measuring the stars (part iii)
DESCRIPTION
Measuring the Stars (Part III). The “ Cosmic Distance Ladder ”. Visual “ Parallax ”. Let’s us “see” 3D images (depth). “ Binocular Vision”…. …but, how to do this to get Astronomical Distances ?. Using Earth’s Orbit as a “Baseline”!. “ Stellar Parallax” …. “ Standard Candles ” - PowerPoint PPT PresentationTRANSCRIPT
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Measuring the Stars(Part III)
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The “Cosmic Distance Ladder”
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Visual“Parallax”
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“Binocular Vision”… Let’s us “see” 3D images (depth)
…but, how to do this to get Astronomical Distances?
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“Stellar Parallax”… Using Earth’s Orbit as a “Baseline”!
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“Standard Candles” as Distance Indicators... :
𝐹𝑙𝑢𝑥∝ 𝐿𝑢𝑚𝑖𝑛𝑜𝑠𝑖𝑡𝑦𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒2
(Measured)(Known,
“Standard Candle”!)
( Can now be Calculated !)
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Main Sequence Stars as
Standard Candles!
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(Both K-type!)
But how to tell apart Main Sequence stars from non-Main-Seq. stars, for Spectroscopic Parallax…?
Small, Dense (Main Seq.) stars have broader Spectral Lines than “puffy” Giant stars… :
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Turning “Variable Stars”into Standard Candles for finding distances... :
Cepheid “Period-Luminosity Relationship”
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If () now known This Rotating Galaxy is a Standard Candle!
Faster Rotation More Gravity More Mass More Light (…we assume…!)
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White Dwarfs (w/companions) always blow up (“Type Ia Supernova”) at the Chandrasekhar Mass (M = 1.4 x MSun):
…Standard Explosion Standard Luminosity Standard Candle!
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Know Distance to a Supernova Know Distance to its Host Galaxy
Can “Map” the Cosmic Large-Scale (Galactic) Structure!
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Brighter Supernovae glow longer than dimmer Supernovae…
Since 1995, Type Ia Supernovae now have very well known Luminosities… Even better Standard Candles!
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1998: Type Ia Supernova Standard Candle data proved that the Expansion Rate of the Universe is Accelerating!
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2011
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“Hubble’s Law”:V = H0 x D
(Velocity = Hubble’s Constant x Distance)
Other Galaxies all Doppler Redshifted… Expanding Universe makes them recede from us!
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Cosmic Distance Mapping the Universe?? Ladder
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Cosmic Distance Ladder Mapping the Universe!