Astronomy Final Exam Overview Earth is in the Milk Way Galaxy located in the Disk of our universe 1 of the 2 largest galaxies Local Group group of about 40 galaxies Solar System Milk Way Galaxy Local Group Clusters of Galaxies 50 1000 gals Nearest Cluster Virgo Voids of space between Super clusters Stars form inside clouds of gas dust by the collapsing of gravity Nuclear Fusion 4 H He releasing a lot of energy After stars die the blow out most of the material they are made of and it is recycled to form new stars Solar System is made of recycled material Early Universe contained only H He and Li 98 H He and 2 other all other elements got there because of supernova explosions The Universe 14 billion years old If something is 12 bill ly away we see it 12 bill years ago when it was only 2 bill years old THE FURTHER AWAY WE LOOK IN DISTANCE THE FURTHER BACK WE LOOK IN TIME Milky way 100 billion stars All of the galaxies are moving away from each other the universe is expanding because of Hubble s Law In the past galaxies were closer together Beginning of the expansion Big Bang Theory THE DISTANCE OF STARS IN GALAXIES DOES NOT CHANGE BC BOUND BY GRAV Accelerating charges produce light electromagnetic radiation because light has both electric and magnetic fields Photons energy in light waves transported by particles Light has wavelength distance between two peaks a frequency number of waves passing each second a speed 300 000 km s always the same an energy depends on wavelength of frequ Speed of light is always constant c wavelength x freq As wavelength frequency v E Hubble s constant x frequency Light with a SHORTER wavelength carries MORE energy Electromagnetic spectrum light colors distinguished by frequency and wavelength The Sun energy from THERMONUCLEAR RxN in the core energy slowly moves outward through processes cool dwarf star spherical ball of hot gas sunspots Photosphere visible layer of the sun the surface cant see passed the photosphere Limb darkening looks darker at the edge than in the middle Central Layers core radiation zone convection zone Outer Layers photosphere chromosphere and corona Core nuclear fusion occurs here Radiation zone energy is transported by radiation Convection zone energy transported by convection Photosphere outer layer of the sun we see this layer Chromosphere very little light Coronoa0 very hot due to magnetic fields Solar Wind 10 000 km above photosphere can escape suns gravity Sunspots low temperature regions in the photosphere appear dark because cooler than surroundings come and go in a few days linked and produced by pairs of magnetic field lines rotation of the sun drags magnetic field lines around with it cause kinks 11 year sunspot cycle BUT really 22 years because they switch from northern to southern hemisphere every 11 years Magnetic field produces solar activity Luminosity total energy per second emitted by an object power Solar flare large explosion on suns surface emitting energy but in seconds rather than days like sunspots Solar corona larger and irregular than sunspot peak hotter than photosphere Coronal mass ejection emits charged particles that can affect the earth Solar wind0 escapes sun through CORONAL HOLES seen in XRAY IMAGES Hydrostatic equilibrium when gas pressure gravity the star is stable reason why the sun does not collapse or expand When gas pressure gravity expands Gas pressure gravity contracts Gas Temp measure of moving atoms in random directions Gas Pressure force of the atoms in their surroundings via there collisions Temp Pressure Tem v Pressure v Gravitational Contraction keeps the sun shining for 40 000 000 years Luminosity energy radiated by the sun Nuclear Fusion light nuclei into heavier nuclei and energy is produced as well NEED temp of at least 10 million K E m c 2 c speed of light Law of conservation of mass and energy mass and energy converted must always remain constant you cant loose mass energy it just converted into the other Particles created in Fusion Deuterium P N Positron antiparticle of E and Neutrino charge less and massless Proton proton chain 4 H He 2 neutrinos energy Missing mass turns into Energy because of law of conserve Of mass and energy Neutrinos are hard to detect Fundamental Properties of Stars Size Luminosity Temperature Mass Distance Velocity Stars can range from 01 R to 1000 R IN SIZE Magnitude Scale system of ranking stars by brightness Luminosity energy emitted by an object each second total power in Watts or J s BIG HOT objects have GREATER LUM than SMALL COOL OBJ Brightness how bright a source appears BRIGHTNESS depends on DISTANCE TO MAKE A STAR HAVE A GREATER LUMINOSITY 1 Make the star BIGGER in size or 2 Make the star HOTTER To measure Luminosity we measure brightness with a CCD camera records how much energy strikes its surface each second Measuring Temperature Look at its color Red cool Blue Hot Reddening scatter away blue light appears red but is really blue Blackbody radiation opaque object that has a temp of 0k that produces radiation in the form of a continuous spectrum the shorter the object the higher the temperature Temperature is related to its peak wavelength The SHORTER the peak of light emitted by the object the HIGHER the objects temperature Hot objects emit light that peaks at SHORT BLUE wavelengths Cool objects emit light that peaks at LONG RED wavelengths GOOD BLACKBLODIES are not transparent Peak of BLACKBODY tells us temperature Three types of spectrum Kirchhoff s laws 1 2 3 Continuous spectrum hot dense energy source full rainbow Emission line spectrum hot low density cloud of gas Black background with colored lines Absorption line spectrum Hot dance energy source rainbow with black cutouts Atoms P N E surrounding the atom atoms are mostly empty space Isotopes same number of protons different number of neutrons Electron distribution of probability around the nucleus that behaves like a point particle on a fixed circular path Ionization when an electron absorbs enough energy to escape the atom It jumps off Photons absorbed by an atom when an electron moves from LOWER to HIGHER energy level EMITTED when electron moves from higher to lower energy level Neon red orange Sodium yellow All stars produce dark line absorption spectra because the outer layers of stars are cooler than the core Hydrogen all absorption lines come from n 2 Spectral type refers to the types of lines in the spectrum temperature oh be a fine guy kiss me O B A F G SUN K M They all