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Announcements Astronomy 101A 10/05/11
Jacobsen Observatory 8:30 - 9:30 pm OPTIONAL (especially if it is not clear)
Review for exam 1 on Friday; exam 1 Monday, 10/10– Will have summer’s exam on-line soon (will
announce) for study purposes– Mix of short answers, fill in blanks, short essay,
reading star map, vocabulary
Exercise on spectral analysis in sections tomorrow - important for next 2 weeks! (and, your scores)
2Wavelength (meters)
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If we could see at IR wavelengths, what would we see?
Radio waves
Infrared Radiation
Microwaves
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Ultraviolet A, B, C
X-Rays
Gamma Rays
The Sun’s UV rays can cause:
* More wrinkles * Sagging skin * Age or liver spots * Tan/sunburn * Eye damage/ cataracts * Skin Cancer
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Messier 82 (M82)
optical
infrared
Color Coded:
Blue - x-ray
Red - optical
Green - wavelength = 3 mm
CO molecule (H2)
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o Define light (electromagnetic radiation) and
describe how we characterize it
o List 3 ways that light is created
o Explain why stars appear to be different colors
and how we use this property
o Distinguish between emission and absorption
spectra by what is happening with the electron in
the atom.
Learning goalsLearning goals
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o Define light (electromagnetic radiation) and
describe how we characterize it
o List 3 ways that light is created
o Explain why stars appear to be different colors and how we use this
property
o Distinguish between emission and absorption spectra by what is
happening with the electron in the atom.
Learning goalsLearning goals
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Light measured in wavelength , frequency or photon energy; light has the velocity c in a vacuum
Why are outer ends “black”?
Define light (electromagnetic radiation) and describe how we characterize it Define light (electromagnetic radiation) and describe how we characterize it
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Light can behave as a wave OR a PARTICLE!
E = h[Planck’s Constant:
EnergyFrequency (nu)
RODS & CONES
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•Oscillation of electric and magnetic fields•Propagates through space and some materials
Electromagnetic Radiation:
o- blackbody radiation (thermal)o- emission as electrons lose energy in an atomo- electrons spiraling in a magnetic field
Produced By:Produced By:
Define light (electromagnetic radiation) and describe how we characterize it Define light (electromagnetic radiation) and describe how we characterize it
List 3 ways that light is created (astronomically speaking) List 3 ways that light is created (astronomically speaking)
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o Define light (electromagnetic radiation) and describe how we
characterize it
o List 3 ways that light is created.
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o Define light (electromagnetic radiation) and describe how we characterize it
o List 3 ways that light is created
o Explain why stars appear to be different colors
and how we use this propertyo Distinguish between emission and absorption spectra by what is happening with the
electron in the atom.
Learning goalsLearning goals
Please take out a full sheet of paper, and put your name, and section (or TA’s name) at the top. Unannounced participation activity!
Please take out a full sheet of paper, and put your name, and section (or TA’s name) at the top. Unannounced participation activity!
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Continuous Spectrum - created by thermal radiator (blackbody radiation)
Hotter stars look more blue-white than cooler stars because hot stars emit most of their light at shorter wavelengths.
€
peak =2.9 ×106
T nm
T = 2.9 ×106
λ peak
K
Wien’s LawWien’s Law
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Star field in Sagittarius Explain why stars appear to be different colors and how we use this property Explain why stars appear to be different colors and how we use this property
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Tutorial: Blackbody Radiation
Violet, green/yellow, red; very little blue or yellow/orange.
a)
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Stars A & B
C
When objects emit light over all wavelengths, they look white, so star A will be whitish. Star C is emitting loght mostly in yellow/red, so will look “redder.”
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Different surface temperatures
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o Define light (electromagnetic radiation) and describe how we characterize it
o List 3 ways that light is created
o Explain why stars appear to be different colors and how we use this property
o Distinguish between emission and absorption spectra
by what is happening with the electron in the atom.
Learning goalsLearning goals
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Physical processes behind emission and absorption by atoms (representation of hydrogen energy levels):
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2
3
456
Ene
rgy
leve
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21 Distinguish between emission and absorption spectra by what is happening with the electron in the atom. Distinguish between emission and absorption spectra by what is happening with the electron in the atom.
22 Distinguish between emission and absorption spectra by what is happening with the electron in the atom. Distinguish between emission and absorption spectra by what is happening with the electron in the atom.
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Idealized Realistic
Distinguish between emission and absorption spectra by what is happening with the electron in the atom. Distinguish between emission and absorption spectra by what is happening with the electron in the atom.
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Emission vs absorption spectra
