grows into a Red Giant Star it will be the size of a soccer field.
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-. When the Sun later goes through the planetary nebula stage and a White Dwarf Star is left at the center it will be the size of an ant on the soccer field.
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-. This theory of the Sun's evolution sprang out of the Herzberg Russell Diagram in 1913. The diagram plots star’s brightness on the vertical axis and a star’s color on the horizontal axis.
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-. The diagram showed a correlation between the star’s mass its luminosity, and, also, its lifetime. The star’s mass controls its life. The mass the star is born with determines the evolution that follows.
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-. When stars are born with enough mass there is enough gravity present to bring the core temperature up to tens of millions of degrees. Hot enough to fuse hydrogen into helium. This is a stable part of the star’s life. It is the Sun we know today which is halfway into its stellar evolution.
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-. What causes a star to evolve into a Red Giant Star?
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-. When the core of the star runs out of hydrogen it can no longer convert hydrogen into helium at its center. So, it begins burning hydrogen in the outer shell surrounding the interior. This causes the outer layers of the star to diffuse and expand. This expansion is called the Red Giant stage.
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-. Stars can lose ther mass as the expanding gas can disperse into interstellar space as solar winds. How much mass the star loses greatly affects its future. Our Sun is expected to lose 46 % of its mass and become an oxygen- carbon cinder 6,500,000,000 years from now.
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-. After the Red Giant phase the Sun begins burning helium into oxygen, eventually shrieking into a White Dwarf Star. This phase of the star’s life is sketchy at best. To learn what really happens astronomers are studying star clusters where thousands of stars are grouped together all the same age, but, all different sizes. All the stars should be the same composition as well because they coalesced from the same interstellar cloud of gas and dust.
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-. Astronomers measure the brightness and colors of all these different stars. The data is plotted in the Herztsprung- Russell diagram. The 47 TUC star cluster’s age is 10,500,000,000 years.
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-. A normal White Dwarf Star on this cluster diagram has a temperature of 25,000 degrees Kelvin. This temperature along with the extreme density of the White Dwarf Star and the resulting pressure on its surface causes hydrogen absorption lines to blur. The lines blur to 5 to 10 times greater line width than those in normal stars. In this way the White Dwarf stars are identified.
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-. By studying the data astronomers have calculated that the star of 5 Solar Mass will lose 80 % of its mass before becoming a White Dwarf Star. The stars may fuse even heavier elements that oxygen and carbon, maybe neon and magnesium.
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- .A star of 3 Solar Mass would lose 75 %of its mass.
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-. They star of 2 Solar Mass would lose 67 % of its mass.
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-. A star 1 Solar Mass, our Sun, will expand to 200 times its present radius. Its surface temperature would drop from 6,000 degrees Kelvin to 3,000 Kelvin. Thus its red color. Yet it will become 1,000 times more luminous due to its enormous size.
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-. The intense luminosity will disperse the outer layers leaving behind a White Dwarf core that will quickly cool. Our Sun will be 54 % of its present weight but will be the same size as the Earth.
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-. This sounds like in an unusual evolution, but, 90 percent of the stars in the Milky Way galaxy will end up as the same cool, dim, White Dwarf Stars. In 6,000,000,000 years our Sun will be an oxygen- carbon cinder. We'll need to move before that happens. An announcement will be made, but, you'll have to wait.
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RSVP, with comments, suggestions, corrections. Index of reviews available ---
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---- www.twitter.com , --- 707-536-3272 ---- Thursday, April 17, 2014 ---
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