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Module 6 Star and Stellar Evolution

The Sun, Our Star

The mass of our Sun = 1M

Density = 1410 kg/m^3

Luminuousity = 74% H, 25% He, 1% other

Surface Temperature = 5800 K

Strong magnetic field

Rotation Period = 25 days

Sun's Atmosphere:

the Sun's atmosphere has several pieces to it first is the photosphere this is the apparent surface of the Sun. This part of the Sun has the lowest and densest regions ofSun .

This is where you would see features such as Sunspots and granulation

The fine structure of the Sun showing off granulation = convection happening on the surface of the Sun, which is fed by lower layers.

The Sun is brighter towards the centre while the outsides are darker.

Looking at images of the Sun we realize that the Sun is always in motion having the surface ever changing.

Sunspots migrate around on the Sun slowly making their way towards the centre (this happens over a 11 year period) then it begins the cycle all over again.

Sunspots are connected to the magnetic field that surrounds the Sun. The magnetic field is closer to the equator of the Sun.

Also solar flares occur when the magnetic field breaks (snaps) and ejects a plasma.

Chromosphere & Corona

Chromosphere is the transition piece of the Sun, the layer between the lower photosphere and the outer corona.

This piece of the Sun's atmosphere is less dense and less bright while still the piece of the Sun where you will see flares. At this piece of the Sun we see the temperature go from 6000K to >10^6K

Corona lies after the Chromosphere and really stretches out from there.

Properties of Stars

Other stars are the most prominent thing in the sky besides our own Sun.

When trying to find out the distance between us and other stars there are several things that we need to take into consideration.

1) Brightness

2) Luminosity

3) The colour of the Star

Also it is known that all stars are classified based off their colouring

We use this things called the HR Diagram (this stands for Hertzsprung-Russell) it looks at the chemical abundances of certain stars in the sky.

Now a way to measure the distance between us and stars that we see in the sky is called Trigonometric Parallax this measures the distance using the our distance from the sun the angle between us and seeing the planet and the angle between the planet and the Sun

d=1/p (parsec)

FUN FACT: the closest stars to our Sun are about 30 light years away and about 4 pc away

these stars are not very crowded and many of them are binary stars.

Brightness of Stars

this is something that is proportional to the distance of the star squared

b= L/4pied^2

Through brightness we measure the luminosity of the stars (luminosity of stars is the energy output of the star), this is different from brightness which can depend on the distance away from us also what stands between us and the star that we are looking at (things that could be absorbing the light).

Luminosity only depends on the emission of the Star

L= 4pier^2 weird symbol T^4

We can never fully measure wavelengths this is because they are travelling from so far away.

When looking into brightness of stars the first thing that we need to consider is the magnitude

(big number = less bright) This scale was made by Herschel & Pogson (1856)

Equations: m1-m2=5 and from that equation we also get the equation b1/b2=100

we know that brightness is related to magnitude

Note: There are several examples found here in the notes about relating brightness and magnitude look over

More equations dealing with Magnitude and Brightness

Magnitude scale relates to brightness

m1-m2=-2.5log(b1/b2)

Distance modulus formula relates to apparent magnitude

m-M = 5log (d/10)

Relating Absolute Magnitude and Luminosity

M1-M2=-2.5log (L1/L2)

Spectra

This is a way of measuring the brightness of stars - it looks at the temperature of the star and then put it onto a graph. The hotter the star the bluer it goes while a "cooler" star sits more in the red colouring

FUN FACT: there processes that stars go through where they change colour.

We also measure stars colour in different wavelengths.

When looking at the colouring of Stars we look at a scale called the B & V = colour index

the brighter the star the more negative the star is.

B&V stands for Blue and Visible this is when you get the standard colours for all the stars

Fun Fact: "dark eye" in low light your eye sees different colouring

stars aren't perfect blackbodies

Stellar Spectra

As we learned earlier there are three types of spectrums to look at stars through

Originally this sequence was the way it is based off the strength of the Hydrogen in a star but now it has been reworked based off the temperature

A way to remember the ordering is

O

Be

A

Fine

Girl

Kiss

Me

while there are classification of each of those letter the classification has gone past that to now include Roman Numerals in each letter

For example our Sun is a G2V star which means that it falls under the G stars then ranking 2 and finally Roman Numeral five

Brown Dwarf Stars have been given their own lettering because they are so much cooler then the other stars

so dwarfs stars are either L or T

The question that this leads to is: What is the smallest faintest and coolest star?

Spectra vs. Photometry

spectra looks at the more detailed line and structures of the stars, the rotation and the magnetic field. While photometry looks for good estimates and using B&V spectrum

Hertzsprung-Diargram

this is a diagram that looks at brightness in relation with the colour of the star

the x-axis is b-vmagnitude)

while the y-axis is the absolute magnitude

Most stars fall along this main line which is called the main sequence.

Some other points that come out on the scale are the giant, supergiant, and white dwarf regions on the HR diagram

Sirius A & B - in notes there are some facts about this I'm not sure how necessary this is for the overall exam (my thoughts are not much).

Other Properties

The question is what can we learn from stars?

We learn a lot from Binary stars

more then half the stars out there are binary stars

from binary stars we can measure the mass (stellar) and radii

Now there are several type of binary stars out there:

1)Visual binary stars: this is when you can see both of the stars that are "binary"

2)Astrometic Binary Stars: this is where one of the stars is too faint to see while the other star is quite bright

3) Spectroscopic Binary Stars: This is where you can't see one star the only reason that you know it is there is because of the wobble that is found with the Doppler Shift

4) Eclipsing Binary Stars: this is when you have a star that will pass in front of the other blocking it from view.

1) Looking at these stars their period is dependent on the motion of one star around the other, you cannot get the mass for the stars individually

2) timescale= orbital period

amplitude = orbital scale

amplitude ratio = radius?

Stellar Mass Equation:

(m1+m2)P^2=a^3=(a1+a2)^3

(m1/m2)=(a1/a2)=(v1/v2)

you can get quite a lot of information from two stars

Once you get the mass of the stars you'll be able to get everything else about them.

4) there are four stages to eclipsing stars one when it is beside the star, when it is front of the other, when it is on the other side of the star and finally when the star is behind the other star

From eclipsing stars you are able to get all the information about the stars.

Stellar Masses: from stellar mass we are able to get all the information like the star's main sequence and then from there determine the stars location and mass.

Knowing a stars mass you know the amount of fuel that the star has. Therefore we know the larger the star is the more fuel it has.

FUN FACT: more then 90% of the stars out there have less mass then our Sun

to estimate the lifetime of a star we use mass/luminosity= M/M^2.5= 1/M^2.5

FUN FACT: the lifetime of the Sun is 10 billion years

smaller star = longer lives

larger stars= shorter lives

Star Clusters

this is when you have a group of star that are all together

there are several different types of groupings for star clusters:

1) Association: this is a group of around 100 star that are short-lived

2) Open Cluster: this has thousands of stars in the cluster

3) Globular Cluster : 100 thousand stars in the cluster

(brighter star = younger stars)

We also have Variable stars

these are stars where the brightness of the stars vary, this can be caused by many things:

- them being eclipsing stars

- instrinsic variable-stars= they pulse in size and brightness and temperature.

Pulsating

1) Cepheid they change brightness in a rotating period of 3 - 50 days they are easy to recognize

2) R R Lyrae - their period is shorter then a day

3) "Long-period" - these are stars that have long periods

4)Rotating -"spotting" stars

Period-Luminosity laws of Cepheid

this looks at the relationship between the brightness, and period to give you the distance

- using the "standard Candle" knowing the brightness and luminosity we can find the distance

equation: b=L/4pied^2

Novae

these are rare stars in the sky that become really really bright and do so for a short period of time, then fades. This all happens very quickly

- it is good to know that these stars repeat this behaviour but sometime it can happen decades if not centuries later

FUN FACT: in 1987 there was the first supernovae to be detected in 30 years by the naked-eye

Supernovae

these are very rare, as it is estimated that every galaxy has one supernovae every 1-3 hundred years

Supernovae are brighter then any other stars in the sky

there are two types of Supernovae:

1) Type 1 which goes bright but then fades away

2) Types 2 slowly fades away

these stars are so bright that you can see them from far away

Stellar Motion

All stars are in constant motion, and we can measure this using the Doppler Shift, we can also measure the transverse velocity of these stars

Through the motion we can figure out the gravity on the star. Also through binary stars we can figure out things like the orbit and masses.

After figuring out the masses of the stars we can use that information to find out the galaxy mass.

Star Formation

When looking at the process for a star to go from just a cloud of gas to a star there are several steps.

1. This whole process begins when a cloud collapses. When this happens the role of rotation and angular momentum helps to form a disk, that along with Solar winds

While the star is being formed it is hidden in a cloud of dust, and can only be seen through the IR

2) Fragmentation this is when the gravity overcomes the gas pressure to help the formation of the star. At this point the cloud cools down and the density increases. As the clouds shrinks and increases the the star Mbalance decreases

The equation for the mass limit for contraction is

Mbalance = 18M sqrt (T^3/n)

this is the balance point or else the star will collapse

Protostar Formation:

the cloud core collapses into a disk and a "outflow" forms along the disk rotation axis.

The conservation of angular momentum

L=mxvxr rotation speed increases as the cloud collapses

as it all rotates it forms a disk and the when stuff is lost in the rotation then the rotation slows down

Then we move to the Main-stage Life of the Star - this is just as the collapse has begun

2) Fragmentation happens - with higher cloud density means smaller masses

3) Core to protostar - this is when gas becomes the central core of the star

Looking at Protostars

this is the first and earliest form of a star

this is when the central parts of the star are there, the rotation of the star is slowing down,

Tc and Pc increase, at the same time some of the gas for the star is being lost

When the star changes from a Protostar it becomes a Star - this is after the accertion process stops and now you can actually see the star for the first time

- this does not mean that the star is finished changing or the creation process the surface is still cooling, the star still needs to go through the fusion process and change form and have the mechanism change the structure. After all that happens does the star become a Main Sequence Star

When looking at the process that the star is going through you wonder

-what is the timescale of all this?

-well it can take anywhere from a million years to a billion (there are options)

What are the mass limits?

the stellar range is ~0.12- 100 Msun

Note: Single stars are rare things to come by

FUN FACT: First Generation stars have a very different process of being formed

So the order of star formation is

Cloud ~> Smaller Cloud ~> Disk ~> Protostar ~> Star

While a star is on the Main Sequence there are changes that go on on the inside of the star that produce changes on the outside of the star.

An example of this is Hydrogen dropping and be converting into Helium

if there is a lower reaction rate then that less energy is being produced

Structural Changes

- the core of a star goes through the a steady core concentration, while low mass stars go through convection our Sun does not

Low Mass Stars

as stars expand and cool they move around on the HR scale - they move up and to the right on the scale (this is a star getting cooler and smaller) while this is happening to the outside of the star the inside is getting hotter

Radius and Luminosity

- over the lifetime a stars luminosity and radius will change (the change together)

Helium Fusion

this is the process that happens when the star get hot and dense enough so that the carbon starts to change in an explosive way, this is called "helium flash"

this only happens to stars - large stars struggle to get hot enough

What happens after the Helium Burning?

1) they don't get hot enough

2) Sometime the burning occurs then it cools and collapses so there is no fusion

3) it ends with a Black hole

LOOK IN NOTES: there is a drawing of this process to look over

Physics behing Stellas Remnants

- this happens to "stars" which are too small, dense and have had no fusion

-their mass is -sometimes the star pressure needs support

Planetary Nebulae

these are nursery beds for not only stars but also for the stars that can be seen by little telescopes

Mass Limits

this looks at the limit for which a star could be formed at or else it will collapse

High Mass Stars

Answering the question: What happens to stars over 8Msun?

Fusion Reaction

- helium is used in the C- O - Ne_ Mg- reaction

- combination of other nuclei occurs as well, as it continues to get hotter

-this is not a long process for massive stars to burn out - last stages happen very quickly

-if a star makes iron it just continues to get denser and denser and smaller

- massive stars just move to the right becoming cooler and cooler

- eventually the core contracts till it explodes

Neutron Star

-eventually composed of just iron

-the core contracts and envelopes expands, the core gets hotter and denser burning shells and producing energy at a much higher rate

- note this all happens very fast, the star explodes as the core implodes forming a supernova

-protons in the core are all forced to turn into neutrons the star emit a hue

- this all accelerates the exploding of the star outside the core

- the core is a pure ball of neutrons, supported by neutron degeneracy

Black Holes

- maximum mass for 8Msun

- the current theory is that when this star breaks dow it forms a black hole

-a black hole is something so dense that not even light can escape it

-stellar mass black holes are theoretical end to the evolution process of massive stars

- there re mini black holes - these are left over from the formation of the universe

- it is believed that black holes are found at the centres of all galaxies

Death of Stars

Stellar Remnants

1) White Dwarf

2) Neutron Stars

3) Black Holes

Supernovae Brightness

- they release an enormous amount of energy and are brighter than galaxies

-remember there are two types of supernova

type 1 supernova star ends being a neutron star

type 2 explodes

- the core remnants is a neutron star or a black hole

Abundance of the Elements

- when the supernova explodes it expels heavy elements into space, and produces new element (heavier than iron) in ejecta

- this is the only known process that makes these elements

- everything after iron on the periodic table is made from supernovae - exploding star

Pulsars

the first one was discovered in 1960's - what happened was there was a signal that pulsed and changed by 4 minutes a day and it was concluded that this was extraterrestrial

It was originally called Little Green Man (LGM) 1

pulsar are regular and sharp. They seem to be stars that can turn on and off ( they are like lighthouse stars) pulsing on when they are facing us, or so it seems

Magnetars

25% of these stars are found from remnants of supernovae and 50% are found from active stars

these are stars that live for about 10, 000 years

they have the strongest magnetic fields, even stronger then that of a pulsar. It is so strong that it causes the star to quake

Besides binary stars this is a very important discovery that was made

Interstellar Medium

when looking out into space, in certain directions we can see wide swaths of gas and dust - this is Interstellar Medium

- it is generally made up of Hydrogen in several forms

1) Molecular

2) Neutral

3) Ionized

Other components are:

1) Cosmic Rays

2) Magnetic fields

3) Soli phase material or dust

When looking into these clouds through IR we can see through the dust and also see 150 molecules that are rare on Earth

Interstellar Dust - causes extinction of visible light, reddens visible light, polarizes visible light

What are the effect of Interstellar Dust?

- great places for chemical reactions

- dust grains are good for infrared radiation

Observation

- interstellar gas is detected by stellar spectra

Structures

- interstellar medium is divided into clouds ones you can see through and ones you can;t

Molecular Clouds

-densest, coolest parts of the interstelar motion

- molecular clouds are where star are made

- measuring mass: most of the mass of the cloud

Other Structures

- supernovae remnants: over 150 in the galaxy

- HII regoins : massive, hot, short-lived stars

- emit strong UV

- glowing ball of gas

Star-Gas - Cycle

Module 7 The Milky Way

The Milky Way - Measuring the Distance

Using imaging from different wavelengths showing the 360 degrees across the sky while on a 20 degree width shows that our galaxy has a similar look at most wavelengths.

Our galaxy is flat like a disk with a bulge in the centre of it

Through most of the wavelengths we see the stars and dust that make up our galaxy

How do we measure the distance of our galaxy?

We use the trigonometric parallax

there are also some statistical techniques that are pretty good

Kinematic technique - this technique works by measuring the velocity (radial), the only problem is that this technique is limited in precision

The main technique is the "Standard Candle"

this looks at the luminosity then works to put the stars on the HR diagram in the place that they would fit in.

With variable stars like Cepheid, Supernovae, and Lyrae are examples of where this measurement would be helpful.

Though it is also important to remember that variable stars are not that common. And when looking at variable stars you are looking at the period - luminosity relationship of the star

When matching stars up on the main sequence allows you to have a guestimate of the distance, then with knowing the distance you are able to know the apparent magnitude and from that then get the absolute magnitude.

Then looking at Galatic Stars

using the R R Lyrae stars we realize that we are not in fact at the centre of the galaxy. The current estimate is that we are 24, 000 light years from the centre of the galaxy, and note that our galaxy is 30 kpc long

Note: In notes I have a drawing of what the galaxy's shaping is also there is a drawing of the components of what a spiral galaxy looks like.

Motions:

to get the mass of our galaxy we need to take into consideration everything that is going on in the galaxy. This includes everything and their orbits, also the things that pass at random through the galaxy.

The Structure of the Galaxy

Like when measuring our Solar System we used speed to find the orbit and then the length of the solar system, we can use a similar method to find the length of the galaxy. Knowing that the innermost disk rotation curve is linear, then using speed and distance from the centre we can measure the mass of the Milky Way

v^2-G (m1+m2) (2/r - 1/a)

or

vcirc = sqrt (GM/r)

Since the rotation curve of the Milky Way is nearly flat we cannot see the end of our galaxy, so these formulas are all estimates because there is no way to ultimately check for sure

P= 2pier/v and (m1+m2)P^2=a^3 are the two formulas for getting an estimate of large masses

FUN FACT: Milky Way mass is ~ 4x10^11 Msun (which is made majority up by stars)

Dark Matter makes up 90% of the mass

What is Dark Matter?

it is something that we can detect the gravity for and in doing so also estimate it's mass, but the problem is we cannot see it because there is no light coming off it. Some ideas of what this dark matter is are:

- planets

- dark dwarfs

- rocks

-exotic particles (this is the main possibility)

There are no satisfactory explanations of dark matter while there are ideas they all have some sort of flaw to them.

Small Stars/ Giant Planets

there are searches for both of these believing that with the planets they will find them when they pass in front of a star blocking out some of the light.

Also this idea is being used to work out the nature and the distribution is space

Summary of our Galaxy Structure

we live in a spiral galaxy that mean our galaxy includes

- disk shape

- bulge in center

- "spiral arms"

the stars that are found in this type of galaxy are short-lived but very bright

The Halo part of our galaxy holds most of the mass for the galaxy, though we do not know why

Using the rotation curve we try to find the lengths of all the spiral arms of the galaxy.

Using rotation curve and then velocity we work to find the mass of the entire galaxy

(velocity looks at us moving and stuff around us moving)

The "Kinematic Distance Estimate" is used to map the structure of the spiral arms in the Milky Way

Then when looking at the hydrogen gas of the galaxy we get a better understanding of the spiral arms.

FUN FACTS: As things pass through our galaxy they slow down and temporarily orbit our galaxy

the gravity works to make things denser and in doing so come closer together

In the spiral arms is where stars are being formed

The spiral dilemma is the idea that spiral galaxies work to wind themselves up over time

To Find the Centre of the Milky Way you are looking at

how fast something is in orbit and how far they are over the mass of the galaxy

When looking towards the centre of our galaxy we don't see anything so we assume that it is a black hole

Types of Galaxies

We type galaxies based off of appearance into three categories

1) Spiral (Sa - Sc, Ba - SaBc)

2) Ellipiticals (E0 - E7)

3) Lenticulars (S0 - SB)

1) these galaxies vary the most in appearance contain a nucleus, arms, bar. They are either considered a bulge or a disk. On ends of these galaxies there are dust, gas and bulge

When looking out and seeing these galaxies it is important to remember that these galaxies are so far away, Just think about the fact that in our sky Andromeda and the Moon are about the same size

4) Irregular Galaxies have very little symmetry to them and often include gas

NOTE: for practice fill out the chart out the features of all Galaxies out there

Using the Extragalatic Distance Scale

it uses the Cephied Variable Star (period luminosity laws)

there is the Hubble Law which helps to describe the expansion of the universe

Tully-Fisher law looks at using the mass to get the brightness

supernovae type = standard candle

Using the Hubble Law we were able to realize that some galaxies are far away and answer the question: How do we get the distance of this?

Hubble Law (more in depth)

- this is used to measure the radial velocity of galaxies using the Doppler Shift

v= Hod

Ho = the Hubble Constant which is 70.4+/- 1.5 km/s/Mpc

you can invert the equation to d=v/Ho

looking at the radial velocity it is often referred to as the redshift, z and z is looking at the fractional change in the measured wavelength. If there is no wavelength change this is the redshift of the local universe

Note: a redshift change of something like z=1 is a very big change one almost reaching the speed of light.

Tully-Fisher Relationship

this is obvious idea that larger galaxies will have more mass, also the larger the galaxy the more likely it is to be brighter,

Note: mass relates to luminosity along with velocity dspersion.

Supernovae

the mechanism is well understood relating to supernovae.

All types of supernovae are almost identical, this is found from doing intense studies into them

IN NOTES: A good diagram explaining how over the course we have started with small measurement and work to the larger ones.

Peculiar Galaxies

-Wanting to understand why some galaxies are so different

Tidal Tail

this is believed to be caused when two galaxies come into contact

Starburst Galaxies

this is the merging of two galaxies together, while stars do not collide the gasses do

Active Galaxies

these are galaxies that have extremely high luminosity (it is the most apparent at the radio wavelength)

the most extreme of this type are called quasars. the most bright pieces seem to be found at the centre

Galaxy Clusters

like stars galaxy can cluster together in what is called either clusters, or superclusters. When looking out into space you will see that some direction are heavily concentrated with galaxies.

FUN FACT: there are most galaxies then stars in the Milky Way

Galaxy Masses and Dark Matter

How do we measure the Mass of a Galaxy?

the main thing that we use is the rotation curve

-this works for spiral galaxies

- it is best measured from (Hi or Hii)

Velocity dispersion - remember that velocity relies on the mass of an object.

We use this information to loo at objects in our galaxy and objects outside our galaxy

Most galaxies have a flat rotation curve so the mass equation is:

G(mMr/r^2)=m(v^2r/r) Mr+V^2r/G * this assumes that the orbit is circular

Velocity Dispersion

you are looking at the brightness and wavelength

mass to light ratio:

M/L = 6M/L for the Milky Way

elliptical galaxies = M/L = 10M/L only old stars

spiral galaxies M/L = 50M/L

tells us about dark matter

Elliptical Galaxies have the most varying masses, they are the largest and smallest masses

FUN FACT: some galaxies orbit each other (like binary stars)

Measuring the mass within a cluster

1) Measure speed and position of cluster

1. Galaxy Orbits - we assume that galaxies orbit around the cluster center, with this in mind we can measure the orbit velocity and measure the distance from the centre. Then from there we apply Kepler's Law to calculate the mass of the cluster

this was the beginning of the use of M/L ratio

this is also when dark matter was proposed

2. Hot Gasses between Galaxies

the hot gasses that are found between galaxies is examined in the in the x-ray

looking at the temperature of these clusters we are able to then find the average speed of the gas particles

3. Gravitational Lensing by Gravity Cluster

the angle in which light bends depends on the mass of the cluster, we are able to calculate clusters mass.

this uses a different description/model of gravity

Gravity Masses and Dark Matter

M/L for most galaxy cluster is greater than 100M/L

- most galaxies have large masses that are made up of mainly Dark Matter - and so this made them invent a theory for Dark Matter

What is Dark Matter?

- it is made up of protons, neutrons, electrons and baryonic matter = this is the stuff that we are made of

- in Dark Matter you have all these things working together.

Note: Dark Matter is something that has yet to be completely solved or understood

The Expanding Universe

The Hubble Relation

- this uses the Hubble law v= Hod, and looks at a large change in wavelengths and corresponds with it's motion in the sky.

The further the redshift the further away the longer the light transfer is

Are we at the centre of the universe?

- the short answer is no, from where ever you are looking it seems that things are all moving away from you (that is where the assumption comes from of being the centre of the universe)

- but we know that the universe is ever expanding but it has been slowed down by gravity, and it all started with the "Big Bang", which was very hot but now everything is cooling down.

The Expansion rate of the Universe is

1/Ho time = d/v but v=1/Ho=d/v

With the Hubble Law it implies that everything was in one central place 13.6 billion years ago

an empty universe = 1/H=13.8

Now looking at the Universe there are several ideas of what type of universe we have. This could be either a bound (will come to an end), or unbound (keeps expanding) universe. In both cases we know that mass does not increase on a straight line. Types of Universe

1) Bound

2) Unbound

3) Empty

To figure out which type of universe we have we look at the critical density

mass densitymass density>critical density = B

if we have kinetic energy of the Universe and the Ho then we are able to find the critical density

Expanding Universe cont.

Using just Hubble's Law is not enough to measure the full expansion of the universe, we also use supernovae o measure our radial velocity for the universe. It is also important to note the impact of gravity on the expansion of the universe

There are 4 types of universe

IN NOTES: There are drawings along with each type of universe

The Big Bang

this is a theory that started with Penzias and Wilson who discovered a noise coming in from everywhere in the sky - coming from the "Big Bang"

the Big Band has Cosmic Microwave Background - some of these prediction were verified, an example is the prediction of the universes temperature (note: the universe is a really good black body)

The universe has cooled down over the time of expansion from 3000K to 3K

this was something that was predicted in 1930's and then later discovered in the 1968. This was all explored by the Cosmic Background Explorer observed the CMB looking at the information that was collected by this exploration device it is easy to see that the universe was not nor is it flat.

The Wilkinson Microwave Anisotropy Probe we are given a better idea of the temperature of the universe.

Note: when looking into the universe there is a lot of uncertainty because there is only one universe to look at.

What is the Universe made of

4.6% baryonic material (all the stuff we know)

23.3% dark matter

72.1% Dark Energy

Evolution of the Universe

We can only look back to the universe when it was 380, 000 years to present

Phases of Evolution:

1) Plank Era this was from beginning to 10^-43 sec

- we are powerless to describe this step

2) GUT Era 10^-43 -10^-38 sec

- this is when there were two forces the GUT and gravity

3) Electroweak Era 10^-38 - 10^-10

- by this stage there were no longer equal amounts of each matter

4) Particle Era

- numerous protons, neutrons and their are anti-particles

5) Nucleosynthesis Era 10^-3 - 3 mins

- hydrogen, helium are all produced by this point, also the temperature has cooled

- the big bang predicts that there are 7 to 1 ratio of protons to neutrons

6) Nuclei Era 3 min - 3.8x10^5 yrs

- universe is opaque

- universe has cooled to 300 K is transparant to radiation now dominated by matter

7) Atoms Era 3.8x10^5 - 10^9 years

- the Cosmic Dark Ages

- no structure and no dense places

- the first stars were formed lighting up the universe

- this provokes the formation of galaxies

8) Era of Galaxies 10^9 - present

- this is the era that we are living in nw

- first galaxies came together 1 billion years ago

Problems with the Big Bang theory1. Where does the structure come from?

2. Why is the large-scale universe so smooth?

3. Why is the density of matter almost exactly the same as the critical density?

- they are continually looking for way to explain these questions

a good answer at this point in time is inflation

Formation of Structure in the Universe

Get this from notes - I'm not fully sure how to re-explain this

Module 8 Extraterrestrial Life

Astrobiology

this is a new scientific discipline which works to study the chemistry of life and search to find it in space

They want to answer the questions:

Are we alone?

- this is something that people have been wondering for many years, it was assumed in 17&18th century that there was life out there. And now we are back at that point where we are wondering the same things again.

MOdule 6

Module 7

MOdule 8