The Heart of the SunThe Heart of the Sun

Energy Generation in Sun-like Energy Generation in Sun-like StarsStars

From whence it came…From whence it came…

All energy generation occurs in the Core of All energy generation occurs in the Core of the Sun ( and other stars)the Sun ( and other stars)

Nuclear Fusion (combining nuclei)Nuclear Fusion (combining nuclei)Lighter elements combine to make heavier Lighter elements combine to make heavier

onesonesSome mass gets converted into energy!Some mass gets converted into energy!

Sun’s FuelSun’s Fuel

All stars are composed primarily of All stars are composed primarily of HydrogenHydrogen

It is the most abundant element in the It is the most abundant element in the UniverseUniverse

Sun is burning Hydrogen into HeliumSun is burning Hydrogen into HeliumNuclear Fusion!Nuclear Fusion!

Hydrogen FusionHydrogen Fusion

Two mechanisms to burn HydrogenTwo mechanisms to burn HydrogenSun-like stars use Proton-Proton chainSun-like stars use Proton-Proton chainLarger stars (1.4 times Sun size) use CNO Larger stars (1.4 times Sun size) use CNO

cycle (carbon, nitrogen, oxygen)cycle (carbon, nitrogen, oxygen)Both are mechanisms to convert Hydrogen Both are mechanisms to convert Hydrogen

to Heliumto Helium

Proton-Proton ChainProton-Proton Chain

Net effect: Converts 4 Hydrogen to 1 Net effect: Converts 4 Hydrogen to 1 HeliumHelium

11H + H + 11H H 22H + eH + e+++ + (happens twice) (happens twice)

22H + H + 11H H 33He + He + (happens twice)  (happens twice)  33He + He + 33He He 44He+He+11H+H+11H + H +

Proton-Proton ChainProton-Proton Chain

There is a mass defect!There is a mass defect!The Helium-4 nucleus is 0.048x10The Helium-4 nucleus is 0.048x10-27-27kg kg

less massive than the 4 Hydrogen-1 nucleiless massive than the 4 Hydrogen-1 nucleiThis mass gets converted into energyThis mass gets converted into energyThe amount of energy for a housefly to The amount of energy for a housefly to

jump .001 inches into the air!jump .001 inches into the air!Not much!Not much!

Proton-Proton ChainProton-Proton Chain

This reaction occurs 10This reaction occurs 103838 times per second times per second5 million tons of Sun’s mass are converted 5 million tons of Sun’s mass are converted

to energy every second!to energy every second!How much of total mass will get converted How much of total mass will get converted

in the Sun’s lifetime? in the Sun’s lifetime? < 0.07% of its mass!< 0.07% of its mass!

Proton-Proton ChainProton-Proton Chain

Need high temperatures and high Need high temperatures and high densities densities

Temp= 8 million KTemp= 8 million KOnly core of Sun is hot and dense enough!Only core of Sun is hot and dense enough!

Matter and AntimatterMatter and Antimatter

Positron is antimatterPositron is antimatterReacts with electronsReacts with electronsAnnihilates!Annihilates!Creates Creates -rays-rays

Solar NeutrinosSolar Neutrinos

Neutrino- “little neutral one”Neutrino- “little neutral one” Interact with almost nothing!Interact with almost nothing!Hard to detectHard to detectEscape from Sun quickly!Escape from Sun quickly!Provide information about internal Provide information about internal

processes of the Sunprocesses of the SunCarry about 2% of energy from P-P chainCarry about 2% of energy from P-P chain

Solar NeutrinosSolar Neutrinos

Appear whenever reaction produces an Appear whenever reaction produces an electron or positronelectron or positron

3 types of neutrinos exist3 types of neutrinos existOnce believed to be masslessOnce believed to be masslessBut now…But now…

Solar Neutrino ProblemSolar Neutrino Problem

2 produced in every P-P chain2 produced in every P-P chain10103838 chains/second chains/secondLots of Lots of ’s!’s!Huge detectors on Earth didn’t detect Huge detectors on Earth didn’t detect

enough (1/3 as many as predicted)enough (1/3 as many as predicted)Where are the Where are the ’s?’s?

Solar Neutrino Solution! Solar Neutrino Solution! (Maybe)(Maybe)

3 kinds of neutrinos3 kinds of neutrinosNot enough electron Not enough electron ’s, too many mu ’s, too many mu ’s’sSome Some ’s have been detected changing ’s have been detected changing

varieties (oscillating)varieties (oscillating)They must have mass to do this!They must have mass to do this!The solar type The solar type ’s have yet to been ’s have yet to been

observed doing thisobserved doing this

SummarySummary

Sun generates energy via Hydrogen fusionSun generates energy via Hydrogen fusionUses Proton-proton chainUses Proton-proton chainThis process generates energy via mass This process generates energy via mass

defectdefectAntimatter existsAntimatter existsSolar neutrino problem solved?Solar neutrino problem solved?