Download Big Bang and Life Cycle of Stars

The Big Bang Theory
How did it all begin?
Astronomers theorize that the universe
came to be in a single moment .
• According to this theory, all the matter and energy of
the universe were at one time concentrated in an
incredibly hot dense region, a form of matter called
plasma.
• At a super heated state, it was too hot for atoms to form,
or other properties such as gravity or electromagnetic
forces to occur
• And then, Billions of years ago all at once, rapid
expansion, and an enormous explosion!!!!!
• Big Bang Theory
Then what?
The universe expanded very quickly
- After a few thousand years, some cooling occurred,
which allowed for the formation of atoms –
- first Hydrogen and Helium, but it had to cool still more
for the other elements to start to form and be neutral
atoms
-Anti-matter also formed, composed of antineutrinos,
positrons, anti protons. (hhmmm?)
- As cooling increased, Gravity pulled atoms together into
gas clouds that then evolved into stars and young galaxies
Age of the universe
Since astronomers know how fast the universe is
expanding, they can infer how long it has been doing
so.
- this is based on evidence of the Red Shift
Now estimated at 13.8 BYA
How could we determine what is happening?
What evidence could be gathered?
Spectroscope Lab
Evidence of the Big Bang
- Cosmic microwave background radiation still
traveling through the universe and can be traced,
which gives evidence that the universe is still
expanding
- the Red shift spectra of distant galaxies is one way
that the expansion can be measured.
- The farther stars or galaxies are from us, and the
faster they are moving away, their visible
spectrum shows up as a shift on a spectrograph
toward the red spectrum.
Light Spectrum background
So what do we think for the future?
• Here are some ideas:
• Open Universe – The universe will continue to
expand
forever.
• Big Crunch – The universe will slow in it’s expansion
and gravity will pull all matter back into a single
point.
• Flat Universe – The universe will slow its expansion
and eventually stop.
Star Questions:
What is the closest star to us?
What makes stars “burn”?
What is the biggest star we know of?
Are all the stars in a constellation actually close to
each other?
How did constellations get their names?
Star Classifications
Stars are classified based on their properties:
-
Color and Temperature – color is a clue to a star’s
temperature, the light emitted indicates how hot a star
is burning.
-
Apparent Brightness - is how bright it really is,
regardless of distance (brightness can be a factor
related to how far away it is)
-
Size and Mass – knowing temp and brightness
astronomers can calculate diameter and volume of a
star.
-
Composition – each star has its own spectrum based
on what it is made of and what percent
Hertzsprung-Russell Diagram
http://aspire.cosmic-ray.org/labs/star_life/hr_diagram.htmlm
Time to graph some stars
Hertzprung-Russell diagram
HR diagrams are also used to estimate the size of
stars and their distances, as well as to infer how
stars change over time.
This chart indicates “main sequence” stars, which
are classified based on their location on the chart.
Keep this in mind as we talk about life cycles of
stars.
Star groupings on the HR diagram –
label them on your graph
Main Sequence Stars – have what characteristics?
Supergiants, - the very bright stars at the top
right are what is their temperature range?
Giants and Red Dwarfs –
- just below them are the Giants
White dwarfs - and to the bottom the dwarfs –
what is the temperature and magnitude range for
these stars?
Do Stars age over time?
The life cycle of a star – Life Cycle in action
1. begins with a nebula – a grouping of gas and dust spread out
over space.
2. Stars form in the densest parts of the nebula, when a
contracting cloud of gas and dust become so dense and hot
that nuclear fusion begins 
- this nuclear fusion is what “fuels” the star
write the definition in your journals
3. Adult stars – spend 90 percent of their life on the main
sequence.
- A star’s mass determines the star’s place and how long
it will stay on the main sequence. ( this is determined by how big
the nebular cloud is at its birth)
Life cycle tidbits:
- The pressure from fusion stabilizes the inward pull of
gravity as a young star develops. Draw this idea in your
journal
- High mass stars burn very bright – but the cost is rapid
use of fuel, and the may last only a few million years.
- A Yellow star in the middle of the main sequence will
burn stably for about 10 billion years. (like our sun)
-
Fusion happening at the core of the star is combines
Hydrogen to make helium. Define Fusion in your
journal
-
How is this different than fission?
Adult Stars
Given: A Stars mass determines its place on the main
sequence and how long it will stay there.
A large mass star, has more gravity exerted on the
core which leads to burning at a higher temperature.
These tend to be the brightest and hottest stars =
Blue stars in the upper left corner of HR diagram.
Small nebulas, produce small cool stars that are long
lived. Less gravitational force, but strong enough for
the core to produce fusion. These are the red, dim
stars in the lower right corner of RH diagram.
Death of a Star – low or medium mass
stars
As these stars reach their last stage, running out of fuel –
there is a collapse internally toward the core ( caused
by ____________).
- Leaving the dying star surrounded by gas clouds
- Due to continual pressure on the core, these stars will
become white dwarfs – which can be about the same
size as the earth, but with the mass of a star.
- Where do they move to on the HR diagram at this point?
- Videos on supernova, perspective, Betelgeuse
Death of a star – Red Giants
As a star burns up its fuel supply of hydrogen, gravity increases
and the core starts to shrink.
- Core temperature heats up and fusion begins, the outer
region of the star expands.
- This star then cools to red, and is so named as a red giant
- When the collapsing core gets hot enough to process helium
fusion, this process leads to production of carbon, oxygen,
etc and the star stabilizes.
- As a red giants fuel continues to rapidly decrease, its end
will result in: a white dwarf, a neutrino, or a black hole……
Death of a High mass star
As a star runs out of fuel and goes into a super giant state – it
starts to fuse elements as big as iron. (atomic # ?)
A high mass star dies quickly, due to rapid fuel consumption.
As gravity increases at the core the collapse produces a
SuperNova – a violent explosion. The elements produced by
this process are ejected out into space.
The heavier elements in our solar system came from a super
nova explosion of another star – including the elements and
atoms that make up your body  (aww stardust)
Star Clusters
There are three basic types of star clusters:
- open cluster like Pleiades, disorganized and
loose appearance, often containing bright super giants
and gas and dust clouds
- association cluster – temporary groupings of
bright young stars
- globular cluster – large group of older stars.
Lack sufficient amounts of gas and dust to form new stars
, can contain more than a million stars
Galaxies
A galaxy is a huge group of individual stars, star
systems, star clusters, dust and gas bound by
gravity.
Galaxies vary in size and shape – draw and define
each of these in your journal.
-Spiral and barred spiral galaxies: have a bulge of
stars in the center with arms extending outward like
a pinwheel. – gas, dust and many young stars
-Elliptical galaxies – are spherical or oval, and
no trace of arms, wide range of sizes, have little
gas or dust, contain old stars
-Irregular galaxies – have a disorganized
appearance, young stars, and large amounts of
gas and dust. Come in many shapes, but
typically smaller than the other galaxies.
Which galaxies can you identify?
And the other unique ones
Ring Galaxy – happens when another smaller galaxy
travels through one already established:
Lenticular galaxy's – an intermediate form between
Elliptical and spiral, with undefined arms
What is a light year?
The measurement of light year – is the speed it takes light
to travel one year.
1 light-year = 9460730472580800 meters (exactly)
• ≈ 5878625 million miles
• ≈ 63241.1 astronomical units
• ≈ 0.306601 parsecs
Lets try a bit of perspective:
http://apod.nasa.gov/apod/ap120312.html
Dark Matter
Dark matter – is matter that does not give off radiation,
but still has gravitational properties.
Dark Matter – cannot be seen directly, but its presence
can be detected by observing its gravitational effects on
visible matter.
With out it in our universe, it would be hard to tell how
fast everything would keep expanding.
What is?
A Supernova A Neutrino –
A Pulsar –
A black hole –
- the result of a star collapsing from gravity so strong that it
passes the neutrino stage, and faster than the speed of
light. Surface gravity is so great that nothing can escape it,
even light,
What is the one thing that each is determined by?
Mass –which leads to gravity that acts on it as it collapses.
Our Sun
Our sun and solar system formed about 4.6 MYA,
and the universe was about 2/3 its present size