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DEEP SPACE
What’s Out There?….
Black Holes
• Regular black holes are thought to form from
heavy stars. When these stars end their lives in
a supernova explosion, their cores collapse and
gravity wins out over any other force that might
be able to hold the star up.
• Eventually, the star collapses so much that it is
contained within its Schwarzschild radius, or
event horizon, the boundary within which light
cannot escape
• Super massive Black hole: power galaxies and
are found at thier centers
Anatomy of a Black Hole
Black Holes
• In normal stars, there is a balance between the inwards
force of gravity and the outwards pressure of the gas.
• If there is too much mass in too little space, nothing can
resist the force of gravity, and the star collapses into a
single point.
• A black hole is an object in which all matter has been
crushed into a single point: a singularity
• The gravitational pull in a black hole is so strong, that
nothing, not even light, can escape
• Einstein's Theory of Relativity: Light is attracted by
gravity.
Black Holes
• This was confirmed in 1919 during a solar
eclipse
• One consequence of this bending of light by
gravity is the existence of gravitational lens
• A massive object (such as a galaxy or cluster of
galaxies) can bend the light of objects behind
them, creating double or multiple images of the
background object, or arcs and rings
Don’t Get too close!
• The minimum distance you can get from a black hole
and still escape its gravitational field (if you are traveling
the speed of light) is called the Schwarzschild radius.
• The surface of an imaginary sphere with radius equal to
the Schwarzschild radius and centered on the black hole
is called the event horizon.
• The Schwarzschild radius of any object depends on its
mass
• For the Earth, it is about 1 centimeter.
• For Jupiter, it is 3 meters.
• For the Sun, it is 3 kilometers
Black holes continued…
• If they are black how do we know they are
there?
• Black holes can be found by:
• 1. Their gravitational effects on other
objects.
• 2. X-ray radiation from material falling into
the black hole.
Pulsars/Neutron stars
• When a massive star isn’t massive enough
to form a black hole it forms a Neutron
star.
• Neutron stars consist of neutrons which is
where they get their name. The are as
densely packed as an atomic nucleus!
• Some neutron stars emit radio waves
through their axis. When this happens we
call them pulsars.
WORM HOLES
• While we can prove a wormhole
mathematically, they probably do
not exist in nature.
• If they did they would be
unstable
• If they were stable they still
would be very unpleasant to
travel through. As you try to pass
through the wormhole, you will
get fried by X-rays and gamma
rays.
White holes
• AA theoretical time
reversal of a black
hole. Matter is
ejected from the white
hole as opposed to
being pulled in. (time
is just reversed)
• Interestingly matter is
still attracted to a
white hole!
Quasars
• Quasars are probably the
most energetic and most
distant objects we see in
space.
• They are an astronomical
source of electromagnetic
energy, including light,
that dwarfs the energy
output of the brightest
stars. A Quasar may
release energy in levels
equal to the output of
dozens of average
galaxies combined
Nebula (FUZZY LIGHT)
Reflection Nebula
• A blue nebulae is called
a reflection
nebulae. They scatter
the blue light from
nearby stars while the
rest of the colors are
allowed to pass through
the cloud
undisturbed. Eventually
the blue light escapes
the cloud and travels to
our eyes.
Emission Nebulas
• A red or pink nebulae
is called an Emission
Nebulae and glows
because it is getting
rid of the extra energy
given to it by nearby
stars.
• The cloud itself is
actually glowing.
• This is a star forming
region
Planetary Nebula
• A planetary nebulae is
formed when a dying sun
sized star begins to shed
its outer layers.
• This ring is only visible for
about 50,000
years. Over time the
nebulae mixes into
surrounding space
eventually becoming too
thin to see.
• Nothing to do with planets
Globular Clusters
A symmetric
collection of 10 of
thousands to
millions of old
stars that share a
common origin.
They are found in
the Halo of our
galaxy and span
100-300 l-y across
Open Cluster
• A loose grouping of
dozens or hundreds
of young stars. They
are found in the
galactic plane, and
spiral arms. They are
formed from the same
interstellar region and
are less than 50 l-y
across.
What the BOK Globule?
GALAXIES
Galaxies Defined
• A large system of stars, together with
interstellar material and *dark matter, held
together by gravity
*Dark Matter: matter that cannot be detected
directly because it doesn’t interact with
light.
Galaxies
• Spirals
• These types can be broken into several classes
depending on their shape and the relative size of the
bulge. Two main types are regular and barred as shown.
• Spiral galaxies are characterized by the presence of gas
in the disk which means a younger population of stars.
Spirals are usually found in areas where their delicate
shape can avoid disruption by tidal forces from
neighboring galaxies. The milky way is a spiral galaxy.
Galaxies
• Ellipticals
• They are characterized
by a uniform luminosity
and are similar to the
bulge in a spiral galaxy,
but with no disk. The
stars are old and there is
no gas present. Ellipticals
are usually found at the
center of clusters.
Galaxies
• Lenticulars
• they possess both a bulge and a disk, they
have no spiral arms. There is little or no
gas and so all the stars are old.
Galaxies
• Irregulars
• They are small galaxies with no bulge and
an ill-defined shape. The Magellenic
clouds are examples.
•
Galaxy classification
E0 Vs E 7
SO- Lenticular
Sa -Sd
Sb
Sa
Sd
Sc
SBa-SBc
An SBb galaxy - NGC
An SBa galaxy - NGC 1300. Better defined
arms which are more
1291. Note the right
centre and tight spirals loosely wound
An SBc galaxy NGC 7741. Even
looser arms, and
a much dimmer
central portion of
the galaxy
PRACTICE GALAXIES