How ________________ Work?

• How do _____________________Shine?– Stars shine because they burn ___________….so

stars are made up of_______________

•Our Sun is a Star, it is the closest _________to Earth, remember the distance from the Earth to the sun is about_______________________________, or 1 AU.•Stars work because they go through a process called_____________________________________.

Stars….What are they Made Of?

• Most stars have an assortment of elements but every star has___________________________________________.

• Why? • Well because __________________________is the answer.

– ___________________ atoms fuse to form 1 Helium atom– _________________________atom has slightly less mass then

the 4 Hydrogen atoms.– The fusion of 4 Hydrogen atoms into one Helium atom release

energy according to Einstein’s famous formula _________________energy equals mass times the velocity of light squared

– This is how a Star shines and why it is made up of Hydrogen and Helium.

– Our Sun is doing this in extreme amounts– And it has a supply to last more than _________________years.

But where does the mass come from?

• Mass of 4 hydrogen nuclei is______________ than that of 1 helium nucleus

• So after fusion a little bit of ____________is left over. This mass deficit appears as the energy of light and neutrinos.

Why do stars __________in the sky?

• Stars twinkle when we see them from the Earth's surface because we are viewing them through thick layers of turbulent (moving) air in the________________________________________________.

• Stars (except for the_______________) appear as tiny dots in the sky; as their light travels through the many layers of the Earth's atmosphere, the light of the star is bent (____________________) many times and in random directions (light is ____________when it hits a change in density - like a pocket of cold air or hot air). This random refraction results in the star winking out (it looks as though the star moves a bit, and our eye interprets this as twinkling).

• Stars closer to the horizon appear to twinkle ______________than stars that are overhead - this is because the light of stars near the horizon has to travel through more air than stars overhead and subject to more refraction. Also, _________________________do not usually twinkle - they are big enough that this effect is not noticeable (except when the air is extremely turbulent).

• Stars would not appear to twinkle if we viewed them from outer space (or from a planet/moon that didn't have an ______________________________).

So Now We Know What They Are Made Of…. How Do They Form?

• All stars start their lives as clouds of gas and dust ( interstellar matter)______________________________.

What Next?

• Stars begin with a slow ___________________________________and dust.

• ___________________pulls the matter together to make the nebula denser and denser, shaping it into a sphere. This is called a____________________.

• A Protostar’s energy comes from the___________________________________. This contraction causes the temperature and pressure to slowly increase.

• The star starts to heat up. A planetary disk can start to form around the protostar.

And……• As gravity continues to collapse the protostar,

temperatures continue to rise creating greater energy for collisions between particles. Once temperatures get _______________________to overcome the repulsion of Hydrogen Nuclei, ____________________begins and a star is born.

• Planets can continue to form around stars.• This is when the star is “ Turned On” The

temperature in which a star is “turned on” is about _______________million degrees C in the star….this ignites fusion.

So What’s Next?

• After the Protostar stage, the star evolves to a ______________________….this is what the Sun is right now!!!

• Hydrogen is continually being converted to Helium. And the energy being released from the gas is enough to prevent gravitational collapse.

• How long a star will do this is dependant upon the temperature of the star…..how much _________________________they consume.

OKAY, What Happens When A Star Consumes All Of Its

Hydrogen? • Then a star will evolve into the

______________________Phase of its life. • Here, the Hydrogen is used up, leaving a Helium

core. _________________________IS GOING ON HERE!!!!!!!!!!!!

• Thus, no source of energy leads to the core not having enough pressure to support itself.

• The core starts to________________________.

________________________

• The collapse of the core actually ____________________the temperature of the star as gravitational energy is converted to heat.

• Some of the energy is radiated outwards causing the outer part of the star to_________________.

• As the star starts to expand, the outer portion of the star will cool, which explains the color of the star…..________________________.

Now, This is Where it Gets Complicated!!

• What happens next to a star actually depends on the mass of the star.

• So here goes……the death of stars….

_______________________Stars• Stars .5 solar mass ( less than

_____________________the mass of the sun) • They consume _________________at a slow

rate.• Thus they are usually_________________ stars. • And actually it does not become much of a red

giant.• Thus, once the Hydrogen is gone the star

becomes a white dwarf. Very tiny objects.

Death of _______________Stars…..The Death

of Our Sun……• Well, they will actually form into a white

dwarf as well….but not so simple like a low mass star.

• See Medium mass stars will become red giants, thus during their collapse from the red giant phase, the gas from the star is going to have to be expelled.

• This process of expelling gas from the star is called at___________________________.

___________________________

• These are spherical clouds that glow.• After our sun produces a planetary nebula, it

will become a_________________________.• A typical white dwarf is about as massive as

the Sun, yet only slightly bigger than the Earth. This makes white dwarfs one of the densest forms of matter, surpassed only by neutron stars and black holes.

White Dwarf to Black Dwarf

• Stars that are comparable in mass to our Sun will become white dwarfs within 75,000 years of blowing off their envelopes. Eventually they, like our Sun, will cool down, radiating heat into space and fading into black lumps of carbon. It may take 10 billion years, but our Sun will someday reach the end of the line and quietly become a black dwarf.

___________________________

• These are up ______________________the mass of our sun.

• These DO NOT fizzle out so gently, these are explosive!!!!

• Remember that these stars have very short life spans.

• These guys, after they go through a Super Red Giant Stage, the as the Super Red Giant starts to collapse they produce a SUPERNOVA.

_________________________

• During a supernova, the star will become_________________________________.

• This occurs when a massive star has consumed all of its nuclear fuel, the heat is no longer there to balance the gravitational field and it collapses.

• Creating a _______________________explosion, that can send out a shock wave. This shock wave blasts out the star’s outer shell..that is the supernova.

After the Supernova

• Well a star’s final journey may be a Neutron Star or a_________________________________.

• A neutron star is about 20 km in diameter and has the mass of about 1.4 times that of our Sun. This means that a neutron star is so dense that on Earth, one teaspoonful would weigh a billion tons! Because of its small size and high density, a neutron star possesses a surface gravitational field about 2 x 1011 times that of Earth. Neutron stars can also have magnetic fields a million times stronger than the strongest magnetic fields produced on Earth.

The Other Option…..____________!!

• A black hole is an object whose ______________________is so strong that not even light can escape from it.

• Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun. If a star that massive or larger undergoes a supernova explosion, it may leave behind a fairly massive burned out stellar remnant. With no outward forces to oppose gravitational forces, the remnant will collapse in on itself. The star eventually collapses to the point of zero volume and infinite density, creating what is known as a " singularity". Around the singularity is a region where the force of gravity is so strong that not even light can escape. Thus, no information can reach us from this region. It is therefore called a black hole, and its surface is called the " event horizon ".

Okay….Lets talk about Black Holes...

• We know how they are formed…but..here is some history about black holes.

• A dying star whose mass exceed several times that of the sun will produce an inward pull of gravity so strong that not even neutron degeneracy can stop its collapse. Such a star is destined to become a black hole.

• Black holes are described by_____________________________, which is an alternate and more accurate theory of gravity than Newton’s theory. Einstein described the effects of gravity in terms of the bending of space and time rather than as a force. Hence, photons (particles of light) will be affected by gravity. Newtonian gravity maintains that photons are not affected since they do not possess mass. Experiments have shown Einstein to be correct.

RELATIVITY AND COSMOLOGY

• The distances and velocities involved in the study of cosmology are so great that the laws and relationships involved in classical (Newtonian) physics must be replaced with the relationships described by Einstein’s Theory of Relativity, often broken down into the Special and General theories of relativity.

• An important feature of the theory of relativity is that no material object or information can travel faster than the speed of light, which is about 300,000 km/sec (or 186,000 miles/sec).

• Special relativity deals with unaccelerated motions (moving in a straight line at constant velocity) whereas general relativity deals with accelerated motions.

• The more comprehensive General Theory of Relativity also includes a theory of gravitation.

• Relativity requires four dimensions (three space dimensions, and time) to display (called “spacetime”), and so is somewhat difficult to conceptualize pictorially.

According to Einstein's General Relativity, all masses curve space.

How does this change our understanding of the gravitational force?

Okay, Let’s Explain Again…….• Newton thought that only objects with mass could

produce a gravitational force on each other. Applying Newton's theory of gravity, one would conclude that since light has no mass, the force of gravity couldn't affect it. Einstein discovered that the situation is a bit more complicated than that. First he discovered that gravity is produced by a curved space-time. Then Einstein theorized that the mass and radius of an object (its compactness) actually curves space-time. Mass is linked to space in a way that physicists today still do not completely understand.

• However, we know that the stronger the gravitational field of an object, the more the space around the object is curved. In other words, straight lines are no longer straight if exposed to a strong gravitational field; instead, they are curved. Since light ordinarily travels on a straight-line path, light follows a curved path if it passes through a strong gravitational field. This is what is meant by "curved space," and this is why light becomes trapped in a black hole. In the 1920's Sir Arthur Eddington proved Einstein's theory when he observed starlight curve when it traveled close to the Sun. This was the first successful prediction of Einstein's General Theory of Relativity.

• One way to picture this effect of gravity is to imagine a piece of rubber sheeting stretched out. Imagine that you put a heavy ball in the center of the sheet. The weight of the ball will bend the surface of the sheet close to it. This is a two-dimensional picture of what gravity does to space in three dimensions. Now take a little marble and send it rolling from one side of the rubber sheet to the other. Instead of the marble taking a straight path to the other side of the sheet, it will follow the contour of the sheet that is curved by the weight of the ball in the center. This is similar to how the gravitation field created by an object (the ball) affects light (the marble).

Black holes are really very simple as they have just two main parts

• The ____________________and the Singularity.• The ________________________is the outer limit

of the black hole. It is the closest thing a black hole has to a surface, but it’s not a physical surface – it’s an invisible bubble in space. The event horizon is the point of no return. Nothing can escape a black hole once it crosses the event horizon and we can never see what happens inside it. However, using math we can get an idea of what it might be like.

___________________________• The _________________________ lies right at the

heart of the black hole. It is in this tiny spot that the entire mass of the black hole is contained. Anything that falls into the black hole is eventually crushed onto the singularity. How a black hole can pack such huge amounts of matter into such a tiny space is a mystery. To fully understand the singularity, scientists will need to combine two famous theories of the Universe: the General Theory of Relativity (that explains the very large) and Quantum Theory (that explains the very small).

A black hole has only a “center” and a “surface”

• The black hole is surrounded by an event horizon which is the sphere from which light cannot escape

• The distance between the black hole and its event horizon is the Schwarzschild radius (RSch= 2GM/c2)

• The center of the black hole is a point of infinite density and zero volume, called a singularity

What will Happen if I fall into a Black Hole? • If you fell towards a black hole, time would seem to flow as normal but

everything around you would speed up. If your journey was long enough, you might see the whole future of the Universe racing by. What’s more, the black hole’s gravity would curve space so strongly that you could see objects that in reality lie behind you.

• Imagine you were falling feet first; your feet would feel more gravity than your head. You would be stretched out in a process called spagettification. For the best chance of surviving a fall into a black hole, you’d be wise to choose a supermassive one; the more mass, the gentler the change in gravity. You’d survive for longer because spagettification occurs more slowly. Unfortunately, no matter what kind of black hole you fall into you will most likely be crushed once you reach the singularity.

Review Again• ___________________(.5 solar mass) --> White

Dwarf• ____________________(Mass under 1.5 times

the mass of the Sun) --> Red Giant --> Planetary Nebula -->White Dwarf --> Black Dwarf

• ________________(Mass between 1.5 to 3 times the mass of the Sun) --> Red SuperGiant --> Supernova --> Neutron Star

• ________________(Mass over 3 times the mass of the Sun) --> Red SuperGiant --> Supernova --> Black Hole

Sun Stats.

• The Sun contains ____________________of all of the mass of the Solar System.

• This is about 333,000 times the mass of the Earth.

• The Sun's diameter is 864,938 miles (1,391,980 km). This is almost ________________times larger than the planet Jupiter and about 109 times as big as the Earth.

___________________________

• ______________________________: The Sun's core has a tremendously high temperature and pressure. The temperature is roughly 15 million °C. At this temperature, nuclear fusion occurs, turning four hydrogen nuclei into a single helium nucleus plus a LOT of energy. This "hydrogen burning" releases gamma rays (high-energy photons) and neutrinos (particles with no charge and almost no mass).

___________________________• Sunspots are relatively cool, dark patches on the

sun's surface. They come in many shapes and sizes; they often appear in groups. These spots are much bigger than the Earth; they can be over 10 times the diameter of the Earth.

• Individual sunspots only last for one to two weeks, but the number of sunspots follows an ______________year cycle. The current sunspot cycle will peak in the middle of 2000. Sunspots are visible from Earth.

Lets Talk About Other Stars. Star Classification

• Stars are classified by their ________________(the elements that they absorb) and their temperature. There are seven main types of stars. In order of decreasing temperature,____________________________.

• An easy mnemonic for remembering these is: "Oh be a fine girl, kiss me."

• ___________________________stars are uncommon but very bright; M stars are common but dim..

•

____________________________

• The Hertzsprung -Russell (H-R) Diagram is a __________________that plots stars color (spectral type or surface temperature) vs. its luminosity (intrinsic brightness or absolute magnitude). On it, astronomers plot stars' color, temperature, luminosity, spectral type, and evolutionary stage. This diagram shows that there are______________ very different types of stars:

Hertzsprung - Russell Diagram….Remember……

• Most stars, including the sun, are “____________________________,"fueled by nuclear fusion converting hydrogen into helium. For these stars, the hotter they are, the brighter. These stars are in the most stable part of their existence; this stage generally lasts for __________________________ billion years.

Remember……

• As stars begin to die, they become giants and supergiants (above the main sequence). These stars have depleted their hydrogen supply and are very old. The core contracts as the outer layers expand. These stars will eventually explode (becoming a planetary nebula or supernova, depending on their mass) and then become white dwarfs, neutron stars, or black holes (again depending on their mass).

And…….

• Smaller stars (like our Sun) eventually become faint white dwarfs (hot, white, dim stars) that are below the main sequence. These hot, shrinking stars have depleted their nuclear fuels and will eventually become cold, dark, black dwarfs

Spectral Classes

Hertzsprung - Russell Diagram• These star classes are put on an easy to read diagram that

ranks a star based on___________________, Absolute Magnitude and temperature.

• Remember that a star’s color indicates the ___________________________of the star.

• The ________________a star is, the faster it burns its life away.

• Hottest stars are ___________________and the coolest are red.

• Very Patriotic-red then white then blue from coolest to hottest.

Important Stars.

• _____________________________Alpha Centauri is the star system that is closest to the Earth. The dimmest star in the system, Proxima Centauri (Alpha Centauri C), is the closest star to us (other than our sun). The stars Alpha Centauri A and Alpha Centauri B are close binary stars.

__________________________(pronounced "beetle juice")

• Betelgeuse (alpha Orionis) is the second-brightest star in the constellation _________________________and one of the brightest stars in the sky. It is a supergiant star, reddish in color, and over 600 million miles in diameter (almost 1,000 times bigger than the Sun but cooler than the Sun). Betelgeuse is about 14,000 times brighter than the Sun. If Betelgeuse were at the center of our Solar System, it would extend beyond the orbit of Jupiter. It is 520 light-years from Earth. It is a variable star, varying in magnitude from 0.3 to 1.2 over a period of about 7 years, averaging about 0.70. It is the only star (other than our sun) for which we have surface images.

____________________________

• Arcturus is the brightest star in the constellation _______________________(the herdsman). It is a red giant (spectral type K1.5IIIp) that is the fourth brightest star in the sky. Arcturus is 34 light-years from Earth.

____________________________• Polaris (alpha UMi) is the current pole star for the

Northern Hemisphere; it is 1 degree from the exact Northern celestial pole. In 1780, Sir William Herschel discovered that Polaris was a double star with a faint companion star. Polaris is a blue-green Cepheid variable star (its size brightness changes periodically, with period of 3.969778 days; it varyies between mag 1.92 and 2.07 Polaris' distance from Earth has been estimated to be from 360 to 820 light years.

• __________________________________________.

___________________________

• Sirius (meaning "scorching" in Greek), also known as the dog star, is the brightest star in the sky (except for the sun). It is in the constellation _______________________(The Great Dog). Sirius is a main sequence star that is about 70 times more luminous than the sun. It is about 8.6 light-years from Earth.

_________________________• A constellation is a group of stars that, when seen from

Earth, form a pattern. • In____________________ the International

Astronomical Union defined the _____________________constellations that are today recognized as the "official" constellations.

• Includes the Zodiac Constellations.• “______________________________" is the name we

give to seeming patterns of stars in the night sky. "Stella" is the Latin word for star and a constellation is a grouping of stars. In general, the stars in these groups are not actually close to each other in space, they just appear to be close when viewed from Earth.

__________________________

• The Zodiac is a family of constellations that lie along the ________________________(the plane in which most of our Solar System lies). Usually, 12 constellations are listed in the Zodiac, but there is actually a thirteenth constellation that crosses the ecliptic, Ophiuchus (between Scorpio and Sagittarius).

_______________________________• Our solar system is almost flat, forming a plane. This plane is

called the ecliptic of our solar system. The ecliptic is the plane of Earth's (and most of the other planets) orbit about the Sun. In the course of a year, the sun appears to trace a path in the sky along the ecliptic. The constellations of the Zodiac lie along the ecliptic.

The 12 Constellations of the Zodiac• ____________________________, the water bearer

____________________________, the ram___________________________, the crab___________________________, the goat___________________________, the twins___________________________, the lion___________________________, the scales___________________________, the fish___________________________, the archer___________________________, the scorpion____________________________, the bull_____________________________, the virgin

Constellations

• Depending on what hemisphere you live, you will only see certain constellations. Meaning you will see different constellations if you lived in the Southern Hemisphere compared to the Northern Hemisphere.

• In addition you will see different constellations with the seasons, meaning there are Summer, Fall, Winter and Spring Constellations.

Circumpolar Constellations

• These are constellations that we can see in the Northern Hemisphere year round and rotate around the North Pole.

• __________________________________________________________________________________________ ( my favorite circumpolar constellation)____________________________________________________________

_______________________ Constellations in the Northern

Hemisphere.• Aquila

CygnusHerculesLyraOphiuchusSagittariusScorpius

______________________Constellations

• Canis MajorCetusEridanusGeminiLynxOrionPerseusTaurus

__________________________• Orion, the Hunter, is by far the most famous seasonal

constellation. No other is more distinct or bright as this northern winter constellation. The famous Orion's Belt makes the hunter easy to find in the night sky.

• First, you should spot Orion's Belt, which is made of three bright stars in a straight line. One of Orion's legs is represented by the bright star Rigel, one of the brightest stars in the night sky. His two shoulders are made of the stars Bellatrix and Betelgeuse. You can see Betelgeuse's reddish color without a telescope.

__________________________

• Ursa Major is probably the most famous constellation, with the exception of Orion.

• The body and tail of the bear make up what is known as the Big Dipper

• Most of the constellation is circumpolar, which means it can be viewed all year long. However, parts of the legs will disappear from the sky in the fall and reappear in the winter.

_________________________

• Ursa Major is full of unique celestial objects. Two of the stars, Dubhe and Merak, are pointer stars. If you are looking at the Big Dipper, the outer edge stars that make up the "bowl" of the dipper are the two stars, with Merak being the one on top. Connect a line between the two, and extend it north a distance about five times the distance between them. It will connect with the North Star, Polaris.

Arc to _____________________…This is a cool Summer Thing.

• If you connect the handle of the dipper with a line, it will lead to the star, Arcturus, in the constellation, Bootes.

• So the Big Dipper points to the North Star -- it also points to other important stars -- you follow the arc of the Dipper's handle and "arc to Arcturus", then "spike to Spica" - two very important stars that we will get to in a minute. So the three stars of the handle are pointers as well.

____________________________

• Cassiopeia is a ________________in her chair.• Remember it is a circumpolar constellation.• The constellation Cassiopeia lies right smack in

the middle of the Milky Way.• Cassiopeia was named for Cassiopeia, the

mother of Andromeda (and the wife of Cephus) in Greek mythology.

____________________________

• Draco the dragon is a circumpolar constellation, which means it revolves around the North pole. It can be seen all year round. Draco is only present in the Northern Hemisphere, so those living in the Southern Hemisphere will never see this long constellation.

____________________________

• Cepheus was king of a land called Ethiopia in Greek myth. He had a wife named Cassiopeia and a daughter, Andromeda.

• Cepheus looks like a house. It is a circumpolar constellation; it never dips under the horizon in the Northern hemisphere.

_________________________• Andromeda is a "V" shaped constellation best

viewed in the fall if you live in the Northern Hemisphere. Andromeda lies close to the north pole, so only a few in the Southern Hemisphere can see this strangely shaped constellation in the spring.

• The Great Andromeda Galaxy is the most distant object visible to the naked eye. You can find this famous galaxy on the right side of Andromeda, about half-way up the constellation.