-EM Radiation I
- The Light-Year: A light-year is the distance light travels in one year.
-Closest galaxy is Andromeda Galaxy
-How do we learn anything at all?
1. We use telescopes to collect faint Electro-Magnetic (EM) radiation from distant o
Ch.7 -Timeline: 1768- 68 nebulae known 1771-Messier publishes list of 103 objects to be avoided by comet hunters (most are galaxies in the constellation Virgo) 1864-General catalog published by J. Herschel 1935-"The Realm of Nebulae" by Hubble: galaxy clu
Ch.10 -Look at Cosmic Nucleosynthesis -Quasars are rare now in the local universe, but were once very common - The very small temperature fluctuations observed by COBE represent (and arise from) fluctuations in the matter distribution in the Early Univers
Ch.1 -There is overwhelming observational evidence for other "Solar Nebulae"; lots of Solar Nebulae within a few hundred light years of us. -Problem with finding extra-solar planets: Stars are millions of times brighter than planets in visible light - the
Ch.2 -Mars "Curiosity" Rover goals: try to find evidence of life, find evidence of lakes and oceans -Mars orbit highly elliptical -We can measure Earth-Mars distance using radar from Arecibo when it is closest to Earth (3x a century) -Has two moons, so ac
Ch.8 - Galaxy clusters are gravitationally bound condensations of galaxies that stand out against the frothy backdrop of walls & voids making up the 3-D distribution of luminous matter. They are the largest and most massive objects that can be observed at
Ch.9 -General Relativity=Einstein's theory of gravity - Special Theory of Relativity: 1) Describes how different observers describe the same event when speeds approach "c" 2) Space and time are not separate things, but are welded together: "space-time" -
Ch.6 -Island Universe pioneers were: Milton Humanson, Edwin Hubble, Charles St. John, Albert Michelson, William Campbell, Walter Adams -Hubble thought that galaxies evolved from left to right: EllipticalsSpirals; was actually SpiralsEllipticals -Halton Ar
Ch. 5 -If you can measure the Recessional Velocity of a galaxy (i.e., Doppler Shift), you can use this to determine its distance=Hubble's Law -Spiral Galaxies (S): pinwheels, large, massive, rich in gas and dust, form 1-3 sun-like stars a year. MWG=spiral
Ch. 4 -What MWG looks like: 2 major spiral arms with numerous "spurs" that form stars. -In MWG Disk, stars and gas clouds have circular orbits around center; stars in Halo and Bulge move along random orbits -Orbital speed of an object in MWG depends on Ke
-Telescopes have 2 functions:
(1) To collect and concentrate weak signals from space. (i.e., optical photons, X-ray
photons, radio photons)
(2) Allow us to see structure in astronomical objects
-Intro to Stars:
-300 billion stars in Milky Way, 10^22 in observable universe
-stars have different colors, luminosities, masses, diameters, ages, distances
-primary accurate technique to measure distance to other stars is the Trigonometric Pa
Chapter 17Star Formation:
- The space between stars is not empty, but is filled with atomic gas, cold molecular gas, and
grains of dust (Interstellar Medium)
Chaotic/fractal in basic structure, Dense/cold gas surrounded by thin/hot gas
matrix, Ordered (b
-Internal Structure of Stars and their Evolution
-Inside Stars the temperature is so high that atoms no longer can hold their electrons.
Atoms a gas of atomic nuclei surrounded by a sea of free electrons plasma.
-The Sun is in a state of Hydros
- EM Radiation II
-Refraction is the bending of light as it passes from one medium (air) into another
- Key point: light travels slightly slower in glass than it does in the air.
-How A Prism Makes A Rainbow:
Different colors (wavelen
-Light Gathering Power ~ Area of mirror ~ (mirror diameter)^2 (LGP ~ d^2.)
-The angular resolution of a telescope refers to the finest detail that it can see in an object.
Measured in arc-seconds
-Magnification is not angular resolution.
Uranus, Neptune, and Pluto
-William Herschel- discovered Georgium Sidus (Uranus) on accident, also
discovered infrared light.
-Orbit of Uranus peculiar, like something/another planet was tugging on it. John
Adams and Urbain Leverrier calculated
-A curious numerical relationship exists in the spacing of the planets orbits= Bodes
Law. Discovered by Johann Titius, made famous by Johann Bode.
-Giuesppe Piazzi discovered Ceres Ferdinandea (Ceres) at 2.8 A.U., right where
The Formation of the Solar System
-Regularity in the Solar System: 1.) All of the planets, asteroids, and short-period
comets are in the same orbital plane (except Pluto). 2.) All planets orbit the Sun in the same
sense as the Sun rotates (cou
-There is overwhelming observational evidence for other Solar Nebulae; lots of Solar
Nebulae within a few hundred light years of us.
-Problem with finding extra-solar planets: Stars are millions of times brighter than
-Intelligent Life on Other Worlds
-Enrico Fermi-Fermis Paradox: Given the size and age of the Milky Way galaxy many
advanced civilizations ought to exist. But we see no evidence of them: no radio
communications, no alien space probes, no alien
Ch.3 -Earliest attempt to determine shape of Milky Way (William Herschel): count number of stars in all directions concluded that MWG was a somewhat flattened and disk-like collection of stars, with Sun at center (accepted until early 1900's) -Globular Cl