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50-500 million K
Gas
10 thousand K
gas
White
Dwarf
Neutron star
Supernova Remnant
Cas A, 17-18 light
years in diameter
Planetary Nebula
Ring Nebula, 1/3
light year diameter
Type II Supernova
Core burns all fuel, from hydrogen all the
way to iron: then the star collapses!
Only Massive (10 solar masses)
or more will do in much less
than the age of the universe
But haven’t been able to use type
IIs, yet! Too hard to calibrate
• Instead we use Type Ia
• Type Ia come from binary star systems that
have one member that is a white dwarf (WD).
• The WD is less than 1.4 solar masses
• Explodes if it goes over (one jelly donut too
many)
• A WD is a star core
• From a “low mass” (4 solar masses,
about)
• Envelope was blown off
• Left with core of less than 1.4 solar
masses,
• NO nuclear burning
• It “sits there” and cools off (unless it
“eats one jelly donut too much)”
• The limit of 1.4 solar masses and is
derived from basic physics
•
The limit has name: Chandrasekhar limit
When accreted mass on white dwarf pushes
the WD over the 1.4 solar mass limit=>
•
• Pow!
• Exceeding limit tends to lead to more
uniform in brightness explosions
• And what isn’t the same (some are
slower than others), we’ve been able
to calibrate
•Need to get extra mass onto WD =>
• Binary system
Mass Transfer!
Bottom line: WL is non-zero!
Are there any ways out?
Yes!
Either SNeIa are different in past
Or “grey dust” or ??
What are some of the problems
• Distant objects might not be same as
same as nearby ones =>
• Standard candles aren’t so standard
• Intervening material which increases with D
might also matter.
• Distant
= faint = hard to “see”
Can distant SNeIa be different
from nearby ones?
• Yes, because the material that makes up
stars depends on when the star formed
=>
• Stellar Evolution, part two:
• stars
explode, dump their material back
to interstellar medium enriched with
“metals” (anything heavier than helium)
• Metals are not made in BB!
• The very first stars in galaxies should be
just H and He.