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UA / Astronomy / PH/AY 101 / What is Diffuse Gas?

What is Diffuse Gas?

What is Diffuse Gas?


School: University of Alabama - Tuscaloosa
Department: Astronomy
Course: AY 101 - Intro to Astronomy - Jeremy Bailin
Professor: Jeremy bailin
Term: Spring 2015
Cost: 50
Name: AY 101 Midterm 2 Study Guide
Description: Covers class notes since past exam
Uploaded: 10/10/2016
6 Pages 4 Views 11 Unlocks

AY 101 - Midterm #2 Study Guide

What is Diffuse Gas?

∙ White light – reflects all colors

Spectrums— [Kirchoff’s Laws]

1. Continuous Spectrum










2. Emission Line Spectrum










3. Absorption Line Spectrum










∙ Temperature is a measurement of thermal energy

o As temperature increases, particles begin to move quicker



o Blue photons have more energy than red photons (blue fire hotter than red) o Higher energy = shorter wavelength = higher temperature

o Lower energy = longer wavelength = lower temperature

Diffuse Gas – photons interact with individual atoms

Dense Material – photons interact with ensembles of atoms

What is Dense Material ?

∙ Negative electrons orbit around positive nucleus, electromagnetic attraction instead of gravity ∙ Can only orbit at fixed energy levels that are quantized (discrete)




Chemical Fingerprints –


∙ The energy levels of the atom depend on the element We also discuss several other topics like What is the function of cerebellum?

∙ The wavelengths of the lines tell you what the gas is made out of Don't forget about the age old question of What lures new firms to enter industry?

∙ Vary from element to element

Electromagnetic energy is different when you have different numbers of protons and electrons

Terrestrial Planets:

∙ Mercury

∙ Mars

∙ Earth

∙ Venus

o “Terra” = earth, made of dense solids (rock, metal)

o Differentiated – dense material sunk to center

How Can We Tell Internal Structures?

∙ Vibrations from earthquakes travel through Earth’s interior

How Can We Tell Internal Structures?

∙ Some types of waves (like soundwaves) can travel through both liquid and solid ∙ Some (transverse) can only travel through solid

∙ Internal heat rises faster than cooling rate for larger planets; big planets cool and solidify slower

Important Physical Processes

∙ Heat from the Sun

o The closer a planet is to the sun, the more energy it receives (hotter surface) o In the absence of other effects, earth would be too cold for liquid water

∙ Greenhouse Gases

o Heat gets trapped, raising temperature

o Most important gases – water vapor, CO2, methane

Geological Activity

∙ If the outside of a planet is molten:

o Tectonics (renews surface)

o Magnetic Field (protects atmosphere)

o Volcanoes (outgas H20, C02, N2)

Earth as an Example

∙ Large, inside is still molten hot

o Volcanoes: provided N2, CO2, H2O; greenhouse effect Don't forget about the age old question of What is the humanitarian reform?

o Tectonics: erase impact craters

o Magnetic Field: protects atmosphere

∙ Moderate distance from sun

o Liquid water temperatures (with greenhouse effect)

o Most CO2 dissolved into oceans, now in seafloor rock

∙ Life

o O2 in atmosphere

o Non-equilibrium chemistry (ozone, excess CO2)


∙ Mainly rock/metal, like Terrestrial worlds

∙ Spaced far apart (70km between neighbors)

Kuiper Belt Objects (DON’T NEED TO MEMORIZE)

∙ Weywot

∙ Quaoar

∙ Sedna

∙ Hi’iaka, Namaka ∙ Makemake ∙ Orcus

∙ Ixion

∙ Varuna

∙ AW197

∙ Eris

∙ Dysnomia

∙ Charon, Hydra, Nix ∙ Pluto

Pluto and Charon

∙ New horizons spacecraft flew past July, data from flyby slowly coming in (will be for years) ∙ Universal expectation: too small, too little tidal forces to keep insides molten. Ought to be dead  worlds covered in craters


∙ Sometimes outer solar system objects get perturbed into orbits that approach the sun ∙ When we measure their orbits, ost go out to either 50-100 AU (Kuiper Belt) or about 100,000 AU  (Oort Cloud) Don't forget about the age old question of Where are pigments that function as attractants stored in a Plant cell?

∙ When a comet begins to heat up, it starts to sublimate into the atmosphere o On Friday, Rosetta Spacecraft soft-crashed into Comet 67P

∙ Tails formed by gasses that sublimate off the nucleus, small dirt grains that come out o Tail always point away from the sun 

∙ Pushed away from the sun by solar wind

Formation of the Solar System

∙ Key Observations:

o Terrestrial v Jovian Planets

o Flat plane with mostly circular orbits

o Most orbits and rotation are in the same direction

Meteor Showers

∙ If Earth passes through the former path of a comet, the dirt grains burn up in our atmosphere Protosolar Nebula

∙ Collapsing very slowly-spinning gas cloud

o Turns gravitational potential energy into thermal energy (heats up)

o Conserves angular momentum as it gets smaller (Spins up and flattens)

∙ Different substances in protosolar nebula condensed (solidified) at different temperatures o More substances could condense farther from the sun, where it was cooler


∙ Small solid planetesimals congregate together to form larger objects

o Rock and metal planetesimals congregate to form rocky/metal objects

o Rock, metal, and ice planetesimals congregate to form (guess what) rocky/metal/icy  objects

Rocky v. Icy Seeds

∙ Within the frost line: Don't forget about the age old question of ∙ Where do my original files need to reside?

o Just rock and metal, which don’t stick well

▪ Think of making a “rockball” compared to a snowball

∙ Outside frost line:

o Rock, metal and ice (more material), ice is stickier (snowballs)

∙ Larger planetary cores can be formed outside the frost line

-Size of protoplanetary cores depends where they form

-Just rock and metal seeds, not sticky, not so much material - small protoplanetary cores

Accretion of Gas 

-if the protoplanetary core is massive enough (10 M(Earth)) OR "10 earth masses" -Gravity of protoplanet is strong enough to attract hydrogen and helium gas -protoplanet acquires gas, becomes more massive

-runaway growth of planet

-Does 10 M(Earth) sound familiar? Why?

-Jovian planets hit 10 earth masses, allowing them to hold more hydrogen and helium -NOTE: main key difference between Jovian and Terrestrial planets (know for exam)

Inner v Outer Planets 

-Inside frost line: rock and metal  

< 10 M(Earth) Don't forget about the age old question of Animal behavior is about what types of interactions?

-Terrestrial Planets

-Outside frost line: Rock, metal, and ice

> 10 M(Earth)

-Grow larger by accretion of hydrogen and helium gas

-Jovian Planets

-Once the sun starts shining, it blows away the protoplanetary nebula (no more gas) and planet  formation ends

Overview of Solar System Formation 

(1) Contact, heat up, spin

(2) Solid rock,, ice particles condense

(3) Rocky and ice planetestimals congregate, accrete gas

(4) remaining gas blown away (sun "turns" on)

-Tends to take 100,000 years > FORMATION < 1,000,000 years

Explanation of Observations 

-Flat rotating solar system

-from flattened rotating gas cloud

-orbits and rotation mostly in the same direction:

-from flattened rotating gas cloud

-Terrestrial v Jovian Planets

-Terrestrial planets form inside the frost line, Jovian planets form outside the frost line NOTE: This also applies to other solar systems

Nebular Hypothesis: equivalent to the big bang theory just in regards to ONLY the formation of  our solar system, not the universe

Extrasolar Planets ("Exoplanets") 

-21 years ago +1 day: no planets had ever been detected outside the solar system -Now: 3533 confirmed planets

-The problem:

-difficult to see a very faint planet because it is right next to a much brighter star

Detecting Exoplanets 

-Main techniques

-transits: if a planet passes in front of a star, the star's light is blocked and it gets fainter -most exoplanets to date have been found this way by the Kepler space  telescope


-planet blocks lot of the star's light (large radius)

-multiple transits in the few short years we have been looking (very  

close to the star)

-perfectly aligned orbit (random chance - only 1% of orbits line up right)

-Radial Velocity: massive planets pull on their starm which wobbles back and forth -motion towards/away from us measurable by Doppler blueshift/redshift -until Kepler, most were discovered this way


-large force (large mass, small distance to star)

-several orbits during the few short years we have been looking (close  

to star)  

-Direct Imaging: Only very occasionally possible if light from star can be blocked out -very few planets have been directly imaged


-bright planet (big, young)

-far from star

Exciting Exoplanet Results 

-planets are common

-at least 50% of stars have at least one planet

-multiple planet systems (like ours) are common

-earth-mass planets in Earth-like orbits exist in other systems

-the closest star to the sun (Proxima Centauri) appears to have an earth-like planet (Proxima B)  (Just announced August 24th of this year)

-kepler-11 has at least 6 planets

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