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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