Stars & Galaxies

1. If you could travel at the speed of light (186,000 miles per second) it would take 100,000 years to cross our galaxy Stars & Galaxies Even on the clearest night, the human eye can only see about 3,000 stars. There are an estimated 100,000,000,000 in our galaxy alone!

2. Stars Constellations • Patterns of stars representing mythological characters, animals, or familiar objects. • Most constellations come from the Greeks. • The stars in a constellation may appear close, however each star can be millions of light-years away from each other. • There are 88 constellations used to divide the night sky.

3. Circumpolar Constellations • Constellations that appear to circle around the North Star, Polaris. • These constellations are visible all year and never go below the horizon. • Ursa Major, Ursa Minor, Draco, Cepheus, Cassiopeia, Camelopardalis

4. Zodiac Constellations • 12 constellations that line up on the ecliptic with the planets. • For about a month, one of these constellations is hidden behind the Sun.

5. Absolute & Apparent Magnitude • Absolute Magnitude refers to the measure of light that a star actually gives off. • Apparent Magnitude refers to the amount of light the Earth receives from the star. The largest recorded starquake occurred on the neutron star SGR 1806-20. It was a 22.7 on the Richter scale. The quake released enough gamma radiation that had it been within 10 ly of Earth (it is 50,000 ly away) it would likely have caused a mass extinction.

6. Measurement in Space • Parallax- the apparent shift in the position of an object when viewed from two different positions. • The closer the object is to the observer, the greater the parallax.

7. Light-years- the distance light travels in one year (9.5 trillion km in one year.) • Proxima Centauri is the closest star to the Sun at 4.3 ly.

8. Blue Blue-white White Yellow-white Yellow Red-orange Red Properties of Stars • Temperature- determined by the star’s “surface” color. From hottest to coolest:

9. Composition • Observed from the light given off by the star using a spectroscope. • A prism in the spectroscope divides the light into its component colors. • The colors present/absent in the spectrum indicate the elements present in the star. Similar to a fingerprint. The telescope on Mount Palomar, California, can see a distance of 7,038,835,200,000,000,000,000 miles.

10. Hydrogen Helium Carbon

11. If a pinhead-size piece of the Sun were placed on Earth, one would have to stand as far as 145 kilometers (90 miles) away to be safe. The Sun The Sun’s Layers • The Sun is a giant ball of gas/plasma. Core- hydrogen is fused into helium giving off massive amounts of energy (Nuclear Fusion.) above 15 million K. Radiative/Convection Zones- area through which the energy travels outwards. Atmosphere- outermost region of the Sun It would take 1,300,000 Earths to fill the sun. Gravity on the sun is 30 times stronger. 70 lbs on Earth would be 1 ton on the sun The sun is…. 109 Earths across 93 million miles away 176 years away at 60 mph Temperatures on the sun range from 7000 to 27,000,000° F

12. The Sun’s Atmosphere • Photosphere- lowest layer of the Sun’s atmosphere. • This is considered the “surface” because this is the part we see from Earth. • Sun’s photosphere is yellow at 6000K • Chromosphere- layer above the photosphere. • Corona- highest & largest layer. • Charged particles reach 2 million K The Earth orbits the sun at an average speed of 107,220 kms per hour.

13. If the sun were the size of a dot on an ordinary-sized letter 'i', then the nearest star would be 10 miles away. • Core • Radiative Zone • Convection Zone • Photosphere • Sunspot • Chromosphere • Corona The light hitting the earth right now is 30 thousand years old. The energy in the sunlight we see today started out in the core of the Sun 30,000 years ago – it spent most of this time passing through the dense atoms that make the sun and just 8 minutes to reach us once it had left the Sun! The temperature at the core of the sun is 13,600,000 kelvins. All of the energy produced by fusion in the core must travel through many successive layers to the solar photosphere before it escapes into space as sunlight or kinetic energy of particles.

14. “Surface” Features Sunspots- cooler dark areas • Appear & disappear regularly • Magnetic storms Prominences- huge, arching columns of gas. Flares- violent eruptions of particles near sunspots. Solar Winds- particles ejected from the Sun’s corona. • Bounce of the Earth’s atmosphere causing the auroras. There is a current scientific hypothesis that the sun possibly has a companion which is currently about 1-1.5 light years away. It is believed that it has an elliptical orbit which, every 26 million years, sends matter towards the earth causing mass Extinction events. The star is predicted to be most likely a red or brown dwarf and has been named Nemesis or “Death Star”.

15. Sunspots Scientists haven’t been able to work out how Stradivari (famous violin maker) made his violins but they think it is due to the wood he used. From 1500s to 1800s the earth underwent a mini ice age due to volcanic activity and decreased solar activity. As a result of the cooling, the trees he used were particularly hard (due to slow growth). If he hadn’t had those trees to work with, his violins might now have been so highly prized. Solar Flares The Sun loses up to a billion kilograms a second due to solar winds Prominences

16. The Sun – An Average Star • Middle-aged star, average absolute magnitude, & average temperature. Multiple star systems • The Sun is NOT part of a multiple star system unlike most stars. • 2 stars is a binary system, 3 stars is a triple-star system (Alpha Centauri system) Star Clusters • Stars that are so close that they move together as a unit.

17. III. Evolution of Stars Classifying Stars Hetrzsprung-Russell Diagram • EjnarHertzsprung & Henry Russell independently charted the relationship between a star’s temperature to its absolute magnitude. • It showed that the hotter stars are also the brightest stars, with a few exceptions. • 90% of all stars fit into a diagonal line in the middle of the graph (Main Sequence.)

19. The Main Sequence • Contains hot, blue giant stars that are very bright to cooler, red dwarf stars that are very dim. • Yellow, medium sized stars are in the middle of the Main Sequence like the Sun.

20. Dwarfs, Giants, & Supergiants • 10% of stars are not main sequence. • Stars that are very hot (white-blue,) but are dim are called the White Dwarfs. • Stars that are cooler (red-orange,) but are very large and bright are called the Red Giants. • The biggest, coolest, & brightest stars are the Red Supergiants.

21. The Solar System Medium to Red Giant The star "Lucy" in constellation Centaurus is actually a huge cosmic diamond of 10 billion trillion trillion carats.

22. The star Antares is 60,000 times larger than our sun. If our sun were the size of softball, the star Antares would be as large as a house. Giants to Supergiants

23. Nuclear Fusion • Four hydrogen nuclei combine to create one helium nucleus. • The mass of one helium nucleus is much less than 4 hydrogen nuclei, so some of the mass is lost in the reaction. • The lost mass is converted into large amounts of energy in the form of light. (Temps in the core exceed 15 million K)

24. Nebula Protostar Main Sequence Evolution of Stars (Cosmology) Step 1. Nebula-stars start out as clouds of dust & gas. Gravity pulls it together. Step 2. Protostar-the mass of gas gets bigger & bigger eventually heating up to 10 million K causing fusion. Step 3. Main Sequence- when the pressure formed by the heat balances the attraction due to gravity it reaches equilibrium.

25. Step 4. If it has: Small Mass • Red dwarf stars with eventually run out of hydrogen and will collapse into a hot, White Dwarf. Medium Mass • Yellow or white stars that will run out H causing the atmosphere to expand and cool into a Red Giant. • He will fuse into a carbon. • It will eventually collapse into a White Dwarf

26. List of things that fuse in a star. All but the fusion of iron is exothermic.

27. Large Mass Stars • Blue stars will expand into Red Giants when they run out of hydrogen and helium fuses into carbon. • Carbon will then fuse into heavier & heavier elements causing the star to expand further into a Red Supergiant. • When iron is formed from fusion, iron can’t be fused so the star collapses violently in a Supernova.

28. Depending on the mass of the core, one of the following will occur: Neutron Star- smaller cores will produce a dense core of neutrons about 20km in diameter. 4 to 8 times the size the sun -supernovae. This blows a star's outer layers into space, the core remains—but it no longer produces nuclear fusion. With no outward pressure from fusion to counterbalance gravity's inward pull, the star condenses and collapses in upon itself. compression from the star's gravity will be so great the protons fuse with the electrons to form neutrons Neutron stars are so dense, that a soup can full of neutron star material would have more mass than the Moon. At 12.5 miles (20 kilometers)—neutron stars boast nearly 1.5 times the mass of our sun, and are thus incredibly dense. Just a sugar cube of neutron star matter would weigh about one hundred million tons on Earth. There is a neutron star that spins on its axis at 1,122 times every second. A neutron star is the strongest magnet in the universe.

29. Black Hole- larger cores will collapse to a super dense point. The gravity near this mass is so strong nothing can escape from it, not even light. Locate using X-rays. • » Event Horizon is the area where nothing can escape. there is a super massive black hole at the center of the Milky Way galaxy. It weighs about 4 million solar masses (it’s over 30,000 light years away.) black holes can’t suck up all of the matter in the Universe. Each black hole has its own event horizon, much like the gravitational field of a planet. If matter is not in that horizon it will never get sucked into the black hole.

31. The cosmos contains approximately 50,000,000,000 galaxies. Galaxies & the Universe Galaxies • Large group of stars, gas, and dust held together by gravity. -Spiral Galaxies- galaxies with spiral arms that wind outward from the center. They can be normal or barred. When you look at the Andromeda galaxy (which is 2.3 million light years away), the light you are seeing took 2.3 million years to reach you. Thus you are seeing the galaxy as it was 2.3 million years ago.

32. -Elliptical Galaxies- common type of galaxy that are oval or egg shaped. -Irregular Galaxies- galaxies that have no distinct shape. cosmic year is the amount of time it takes the Sun to revolve around the center of the Milky Way, about 225 million years.

33. Hubble Deep Field You are looking back into the past by 13 billion years in this picture Each spot of light isn’t a star…. It’s an entire galaxy. About 1500 of them. Deep Field Video

34. The Milky Way • Spiral galaxy that is about 100,000 ly across. • Out solar system is located about half-way out on one of the spiral arms. • Like many galaxies, the Milky Way has a super massive Black Hole at its core. Sun is 23,000 light-years from it's center We are moving through space at the rate of 530km a second

35. Origin of the Universe • Steady State Theory- the Universe has always been the same as it is today. • Oscillating Model- the Universe expands and contacts in a cycle. • Big Bang Theory- the Universe started with a bang and has expanded ever since.

36. Expansion of the Universe • Doppler Shift- the changing of the wavelength of sound or light as an object gets closer or further away. • Red Shift- as a star or galaxy gets further away from the Earth, its light will expand (stretch) producing a longer wavelength (red) in the spectroscope. • Blue Shift-as a star or galaxy gets closer to the Earth, its light will get compressed (squeezed) producing a shorter wavelength (blue) in the spectroscope.

37. » Most galaxies show red shift, therefore the Universe is expanding.

38. The Big Bang Theory • All energy & matter was created in an instant with an initial explosion. • The matter rapidly expanded throughout space in a swirling, dense mass. • Matter began to collect into clumps. As matter cooled, hydrogen & helium gases formed. • Eventually the first stars will form followed by galaxies, etc while still expanding.

40. Quasars are extremely distant objects in our known universe. They are the furthest objects away from our galaxy that can be seen. Quasars are extremely bright masses of energy and light. The name quasar is actually short for quasi-stellar radio source or quasi-stellar object. A quasar is believed to be a supermassive black hole surrounded by an accretion disk. When we look at quasars which are 10-15 billion light years away, we are looking 10-15 billion years into the past.