Astronomy Test 2
Terms
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- Light as a wave
- Electric and magnetic fields that travel=Electromagnetic wave
- What EM waves can human eyes detect?
- 400nm-700nm
- Light as a particle (photon)
- Photon energy is proportional to 1/wavelenth
- Longer wavelength equals...
- less energy
- The electromagnetic spectrum
- Gamma ray, xray, ultraviolet, visible, infared, microwave, radio
- Two atmospheric windows
- visible, radio
- Telescopic Functions
-
Light gathering Power
Resolving Power
Magnifying power - Issac Newton
- Cut a slit in a curtain and passed the light through a prism for the colors
- Fraunhofer
- Passed light through curtain onto a diffraction grating and found dark lines. Labeled them.
- Bunsen and Kirchoff
- Passed light through heated chemicals and found bright lines. Discovered sodium on the sun
- Kirchoff's 1st Law
- If light passes through a hot, hig density solid, liquid, or gas, you get a continuous spectrum
- Kirchoff's 2nd Law
- Hot, low density gas gives off a bright line spectrum
- Kirchoff's 3rd Law
- Source of continous spectrum light passes through a cooler, low density gas creating a dark line spectrum
- Bohr
- Spectral lines are due to atomic electrons changing energy levels
- Photons are Absorbed
- dark line spectrum
- Photons are Emitted
- Bright Line Spectrum
- Balmer Series
- Electrons jumping up or down from energy level 2
- Parallax
- apparent change in an objects position due to a change in the observers location
- Parallax Method
- distance in parsecs=1/parallax angle in arc seconds
- Parallex Measurements Largest to smallest
- 0.77 arc sec-0.002 arc sec
- Apparent Magnitude
- how bright a star appears to be (negative is brighter)
- Absolute Magnitude
- measure of the light output of a star
- When does (m) = (M)?
- When the distance is 10pc
- Range of M for stars
- -10 to +20
- Luminosity
- measure of the light output of a star
- Rangle of L for stars
- 10 to the power of 6-10 to the power of -6
- Proper Motion
- motion perpendicular to the line of sight-moving side to side
- Radial motion
- motion along the line of sight-moving toward or away
- Doppler Effect-Moving towards
- Blue
- Moving away
- Red
- Black Body
- hot solid, liquid, or a hot, high density gas
- Black Body Radiation
- light emitted by a hot object
- Wien's Law
- temperature is proportional to 1/wavelength max
- What is Wien's law saying?
- cool stars are red, hot stars are blue
- Stefan Boltzmann Law
- L is proportional to radius squared * temperature to the fourth power
- Are stars black bodies?
- Almost, they have valleys in the dark line
- What type of spectra does a star give off?
- A dark line
- What can we find from a stars spectrum?
-
Chemical Composition
Radial Motion
Surface Temperature - Chemical composition
- by line patterns
- Surface Temperature
- strength of spectral lines
- Stellar Spectral Types
- OBAFGKM
- Hertzsprung-Russell Diagram
- M vs. Spectral Type
- Stellar Size
- Stefan Boltzmann law-range from 0.01R Sun-1000R Sun
- Stellar Mass
- mass a/mass b=distance b/distance a
- Newton's form of Kepler's 3rd Law
- mass a + mass b= a AU cubed/P years squared
- Range of masses
- 0.08 solar masses-100 solar masses
- Stellar density range
- 10 to the -6g/cm cubed-10 to the 7 g/cm cubed
- Innerstellar Medium Composition
- 3/4 hydrogen, 1/4 helium, 2% heavier elements
- ISM Density
- 1 atom/cm cubed
- Giant Molecular Clouds density, size, and temperature
-
100 atoms/cm cubed
big
cold - Hydrostatic Equilibrium
- balance between inward gravity and outward energy released from fusion
- How do stars form
- Shockwave goes through giant moecular cloud creating dense cores. Gravity starts to collapse these dense cores. A protostar (nucleus) forms in the dense core. Protostar gives off heat and creates energy. Hydrostatic Equilibrium occurs.