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The Rest of the Universe Chapter 9 CPO Science Where are you? The Earth circles the sun The sun is one of billions of billions of stars. To measure distances between stars we a distance measurement called the Light- year 1 light-year is the distance light travels in one year. Since light travels at 186,000 miles per second, A light year is approximately 6 trillion miles Andromeda The Cosmic Zoo Stars Planets Gas Nebulae Star Clusters Galaxies Clusters of Galaxies Large-scale structures Stars Are formed by the same forces Have different Size Composition Temperature Color Mass Brightness Composition Determined with a spectroscope by the colors of light it gives off The lightest element Hydrogen makes up 60 - 80 % of a star Helium is second most 96-99 % is hydrogen and helium rest is other elements The Electromagnetic Spectrum Chemistry from Spectra Emission Spectra Chemistry from Spectra Absorption Spectra Spectroscope Breaks the light of a star up into its colors Called a spectrum Kind of spectrum tells scientists what the star is made of which way and how fast it is moving Analyzing Stellar Spectra Anomalies in positions of absorption bands Normal Spectrum • Spectra from stars will have lines missing Size 5 main categories Medium sized - like our sun from 1/10 size of sun to 10 times it’s size Giant stars- 10 to 100 times bigger than the sun Supergiant stars- 100 to 1000 times bigger than the sun The Red Giant Size White dwarfs- smaller than 1/10 the size of the sun Neutron stars - smallest stars - about 16 km in diameter Temperature Blue Color also indicates temperature White hottest surface 50000 °C Yellow coolest -3000°C Red-orange Red 35,000 °C 10,000 °C 6,000 °C 5,000 °C 3,000 °C Brightness Magnitude - measure of brightness Apparent magnitude - how bright it looks from earth Absolute magnitude - how bright it really is Variable stars - brightness changes from time to time Cephid variables - pulsating variableschange both brightness and size Hertzsprung-Russell diagram Found that as temperature increased, so did absolute magnitude 90% of stars followed this pattern Called main sequence stars Other 10% were once main sequence stars but have changed over time Absolute Magnitude Supergiants 50000 Giants 20000 10000 6600 6000 5000 3000 Star Life Cycles Stars change over time New stars form from nebulae Gravity pulls the dust and gas together Mostly hydrogen Forms a spinning cloud Hydrogen atoms hit each other and heat up Star Life Cycle When the temperature reaches 15,000,000 °C fusion begins Makes a protostar - a new star What determines the life cycle of the star is how much mass it starts with. Star Birth The Solar System - Its Origin and Early Development Our solar system, part of the Milky Way galaxy, consists of the Sun, nine planets, 64 known moons, many asteroids, millions of comets and meteorites, as well as interplanetary dust and gases Neutron Stars If the star started out 6 to 30 times the mass of the sun, the core of the exploding star becomes a neutron star. As massive as the sun, but only 16 km across. Neutron stars spin rapidly and give off pulses of radio waves If these radio waves come in pulses it is called a pulsar Black holes If the star was bigger than 30 times the mass of the sun The left over core becomes so dense that light can’t escape its gravity. Becomes a black hole. Grab any nearby matter and get bigger As matter falls in, it gives off x-rays. That’s how they find them How far are the stars? How big is the Universe? We can measure distances to stars by two methods One method – parallax is only good for the very nearest stars The other method – comparison of magnitudes is more complex, but it can be used for even the farthest stars and galaxies. Measure the angle to the star Wait half a year Measure the angle to the star Triangle tells distance Distance to stars Parallax works only to 100 light-years More than 100 light-years they use a complicated formula based on apparent and absolute magnitude. More than 7 million light-years they use the red shift Doppler Effect Change in wavelength caused by the apparent motion of the source. Cars moving by you Same things happen to light Light from objects coming toward you is compressed looks more blue Light from objects away looks more red Using the Doppler Effect to Measure Velocity Blueshift Redshift Animation http://lectureonline.cl.msu.edu/~mmp/appli st/doppler/d.htm Edwin Hubble at Mt. Wilson Hubble’s observations at the 100 inch during the 1920’s led him to the conclusion that the universe is expanding, and that an object’s recession velocity is proportional to its distance from the observer. Hubble guiding the Hooker 100 inch telescope in 1923. The Hooker 100 inch telescope atop Mt. Wilson near Pasadena, CA. It was the largest telescope in the world from 1917-1947. Deep Hubble Space Telescope Image A deep image of an “empty” portion of the sky with the Hubble Space Telescope reveals that the universe is filled with galaxies- many just like our own. The light we see from the most distant galaxies has traveled approximately 10 billion years to reach us. Hubble’s Law Nearly all galaxies in the Universe display RED SHIFT The amount of RED SHIFT is related to the relative distance to the galaxy. FARTHER galaxies show GREATER RED SHIFT Example of Red Shift Normal Spectrum Shifted Spectrum Hubble’s Law – What does it mean? Is the Earth the center of the Universe after all and everything is moving away from us? Does it depend on frame of reference? Would Hubble’s Law apply if we looked at the Universe from another location? Why is everything moving away? Hubble’s Observation/ Hubble’s Insight All galaxies appear to be moving away from the center of the Universe because the Universe is expanding. The existence of RED SHIFT and the pattern that it shows (greater shift for farther galaxies) is consistent with a pattern produced by an explosion – THE BIG BANG!! What was the Big Bang? Prior to the Big Bang – there was no Universe A single super-massive object exploded Explosion creates Universe Matter, space and time are created Explosion was approximately 15 billion years ago Currently the best theory to explain the origin of the Universe Supported by multiple lines of evidence News Flash: NASA/CNN report first stars formed early than once thought Evidence in support of Big Bang Theory Hubble’s Law and pattern of red shift Cosmic Background Radiation Mathematical models Particle physics theory Cosmic Microwave Background Arno Penzias and Robert Wilson were trying to make observations of radio emissions from a distant supernova and then hoped to make a map of radio emissions from the Milky Way. They adapted a radio dish previously used for communication satellites. They were startled to find that no matter where they pointed the antenna, they measured the same low-level radio signal. After great efforts to determine that there was nothing wrong with the antenna, they concluded that the signals were real and a property of the universe. Penzias and Wilson, 1965 Arecibo Dish, Puerto Rico New Insights into the Big Bang Recent mapping of microwave and temperature variations suggest that the Universe may be flat – not spherical! Implications? The Big Bang 10-35 seconds generates space & time, as well as all the matter & energy universe will ever hold For small fraction of a sec., the universe is an infinitely dense, hot fireball The Universe Takes Shape -- 10-6 sec. universe continues to expand → less dense & cooler. now basic forces in nature become distinct: Gravity & “strong force” (holds nuclei of atoms together), followed by the weak & electromagnetic forces. By end of 1st second, universe consists of particles & energy -- smash together → form protons & neutrons. Formation of Basic Elements -- 3 sec. nuclei of simple elements hydrogen, helium and lithium form (will be another 300,000 yrs before electrons are captured into orbits around these nuclei to form stable atoms). The Radiation Era -- 10,000 years most of the energy left from the “fireball” is in the form of radiation - different wavelengths of light, X rays, radio waves & ultraviolet rays • • Birth of Stars & Galaxies -- 300 my after BB (still ~ 12 to 15 by before the present). pockets of gas become more and more dense as a result of gravitational attraction. Stars ignite within these pockets groups of stars become the earliest galaxies. •Birth of the Sun -- 5 Billion Years Before Present (BP) • Sun forms w/in cloud of gas in spiral arm of Milky Way Galaxy. • vast disk of gas & debris swirls around new star → gives birth to planets, moons, & asteroids . Looking at the night sky is literally looking into the past!!