ASTR 1345 1st Edition Lecture 4 Outline of Last Lecture I. Speed of LightII. The SunIII. Black Holes/ Dark MatterIV. Major Physical TheoriesOutline of Current Lecture I. Powers of Ten A. Positive B. NegativeII. Astronomical Units and ParsecIII. The Night SkyA. Definition of an AsteroidB. Definition of a Black holeC. Definition of a CometD. Definition of a MeteoroidE. Groups of GalaxiesF. Definition of AsterismsG. Definition of a Celestial SphereH. Definition of a ConstellationCurrent Lecturel.A. T (tera)=10^12=1,000,000,000,000= one trillionG (giga)=10^9=1,000,000,000=one billionM (mega)=10^6=1,000,000=one millionK (kilo)=10^3=1,000=one thousand10^2=100=one hundred10^1=10 10^0=1B. c (centi)=10^-2=.01= one hundredthm (milli)=10^-3=.001=one thousand(micro)=10^-6=.000,001=one millionthn (nano)=10^-9=.000,000,001=one billionthp (pico)=10^-12=.000,000,000,001=one trillionthThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.ll.Astronomical Units (AU) is the average distance of the Sun from the Earth. 1 AU=93 million miles=1.50X10^8 km. A Light Year (ly) is the distance that light travels through space in 1 year. 1ly=63,000 AU (about 6 trillion miles). Parsec (pc) is three times larger than a light year. 1 pc= 3.26 ly (about 20 trillion miles). A Parsec is the distance from Earth at which the length of 1 AU subtends an angle of 1 arcsec. 1 mile=1.6 km.lll.A. Asteroid-any of the rocky objects larger than a few hundred meters in diameter that orbits the Sun.B. A black hole is an object whose gravity is so strong that the escape velocity from it exceeds the speed of light.C. Comet-small body of ice and dust in orbit about the Sun. While passing near the Sun the comets’ vaporized ices give rise to a coma, tails, and a hydrogen envelope.D. Meteoroid-small rock in interplanetary space. E. Groups of galaxies are held together by gravity in clusters and clusters of galaxies are held together by gravity in super clusters. Huge quantities of intergalactic gas are found between galaxies. The human eye can only detect 6,000 stars in the entire sky. At any one time you can see 3,000 stars in dark skies because only half of the stars are above the horizon—the boundary between Earth and sky.F. Asterisms-patterns in the sky found by bright stars.G. Celestial Sphere-hypothetical sphere of very large radius centered on an observer. It is the apparent sphere of the night sky.H. Constellation-any of the 88 contiguous regions that cover the entire celestial sphere, including all objects in each region. Also a configuration of stars named after an object, person or
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