test 2: overview. the total energy radiated from entire surface every second is called the...
TRANSCRIPT
![Page 1: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/1.jpg)
Test 2: Overview
![Page 2: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/2.jpg)
The total energy radiated from entire surface every second is called the luminosity. Thus
Luminosity = (energy radiated per cm2 per sec) x (area of surface in cm2)
For a sphere, area of surface is 4R2, where R is the sphere's radius.
![Page 3: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/3.jpg)
The "Inverse-Square" Law Applies to Radiation
apparent brightness 1D2
D is the distance between source and observer.
Each square gets 1/9 of the light
Each square gets 1/4 of the light
![Page 4: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/4.jpg)
The frequency or wavelength of a wave depends on the relative motion of the source and the observer.
![Page 5: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/5.jpg)
Types of Spectra
1. "Continuous" spectrum - radiation over a broad range of wavelengths(light: bright at every color).
3. Continuous spectrum with "absorption lines": bright over a broad range of wavelengths with a few dark lines.
2. "Emission line" spectrum - bright at specific wavelengths only.
![Page 6: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/6.jpg)
Kirchhoff's Laws
1. A hot, opaque solid, liquid or dense gas produces a continuous spectrum.
2. A transparent hot gas produces an emission line spectrum.
3. A transparent, cool gas absorbs wavelengths from a continuous spectrum, producing an absorption line spectrum.
![Page 7: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/7.jpg)
The pattern of emission (or absorption) lines is a fingerprint of the element in the gas (such as hydrogen, neon, etc.)
For a given element, emission and absorption lines occur at the same wavlengths.
Sodium emission and absorption spectra
![Page 8: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/8.jpg)
Stellar Spectra
Spectra of stars are different mainly due to temperature and composition differences.
Star
'Atmosphere', atoms and ions absorb specific
wavelengths of the black-body spectrum
Interior, hot and dense, fusion
generates radiation with black-body
spectrum
![Page 9: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/9.jpg)
The Nature of Atoms
The Bohr model of the Hydrogen atom:
_
+proton
electron
"ground state"
_
+
an "excited state"
Ground state is the lowest energy state. Atom must gain energy to move to an excited state. It must absorb a photon or collide with another atom.
![Page 10: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/10.jpg)
But, only certain energies (or orbits) are allowed:
__
_
+
The atom can only absorb photons with exactly the right energy to boost the electron to one of its higher levels.
(photon energy αfrequency)
a few energy levels of H atom
![Page 11: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/11.jpg)
When an atom absorbs a photon, it moves to a higher energy state briefly
When it jumps back to lower energy state, it emits a photon - in a random direction
![Page 12: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/12.jpg)
Ionization
+
Hydrogen
_
++
Helium
"Ion"
Two atoms colliding can also lead to ionization.
_
_
Energetic UV Photon
Atom
Energetic UV Photon
![Page 13: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/13.jpg)
13Radio Window
![Page 14: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/14.jpg)
Optical Telescopes - Refracting vs. Reflecting
Refracting telescope
Focuses light with a lens (like a camera).
<-- object (point of light) image at focus
Problems:
- Lens can only be supported around edge.
- "Chromatic aberration".
- Some light absorbed in glass (especially UV, infrared).
- Air bubbles and imperfections affect image quality.
![Page 15: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/15.jpg)
Chromatic Aberration
Lens - different colors focus at different places.
white light
Mirror - reflection angle doesn't depend on color.
![Page 16: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/16.jpg)
Reflecting telescope
Focuses light with a curved mirror.
<-- object image
- Can make bigger mirrors since they are supported from behind.
- No chromatic aberration.
- Reflects all radiation with little loss by absorption.
![Page 17: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/17.jpg)
Image of Andromeda galaxy with optical telescope.
Image with telescope of twice the diameter, same exposure time.
![Page 18: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/18.jpg)
Resolving Power of a Mirror
(how much detail can you see?)
fuzziness you would see with your eye.
detail you can see with a telescope.
Andromeda Galaxy: (a) 10 arcminutes, (b) 1 arcminute, (c) 5 arcseconds, and (d) 1 arcsecond
![Page 19: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/19.jpg)
Seeing
*
dome
Air density varies => bends light. No longer parallel
Parallel rays enter atmosphere
CCD
No blurring case. Rays brought to same focus.
* Sharp image on CCD.
Blurring. Rays not parallel. Can't be brought into focus.
Blurred image.
![Page 20: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/20.jpg)
Radio Telescopes
Large metal dish acts as a mirror for radio waves. Radio receiver at focus.
Surface accuracy not so important, so easy to make large one.
angular resolution α wavelengthmirror diameter
D larger than optical case, but wavelength much larger (cm's to m's), e.g. for wavelength = 1 cm, diameter = 100 m, resolution = 20".
Jodrell Bank 76-m (England)But angular resolution is poor. Remember:
![Page 21: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/21.jpg)
Interferometry
A technique to get improved angular resolution using an array of telescopes. Most common in radio, but also limited optical interferometry.
D
Consider two dishes with separation D vs. one dish of diameter D.By combining the radio waves from the two dishes, the achieved angular resolution is the same as the large dish.
![Page 22: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/22.jpg)
Orbits of Planets
All orbit in same direction.
Most orbit in same plane.
Elliptical orbits, but low eccentricity for most, so nearly circular.
![Page 23: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/23.jpg)
Two Kinds of “Classical” Planets
"Terrestrial"
Mercury, Venus,Earth, Mars
"Jovian"
Jupiter, Saturn, Uranus, Neptune
Close to the SunSmall
Far from the SunLarge
Few MoonsNo RingsMain Elements Fe, Si, C, O, N:we learn that from the spectra
Mostly RockyHigh Density (3.3 -5.3 g/cm3) reminder: liquid water is 1 g/cm3
Slow Rotation (1 - 243 days)
Mostly GaseousLow Density (0.7 -1.6 g/cm3)
Many MoonsRingsMain Elements H, He
Fast Rotation (0.41 - 0.72 days)
![Page 24: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/24.jpg)
Dwarf Planets compared to Terrestrial Planets
"Terrestrial"
Mercury, Venus,Earth, Mars
Dwarf Planets
Pluto, Eris, many others
Close to the SunSmall
Far from the SunVery small
Few MoonsNo RingsMain Elements Fe, Si, C, O, N
Mostly RockyHigh Density (3.3 -5.3 g/cm3)Slow Rotation (1 - 243 days)
Rock and IceModerate Density (2 - 3 g/cm3)
Few MoonsNo RingsMain Elements Fe, Si, C, O, N And an icy surface
Rotation?
![Page 25: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/25.jpg)
Early Ideas
René Descartes (1596 -1650) nebular theory:
Solar system formed out of a "whirlpool" in a "universal fluid". Planets formed out of eddies in the fluid. Sun formed at center. Planets in cooler regions. Cloud called "Solar Nebula".
This is pre-Newton and modern science. But basic idea correct, and the theory evolved as science advanced, as we'll see.
![Page 26: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/26.jpg)
A cloud of interstellar gas
The associated dust blocks starlight. Composition mostly H, He.
a few light-years,or about 1000times bigger thanSolar System
Too cold for optical emission but some radio spectral lines from molecules. Doppler shifts of lines indicate clouds rotate at a few km/s.
Clumps within such clouds collapse to form stars or clusters of stars. They are spinning at about 1 km/s.
![Page 27: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/27.jpg)
Now to make the planets . . .
Solar Nebula:
98% of mass is gas (H, He) 2% in dust grains (Fe, C, Si . . .)
Condensation theory: 3 steps:
1) Dust grains act as "condensation nuclei": gas atoms stick to them => growth of first clumps of matter.
2) Accretion: Clumps collide and stick => larger clumps. Eventually, small-moon sized objects: "planetesimals".
3) Gravity-enhanced accretion: objects now have significant gravity. Mutual attraction accelerates accretion. Bigger objects grow faster => a few planet-sized objects.
![Page 28: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/28.jpg)
Result from computer simulation of planet growth
Shows growth of terrestrial planets. If Jupiter's gravity not included, fifth terrestrial planet forms in Asteroid Belt. If Jupiter's gravity included, orbits of planetesimals there are disrupted. Almost all ejected from Solar System.
Simulations also suggest that a few Mars-size objects formed in Asteroid Belt. Their gravity modified orbits of other planetesimals, before they too were ejected by Jupiter's gravity.
Asteroid Ida
![Page 29: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/29.jpg)
The Structure of the Solar System
~ 45 AU~ 5 AU
L4
L5
L3
![Page 30: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/30.jpg)
Asteroids and meteoroids have rocky composition; asteroids are bigger.
(above) Asteroid Ida with its moon, Dactyl
(below) Asteroid Gaspra
(above) Asteroid Mathilde
Interplanetary Matter: Asteroids
![Page 31: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/31.jpg)
Comets are icy, with some rocky parts.
The basic components of a comet
Interplanetary Matter: Comets
![Page 32: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/32.jpg)
Oort Cloud
The size, shape, and orientation of cometary orbits depend on their location. Oort cloud comets rarely enter the inner solar system.
![Page 33: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/33.jpg)
Meteor Showers
Meteor showers are associated with comets – they are the debris left over when a comet breaks up.
![Page 34: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/34.jpg)
Earth's Internal Structure
Crust: thin. Much Si and Al(lots of granite). Two-thirds covered by oceans.
How do we know? Earthquakes. See later
Mantle is mostly solid, mostly basalt (Fe, Mg, Si). Cracks in mantle allow molten material to rise => volcanoes.
Core temperature is 6000 K. Metallic - mostly nickel and iron. Outer core molten, innercore solid.
Atmosphere very thin
![Page 35: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/35.jpg)
EarthquakesThey are vibrations in the solid Earth, or seismic waves.
Two kinds go through Earth, P-waves ("primary") and S-waves ("secondary"):
![Page 36: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/36.jpg)
Like all waves, seismic waves bend when they encounter changes in density. If density change is gradual, wave path is curved.
S-waves are unable to travel in liquid.
Thus, measurement of seismic wave gives info on density of Earth's interior and which layers are solid/molten.
But faint P wavesseen in shadow zone,refracting off denseinner core
Curved paths ofP and S waves:density must slowlyincrease with depth
Zone with no S waves:must be a liquid corethat stops them
No P waves too:they must bend sharplyat core boundary
![Page 37: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/37.jpg)
Earthquakes and volcanoes are related, and also don't occur at random places. They outline plates.
Plates moving at a few cm/year. "Continental drift" or "plate tectonics"
![Page 38: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/38.jpg)
What causes the drift?
Convection! Mantle slightly fluid and can support convection. Plates ride on top of convective cells. Lava flows through cell boundaries. Earth loses internal heat this way.
Cycles take ~108 years.
Plates form lithosphere (crust and solid upper mantle).Partially melted, circulating part of mantle is asthenosphere.
![Page 39: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/39.jpg)
When plates meet...
1) Head-on collision (Himalayas)
2) "Subduction zone" (one slides under the other) (Andes)
3) "Rift zone" (two plates moving apart) (Mid-Atlantic Ridge)
4) They may just slide past each other (San Andreas Fault)
side view
top view
=> mountain ranges, trenches, earthquakes, volcanoes
![Page 40: Test 2: Overview. The total energy radiated from entire surface every second is called the luminosity. Thus Luminosity = (energy radiated per cm 2 per](https://reader036.vdocuments.mx/reader036/viewer/2022062423/56649e495503460f94b3c9ce/html5/thumbnails/40.jpg)
The Greenhouse Effect
Main greenhouse gases are H
2O and
CO2 .
If no greenhouse effect, surface would be 40 oC cooler!