Astronomy Exam Review EarthMoon Sun system Moon Tides Eclipses General features of the sky types of orbits and rotations in the o Tides are controlled by gravitational attractions of astronomical masses The o Solar Eclipse when the moons shadow crosses the Earth s surface Occurs 2 to 5 times a year but most are partial eclipses o Lunar Eclipse when the Moon moves into the Earth s shadow Occurs every 6 months o Ecliptic the path of the sun on the celestial sphere Note Does NOT line up with equator except for 2 spots Equinoxes o The moon tilted 5 to the plane of the Earth s Orbit Measuring stars Blackbody curves and temperatures luminosity mass parallax spectral classes binary systems o Stellar parallax d 1 p The larger the star the sooner it dies Stellar mass Fuel available Luminosity Rate of using fuel o Spectroscopic parallax on the main sequence and off the main sequence Measure the star s apparent brightness and spectral type o Apparent brightness and the distance to star to determine luminosity o Blue stars are hotter red are cooler o OBAFGKM Our Sun is a G AU parsecs arc seconds LY o AU Earth s average distance to the Sun 1 50 x 10 8 km o Parsec Short for Parallax Second used to measure distances to stars distance measured in parsecs 1 parallax measured in arcseconds o Arc seconds Parallaxes of stars can be tiny So they break it up An arcminute is 1 60th of a degree And an arcsecond is 1 60th of an arcminute o Light Year the distance light travels in 1 year Roughly 9 5 trillion kilometers Objects in the solar system planets moons KBO s Kuiper belt Oort cloud comets meteoroids asteroids general characteristics orbits rotation axes magnetic field atmospheres etc o Jupiter o Saturn o Uranus No Solid Surface Metallic Hydrogen core 3 rotation of axis 10 for magnetic axis Prograde rotation 27 rotation of axis Nickel Iron and rock core Prograde rotation 30 rotation of axis Retrograde rotation 17x bigger than earth Ice Giant hydrogen and helium but also have water ammonia and methane o All planets except Uranus and Neptune formed by dynamos Dynamos converting flow energy into magnetic energy o Mercury o Venus o Mars 1 30 of a tilt 800 F during the day Surface like moon Prograde rotation 177 3 tilt Retrograde rotation Volcanic surface smooth volcanic plains Sulfur in air recent volcanic activity 25 tilt Prograde rotation Iron oxide on surface make it reddish o Pluto and Charon orbit around each other Pluto 1 500th the mass of Earth 2300km diameter Atmosphere of nitrogen and methane Charon 10 of that 1200km in diameter Atmosphere of nitrogen and methane o Eris more distant and more massive than pluto Sun structure and features how powered and how known o Core is where nuclear fusion takes place o Radiation zone relatively transparent o Convection zone relatively opaque granulated o Photosphere also granulated large eruptions may occur here o Chromosphere small solar storms emit spicules narrow cooler jets of gas o Transition zone o Corona seen during an eclipse outer band much hotter than layers below it must have a heat source probably electromagnetic interactions o Sun spots appear dark bc cooler than surroundings o Nuclear fusion requires like charged nuclei to get close enough hot enough to fuse over 10 million K o Neutrinos are emitted directly from the core of the Sun and escape interacting with virtually nothing Unfortunately they don t interact with earth based detectors so they re tough to pick up on o Experiment with vat of Cl turning into radioactive Argon o Nuclear fusion whats fusing How do we know neutrino Stellar evolution HR diagrams trajectories of low medium and high mass stars from birth to death age of star clusters ultimate fate white dwarf neutron star black hole etc and the relevant masses o o Star evolution http aspire cosmic ray org labs star life hr interactive html Kepler s Law Roche limit Doppler shift E mc2 o Kepler s Law P 2 A 3 P Orbital Period A Semi Major Axis o Roche Limit For a planet and satellite of comparable density tidal forces will break up the satellite if it gets within 2 44 planetary radii due to differential gravitational forces This is where the tidal forces of the planet are too strong for a moon to survive this is where rings are formed Ages of main objects Sun Earth Globular clusters Milky Way Universe o Sun 4 57 Billion years old o Earth 4 54 Billion years old o Globular Clusters 12 7 Billion years old o Milky Way 13 2 Billion years old o Universe 13 77 Billion years old More recent material Galaxy types Hubble for classification o Elliptical galaxies Shaped like an elongated sphere Ranges from E0 circle to E7 Flat o Spiral galaxies 3 main components a bulge disk and halo Bulge circle in the very center Disk made up of dust gas and younger stars Makes the arms of the spiral Our sun is in an arm of our galaxy Halo loose spherical structure arounf the bulge and some of the disk Contains old clusters of stars globular clusters o Irregular galaxies No regular or symmetrical structure Divided into Irr I and Irr II Irr I have regions of hydrogen gas and many young hot stars Irr II have large amounts of dust that block most of the light from the stars Standard Candles distance determinations Cosmic Distance Ladder Fig 15 17 o Different ways to determine distance o Similar to a band spread across a field their sound does not sound crisp They must be compact for a clean note o AGN s have a limit as to how big they can be in order to change color that we can see from distances away Galaxy Clusters super clusters Local group Virgo o Galaxy Clusters hundreds of galaxies bound by gravity o Super Clusters large groups of smaller galaxy groups and galaxy clusters o Local Group group of galaxies Milky Way included Contains more than 54 galaxies counting dwarf galaxies Center between Milky Way and Andromeda galaxies o Virgo Cluster cluster of galaxies with up to between 1300 2000 galaxies forms heart of the Virgo Supercluster Local group is an outlying member Hubble Law red shift recession velocity distance age of the universe o Hubble s Law the universe is infinitely expanding Meaning the past universe was much smaller o Red shift the universe expanding Objects moving further away o Recessional velocity galaxies in the past receded faster than predicted BUT NOT AGN s study Section 15 5 Seyferts Radio Quasar Normal Galaxies IN THIS CASE o Early universe o AGN s we see depend on perspective See figure 15 19 o AGN s need a central engine and source of