nsci 314 life in the cosmos 3 – stars and their evolution (continued) and basic properties of life...
TRANSCRIPT
NSCI 314
LIFE IN THE COSMOS
3 – STARS AND THEIR EVOLUTION (CONTINUED)AND
BASIC PROPERTIES OF LIFE
Dr. Karen KolehmainenDepartment of Physics
CSUSB
COURSE WEBPAGE:http://physics.csusb.edu/~karen
REVIEW OF STAR FORMATION FORMED FROM A NEBULA (DENSER PART OF
THE INTERSTELLAR MEDIUM) NEBULA CONTRACTS DUE TO GRAVITY SPINS FASTER AND FLATTENS INTO A DISK
AS IT CONTRACTS GETS HOTTER, EVENTUALLY HOT ENOUGH
FOR NUCLEAR FUSION (H TO He) TO BEGIN IN THE CENTER
NOW IT IS A MAIN SEQUENCE STAR PLANETS AND SMALLER OBJECTS FORM
FROM MATERIAL LEFT OVER
HIGH TEMPERATURE IS NECESSARY FOR NUCLEAR FUSION. THE NUCLEI MUST BE MOVING FAST ENOUGH TO COLLIDE DESPITE THEIR ELECTRICAL REPULSION.
•IN THE CORE OF A MAIN SEQUENCE STAR, TEMPERATURE IS ABOUT 15 MILLION K (27 MILLION oF).
HYDROGEN NUCLEI (PROTONS) FUSE TO FORM HELIUM.
•FOUR 1H (PROTONS) FUSE TO ONE 4He + ENERGY.
•TWO OF THE PROTONS ARE CONVERTED TO NEUTRONS.
WHERE DOES THE ENERGY COME FROM?
•ONE 4He IS 0.7% LIGHTER THAN FOUR 1H COMBINED.
•THE LOST MASS IS CONVERTED TO ENERGY.
E = m c 2
ENERGY = MASS x (SPEED OF LIGHT)²
NUCLEAR REACTIONS IN MAIN SEQUENCE STARS
THE SUN CONVERTS 4 BILLION kg OF MATTER INTO ENERGY EACH SECOND.
THE SUN HAS SUFFICIENT HYDROGEN TO DO THIS FOR 100 BILLION YEARS, BUT WILL STOP AFTER ABOUT 10 BILLION YEARS BECAUSE ONLY THE CORE UNDERGOES FUSION. (THE OUTER PARTS OF THE STAR AREN’T HOT ENOUGH FOR FUSION.)
WHEN HYDROGEN IN THE CORE RUNS OUT, THIS MARKS THE END OF THE MAIN SEQUENCE LIFETIME.
THE MORE MASSIVE THE STAR, THE SHORTER THE MAIN SEQUENCE LIFETIME.
•EVEN THOUGH THERE IS MORE HYDROGEN TO FUSE, FUSION PROCEEDS SO MUCH MORE RAPIDLY (BECAUSE IT IS HOTTER) THAT THE HYDROGEN IN THE CENTER DOESN’T LAST AS LONG.
NUCLEAR REACTIONS IN MAIN SEQUENCE STARS
MAIN SEQUENCE STARSALL PROPERTIES OF A MAIN SEQUENCE STAR
DEPEND ON ITS MASS.–MORE MASSIVE STARS ARE LARGER.–MORE MASSIVE STARS ARE HOTTER.–MORE MASSIVE STARS ARE BLUER.–MORE MASSIVE STARS ARE BRIGHTER.–MORE MASSIVE STARS HAVE SHORTER
LIFETIMES. • EVEN THOUGH THEY HAVE MORE NUCLEAR FUEL,
THEY USE IT UP MORE QUICKLY BECAUSE OF THEIR HIGHER TEMPERATURES.
Brightness (Sun = 1)
SpectralType
Number of Stars in MW
Percent ofTotal
100,000
500
10
2
0.9
0.2
0.005
O
B
A
F
G
K
M
5 million
10 million
500 million
1 billion
10 billion
100 billion
1 trillion
80,000
360 million
2.4 billion
12 billion
28 billion
60 billion
290 billion
0.00002 %
0.09 %
0.6 %
3 %
7 %
15 %
73 %
Lifetime(Years)
PROPERTIES OF MAIN SEQUENCE STARS
AT THE END OF THE MAIN SEQUENCE LIFETIME… THE OUTER PART OF THE STAR EXPANDS (BY UP TO 200
TIMES), BRIGHTENS (BY UP TO 100 TIMES), AND COOLS TO 3,000 K. THE STAR BECOMES A RED GIANT. IN MASSIVE STARS, A SECOND STAGE OF EXPANSION AND COOLING PRODUCES A SUPERGIANT.
MEANWHILE, THE CORE CONTRACTS AND HEATS UP UNTIL HELIUM BEGINS TO FUSE TO FORM CARBON AND HEAVIER ELEMENTS.
THE STAR GOES THROUGH OCCASIONAL EPISODES OF INSTABILITY, WITH RAPID OSCILLATIONS IN SIZE, TEMPERATURE, AND BRIGHTNESS.
He FUSES INTO CARBON , NITROGEN AND OXYGEN + ENERGY. IN LOW MASS STARS, FUSION STOPS HERE BECAUSE IT NEVER GETS HOT ENOUGH TO FUSE C, N, AND O TO EVEN HEAVIER ELEMENTS.
IN MASSIVE STARS, CARBON FUSES TO FORM HEAVIER ELEMENTS, WHICH AGAIN FUSE TO FORM EVEN HEAVIER ELEMENTS, EVENTUALLY RESULTING IN IRON. AT EACH STEP, ENERGY IS PRODUCED.
FUSION OF IRON TO EVEN HEAVIER ELEMENTS WOULD REQUIRE ENERGY AS AN INPUT INSTEAD OF RELEASING ENERGY. (THE NUCLEUS THAT WOULD RESULT FROM FUSION IS HEAVIER THAN THE NUCLEI THAT WOULD FUSE TO FORM IT.)
THIS ENERGY IS UNAVAILABLE, SO FUSION DOESN’T PROCEED BEYOND IRON, NO MATTER HOW MASSIVE THE STAR.
NUCLEAR REACTIONS IN RED GIANTS AND SUPERGIANTS
LATE STAGES OF STELLAR EVOLUTION FOR SOLAR-TYPE (LOW MASS) STARS
PLANETARY NEBULA: THE OUTER PART OF THE STAR IS EJECTED. THE EJECTED MATERIAL EXPANDS, COOLS, AND ENRICHES THE INTERSTELLAR MEDIUM WITH HEAVIER ELEMENTS (FUSION PRODUCTS). THE CORE OF STAR REMAINS IN THE CENTER OF THE NEBULA, AND BECOMES A …
WHITE DWARF: CORE OF THE ORIGINAL STAR LEFT AFTER OUTER PARTS ARE EJECTED. IT SHRINKS TO ABOUT EARTH-SIZE, AND IS VERY DENSE. (A TEASPOONFUL OF WHITE DWARF MATERIAL WOULD WEIGH ABOUT A TON.) THERE IS NO MORE FUSION, SO THE WHITE DWARF COOLS AND DIMS (VERY, VERY SLOWLY) UNTIL EVENTUALLY IT BECOMES A …
BLACK DWARF: NO MORE LIGHT EMITTED. STELLAR CORPSE IS A DENSE SOLID BALL OF CARBON, NITROGEN, AND OXYGEN. THE UNIVERSE ISN'T OLD ENOUGH FOR BLACK DWARFS TO HAVE FORMED YET.
LATE STAGES OF STELLAR EVOLUTION FOR MASSIVE STARS SUPERNOVA (TYPE II)
– IRON CORE OF RED SUPERGIANT COLLAPSES UNTIL NUCLEI COLLIDE WITH EACH OTHER.
– NUCLEI BOUNCE APART VIOLENTLY, PUSHING MATERIAL OUTWARD AND CAUSING STAR TO EXPLODE.
– LOTS OF ENERGY IS RELEASED IN EXPLOSION, STAR BRIGHTENS ENORMOUSLY.
– ENERGY OF EXPLOSION CAUSES FUSION OF HEAVY ELEMENTS (EVEN HEAVIER THAN IRON).
– EJECTED MATERIAL FORMS A SUPERNOVA REMNANT, WHICH EXPANDS AND ADDS MATERIAL (ENRICHED IN HEAVY ELEMENTS) TO THE INTERSTELLAR MEDIUM.
NEUTRON STAR OR BLACK HOLE: CORE OF ORIGINAL STAR LEFT OVER AFTER THE SUPERNOVA EXPLOSION, EXTREMELY DENSE
“BEFORE AND AFTER” PICTURES OF A SUPERNOVA
NEUTRON STAR BALL OF NEUTRONS (LIKE ONE BIG NUCLEUS)
MASS BETWEEN ABOUT 1.4 AND 3 SOLAR MASSES
RADIUS ABOUT 10 km
VERY HIGH DENSITY – ONE TEASPOONFUL OF NEUTRON STAR MATERIAL WOULD WEIGH A BILLION TONS
MANY NEUTRON STARS EMIT PULSES OF RADIO WAVES AND OTHER ELECTROMAGNETIC RADIATION, AND ARE OBSERVED AS PULSARS
BLACK HOLE IF THE STELLAR CORE LEFT AFTER A
SUPERNOVA IS SUFFICIENTLY MASSIVE (MORE THAN ABOUT 3 SOLAR MASSES), IT COLLAPSES TO FORM A BLACK HOLE
EVEN HIGHER DENSITY THAN A NEUTRON STAR
ESCAPE VELOCITY EXCEEDS THE SPEED OF LIGHT
ESCAPE VELOCITY SPEED NEEDED WHEN TAKING OFF FROM THE SURFACE OF
A PLANET OR OTHER OBJECT IN ORDER TO ESCAPE THE OBJECT’S GRAVITY (TECHNICALLY, TO ESCAPE TO AN INFINITE DISTANCE AWAY, SLOWING TO ZERO SPEED IN THE PROCESS).
EARTH'S ESCAPE VELOCITY IS 11 km/s.
THE MORE MASSIVE THE OBJECT YOU'RE ESCAPING FROM, THE LARGER THE ESCAPE VELOCITY.
THE SMALLER THE RADIUS OF THE OBJECT YOU'RE ESCAPING FROM, THE LARGER THE ESCAPE VELOCITY.
THEREFORE, A MASSIVE BUT SMALL OBJECT (i.e., A DENSE OBJECT) HAS A LARGE ESCAPE VELOCITY.
BLACK HOLE ESCAPE VELOCITY EXCEEDS THE SPEED OF LIGHT. THEREFORE NOTHING CAN ESCAPE, NOT EVEN LIGHT. AN “EVENT HORIZON” SEALS OFF THE INTERIOR FROM THE REST
OF THE UNIVERSE. THE EVENT HORIZON HAS A RADIUS OF SEVERAL km FOR A
STELLAR MASS BLACK HOLE. MATTER INSIDE EVENT HORIZON PROBABLY CONTRACTS TO A
“SINGULARITY” – INFINITE DENSITY! CAN SOMETIMES BE DETECTED VIA GRAVITATIONAL EFFECTS
ON OTHER OBJECTS (E.G., IN A DOUBLE STAR SYSTEM) AND/OR VIA X-RAYS EMITTED BY MATTER FALLING IN.
IN ADDITION TO STELLAR-MASS BLACK HOLES FORMED AT END OF LIVES OF MASSIVE STARS, LARGER BLACK HOLES EXIST IN THE CENTER OF MOST GALAXIES (INCLUDING THE MILKY WAY).
A CLOSED SYSTEM AND ITS ENVIRONMENT
CLOSED SYSTEM
MATTER ENERGY
MATTER ENERGY
AN OPEN SYSTEM AND ITS ENVIRONMENT
OPEN SYSTEM
MATTER ENERGY
WASTE ENERGYWASTE MATTER
ENTROPY AND ORDER ENTROPY: A MEASURE OF THE DISORDER IN A
SYSTEM
– LOW ENTROPY = HIGHLY ORDERED
– HIGH ENTROPY = VERY DISORDERED OR MESSY SECOND LAW OF THERMODYNAMICS:
– IN ANY CLOSED SYSTEM (MEANING THAT NOTHING ENTERS OR LEAVES), NO PROCESS CAN OCCUR IN WHICH THE SYSTEM'S ENTROPY DECREASES. IN OTHER WORDS, A CLOSED SYSTEM CAN'T BECOME MORE ORDERED (LESS MESSY) AS TIME GOES ON.
– THEREFORE, THE AMOUNT OF DISORDER IN A CLOSED SYSTEM EITHER INCREASES WITH TIME OR IT DOESN’T CHANGE WITH TIME. USUALLY, THE ENTROPY INCREASES WITH TIME, i.e., A CLOSED SYSTEM GETS MESSIER AS TIME GOES ON.
ENTROPY AND ORDER
SECOND LAW OF THERMODYNAMICS: IN ANY CLOSED SYSTEM, NO PROCESS CAN OCCUR IN WHICH THE ENTROPY DECREASES WITH TIME, i.e., A CLOSED SYSTEM CANNOT BECOME MORE ORDERED WITH TIME.
WHAT ABOUT THE ENTROPY OF AN OPEN SYSTEM?
AN OPEN SYSTEM INTERACTS WITH ITS ENVIRONMENT. IF WE INCLUDE THE ENVIRONMENT AS PART OF THE SYSTEM (INSTEAD OF SOMETHING OUTSIDE OF THE SYSTEM), WE NOW HAVE A CLOSED SYSTEM, AND ITS TOTAL ENTROPY CAN'T DECREASE WITH TIME. HOWEVER, THE ENTROPY OF THE ORIGINAL OPEN SYSTEM CAN DECREASE, AS LONG AS THE ENTROPY OF ITS ENVIRONMENT INCREASES BY AN EVEN LARGER AMOUNT.
LIFE: ENTROPY DECREASES WITHIN AN ORGANISM AS RAW MATERIALS ARE REARRANGED IN HIGHLY ORDERED WAYS. HOWEVER, THE ORGANISM IS AN OPEN SYSTEM, AND THE ENTROPY OF ITS ENVIRONMENT INCREASES.
LIFE AND ITS ENVIRONMENT
ORGANISMENTROPY DECREASES
MATTER ENERGY
WASTE MATTER WASTE ENERGY
ENVIRONMENTENTROPY INCREASES
WHAT IS LIFE? HARD TO DEFINE, BUT LET'S LIST SOME
OF ITS PROPERTIES. NECESSARY PROPERTIES:
– USES ENERGY– INTERACTS WITH ITS ENVIRONMENT– MAINTAINS A LOW ENTROPY (HIGH DEGREE
OR ORDER OR COMPLEXITY) INTERNALLY LIKELY (BUT MAYBE NOT NECESSARY)
PROPERTIES:– GROWS AND DEVELOPS– REPRODUCES– MUTATES AND EVOLVES
REQUIREMENTS FOR LIFE MATTER:
PRODUCED IN BIG BANG (H & He) AND STARS (HEAVIER ELEMENTS)
ARE CERTAIN ELEMENTS NEEDED? STABLE ENERGY SOURCE:
LOW MASS MAIN SEQUENCE STARS (OR SOMETHING ELSE?)
PROTECTED ENVIRONMENT:PLANETARY OR LUNAR SURFACES
PLANETARY OR LUNAR INTERIORS
THICK PLANETARY OR LUNAR ATMOSPHERES CHEMICAL SOLVENT (LIQUID): WATER (OR SOMETHING ELSE?)
APPROPRIATE TEMPERATURE RANGE: NEEDED TO KEEP THE SOLVENT LIQUID (APPROXIMATELY 0 TO
100o C IF WATER IS THE LIQUID SOLVENT)
IF IT’S TOO HOT, COMPLEX STRUCTURES ARE BROKEN APART
IF IT’S TOO COLD, INTERACTIONS ARE TOO SLOW
Sun Earth Earth’s Crust
Hydrogen
Helium
Oxygen
Carbon
Neon
Nitrogen
Magnesium
Silicon
Iron
Sulfur
Argon
Aluminum
Calcium
Sodium
Nickel
Chromium
Phosphorus
90.99%
8.87
0.078
0.033
0.011
0.010
0.004
0.003
0.003
0.002
0.0003
0.0003
0.0002
0.0002
0.0002
0.00003
0.00003
Oxygen
Iron
Silicon
Magnesium
Sulfur
Nickel
Aluminum
Calcium
Sodium
Chromium
Phosphorus
50%
17
14
14
1.6
1.1
1.1
0.74
0.66
0.13
0.08
Oxygen
Silicon
Aluminum
Iron
Calcium
Sodium
Potassium
Magnesium
Titanium
Hydrogen
Phosphorus
Manganese
Fluorine
Strontium
Sulfur
47%
28
8.1
5.0
3.6
2.8
2.6
2.1
0.44
0.14
0.10
0.10
0.063
0.038
0.026
Earth’s Atmosphere Bacteria Human Beings
Nitrogen
Oxygen
Argon
Carbon**
Neon
Helium
78%
21
0.93
0.03
0.0018
0.00052
Hydrogen
Oxygen
Carbon
Nitrogen
Phosphorus
Sulfur
63%
29
6.4
1.4
0.12
0.06
Hydrogen
Oxygen
Carbon
Nitrogen
Calcium
Phosphorus
Sulfur
61%
26
10.5
2.4
0.23
0.13
0.13
BOTTOM LINE:
THE ELEMENTS THAT MAKE UP TERRESTRIAL LIVING ORGANISMS ARE VERY COMMON IN STARS AND IN THE INTERSTELLAR MATERIAL FROM WHICH STARS AND PLANETS ARE FORMED.
IN LIVING THINGS, THE ATOMS OF THESE ELEMENTS ARE ORGANIZED IN ORGANIC MOLECULES, MANY OF WHICH ARE LARGE AND COMPLEX.
ORGANIC MOLECULESMOLECULE: A COMBINATION OF TWO OR MORE ATOMSEXAMPLES: H2O CO2 CH4 NH3 H2 N2 O2 C2H5O2N
ORGANIC MOLECULE: A MOLECULE COMPOSED OF CARBON AND HYDROGEN ATOMS (AND OFTEN OTHER ELEMENTS ALSO)
EXAMPLES: CH4 C2H5O2N
MONOMER: A SIMPLE ORGANIC MOLECULE SUCH AS AN AMINO ACID, SIMPLE SUGAR, FATTY ACID, OR GENETIC BASE
POLYMER: A LARGE ORGANIC MOLECULE COMPOSED OF A CHAIN OF REPEATING MONOMERS
EXAMPLES OF POLYMERSCARBOHYDRATES: STARCHES, CELLULOSE, SUCROSE.
MONOMERS: SIMPLE SUGARS, GLUCOSE
LIPIDS: FATS, CHOLESTEROL, HORMONES, CELLULAR MEMBRANES.
MONOMERS: FATTY ACIDS
NUCLEIC ACIDS: DEOXYRIBONUCLEIC ACID (DNA) & RIBONUCLEIC ACID (RNA).
MONOMERS: GENETIC BASES
PROTEINS: STRUCTURAL PROTEINS FOR BONE, ORGANS, TISSUE, AND MEMBRANES; ENZYMES, CHEMICAL SENSORS AND TRANSPORTERS.
MONOMERS: AMINO ACIDS
NEXT TIME: LET’S EXAMINE NUCLEIC ACIDS AND PROTEINS IN MORE DETAIL.