Stellar Classification and HR Diagram Quiz

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Questions and Answers

What is the subclassification for supergiant stars?

  • IIa or IIb
  • IIIa or IIIb
  • Ia or Ib (correct)
  • IVa or IVb

What is the key indicator used to assess the age of star clusters?

  • Color index
  • Distance from Earth
  • Luminosity in solar units
  • Turnoff point on the main sequence (correct)

What is the point of entry to the main sequence called?

  • Post-main sequence
  • Zero age main sequence (ZAMS) (correct)
  • Protostar stage
  • Supergiant stage

What are the stars in a star cluster like in terms of age and distance?

<p>Same age and about the same distance from Earth (B)</p> Signup and view all the answers

What is the conventional way to denote stars?

<p>Spectral class followed by luminosity class Roman numerals (D)</p> Signup and view all the answers

What does the y-axis of the Hertzsprung-Russell diagram represent?

<p>Luminosity in units of the Sun’s luminosity (C)</p> Signup and view all the answers

How are stellar colors determined?

<p>By employing a method of determining their temperature via filters (C)</p> Signup and view all the answers

What is the significance of the Hubble redshift in the context of star classification?

<p>It contributed to the understanding of the existence of other galaxies (B)</p> Signup and view all the answers

What is the purpose of the B-V color index?

<p>To derive the temperature of a star (A)</p> Signup and view all the answers

When were the classes L and T added to the classical Harvard sequence for star classification?

<p>In 1999 (C)</p> Signup and view all the answers

Flashcards

Supergiant star subclassifications?

Ia (most luminous) or Ib (less luminous)

What is the 'turnoff point'?

The point where stars begin to leave the main sequence on a color-magnitude diagram.

What is Zero Age Main Sequence (ZAMS)?

The stage when a star first joins the main sequence, beginning hydrogen fusion in its core.

Star cluster characteristics?

Stars within a cluster share similar ages and distances from Earth.

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Standard star notation?

Spectral class (OBAFGKM) followed by luminosity class (Roman numerals I-V).

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Y-axis of H-R diagram?

The y-axis represents a star's brightness compared to the Sun.

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How are stellar colors found?

Temperature determination using color filters.

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Hubble redshift significance?

Demonstrated the expansion of the universe and the existence of other galaxies.

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Purpose of B-V color index?

Used to estimate a star's temperature by measuring the difference in magnitude between blue and visual (green-yellow) filters.

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When were L and T spectral classes added?

These were added in 1999 to classify cooler objects like brown dwarfs.

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Study Notes

Supergiant Stars

  • Subclassification of supergiant stars is based on luminosity classes (Ia, Iab, Ib)

Star Clusters

  • Age of star clusters is assessed by main-sequence turn-off point (MSTOP)
  • Stars in a star cluster are similar in age and distance from the Sun

Star Classification

  • Conventional way to denote stars is by a combination of letters and numbers (e.g., HD 123456)
  • Stars enter the main sequence at the Zero-Age Main Sequence (ZAMS)

Hertzsprung-Russell Diagram

  • Y-axis of the H-R diagram represents luminosity or absolute magnitude

Stellar Colors

  • Stellar colors are determined by the surface temperature of the star
  • Colors are typically measured using a color index, such as B-V (blue minus visual)

Hubble Redshift

  • Hubble redshift is a significant indicator of a star's recession velocity, which is used in star classification

B-V Color Index

  • B-V color index is a measure of a star's surface temperature and is used to classify stars

Harvard Sequence

  • Classes L and T were added to the classical Harvard sequence for star classification in the 1990s and 2000s

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