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Concepts
things to remember
43
Astronomy
Undergraduate 3
12/15/2010

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Term
Light
Definition
-Electromagnetic radiation
-A form of energy
-acts like a wave AND a particle
-higher energy
-shorter wavelength
-bluer energy
-particles are called photons
-photon energy depends on wavelength
Term
Electromagnetic spectrum
Definition
Bluer----->Redder
-blue is shorter wavelengths
-red is longer wavelengths
Term
Light Year
Definition
-distance light travels in 1 year
-when we see an object, we see it as it was when light left it
Term
Star balance
Definition
-Gravity vs. Radiation
-90% H gas
Term
Star balance
Definition
-Gravity vs. Radiation
-90% H gas
Term
Nuclear Energy
Definition
4 H nuclei fuse into 1 He nucleus
Core: t~10^7
-Need High pressure and Temp
Term
Sun
Definition
T=5800 K
Radius= 7 X 10^8
Mass= 2 X 10^30
Luminosity= 3.8 X 10^26
-G Star
Term
Big Stars
Definition
-burn hot, blue
-burn bright
-burn fast
Term
small stars
Definition
-burn cool, red
-burn faint
-burn slow
Term
photo- ionization
Definition
photon with Electrons greater than threshold ionize
Term
H recombination
Definition
-recombines to excited states
-spontaneously de-excite
-produce photons only at transition electrons: Emission Line
Term
Emission-Line Spectrum
Definition
-Different Elements show unique patterns of emission lines
-transparent gas


-if the telescope was focused on the "cloud"

-E=hc/wavelength
Term
Absorption line spectrum
Definition
-if the telescope was pointed at star "THROUGH CLOUD"
-opaque gas
Term
Spectral types
Definition
O.B.A.F.G.K.M LT

(oh be a fine girl kiss me.....later though)

-classifies surface temperature
-Absorption line spectra
-ionization:energy==temperature
Term
Collisions
Definition
-ionize and excite
-depends on gas temp
Term
The Magnitude Scale
Definition
-0-6 naked eye
-bigger number is fainter
M=absolute brightness
m=apparent brightness
Term
pulsating variable stars
Definition
Cephei variables >300 L
RR Lyrae variables 100 L
Scuti variables 30-70L
Term
period-luminosity relation
Definition
-the longer the period the higher the luminosity
Term
Telescope advantages
Definition
-light collecting area: the larger the more light
-angular resolution: larger telescopes show finer detail
Term
Start of Golden Age
Definition
-pre-16th century: Basic Star charts vs. Illustrations
-16th Centruy: Accuracy + Artistry!!!!

Renaissance:
printing press
technology
exploration
Term
Sidereal day
Definition
face same star in 24 sidereal hours
Term
Stars burn out
Definition
-greater than 8 solar masses
Term
Black Hole
Definition
-black hole surface= event horizon
-NOTHING escapes event horizon
-thus no contact with anything inside
- gravity different only near Event Horizon
Term
Tidal forces
Definition
-lethal forces near 3 solar masses in event horizon
-stretch and squeezed
Term
Accretion disk
Definition
-strong gravity but tiny sink hole
-friction heats piled up infalling matter
-opaque and dense: hot thermal spectrum
Term
Main Sequence
Definition
-Stars have H-HE fusion IN CORE
Term
core vs. shell burning
Definition
H shell burning faster
-star swells
-he core grows, heats

Start Core He burning
-Star Hotter
-Burns Fainter
-Star Shrinks

Start He shell Burning
-Star Swell
-C core grows
Term
open clusters
Definition
pleiades
hyades
Term
M2 Globular cluster
Definition
500,000 stars
diameter 180 Ly
Age 13 BY
distance 38,000 LY
Term
M72 Globular cluster
Definition
100,000 stars
diameter 50LY
age 13BY
Distance 60,000 LY
Term
The Hyades
Definition
-5 sisters
-Nearest star cluster
*distance 150 LY
-age 65 million

Open Cluster
-300 smaller stars
-diameter 18 LY
Term
The Pleiades
Definition
M45, The seven sisters
-distance 430 LY
-Age 100 million yr
-open cluster
*1000+ smaller stars
Term
Open Vs. Globular
Definition
Open
-less than 10^4 stars
-age less than 8 BY
-disperse rapidly

Globular
-10^5 stars
-age 10-13BY
MW halo
-disperse slowly
Term
Iron
Definition
is dead end for fusion
Term
Supernova
Definition
-bright as a host galaxy
Term
End of the Golden Age
Definition
19th c:Technical vs. Popular
20th c:Figures de-emphasized
21st c:Digitized catalogs, software
Term
Synchrotron Continuous spectrum
Definition
Emitted at all wavelengths
-often seen in radio, x-ray, where stars are faint
-Emitted by electrons moving near speed of light around strong magnetic fields
-indicate extreme, relativistic conds
Term
Gravity wins if
Definition
H fusion ignites: star forms
H fusion fails: brown dwarf
Term
Binary Stars
Definition
-Visual
-Astronmetric
-Eclipsing
-Composite Spectrum
-Spectroscopic
Term
Eclipsing Binary
Definition
An eclipsing binary star is a binary star in which the orbit plane of the two stars lies so nearly in the line of sight of the observer that the components undergo mutual eclipses.
Term
Astrometric Binaries
Definition
are relatively nearby stars which can be seen to wobble around a point in space, with no visible companion.
Term
Binary Mass Transfer
Definition
Roche Lobes: surfaces of equal gravity force
Term
spectroscopic
Definition
-doppler effect
*red shift
*blue shift
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