Messier's Catalogue and Shapley-Curtis Debate
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Questions and Answers

What significant shift in understanding did Shapley contribute to astronomy?

  • He moved the solar system from the center of the universe. (correct)
  • He suggested that the Earth is at the center of the universe.
  • He confirmed that the Milky Way was the only galaxy.
  • He discovered the existence of black holes.

    • What does the cosmic distance ladder aim to achieve?

  • It helps measure distances to celestial objects over a large range of scales. (correct)
  • It provides a singular method of distance measurement in astronomy.
  • It categorizes galaxies based on their distance from Earth.
  • It helps to categorize stars into different types based on size.

    • Which term refers to objects whose intrinsic properties are known, used to measure astronomical distances?

  • Standard ruler
  • Distance marker
  • Standard candle (correct)
  • Astronomical guide

    • What is a standard ruler in the context of the cosmic distance ladder?

    <p>An object whose size is known.</p> Signup and view all the answers

    Why is it difficult to use some methods for astronomical distance measurement?

    <p>Intrinsic properties of celestial objects are often unknown.</p> Signup and view all the answers

    What did Charles Messier's catalogue primarily include?

    <p>Fuzzy objects later termed spiral nebulae</p> Signup and view all the answers

    What was one of Shapley's arguments regarding the nature of the spiral nebulae?

    <p>Their relative size suggests they are part of the Milky Way.</p> Signup and view all the answers

    Which observation led Maanen to believe spiral nebulae might not be part of the Milky Way?

    <p>The rotation of a spiral nebula over a few years.</p> Signup and view all the answers

    What central question arose from the Shapley-Curtis debate?

    <p>What is the nature of our galaxy and spiral nebulae?</p> Signup and view all the answers

    How did Curtis argue against Shpley's claims about the spiral nebulae?

    <p>By noting the dark paths present in photographs of nebulae.</p> Signup and view all the answers

    What conclusion did Curtis reach regarding spiral nebulae?

    <p>They are distant galaxies similar to the Milky Way.</p> Signup and view all the answers

    What were the nova occurrence rates in the Milky Way compared to M31 significant for?

    <p>Arguing the uniqueness of M31.</p> Signup and view all the answers

    What was one major aspect Shapley used to contest Curtis's point about the spiral nebulae?

    <p>Their brightness during a nova event.</p> Signup and view all the answers

    Study Notes

    Messier's Catalogue and the Shapley-Curtis Debate

    • Charles Messier, a French comet hunter, created a catalogue of astronomical objects, including fuzzy objects later identified as spiral nebulae.
    • Messier numbers are still used to refer to these objects.
    • The nature of our galaxy and the nature of spiral nebulae were key questions in the Shapley-Curtis debate.

    Shapley's Arguments

    • Shapley estimated the Milky Way (MW) was much larger than previously thought, placing the solar system thousands of light-years from the galactic centre.
    • He argued spiral nebulae were within the MW based on three main arguments:
      • Relative size: If spiral nebulae were similar in size to the MW, they would need to be millions of light-years away, which Shapley considered unlikely.
      • Relative brightness of novae: A nova in Andromeda (M31) briefly outshone the nebula, implying, according to Shapley, excessive energy output if it were a distant galaxy.
      • Maanen's observations: Observations of spiral nebulae rotating over a few years suggested velocities exceeding light speed if they were outside the MW, which was considered impossible.

    Curtis's Arguments

    • Curtis supported the "island universes" theory, suggesting spiral nebulae are distant galaxies like the MW.
    • He used scientific publications to support his arguments, including:
      • Dark paths: Photographs of spiral nebulae showed dark paths similar to those observed within the MW, implying they could be distant galaxies.
      • Nova occurrences: A higher rate of nova occurrences in M31 compared to the MW suggested it was a distinct astronomical object rather than a small section of the MW.

    Shapley and Curtis's Contributions

    • Shapley significantly altered our understanding of the MW's size and the solar system's position within it.
    • Curtis established that our galaxy is one of many in a vast universe.

    Cosmic Distance Ladder

    • Measuring cosmic distances requires various methods, not a single universal method.
    • The cosmic distance ladder consists of a series of methods that build on each other, to get progressively longer distances, because methods can't be directly used on all ranges.
    • Methods often relate to standard candles or standard rulers:
      • Standard candle: objects with known intrinsic luminosity used to measure distance from apparent brightness.
      • Standard ruler: objects with known size used to measure distance from apparent size.
    • Fundamental distance measurement methods don't rely on the object's nature.

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    Description

    Explore the pivotal arguments of the Shapley-Curtis debate about the size and nature of our galaxy. Delve into Charles Messier's contributions to astronomy and how his catalogue influenced perceptions of spiral nebulae. Understand the dynamics between the Milky Way and these celestial objects through key observations.

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