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Understanding the Cosmic Distance Ladder: From Stellar Parallax to Type Ia Supernovae

Explore the intricate methods of measuring astronomical distances using the Cosmic Distance Ladder. This comprehensive guide delves into stellar parallax, employing Earth's orbit as a baseline, and standard candles, including main sequence stars and Type Ia supernovae. Discover the significance of the Cepheid period-luminosity relationship and how it assists in determining distances to galaxies. By understanding these concepts, we can map the universe and comprehend its accelerating expansion, evidenced by Hubble's Law and supernova luminosities.

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Understanding the Cosmic Distance Ladder: From Stellar Parallax to Type Ia Supernovae

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Presentation Transcript

  1. Measuring the Stars (Part III)

  2. The “Cosmic Distance Ladder”

  3. Visual “Parallax”

  4. Let’s us “see” 3D images (depth) “Binocular Vision”… …but, how to do this to get Astronomical Distances?

  5. Using Earth’s Orbit as a “Baseline”! “Stellar Parallax”…

  6. “Standard Candles” as Distance Indicators... : (Known, “Standard Candle”!) (Measured) ( Can now be Calculated !)

  7. Main Sequence Stars as Standard Candles!

  8. 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… : (Both K-type!)

  9. Turning “Variable Stars” into Standard Candles for finding distances... : Cepheid “Period-Luminosity Relationship”

  10. FasterRotation MoreGravity  MoreMass MoreLight(…we assume…!) If () now known This Rotating Galaxy is a Standard Candle!

  11. 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!

  12. Know Distance toaSupernova Know Distance to its Host Galaxy Can “Map” the CosmicLarge-Scale (Galactic) Structure!

  13. Brighter Supernovae glow longer than dimmer Supernovae… Since 1995, Type Ia Supernovae now have very well known Luminosities…  Even betterStandard Candles!

  14. 1998: Type Ia Supernova Standard Candle data proved that the Expansion Rate of the Universe is Accelerating!

  15. 2011

  16. Other Galaxies all Doppler Redshifted… Expanding Universemakes them recede from us! “Hubble’s Law”: V = H0 x D (Velocity = Hubble’s Constant x Distance)

  17. Cosmic Distance  Mapping the Universe?? Ladder

  18. Cosmic Distance Ladder  Mapping the Universe!

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