Red supergiant, star name.Like other starsMain prefacePeriod,hydrogenIt will combine into helium, but red supergiants have a shorter life span.One more than 10 timesSolar massThe core of a star will exhaust its hydrogen in ten million years.Due to its huge mass, the temperature and density at its core are high enough to make helium junction synthesize carbon and form at the same timeHydrogen combustionShell.The helium core can burn steadily because the star's gravity is large enough to control it.Because heat is generated by the core, the outside of the star will expand more thanRed GiantWhen it is still large, it forms the Red Supergiant.
BetelgeuseIt is one of the famous red super stars.[2]
The hydrogen in the central region of the star is depleted to form heliumNucleosphereAfter that, hydrogen fusionThermonuclear reactionCannot continue in the central area.At this time, the gravitational pressure is notRadiation pressureTo balance, the central region of the star will be compressed and the temperature will rise sharply.The layer of hydrogen and helium close to the central helium sphere after its temperature risesmixed gas When heated to the temperature that triggers hydrogen fusion, the thermonuclear reaction starts again.So the helium sphere gradually increases,Hydrogen combustionThe layer also expands outward, causing the outer material of the star to expandRed GiantOr red supergiant transformation.During conversion, the energy generated by the hydrogen combustion layer may be more thanMain sequence starMore time, but starssurface temperature Instead of rising, it will fall.[1]
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The outer layer is subjected tocohesionThe gravity decreases, even if the temperature decreasesExpansion pressureIt can still resist or exceed gravity. At this time, the radius of the star andSurface areaThe degree of increase exceeds the outputEnergy rateTherefore, although the total luminosity may increase, the surface temperature will decrease.Quality is higher than 4 timesSolar massWhen a large star of 20% re initiates hydrogen fusion outside the helium core, the energy released outside the core does not increase significantly, but the radius increases many times, so the surface temperature drops from tens of thousands of K to 3000~4000 K, becoming a red supergiant.Small and medium-sized stars with mass less than 4 times the solar mass enterRed GiantAt the stage, the surface temperature drops, but the luminosity increases sharply, because their outer layer expansion consumes less energy and has more production capacity.
Once a red giant star forms, it will move towards the next stage of the star——White dwarfGo ahead.When the outer region expands rapidly, the helium nucleus is affected byReaction forceHowever, it shrinks inwards strongly, and the compressed material keeps getting hot. Finally, the core temperature will exceed 100 million degrees, which will igniteHelium fusion。The final result will be a white dwarf star in the center.
Known onGalaxyThe four largest red supergiants are UY Shield, VV Cepheus, VX Sagittarius andCepheid IV。(Pay attention to distinguish between bonus superstars andRed super giant。）The mass of many red supergiants allows that the final product of their core isironAs elements approach the end of their life cycle, the elements they will develop will become heavier and heavier, and the heavier elements will be closer to the core.Relatively speaking, the stage of a red supergiant is very short, lasting only hundreds of thousands to millions of years.Most high mass red supergiants will develop into Wolf Rayet stars, while lower mass red supergiants will end their lives as type II supernovae.
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Red supergiant
The elements of nature are not justhydrogen, helium, carbon and oxygen, life materials, wood, soil and rock all contain some silicon, magnesium, sulfur, phosphorus, iron and othersHeavy atomThere are more than 20 protons and neutrons in the nucleus of these atoms.These elements cannot be made in the sun and most stars, only eight timesSolar massOnly the above can be generated.
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They are still from stars, but only a small number of stars, that is, those with the largest mass.Only after leaving the LordChronologyOnly stars with mass greater than SM can produce heavyNucleus。The core of the star compressed by the outer weight is the "alchemy furnace", and the raw materials are hydrogen andHelium combustionThe smelting process starts when the temperature rises to 6 × 10 ^ 8 K.At this temperature, carbon can no longer be kept. They collide with each other and polymerize into neon and magnesium. A production line is established here, because each new thermonuclear reaction releases more energy, making the temperature rise higher, thus making new transformation possible.
At 10 ^ 9 ℃, the neon core captures a helium core and forms magnesium. At 1.5 × 10 ^ 9 ℃, oxygen also begins to fuse, producing a series of heavier elements: sulfur, silicon and phosphorus. At 3 × 10 ^ 9 ℃, silicon begins to fuse and causes hundreds of kindsnuclear reaction, makestoveThe temperature inside is getting higher and higher.In the thousands of reactions in the future, heavier and more precious elements were produced.This is the final stage of stellar life, and these reactions become more and more sudden. The heavier the elements, the shorter the burning time.For a "model" star whose mass is 25 times the mass of the sun, carbon combustion lasts for 600 years, neon for 1 year, oxygen for 6 months, and silicon for only 1 day.
nuclear fusionIt is not possible to continue at this rate without limitation. The torrent of reaction finally converges towards one element: iron.Iron's atomic nucleus is more special. Among them, 56 protons and neutrons are so tightly bound that the energy required to fuse them is far more than the energy released by their fusion.So iron becomes the last ash of the core of a massive star.A star consists of a core that has stopped thermonuclear reaction and an outer layer that is still burning in succession.The star has to constantly expand its shell to adjust its balance. It will expand to a huge scale and become a red supergiant.
Red supergiant is the largest star in the universe.If such a star is placed at the center of the solar system, it will swallow many planets, even Jupiter.The internal structure of a red supergiant is sometimes depicted as an onion, because it contains many differentchemical elementOfConcentric layer。The lightest elements burn in the outer layer with the lowest temperature, while the heaviest elements burn in the inner layer close to the sluggish iron core.
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Betelgeuse
Antares
OrionThere are many bright stars, the most famous of which isBetelgeuse(Betelgeuse), which is a red supergiant with a radius varying from 650 to 1200 times of the sun. If it is placed in the position of our sun, its periphery will exceed Jupiter.The change of the radius makes its brightness change with it, and the brightness will change from 0.4 to 1.3.
It is about 640 light years away from us, because it is so close and large, it becomes asunlightIn addition, for the first time, humans can resolve the surface size of stars.Betelgeuse has come to the end of its life. It is speculated that it may becomeSupernova。
August 27, 2020Month willWhen visiting Tianyu, the public can enjoy the beautiful figure of "Red Super Star" following "Moon Girl" in the southern sky.[3]
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The observation found that a red supergiant shrank mysteriously.
American researchers said on June 9, 2009 that in the past decade, the red supergiant star Betelgeuse, located in the constellation Orion, has mysteriously shrunk in size.Astronomers say they don't know why this strange situation happened.
Charles Townes, a professor who participated in this study and inventor of laser, said in a statement on the same day: "The new measurement found that in the past 15 years, the diameter of 'Betelgeuse' has shrunk by 15%, its reduction is gentle, but it is accelerating year by year."
"Betelgeuse" has a radius of 5Astronomical unit, which is 5 times the distance from the earth to the sun.If you put it onsolar systemIts surface almost reachesJupiterTrack.This means that "Betelgeuse" has shrunk by equivalent toVenusDistance to the sun.Today, "Betelgeuse IV" is still hugeSpace telescopeObserved, it still belongs to a small number of stars in the form of discs rather than light spots.But as a red supergiant, it has almost reached the end of its life.
Another researcher, Edward Wishner, said that they did not know why“Betelgeuse”The volume will shrink, "YesGalaxyAs far as the universe is concerned, including the red super giant that is approaching the end of life, there are still too many unknowns.
The researchers said that they would continue to study Betelgeuse to see whether it continued to shrink or expand.The researchers also pointed out that although the size of Betelgeuse is shrinking, its brightness has not significantly darkened in the past 15 years.
This research achievement was published in theCaliforniaPasadenaHeldAmerican Astronomical SocietyIt was announced at the meeting and has been published in Astrophysical Journal Newsletter.
The sun is expected toRed GiantThe stage will last for about 10 ^ 9 years, and the luminosity will rise to about 10 ^ 3 times.At that time, the temperature of the ground will rise dozens of times, and the Earth will become Venus.
