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WONDERS OF THE UNIVERSE SUPERNOVA MADE BY:- AKSHAY MEHRA 1

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WONDERS OF THE UNIVERSE

SUPERNOVAMADE BY:-

AKSHAY MEHRA

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SUPERNOVA IS A STELLAR EXPLOSION WHICH IS EXTREMLY LUMINOUS AND CAUSES A BURST OF RADIATION THAT OFTEN BRIEFLY OUTSHINES AN ENTIRE GALAXY, BEFORE FADING FROM VIEW OVER SEVERAL WEEKS OR MONTHS.

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What causes a sr to blow up?

GRAVITY GIVES THE SUPERNOVA ITS ENERGY.

FOR TYPE II SUPERNOVAE, MASS FLOWS INTO THE CORE BY THE CONTINUED FORMATION OF IRON BY NUCLEAR FUSION. ONCE THE CORE HAS GAINED SO MUCH MASS THAT IT CANNOT WITHSTAND ITS OWN WEIGHT, THE CORE IMPLODES .

FOR A TYPE IA SUPERNOVA, THE ENERGY COMES FROM THE RUNAWAY FUSION OF CARBON AND OXYGEN IN THE CORE OF A WHITE DWARF.

WHY STARS BLOW UP?

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TYPES OF SUPERNOVA1.TYPE IA

2.TYPE IB AND IC

3.TYPE II3.1 CORE COLLAPSE3.2 LIGHT CURVES AND

UNUSAL SPECTRA

4.PAIR INSTABILITY TYPE

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TYPE IAWHEN A STAR ACCRETED ENOUGH MATTER TO REACH THE CHANDRASHEKHAR LIMIT IT CAN NO LONGER SUPPORT THE BULK OF ITS PLASMA WOULD BEGIN TO COLLAPSE CURRENT MODELS1.CLOSE BINARY STAR SYSTEM:

LARGER STAR CONVERTS TO A RED GIANT. IT SHEDS MOST OF ITS MASS UNTIL IT CAN NO LONGER SUSTAIN NUCLEAR FUSION. FINALLY THE SMALLER UNDERGOES THE SAME PROCESS AND ENTER INTO A SUPERNOVA.

2. COMBINING OF WHITE DWARFS:INVOLVES MERGING OF TWO WHITE DWARF STARS OR ANY OTHER COMPANION FOR A SUPERNOVA

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TYPE IB & IC

THIS TYPE OF SUPERNOVA OCCUR WHEN MASSIVE STARS RUN OUT OF FUEL AT THEIR CENTERS .

TYPE IB SUPERNOVA ARE THOUGHT TO BE THE PROGENITORS OF THE COLLAPSE OF A MASSIVE WOLF-RAVET STAR.

A FEW PERCENT OF TYPE IC SUPERNOVA MAY BE THE PROGENITORS OF GAMMA RAY BURSTS .

AN EXAMPLE OF THIS TYPE OF SUPERNOVA IS SN 2008D.

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TYPE II

IN THE CORE OF THE STAR HYDROGEN IS FUSED INTO HELIUM AND THE THERMAL ENERGY RELEASED CREATES AN OUTWARD PRESSURE WHICH PREVENTS THE COLLAPSE.

EACH TIME CORE COLLAPSES,AND THE COLLAPSE IS HALTED BY THE IGNITION OF A FURTHER PROCESS INVOLVING MORE MASSIVE NUCLEI AND HIGH TEMPERATURES AND PRESSURES.

FINALLY ALL FUEL IS CONSUMED WHEN SILICON CONVERTS TO IRON .ULTIMATELY CHANDRASEKHAR LIMIT IS EXCEDED AND THE CORE IMPLODES DUE TO ITS OWN MASS WITH NO MORE FUSION PROCESS LEFT TO PREVENT THE COLLAPSE.

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CORE COLLAPSEWITHIN A MASSIVE, EVOLVED STAR

(A) THE ONION-LAYERED SHELLS OF ELEMENTS UNDERGO FUSION, FORMING AN IRON CORE (B) THAT REACHES CHANDRASEKHAR-MASS AND STARTS TO COLLAPSE. THE INNER PART OF THE CORE IS COMPRESSED INTO NEUTRONS (C)CAUSING INFALLING MATERIAL TO BOUNCE (D) AND FORM AN OUTWARD-PROPAGATING SHOCK FRONT (RED). THE SHOCK STARTS TO STALL (E), BUT IT IS RE-INVIGORATED BY A PROCESS THAT MAY INCLUDE NEUTRINO INTERACTION. THE SURROUNDING MATERIAL IS BLASTED AWAY (F) LEAVING ONLY A DEGENERATE REMNANT.

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GRAPH OF THE LUMINOSITY AS A FUNCTION OF TIME

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LIGHT CURVES

THE LIGHT CURVES FOR TYPE II SUPERNOVAE ARE DISTINGUISHED BY THE PRESENCE OF HYDROGEN BALMER ABSORPTION LINES IN THE SPECTRA. THE DIFFERENCE IN THE SHAPE OF THE TYPE II-L SUPERNOVAE LIGHT CURVE IS BELIEVED TO BE CAUSED BY THE EXPULSION OF MOST OF THE HYDROGEN ENVELOPE OF THE STAR.

THE PLATEAU PHASE IN TYPE II-P SUPERNOVAE IS DUE TO A CHANGE IN THE OPACITY OF THE EXTERIOR LAYER.

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UNUSUAL SPECTRAOF THE TYPE II SUPERNOVAE WITH UNUSUAL FEATURES IN THEIR SPECTRA

TYPE IIN SUPERNOVAE MAY BE PRODUCED BY THE INTERACTION OF THE EJECTA WITH CIRCUMSTELLAR MATERIAL.

TYPE IIB SUPERNOVAE ARE LIKELY MASSIVE STARS WHICH HAVE LOST MOST, BUT NOT ALL, OF THEIR HYDROGEN ENVELOPES THROUGH TIDAL STRIPPING BY A COMPANION STAR.

THE PEAK ABSOLUTE MAGNITUDE OF TYPE II SUPERNOVAE VARIES FROM ONE TO ANOTHER, BUT THEY ARE DIMMER THAN TYPE IA.

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WHEN THE CORE TEMPERATURE OF A STAR OF OVER ABOUT 140 SOLAR MASSES BECOMES SO HIGH THAT PHOTONS CONVERT SPONTANEOUSLY TO ELECTRON-POSITRON PAIRS, REDUCING THE PHOTON PRESSURE SUPPORTING THE STAR'S OUTER LAYERS AND TRIGGERING A COLLAPSE THAT LEADS TO A SUPERNOVA EXPLOSION.

THIS PAIR-INSTABILITY SUPERNOVA CREATES A LARGER QUANTITY OF ELEMENTS HEAVIER THAN HELIUM ("METALS“)

IT IS BELIEVED THAT SUPERNOVA SN 2007B WAS OF THIS TYPE; IT WAS DISTINGUISHED FROM OTHER SUPERNOVAE BY VERY LONG DURATION

PAIR INSTABILITY TYPE

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SOURCE OF HEAVY ELEMENTSTHE HEAVIER ELEMENTS ARE PRODUCED

BY NUCLEAR FUSION (FOR IRON-56 AND LIGHTER ELEMENTS), AND BY NUCLEOSYNTHESIS DURING THE SUPERNOVA EXPLOSION FOR ELEMENTS HEAVIER THAN IRON.

SUPERNOVAE ARE CANDIDATE SITES FOR THE R-PROCESS, WHICH IS A RAPID FORM OF NUCLEOSYNTHESIS. THE REACTIONS PRODUCE HIGHLY UNSTABLE NUCLEI THAT ARE RICH IN NEUTRONS WHICH ARE UNSTABLE AND RAPIDLY BETA DECAY INTO MORE STABLE FORMS.

THE R-PROCESS REACTION, WHICH IS LIKELY TO OCCUR IN TYPE II SUPERNOVAE, PRODUCES ABOUT HALF OF ALL THE ELEMENT ABUNDANCE BEYOND IRON, INCLUDING PLUTONIUM AND URANIUM

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WHAT OF OUR SUN?THE SUN DOES NOT HAVE ENOUGH MASS TO BECOME A SUPERNOVA

WHEN THE SUN COMES TO THE END OF ITS LIFE (IN ABOUT 5 BILLION YEARS) IT WILL SLOWLY EMERGE INTO A RED GIANT. THE DYING SUN WILL THEN THROW OFF ITS OUTER LAYERS, FORMING A NEBULA. THE ONLY OBJECT REMAINING WILL BE THE EXTREMELY HOT CORE, WHICH WILL SLOWLY COOL AND THEN FADE AS A WHITE DWARF OVER MANY BILLIONS OF YEARS.

OUR SUN IS PROBABLY THE THIRD STAR TO EXIST IN THIS COSMIC NEIGHBOURHOOD, AND OUR SOLAR SYSTEM FORMED FROM THE PARTICLES LEFT OVER FROM PRIOR STARS DESTROYING THEMSELVES IN SPECTACULAR MANNER

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MILKY WAY CANDIDATES SEVERAL LARGE STARS WITHIN THE MILKY WAY HAVE BEEN SUGGESTED AS POSSIBLE SUPERNOVAE WITHIN THE NEXT MILLION YEARS. THESE INCLUDE

RHO CASSIOPEIAE ETA CARINAE, RS OPHIUCHI, U SCORPII,..........

SEVERAL REMAIN UNKNOWN AS THEY MAY BE IN WHITE DWARF STAGE OF TYPE IA.

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CONCLUSION