Transcript Document 26742

Evolution of the Universe
From the Big Bang to the Big Chill
Dan Caton
What we will look at
The Big Bang
Star formation
(with or without planets)
Stellar evolution and death
The Big Chill
------------- Questions and Break ----------The search for (intelligent?) life in the
Universe
The Smoking Gun: Galaxies and their motions
Several
hundred
billion stars
Their
motions
revealed the
expansion
of the
Universe
Billions of Galaxies
Hubble Ultra-Deep
Field
11.3 days of
exposure time
3 arc-minutes in
size
10,000 galaxies
Seeing back to
within 800 million
years of Big Bang
Let’s look at
galactic motions….
Vesto M. Slipher
In 1914 found 11 of 15
spiral 'nebulae' spectra
showed spectral lines
Doppler shifted toward
the red.........
Milton Hummason
In 1920's, worked
his way up at Mt.
Wilson to be night
assistant and
observer.
Photographed
spectra of many
galaxies using...
… the 100-inch Mt. Wilson telescope
These interpreted by...
Edwin Hubble, who found that velocity proportional to distance
Plot means expansion
Uniform
expansion
means
velocities
are
proportion
al to
distance
No
“center”—
every
location
looks like
center!
Back up the Expansion: Big Bang
Big Bang!
Remnants of BB were Predicted
In 1960 it was predicted that we should see the remnants of the
Big Bang, Princeton physicists Robert Dicke and P. J. Peebles
Discovery!
• Penzias and Wilson
discover it in 1965
• Bell Labs / satellite
communications
• detected isotropic static
• got 1978 Nobel prize in
physics
Spectrum: 3o Kelvin “Blackbody”
Origin of the 3o Cosmic Background
Evidence of initial structure
Wilkinson Microwave Anisotropy Probe (launched 6/01) – more details later…
The Stellar Era (now)
Current era of star formation will continue
100 trillion (1014) years: stellar era ends
Let’s make some stars…
Star Formation: the Nurseries
Stars began
to form in
areas of gas
and dust
very soon
Some
fraction form
with planets
Triggers needed
for star formation
Shock wave from
passage of spiral
arm in galaxy.
Hot young blue
stars define
formation regions
Triggers for star formation
Supernovae –
either the death of
massive stars or
explosion of
accreted material
in a binary star
system, create
shock waves in the
region
Outshines the rest of
the galaxy
Used as a “standard
candle” for finding
galactic distances
Triggers for star formation
Energetic
ultraviolet
light from
new, hot
stars
generate
shock
waves
that
trigger
other stars
to form.
Proto-stars form in collapse…
Seen in
visible and
infrared
images from
HST here.
Initially heat
from energy
of
gravitational
collapse
Then …
Stars’ energy source: fusion
Proton-proton cycle
Converts hydrogen to
helium:
Two protons combine to
deuterium + positron +
neutrino
Another proton combines
with this to make isotope
of helium + gamma ray
Two of these He combine
to make He plus two
protons
Final mass less than
ingredients by E = mc2
Products ….
Products: gamma rays and neutrinos
Gamma rays take random
walk out of star, absorbed
and re-emitted at lower
temperatures and longer
wavelengths
Neutrinos leave directly with
little interaction with matter.
Used as a probe of solar
nuclear process…
Subsequent Evolution
These
processes
replenish the
Universe with
gas and dust…
Stellar
Evolution
The Lightweights
Structure of evolving Low-Mass stars
Core heats
up and
starts
burning He
Outer
atmosphere
expands
and cools
Firewood and the fireplace…
M57: the
Ring Nebula
Outer atmosphere
is gently puffed off
in a so-called
“planetary” nebula
Remaining core
becomes a “white
dwarf,” like
these…
… White dwarfs
Real White dwarfs
• Very dense—stellar
mass within planet size
•Supported from collapse
by electron degeneracy
• Mass must be less than
the Chandrasekhar limit
of 1.4 solar masses
Subrahmanyan Chandrasekhar.
High mass stars’ fate
Grows to become a red supergiant….
Fusing iron…
Endothermic reactions
Stages of Evolution
Type II
What will happen to falling matter?
A) both balls (all
matter) will
bounce to their
combined heights
B) The big ball
(core) will stop
the small ball
C) The small ball
(ejecta) will
bounce out more
Core
Rebound is violent!
Infalling matter
rebounds
dramatically due to
conservation of
momentum
Outer material is
still falling in while
inner core is
already
rebounding
outward
Core
Prominent Historical
Supernovae
Year
Observer
Status
1054
China, Japan
Crab Nebula
Tycho et al.
Tycho's
remnant
1604
Kepler et al.
Kepler’s
remnant
1987
Southern
hemisphere
monitored
1572
Supernova 1054
Seen by Chinese in
1054 AD
Possibly recorded
by native Americans
in Chaco Canyon
Not seen in Europe?
Visible in daylight for
weeks
Today …
Crab Nebula (M1) “supernova remnant”
Tycho’s Star’s SNR
1572
X-ray
image
from
Chandra
satellite
SN1987A in the Large Magellanic
Cloud
Ian Shelton, Univ. Toronto, working in Chile
LMC satellite of Milky Way Galaxy, 170kly
away
Important: first ‘nearby’ SN in modern times
The Future
What can we tell from
measurements of the
expansion of the
Universe?
Recent data..
Look at details at upper end…
Models vs. data scatter
Our new fate?
Let’s look at current model of the future… three more eras
The Degenerate Era
Most of the mass is locked up in
degenerate stars, those that have blown
up and collapsed into black holes and
neutron stars, or have withered into white
dwarfs.
Energy in this era is generated through
proton decay and particle annihilation.
Ends in 1037 years.
The Black Hole Era
Protons have decayed (t >1033 yr?
undetected yet) and black holes have
evaporated.
After the epoch of proton decay, the only
stellar-like objects remaining are black
holes of widely disparate masses, which
are actively evaporating during this era.
Ends at ~10100 years
The Dark Era
Only the waste products from these
processes remain: mostly photons of
colossal wavelength, neutrinos, electrons,
and positrons.
For all intents and purposes, the universe
as we know it has dissipated… the truly
Big Chill
The (real) end.