Nebulae: From Kant's Proposal to Hubble's Discoveries
What are nebulae??
•
1755 Kant proposed nebulae are
“island universes”
•
Are Nebulae within or outside of
our galaxy??
•
Nebula comes from a Greek word
meaning Cloud
April 1920, National Academy of
Sciences , Washington, DC
•
Harlow Shapley (had determined size of Milky Way
Galaxy) pushed that nebulae were relatively close
by objects.
•
Heber Curtis championed view that spiral nebulae
were rotating systems of stars like our own galaxy.
•
Debate was heated but eventually a draw as neither
side could provide convincing evidence for either
view
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Edwin Hubble
•
Oct 6, 1923 Historic Photo of
M31(Andromeda Galaxy)
•
Discovered a Cepheid variable star (thought it
was a nova)
•
Used formulas to determine the galaxy was
750 kpc (2.5 million ly) away and it was 70
kpc in diameter (recall Milky Way is only 50
kpc in diameter)
•
Nebula was not “Near by”
•
December 30, 1924 Hubble presents his
findings to American Astronomical Society
•
Shapley-Curtis “Debate” effectively settled
•
The Universe is a big place!!
•
Tidal forces from Milky Way
believed to be source of star
formation in the two Magellanic
Clouds
Hubble Classification of Galaxies
•
4 Classes of Galaxies
•
S – Spirals
•
SB – Barred Spirals
•
E – Ellipticals
•
Irr – Irregulars
Spirals
•
Arched lanes of stars
•
Spiral Arms containing young hot blue
stars and associated H II regions
•
Strong heavy elements present so lots
of Population I stars in spiral arms
•
Central bulges low star formation rate
dominated by Population II stars
Spirals – Sub-divided
•
Sa – Large central bulges
~4% of galactic mass in gas and dust
•
Sb – Medium sized central bulges
~8% of galactic mass in gas and dust
•
Sc – Small central bulges
~25% of galactic mass in gas and dust
Barred Spiral Galaxies
•
Spirals originate at the end of a bar shaped region
which passes through the nucleus of the galaxy
rather than originating from the nucleus itself.
•
Hubble again applied a, b, and c to rate the size of
the central bulge with a being largest and c being
smallest
•
As with ordinary spirals this difference of a through
c may be due to amount of gas and dust in the
galaxy.
•
Bars appear to form naturally in Spirals from computer
simulations
•
Barred Spirals outnumber Spirals by about two to one
•
Milky Way may be Barred Spiral
•
Bars appear to form naturally in Spirals from computer
simulations
•
Barred Spirals outnumber Spirals by about two to one
•
Milky Way may be Barred Spiral
•
A theory why all Spirals don’t have bars proposes that if a
galaxy is surrounded by a large enough halo of Dark
Matter bar will not form.
•
Milky Way may have such a halo?
Ellipticals
•
No Spiral Arms
•
Further sub-divided by numbers
–
E0 is roundest
–
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–
Category based on observation from Earth,
may not be completely accurate
•
Mostly Population II stars, little to no new
star formation occurring in these galaxies
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Hubble Tuning Fork Diagram
•
Hubble originally proposed that it represented evolution of
galaxies
•
Ellipticals would evolve into Spirals
•
Ellipticals have little to no rotation
•
Modern view is diagram represents grouping by rotation
•
Ellipticals are galaxies with little to no rotation Spirals
“class c” have greatest rotations
Types of Irregular Galaxies
•
Type I – Many OB associations and
H II regions
•
Type II – Asymmetrical shapes implying
they resulted from collisions
with other galaxies or have
violent activity occur within
their nucleus
Grouping of Galaxies
•
Groups of Galaxies are called Clusters
•
Rich Clusters have many galaxies
•
Poor Clusters have few galaxies and are sometimes
called groups
•
Poor Clusters outnumber Rich Clusters
•
Milky Way (our galaxy) is part of the Local Group ~30
galaxies (most are dwarf ellipticals)
Categorizing Clusters
•
Regular – Spherical in shape obvious
concentration of galaxies at
its center
•
Irregular – Not Regular!
•
Local Group is irregular
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Shape of Clusters
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Shape of Cluster is determined by which type of galaxies
dominate its make-up
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Regular Clusters have mostly ellipticals and lenticular
galaxies
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Irregular Clusters have a more even mixture of galaxies
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Groupings of Clusters
•
Clusters group to form Superclusters
•
Typically dozens of clusters spread over a a region
of space 30 Mpc across
1980’s mapping of clusters
•
Use redshifts to get a 3-dimensional mapping of
galaxy locations.
•
Discovery of spherical voids which are either empty
or contain Hydrogen clouds or dim galaxies
•
Voids are about 30 to 120 Mpc in diameter
•
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surfaces surrounding and between the Voids
•
Think soapsuds in a sink with soapfilms surrounding
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•
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•
Great Wall extends ~150 Mpc along the arc
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•
Southern Wall extends ~100 Mpc
•
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galaxies appears to be fairly uniform
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•
21 cm radiation show connections of Hydrogen gas
between galaxies indicating previous interactions
•
As with the M 82, M 81 and NGC 3077,
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Hydrogen gas connections
Colliding Galaxies?
•
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•
Collisions unlikely to result in Star on Star
collisions, too much empty space
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•
Starburst galaxies due to compression of
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The Mice
https://apod.nasa.gov/apod/ap150201.html
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Cluster is 8 Billion ly away
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Colliding Galaxies
•
Galactic deformations due to tidal forces
•
Stars may be ejected from galaxy
•
Often the colliding galaxies repeatedly collide until they
merge and form one new galaxy – Galactic Cannibalism!!
•
Milky Way on track to collide with Andromeda (M 31) in ~
6 billion years
Third Method to form Spiral Arms?
•
Close encounters between galaxies may provide another
way to form spiral arms in addition to Density Wave model
or Self-Propagating Star Formation
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Why do clusters stay together?
•
Observed measurements of galactic
speeds from Doppler shift
measurements indicate that galaxies are
moving too fast to remain in a cluster.
•
The amount of mass required to keep
them gravitationally bound is not present
in the visible mass
•
Answer is of course Dark Matter
How to Determine Distances to Galaxies??
•
Standard Candles
–
Luminous to shine at great distances
–
Luminosity known to a great degree of
precision
–
Light curve should be identifiable, what
kind of variable star
–
Common enough to allow for many
measurements and hence many checks
•
Use Intensity
α
1/d
2
“Standard” Candles??
•
Not all objects are “Standard”
•
Type Ia Supernova’s – Not all have same
peak luminosity.
•
Relationship between rate of decrease in
luminosity and peak luminosity
•
Tully-Fisher Relation
–
Use 21 cm radiation
–
Line is broadened due to one edge of
galaxy is rotating towards us, blue-
shifted, and one edge is rotating away
from us, red-shifted.
–
Rotational velocity provides Mass
–
Mass provides number of stars
–
Number of provides luminosity
•
Fundamental Plane (3 points define
a plane)
–
Relate Size, Motion, and
Brightness
–
Measure Motion and Brightness,
determine Size
–
Use apparent Size to Actual Size to
get distance
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http://www.noao.edu/staff/shoko/tf.html
•
Here, Tully-Fisher relations of
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represent a cluster called Abell
1367 which is much farther
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is shown in the upper part of
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relative
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distances of two clusters is
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D as indicated.
Very Large Array (N.M.)
Lasers vs. Masers
LASER – Light Amplification by Stimulated
Emission of Radiation
MASER – Microwave Amplification by
Stimulated Emission of Radiation
https://skullsinthestars.files.wordpress.com/2008/09/spatialcoherence.jpg
https://www.sciencenews.org/sites/default/files/2016/04/043016_
et-cc_transit-760_png24_free.png
http://amasci.com/graphics/cohr2.jpeg
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1920’s Hubble and Humanson
•
Photographed spectra of many galaxies with the 100 inch
Mt Wilson telescope
•
They found most spectra were red-shifted (ie moving away
from us)
•
They found the amount of red-shifting was directly
proportional to how close they were to us, more distant
galaxies had greater red-shifts than nearby galaxies
•
Redshift (z)
•
Doppler Shift
•
Hubble Law
H
0
is between 40 and 90 km/s/Mpc
Relativistic Vs Non-Relativistic Redshifts for speed
•
Consider z = 0.32
•
Consider z = 2.0
Uncertainty in H
0
•
Redshifts fairly reliable
•
Distances are not
•
Book uses 22 km s
-1
Mly
-1
=71.7 km s
-1
Mpc
-1
•
Doppler Red-Shift – the radiation is changed (longer
wavelength) because of relative motion between the
source and the observer.
•
Gravitational Red-Shift – the radiation is changed
(longer wavelength) because either time or space
changes.
•
Cosmological Red-Shift – the actual space is changed
(larger distances between points of space) this causes
wavelengths to lengthen or shift to the red end of the
spectrum.
Quasars
•
Quasars and
Active Galaxies
emit more
luminosity than
can be
accounted for
by starlight only
•
Active Galaxies
have
luminosities that
fluctuate over
periods of
months, weeks,
or sometimes
days
http://en.es-static.us/upl/2016/03/3C272-quasar.jpg
3C 273
http://chandra.si.edu/graphics/xray_sources/3c273/map2.gif
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http://pages.astronomy.ua.edu/keel/agn/3c273.gif
Grote Reber in 1937 in his back yard in Wheaton, Illinois
http://www.nrao.edu/whatisra/images/grote2.gif
By 1944
•
Sagittarius A – Galactic nucleus
•
Cassiopeia A – Supernova Remnant
–
Both inside of Milky Way
•
Cygnus A - Where ??
Cygnus A (3C 405) z = 0.056 (230 Mpc) first observed in 1951
http://www.gothosenterprises.com/black_holes/images/cygnusA-nrao.jpg
Cygnus A
•
First Photographed by Baade and Minkowski in 1951
•
Spectrum showed strong emission lines
•
Normally galaxies show absorption lines as light gets absorbed by star
atmospheres.
•
Emission lines were strongly redshifted by 5.6% ( z = 0.056)
http://www.astro.cornell.edu/academics/courses/astro201/images/
cygnusA_diag.gif
https://4.bp.blogspot.com/-
DFI7RElLBkc/UNMrI8r52LI/AAAAAAAAEsY/ejZweT686fs/s1600/
Cygnus+A.jpg
•
Amount of Luminosity for Cygnus A is
10
7
times the amount of luminosity for an
ordinary galaxy
•
1960 Sandage discovered a star at the
location of a strong radio source 3C 48
•
Also contained Strong Emission lines
•
Unable to identify chemical composition
Quasar 3C 48 z =0.367 (1300 Mpc)
http://www.calpoly.edu/~rechols/astropicslab1/quasar.jpg
1962
•
3C 273 Discovered
•
Has a jet coming off one side
•
Again Chemical Composition
could not be figured out
1963 – Break Through!!
•
Schmidt took another look at 3C 273 ‘s
Spectrum
•
He realized there were four emission lines
with the same pattern as four lines in the
Balmer portion of the Hydrogen spectrum
•
Lines were Red-Shifted!!!
•
Recognizing that, distances could be
determined and these objects are outside
of Milky Way
•
3C 273 was determined to have a redshift
of z = 0.158
•
3C 48 was determined to have even
larger redshift of z = 0.367
•
Because of their strong Radio emission
and star like appearance, these objects
were called Quasi-Stellar Radio Sources
and later this was shortened to Quasars
Quasars look like stars but have huge redshifts
These redshifts show that
quasars are several
hundred megaparsecs or
more from the Earth,
according to the Hubble
law
https://mgh-
images.s3.amazonaws.
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18045-24-6IP1.png
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astropicslab1/quasar.jpg
•
Later there were discovered High Redshift
objects that were quiet in Radio Emissions
These were called initially Quasi-stellar
Objects - QSO’s
•
Now Quasars apply to both
•
~10% of Quasars are Radio-loud
•
More than 10,000 Quasars are known
today, all have star like appearances
•
All have large Redshifts 0.06 < z < 5.8,
Most are at least z = 0.3 (fairly far away)
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http://crab0.astr.nthu.edu.tw/~hchang/ga2/f2702-3C273sp2.JPG
Why Skeptical that Quasars exist??
•
Quasars are so much more luminous than
other objects (such as normal Galaxies)
that it just seemed impossible.
•
Active Galaxies discovered that bridge the
energy gap between normal Galaxies and
Quasars
•
1943 Seyfert discovered a series of very
luminous Spiral Galaxies. These are now
known as Seyfert Galaxies
Seyfert galaxies seem to be nearby, low-luminosity, radio-quiet quasars
Seyfert galaxies are spiral galaxies with bright nuclei that are strong
sources of radiation
http://astronomer.wpengine.netdna-cdn.com/wp-
content/uploads/2011/04/ngc7742_hst.jpg
Seyfert Galaxies
•
About as luminous as a weak Quasar
•
Little to no radio activity
•
Seyfert’s appear to often be the result of
colliding galaxies or are seen in pairs of
galaxies which are interacting
•
NGC 1275 is actually a colliding Spiral
galaxy with an Elliptical galaxy
NGC 1275 (75 Mpc) Seyfert
http://cdn.spacetelescope.org/archives/images/screen/opo9202a.jpg
https://apod.nasa.gov/apod/ap131006.html
NGC 1275 (75 Mpc) Seyfert – Visible Light
NGC 1275 (75 Mpc) Seyfert – X-Ray
https://apod.nasa.gov/apod/ap051208.html
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Luminous
Center
Types of Seyfert Galaxies
•
Type 1 have both broad and narrow
emission lines, usually with narrow
weak emission lines superimposed
over the broad lines
•
Type 2 have only narrow emission
lines
Type 1 Seyfert galaxy, NGC 5548 (to the left)
normal spiral galaxy of similar distance and type, NGC 3277 (on the right).
http://www.astr.ua.edu/gifimages/ngc5548.gif
NGC 3393 Type 2 Seyfert Galaxy
http://nrumiano.free.fr/Fgalax/actives.html
•
Type 2 Seyfert due to looking at the
accretion disk more edge on so that only
a small amount of the gas spiraling
inward is seen
•
Type 1 Seyfert due to looking at the
accretion disk more along a pole which
would allow more of the turbulent gasses
to be observed
Radio Galaxies
•
Radio Galaxies are Elliptical Galaxies
•
They are Strong in Radio Radiation
•
Have similar Luminosities as Seyfert
Galaxies
•
First one discovered in1918 by Curtis,
M 87
Seyfert Galaxies
•
About as luminous as a weak Quasar
•
Little to no radio activity
•
Seyfert’s appear to often be the result of
colliding galaxies or are seen in pairs of
galaxies which are interacting
•
NGC 1275 is actually a colliding Spiral
galaxy with an Elliptical galaxy
Types of Seyfert Galaxies
•
Type 1 have both broad and narrow
emission lines, usually with narrow
weak emission lines superimposed
over the broad lines
•
Type 2 have only narrow emission
lines
•
Type 2 Seyfert due to looking at the
accretion disk more edge on so that only
a small amount of the gas spiraling
inward is seen
•
Type 1 Seyfert due to looking at the
accretion disk more along a pole which
would allow more of the turbulent gasses
to be observed
Radio Galaxies
•
Radio Galaxies are Elliptical Galaxies
•
They are Strong in Radio Radiation
•
Have similar Luminosities as Seyfert
Galaxies
•
First one discovered in1918 by Curtis,
M 87
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https://apod.nasa.gov/apod/ap1
10828.html
Types of Radiation from M 87
•
Thermal Radiation (Black Body
Radiation) is very prominent in the
Central region of M 87
•
Non-Thermal Radiation (Synchrotron
Radiation) is more pronounced in the Jet
Radiation of M 87
•
Jet radiation is Polarized, Black Body is
unpolarized but Synchrotron is usually
Polarized
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Radio Galaxies
•
Radio Galaxies usually have two
Radio Lobes that span 5 to 10 times
the size of the parent galaxy usually a
Giant Elliptical Galaxy which sits in
between the lobes
•
These galaxies are often referred to
as double radio sources
Radio Galaxies
•
Often found near center of Rich
Clusters
•
Probably subject to collisions and
mergers as Seyfert’s are
•
Energy output is on par with
Seyfert’s
•
Recently Quasars have been
discovered in between radio lobes
(both lobes and Quasar are highly
redshifted)
•
Speculation exists that Seyfert
Galaxies may be former Radio Quiet
Quasars
•
Radio Galaxies are former Radio
Loud Quasars
•
Blazars are
bright, starlike
objects that
can vary
rapidly in their
luminosity
•
They are
probably radio
galaxies or
quasars seen
end-on, with a
jet of
relativistic
particles
aimed toward
the Earth
http://www.calvin.edu/academic/phys/observatory/images/Astr212
.Fall2002/BLLac/
http://planetfacts.org/blazar/
A blazar is a compact energy source
fueled by
supermassive black holes
.
They are considered one of the most
dangerous phenomena in space.
These extragalactic objects were first
seen and discovered around 1972,
thanks to the technology of A Very Long
Baseline Interferometry. The name was
coined by astronomer Ed Spiegel in
1978. Blazars are usually divided into
two, the BL Lacertae objects (BL Lac)
and the Optically Violent Variable (OVV)
quasars. There are also a few
intermediate blazars, which have the
properties of both the BL Lac and the
OVV.
http://planetfacts.org/blazar/
Blazars emit high-energy plasma
jets so fast that it’s almost at the
speed of light. A blazar is actually
a compact type of quasar, which is
a galaxy far from the Milky Way.
This means that a blazar is a
member of active galaxy out in the
universe. Blazars are
characterized by their high speed
and high energy. They are also
extremely powerful. A blazar is
usually an exciting topic for
scientists when it comes to
extragalactic astronomy.
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Blazars
•
1929 BL Lacertae was discovered and thought
to be a variable star due to the variability of its
brightness
•
However, the light from the central part had no
features, no emission lines, no absorption lines
•
1970’s the central light was blocked and the
remainder of the light (fuzz) around the center
showed normal spectral evidence of an elliptical
galaxy
Blazars
•
The Light from the center appears to be
polarized synchrotron radiation
•
Objects were originally known as BL Lac
objects but now, they are just called Blazars
•
It is now believed that they are double radio
sources (elliptical galaxies) which are oriented
so one of the two jets is towards us
•
Further Evidence of this idea that Jets are
aimed at us comes from apparent Faster Than
Light motion!!
Quasars Vs Blazars
•
Quasars generally exhibit lower
superluminal speeds typically
(1 to 5) x c
•
Blazars typically (5 to 10) x c
•
Blazar jets are assumed to be aimed
more directly towards us than
Quasar jets are
https://www.astroleague.org/files/obsclubs/ActiveGalact
icNuclei/AGN_Program_2015_Grid.jpg
Active Galaxies
•
Seyfert Galaxies – Spirals
•
Radio Galaxies – Ellipticals
•
Quasars
–
Radio Quiet – Spirals
–
Radio Loud – Ellipticals
•
Blazars
•
All have active Galactic Nuclei !!
Limit on Size of Active Objects
•
Variations in the intensity of an object can
place a limit on how big it is
•
Consider an active object 1 ly in diameter
•
It suddenly “Flashes”
•
Near side emitted photons reach us
•
Middle photons reach us 6 months later
•
Far side photons reach us 1 year later
•
Intensity increase lasts a full year
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•
Some Active galaxies flicker in such
a way their volume is ~ 1 light day
across
•
Energy of a Thousand galaxies being
emitted from a volume the size of our
Solar System !!
•
Obvious candidate
Black Hole
Supermassive Black Holes at Galaxy Centers
•
As early as 1968, Lynden-Bell proposed that
Black Holes were responsible for Active
Galaxies
•
Gravitational energy of gases falling into Black
Holes would provide power for the immense
radiation being seen from these galaxies
•
However these Black Holes are much larger
than the 5 to 10 M
(
)
Black Holes in binary
systems
Limits on Luminosity by a Black Hole
•
Amount of Radiation from an Accretion disk is
known as the Eddington Limit
•
If the Luminosity exceeds this limit, there is too
much radiation pressure present to allow
additional gas to fall inward towards the Black
Hole
•
The gases would be pushed outward instead
•
With gas pushed away, the luminosity fades
and the pressure is reduced, so gas begins to
fall inward again
Eddington Limit
•
L
Edd
is the maximum luminosity that can be
radiated by accretion on a compact object
•
M is the mass of the compact object
•
M
(
)
and L
(
)
are the Standard Solar Mass and
Solar Luminosity respectively
Quasar 3C 273
•
L
3C 273
= 3 x 10
13
L
(
)
•
Assume that this is
the Eddington Limit
•
Mass of Black Hole in
3C 273 ~ 1 Billion
Solar Masses
•
Milky Way Galaxy probably has a Black
Hole in its center of about 3 Million Solar
Masses
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•
Rotational Speeds are not constant
in the core of the galaxy as other
models have predicted
•
Nor do they tend toward zero, but
rather there are steep peaks on
either side of the exact center
•
These peaks indicate extremely
large mass contained within ~ 5
arcseconds of galaxy center
•
Measurements on M 31 indicate a Black Hole at its
center of 30 Million M
(
)
in a volume of 5 pc
•
New Techniques using better resolving telescopes
(such as the X-ray Chandra Scope) have indicated a
number of galactic black holes as they can resolve
down to about 0.5 arcseconds
•
Quasars not so useful as they are so far away they
have too small an angular size.
•
However no other source of energy seems plausible
to create Quasar’s energy output
How Does a Black Hole Explain Active
Galaxies??
•
Good Model should explain all facets of Active
Galaxies
–
Large Luminosity
–
Unusual Spectra
–
Variable Light Output
–
Strong Energetic Jets
•
Unified Model Proposes all Active Galaxies are
different views of same type of object Supermassive
Black Hole with an Accretion Disk
•
Gasses in Accretion Disk follow Kepler’s third
law (conservation of Angular Momentum) –
Gasses on inner orbits travel faster than
gasses on outer orbits
•
Faster inner gasses have friction with slower
outer gasses cause outer gasses to lose
kinetic energy and thus fall inward
•
As gasses fall inward they are gravitationally
compressed to high temperatures causing
them to glow (Luminosity)
•
Variations in gas density will
cause variations in gravitational
compression which will cause
variations in temperatures and
hence variations in Luminosity
(Variations in Active Galaxy
Luminosity)
•
Inward motion towards center of Accretion disk
is stopped abruptly near hole due to
conservation of Angular Momentum
•
Inertia wants rotating objects to move outward
as their rotational speed increases (pizza
dough)
•
The point at which the inward force due to
gravity of Black Hole is balanced by this
outward movement due to inertia creates the
inner edge of the Accretion disk
•
This inner edge is also where a
shockwave is created due to this sudden
stopping of inward flow
•
To relieve the pressure created by this
shockwave outward flows develop as
shown perpendicular to the Accretion disk
•
The particles leaving are traveling at high
rates of speed and are thus Relativistic
particles
•
These Relativistic Particles are also
charged, hence they create and drag
Magnetic Fields with them
Forming Jets
•
Recall with our Sun, differential rotation rates
between the equator and the poles and the
fact that magnetic fields are anchored
somewhat to plasma, caused twisting of the
Sun’s magnetic field eventually creating
sunspots
•
In the Accretion Disk Outflows, again recall
the inner part of the accretion disk is moving
more rapidly than the outer parts thus the
magnetic field of the accretion disk is being
distorted into a helix shape
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http://cdn.spacetelescope.org/archives/images/screen/opo9547a.j
pg
Recent Evidence for Unified Theory
•
Hubble Space Telescope views of NGC
4261 Shows two radio lobes extending
15 kpc from the nucleus of the galaxy
•
A magnified view shows a disk ~250 pc
in diameter at center of galactic nucleus
•
Doppler measured speed of gas and dust
indicate a mass of 1.2 x 10
9
M
(
)
must
exist
NGC 4261 (Virgo Cluster) (30 Mpc)
https://en.wikipedia.org/wiki/NGC_4261b
http://astronomyonline.org/Cosmology/Images/Orientation.gif
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http://nrumiano.free.fr/Images_gx/galax_actives_E.jpg
Why No New Quasars?
•
Over time the available gas and dust that could
be accreted to a Black Hole is used up.
•
The acretion disk is used up. Unless new
material comes near the black hole, no more
fuel.
•
The rest of galaxy is not gone. The material is
just not close to the black hole.
•
Galactic Collisions and mergers could provide
new fuel sources
http://thequantumlife.tumblr.com/post/16160919791/gravity-
bends-more-than-just-space-it-bends
Planck Era ends when Gravity
Separates out from Grand Unified
Force
GUT Era ends when Strong Force
Separates from Electroweak Force.
This results in release of enormous
amounts of energy causing Inflation.
In 10
-36
seconds objects the size of
atomic nuclei grow to the size of solar
systems!
Electroweak Era ends when the Weak
Force separates from the
Electromagnetic Force.
From this point on the Universe has
Four Distinct Fundamental Forces.
Theory of Electroweak force
predicted the existence of the W and
Z Bosons (Weak Bosons) these
bosons were discovered in 1983 in
high energy accelerator experiments.
This is really as far back as theories
have fully confirmed the Physics.
During Particle Era all sorts of exotic
sub-atomic particles are being created
in matter-antimatter pairs. Objects
such as quarks exist freely. By end of
era quarks become locked up in larger
particles such as protons, neutrons,
etc.
Particle Era ends when Universe has
cooled to a point where protons and
anti-protons can no longer form from
vacuum energy.
If there were equal numbers of proton
and anti-protons, all of them would
have annihilated and there would be
only photons and no matter.
There was 1 extra proton for each
1 Billion proton-anti-proton pairs!
During Nucleosynthesis era nuclei are
fusing and forming heavier nuclei, but
gamma rays are colliding with them
and breaking them apart.
Nucleosynthesis Era ends when the
density universe is too low for fusion to
continue. Temperature is still higher
than that found in the core of our Sun
but nuclei are too far apart.
Composition of Universe at this point
is 75% Hydrogen 25% Helium and
trace amounts of other things. Pretty
much what we found today outside of
stars.
During the Nuclei Era the Universe is
a plasma of free moving protons
(Hydrogen nuclei), Helium nuclei, and
free electrons. Photons are constantly
colliding with electrons being
temporarily absorbed and re-emitted.
Hydrogen and Helium atoms try to
form capturing electrons but photons
break them apart quickly.
Just as in the core of our Sun photons
cannot move very far before being
absorbed and then re-emitted, they
take a very long time to move
anywhere and as a result the universe
is DARK. The temperature is so high
that there is the dense sea of photons
bouncing around all these free
electrons.
Era of Nuclei ends when the Universe
cools enough through expansion that
nuclei can begin to bind electrons to
them and form neutral atoms. Now
the photons stop being so dense and
the Universe becomes
TRANSPARENT!
This occurs when the Universe is
about 380, 000 years old!
Era of Atoms ends when Gravity
Begins to attract matter and forms
proto-galactic clouds. These clouds
begin to form Stars and Galaxies
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Peak of 3000 K Blackbody Radiation
is 1000 nm = 1 micrometer (10
-6
m)
Since the time of T = 380,000 years
Universe has expanded about 1000 x
in size. Peak should be shifted to
1000 x 10
-6
m or 10
-3
m or 1 mm!
Neutrons are slightly more massive than
Protons. Neutrons need slightly more
energy to form than Protons.
When Universe’s temperature is > 10
11
K,
particles change into each other equally.
When temps fall below 10
11
K, Neutrons
convert to Protons but the reverse stops.
Protons begin to outnumber Neutrons!
How do we KNOW Inflation Happened?
Examine temperature variations in
Microwave Background Radiation.
IF Universe is “Flat” largest variations
should occur separated by about 1 degree
of angular separation in the sky.
In 1755, Kant proposed that nebulae are island universes, sparking a debate on their nature within or outside our galaxy. Shapley and Curtis debated whether spiral nebulae were rotating systems like our Milky Way. Hubble's observations of the Andromeda Nebula led to the realization that it is a galaxy. His discovery of the distance to M31 settled the debate in 1924. The classification of galaxies by Hubble further enhanced our understanding of nebulae and their various forms.
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What are nebulae?? 1755 Kant proposed nebulae are island universes Are Nebulae within or outside of our galaxy?? Nebula comes from a Greek word meaning Cloud
April 1920, National Academy of Sciences , Washington, DC Harlow Shapley (had determined size of Milky Way Galaxy) pushed that nebulae were relatively close by objects. Heber Curtis championed view that spiral nebulae were rotating systems of stars like our own galaxy. Debate was heated but eventually a draw as neither side could provide convincing evidence for either view
The Andromeda Nebula The Great Nebula in Andromeda, also known as M31, can be seen with even a small telescope. Edwin Hubble was the first to demonstrate that M31 is actually a galaxy that lies far beyond the Milky Way. M32 and M110 are two small satellite galaxies that orbit M31.
Edwin Hubble Oct 6, 1923 Historic Photo of M31(Andromeda Galaxy) Discovered a Cepheid variable star (thought it was a nova) Used formulas to determine the galaxy was 750 kpc (2.5 million ly) away and it was 70 kpc in diameter (recall Milky Way is only 50 kpc in diameter) Nebula was not Near by
December 30, 1924 Hubble presents his findings to American Astronomical Society Shapley-Curtis Debate effectively settled The Universe is a big place!!
Tidal forces from Milky Way believed to be source of star formation in the two Magellanic Clouds
Hubble Classification of Galaxies 4 Classes of Galaxies S Spirals SB Barred Spirals E Ellipticals Irr Irregulars
Spirals Arched lanes of stars Spiral Arms containing young hot blue stars and associated H II regions Strong heavy elements present so lots of Population I stars in spiral arms Central bulges low star formation rate dominated by Population II stars
Spirals Sub-divided Sa Large central bulges ~4% of galactic mass in gas and dust Sb Medium sized central bulges ~8% of galactic mass in gas and dust Sc Small central bulges ~25% of galactic mass in gas and dust
Barred Spiral Galaxies Spirals originate at the end of a bar shaped region which passes through the nucleus of the galaxy rather than originating from the nucleus itself. Hubble again applied a, b, and c to rate the size of the central bulge with a being largest and c being smallest As with ordinary spirals this difference of a through c may be due to amount of gas and dust in the galaxy.
Bars appear to form naturally in Spirals from computer simulations Barred Spirals outnumber Spirals by about two to one Milky Way may be Barred Spiral
Bars appear to form naturally in Spirals from computer simulations Barred Spirals outnumber Spirals by about two to one Milky Way may be Barred Spiral A theory why all Spirals don t have bars proposes that if a galaxy is surrounded by a large enough halo of Dark Matter bar will not form. Milky Way may have such a halo?
Ellipticals No Spiral Arms Further sub-divided by numbers E0 is roundest E7 is flattest Category based on observation from Earth, may not be completely accurate Mostly Population II stars, little to no new star formation occurring in these galaxies
Giant Elliptical Galaxies The Virgo cluster is a rich, sprawling collection of more than 2000 galaxies about 17 Mpc (56 million ly) from Earth. Only the center of this huge cluster appears in this photograph. The two largest members of this cluster are the giant elliptical galaxies M84 and M86. These galaxies have angular sizes of 5 to 7 arcmin.
A Dwarf Elliptical Galaxy This diffuse cloud of stars is a nearby E4 dwarf elliptical called Leo I. It actually orbits the Milky Way at a distance of about 180 kpc (600,000 ly). Leo I is about 1 kpc (3000 ly) in diameter but contains so few stars that you can see through the galaxy s center.
A Lenticular Galaxy NGC 2787 is classified as a lenticular galaxy because it has a disk but no discernible spiral arms. Its nucleus displays a faint bar (not apparent in this image), so NGC 2787 is denoted as an SB0 galaxy. It lies about 7.4 Mpc (24 million ly) from Earth in the constellation Ursa Major.
Hubbles Tuning Fork Diagram Edwin Hubble s classification of regular galaxies is shown in his tuning fork diagram. An elliptical galaxy is classified by how flattened it appears. A spiral or barred spiral galaxy is classified by the texture of its spiral arms and the size of its central bulge. A lenticular galaxy is intermediate between ellipticals and spirals. Irregular galaxies do not fit into this simple classification scheme.
Hubble Tuning Fork Diagram Hubble originally proposed that it represented evolution of galaxies Ellipticals would evolve into Spirals Ellipticals have little to no rotation Modern view is diagram represents grouping by rotation Ellipticals are galaxies with little to no rotation Spirals class c have greatest rotations
Types of Irregular Galaxies Type I Many OB associations and H II regions Type II Asymmetrical shapes implying they resulted from collisions with other galaxies or have violent activity occur within their nucleus
Grouping of Galaxies Groups of Galaxies are called Clusters Rich Clusters have many galaxies Poor Clusters have few galaxies and are sometimes called groups Poor Clusters outnumber Rich Clusters Milky Way (our galaxy) is part of the Local Group ~30 galaxies (most are dwarf ellipticals)
Categorizing Clusters Regular Spherical in shape obvious concentration of galaxies at its center Irregular Not Regular! Local Group is irregular
The Hercules Cluster https://apod.nasa.gov/apod/ap140625.html
The Hercules Cluster This irregular cluster of galaxies is about 200 Mpc (650 million ly) from Earth. The Hercules cluster contains many spiral galaxies, often associated in pairs and small groups.
https://apod.nas a.gov/apod/ap14 0625.html
Shape of Clusters Shape of Cluster is determined by which type of galaxies dominate its make-up Regular Clusters have mostly ellipticals and lenticular galaxies Irregular Clusters have a more even mixture of galaxies
The Local Group http://www.atlasoftheuniverse.com/localgr.html
The Local Group This illustration shows the relative positions of the galaxies that comprise the Local Group, a poor, irregular cluster of which our Galaxy is part. (The blue rings represent the plane of the Milky Way s disk; 0 is the direction from Earth toward the Milky Way s center. Solid and dashed lines point to galaxies above and below the plane, respectively.) The largest and most massive galaxy in the Local Group is M31, the Andromeda Galaxy; in second place is the Milky Way, followed by the spiral galaxy M33. Both the Milky Way and M31 are surrounded by a number of small satellite galaxies.
The Canis Major Dwarf Discovered in 2003, this dwarf elliptical galaxy is actually slightly closer to Earth than is the center of the Milky Way Galaxy. This illustration shows the stream of material left behind by the Canis Major Dwarf as it orbits the Milky Way. This material is torn away by the Milky Way s tidal forces.
The Coma Cluster This rich, regular cluster is about 90 Mpc (300 million light-years) from the Earth. Almost all of the spots of light in this image are individual galaxies of the cluster. Two giant elliptical galaxies, NGC 4889 and NGC 4874, dominate the center of the cluster. The bright star at the upper right is within our own Milky Way Galaxy, a million times closer than any of the galaxies shown here.
Nearby Clusters of Galaxies This illustration shows a sphere of space 800 million ly (250 Mpc) in diameter centered on the Earth in the Local Group. Each spherical dot represents a cluster of galaxies. To better see the three-dimensionality of this figure, colored arcs are drawn from each cluster to the green plane, which is an extension of the plane of the Milky Way outward into the universe. Note that clusters of galaxies are unevenly distributed here, as they are elsewhere in the universe.
Structure in the Nearby Universe This composite infrared image from the 2MASS (Two-Micron All-Sky Survey) project shows the light from 1.6 million galaxies. In this image, the entire sky is projected onto an oval; the blue band running vertically across the center of the image is light from the plane of the Milky Way. Note that galaxies form a lacy, filamentary structure. Note also the large, dark voids that contain few galaxies.
Groupings of Clusters Clusters group to form Superclusters Typically dozens of clusters spread over a a region of space 30 Mpc across
1980s mapping of clusters Use redshifts to get a 3-dimensional mapping of galaxy locations. Discovery of spherical voids which are either empty or contain Hydrogen clouds or dim galaxies Voids are about 30 to 120 Mpc in diameter Galaxies are concentrated in Sheets on the surfaces surrounding and between the Voids Think soapsuds in a sink with soapfilms surrounding air bubbles
Great Walls of Galaxies In the 3-D map we find two large structures the Great Wall in the northern part of the map and the Southern Wall in the southern part of the map. Great Wall extends ~150 Mpc along the arc and 5 Mpc perpendicular to the surface Southern Wall extends ~100 Mpc On scales above 100 Mpc, distribution of galaxies appears to be fairly uniform
X-ray Emission from a Cluster of Galaxies (a) An X-ray image of this cluster of galaxies shows emission from hot gas between the galaxies. The gas was heated by collisions between galaxies within the cluster. (b) The galaxies themselves are too dim at X-ray wavelengths to be seen in (a), but are apparent at visible wavelengths. This cluster, one of many cataloged by the UCLA astronomer George O. Abell, is about 300 Mpc (1 billion ly) from Earth in the constellation Serpens.
The M81 Group (a) The starburst galaxy M82 (see Figure 24-26) is part of a cluster of about a dozen galaxies. This wide-angle visible-light photograph shows the three brightest galaxies of the cluster. The area shown is about 1 (b) This false-color radio image of the same region, created from data taken by the Very Large Array, shows streamers of hydrogen gas that connect the three bright galaxies as well as several dim ones. across.
21 cm radiation show connections of Hydrogen gas between galaxies indicating previous interactions As with the M 82, M 81 and NGC 3077, Milky Way and Large Magellanic Cloud have similar Hydrogen gas connections
Colliding Galaxies? Collisions produce hot intracluster gas at temperatures between 107 and 108 k Collisions unlikely to result in Star on Star collisions, too much empty space between Starburst galaxies due to compression of gas within the galaxy causing star birth
The Mice https://apod.nasa.gov/apod/ap150201.html
The Antennae Galaxies http://apod.nasa.gov/apod/ap971022.html
M64: The Sleeping Beauty Galaxy -Gas rotates opposite direction of the stars!! http://antwrp.gsfc.nasa.gov/apod/ap040211.html
Warped Spiral Galaxy ESO 510-13 (150 Million ly) http://antwrp.gsfc.nasa.gov/apod/ap030607.html
Warped Spiral Galaxy ESO510-13 (150 Million ly) http://antwrp.gsfc.nasa.gov/apod/ap990512.html
NGC 1410/1409: Intergalactic Pipeline http://antwrp.gsfc.nasa.gov/apod/ap010112.html
Cluster is 8 Billion ly away http://antwrp.gsfc.nasa.gov/apod/ap990722.html
Sagittarius Dwarf to Collide with Milky Way http://antwrp.gsfc.nasa.gov/apod/ap980216.html
Colliding Galaxies Galactic deformations due to tidal forces Stars may be ejected from galaxy Often the colliding galaxies repeatedly collide until they merge and form one new galaxy Galactic Cannibalism!! Milky Way on track to collide with Andromeda (M 31) in ~ 6 billion years
Third Method to form Spiral Arms? Close encounters between galaxies may provide another way to form spiral arms in addition to Density Wave model or Self-Propagating Star Formation http://phys.org/news/2013-04-insights- spiral-galaxies-arms.html
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