Astronomy Exam Review - Tides, Eclipses, General features of the sky, types of orbits and rotations in the EarthMoon-Sun system.o Tides are controlled by gravitational attractions of astronomical masses (The Moon)o Solar Eclipse, when the moons shadow crosses the Earth’s surface Occurs 2 to 5 times a year, but most are partial eclipseso Lunar Eclipse, when the Moon moves into the Earth’s shadow. Occurs every 6 monthso Ecliptic- the path of the sun on the celestial sphere. (Note: Does NOT line up withequator, 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 systemso 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 typeo Apparent brightness and the distance to star to determine luminosityo Blue stars are hotter, red are coolero 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 kmo 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 arcminuteo 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 No Solid Surface, Metallic Hydrogen core 3* rotation of axis (-10* for magnetic axis) Prograde rotationo Saturn 27* rotation of axis Nickel, Iron and rock core, Prograde rotationo Uranus 30* rotation of axis, Retrograde rotation 17x bigger than earth Ice Giant, hydrogen and helium, but also have water, ammonia, and methaneo All planets except Uranus and Neptune formed by dynamos Dynamos-converting flow energy into magnetic energyo Mercury 1/30* of a tilt 800* F during the day Surface like moon, Prograde rotationo Venus 177.3* tilt, Retrograde rotation Volcanic surface, smooth, volcanic plains Sulfur in air= recent volcanic activityo Mars 25* tilt, Prograde rotation Iron oxide on surface make it reddisho 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 methaneo 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 transparento Convection zone-relatively opaque, granulatedo Photosphere-also granulated, large eruptions may occur hereo Chromosphere-small solar storms emit spicules, (narrow, cooler jets of gas)o Transition zoneo Corona- seen during an eclipse, outer band, much hotter than layers below it—must have a heat source, probably electromagnetic interactionso Sun spots appear dark bc cooler than surroundingso 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 Argono 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)oo Star evolution- http://aspire.cosmic-ray.org/labs/star_life/hr_interactive.html- Kepler’s Law, Roche limit, Doppler shift, E = mc2o Kepler’s Law P^2=A^3 P=Orbital Period A=Semi-Major Axiso Roche Limit For a planet and satellite of comparable density, tidal forces will break upthe 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, Universeo Sun- 4.57 Billion years oldo Earth- 4.54 Billion years oldo Globular Clusters- 12.7 Billion years oldo Milky Way- 13.2 Billion years oldo 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. 15.17o Different ways to determine distanceo Similar to a band spread across a field, their sound does not sound crisp They must be compact for a clean noteo AGN’s have a limit as to how big they can be in order to change color that we cansee from distances away- Galaxy Clusters, super clusters, Local group, Virgoo Galaxy Clusters- hundreds of galaxies bound by gravityo Super Clusters- large groups of smaller galaxy groups and galaxy clusterso Local Group-group of galaxies (Milky Way included). Contains more than 54 galaxies, counting dwarf galaxies. Center between Milky Way and Andromeda galaxieso 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 universeo Hubble’s Law- the universe is infinitely expanding Meaning the past universe was much smallero Red shift- the universe
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