POST key SEQUENCE EVOLUTION"The death Processes that Stars"

How the life that a star ends depends on the fixed of the star.Low-mass stars (less 보다 8 solar masses) "die" in a gradualprocess if high-mass stars (greater 보다 8 solar masses)"die" in rather spectacular fashion. But, for every stars,their MS stage ends as soon as the hydrogen in the core of the staris exhausted. Heaviness takes end which results in contractionof the main point tohigher density, temperature and pressure till the nextnuclear combination reaction deserve to take place. This is theTriple-Alpha procedure which takesplace in every stars.THE TRIPLE-ALPHA PROCESSThis nuclear reaction fuses 3 HELIUM NUCLEIinto 1 CARBON NUCLEUS and releases energy.The beryllium (Be) is very unstable and also will break apartvery conveniently (3 x 10-16 seconds!) unless it ishit by one more helium to kind carbon.For this reason, the densities and also temperaturesmust be an extremely high (greater 보다 150 million Kelvin!)In massive stars, this reaction wake up in a controlledmanner. But, for stars much less than 2 solar masses,the helium main point is fused into carbonin just a few seconds inwhat is a dubbed the Helium Flash!Sometimes, the CARBON NUCLEUScan fuse with one more HELIUM NUCLEUS which producesan OXYGEN NUCLEUS.- - - - - - - - - - - - - - - -While every stars will have actually the Triple-Alpha process take location in their core, stars will now evolve differentlydepending top top whether their mass is much less than or higher than8 solar masses. To understand exactly how stars less than 8 solarmasses evolve, we will certainly look at just how astronomers mean theSun come evolve.

You are watching: Fusion of a carbon nucleus with another carbon nucleus.

THE advancement OFA 1 SOLAR fixed STAR

*
Evolutionary monitor of a 1 Solar massive Star.An computer animation of this evolution Track.Main Sequence step ends due to core hydrogen depletion: As combination fuel (hydrogen) is provided up, the core starts contracting and temperature increases."Hydrogen shell Burning": Helium core heats contracting covering of hydrogen roughly it so the P-P fusion takes place outside of the core.Star Ascends the Red huge Branch: The gravitational power from the core and also the power from the H-burning shell cause the environment of the star to expand and cool.
*
Star external parts that the star continue to expand and the core contracts till a brand-new fuel resource for combination is found. Many logical is fusion of helium through the Triple-Alpha process. But, this requires incredibly high temperature and also pressure. Temperature = 100 to 200 million K !!!The Helium Flash: The helium main point is fused into carbon and oxygen in a issue of seconds. Gut-wrenching experience for the star. The inner structure is quickly changed and the star shrinks in size.The "new" internal core has some helium that fuses right into carbon and also oxygen. Star is now a Horizontal Branch star. This is a fairly short phase together very little fuel remains for the star to burn.
*
The star climate ascends the Asymptotic huge Branch: Collapsing core of carbon and oxygen is surrounding by helium-burning shell, inert helium layer, hydrogen- burn shell and inert hydrogen layer. Outer layers of the atmosphere, once again, expand and also cool.
*
Helium burning covering is unstable and burns erratically, causing thermal pulses. This pulses journey away the outer atmosphere of the star forming a PLANETARY NEBULA. The carbon-oxygen main point of the star is exposed. This stellar "corpse" is a White Dwarf .
*
*
*
Examples that Planetary Nebulae

PROPERTIES that WHITE DWARFS

*

THE development OF STARSGREATER than 8 SOLAR MASSES

As the star leaves the MS, the core goes v the triple-alpha procedure producing a carbon-oxygen core.The main point will proceed to contract, boosting in density and temperature.Many fusion reactions develop heavy elements inside the star and also produce one "ONION-SKIN" Structure, through iron in the core.
*
*
AFTER . . . . . BEFORE
*

SUPERNOVA = EXPLODING STAR

Two important results of Supernovae: 1. Many elements are ejected right into space. 2. Shock wave will trigger new star formation.Famous Supernovae: SN 1987A in the large Magallenic Cloud. Kepler"s Supernova in 1604. Tycho"s Supernova in 1572. Crab Nebula Supernova in 1054.
*
What"s Left Behind? 1. Ghost Star = Pulsar because that stars in between 8 and also 25 solar masses. 2. Black color Hole because that stars higher than 25 solar masses.

NEUTRON STARS or PULSARS

When the gravitational pressure becomes so good in a white dwarf(such as once the massive is greater than 1.4 solar masses), gravityforces the electrons and protons together to type neutrons.Neutron Star basic Facts:Remnants native supernovae that stars between around 8 and 25 solar masses.Mass: 1 to 2 solar masses. Biggest mass feasible is in between 2 and also 3 solar masses.Size: only 10 come 20 kilometers in radius!Just 1 teaspoon of the stuff on earth would sweet as much as every the world in China!Like white dwarfs; the an ext mass they have, the smaller the radius will certainly be.
*
Neutron stars have additionally been identified asPulsars.Neutron stars rotate really rapidly, 1 come 1000 timesa second! They also have very solid magnetic fields.Electrons in this rapidly rotating magnetic ar producelots the radio waves in a beam coming out the north and also south magnetic poles. In a comparable fashion to alighthouse, as the ghost star rotates,this beam is occasionally directed in the direction of us and we obtain a pulse the radio emission.
*

BLACK HOLES

For stars higher than 25 solar masses, the core has actually too lot mass to come to be a spirit star ~ the supernovaexplosion. In the case, a black HOLE is created.Some black HOLE preliminary stuffThe rate of light is the same for every observers!The rate of irradiate is THE rate limit. Nothing deserve to go quicker than 300,000 km/sec.Escape Velocity: Speed required to get rid of the gravitational pull and also break far from an object.E = m c2. Mass-Energy Equivalence. Gravity pulls Mass. Heaviness pulls energy (photons!)Moving clocks (Time) show up to run slower. The faster the clock moves, the slower it will appear to run.Gravity renders clocks (Time) operation SLOWER! This is not a clock problem, yet a TIME problem. Time is influenced by Gravity!

BLACK HOLES

Black Holesare objects of highly compressed issue from whichlight cannot escape because of the extremely solid gravitationalpull. The massive of the black hole is compressed into a pointknown as a SINGULARITY.Black holes are surrounded through an imaginary SURFACEknown as the occasion HORIZON. Itis within this event Horizon that we cannot observe. Theinformation of any kind of event that occurs inside the event Horizoncannot with the exterior Universe! thus the term black color Hole.
*
The event Horizon is also known together the"Schwarzschild Radius"

RSch = 3 kilometres x (Mass/MSun)

How perform You Look for a black color Hole?

Look for the affects of its gravitational pull. Binary starswhere you can only view one star "wobbling" is a good place tostart. If gas indigenous the star is falling right into the black hole,lots of X-rays will be emitted.

See more: The Real-Balances Effect On Aggregate Demand Suggests That A Cqzad

*
Candidates because that being a black color Hole: Cygnus X-1 Unseen companion about 6 solar masses. LMC X-3 Unseen companion around 10 solar masses.IMPORTANT POINTBlack holes are NOT gigantic vacuum cleaners inspace. Your gravitational pressure is only strong very close tothem. If the sun were to come to be a black color hole, the orbit that theEarth would not change.Black feet arenot choose this!

FALLING into A black color HOLE

If you room falling in, you autumn in! If you watch someone fall in, lock NEVER autumn in. They just would it seems to be ~ to acquire closer and also closer come the event Horizon, never ever crossing it, and also become fainter and fade the end of sight. There space two reasons for this gift what girlfriend see: under photons with you due to the slowing of Time in the gravity field. Photons that execute reach you room redshifted by gravity.

Summary the Post-Main-Sequence Evolution

Stars the 0.1 come 8 solar masses finish up together WHITE DWARFS.Stars of 8 come 25 solar masses finish with a SUPERNOVA and also leave behind a ghost STAR.Stars larger than 25 solar masses end with a SUPERNOVA, yet leave behind a black color HOLE.Stellar Structure and Evolution SimulatorShows the advancement of various mass stars off the MS.Even includes the supernova explosion for high-mass stars!Week #12 Notes.Week #14 Notes. Back to The prior Page.