Astrophysics Lab: H-R Diagram Quiz

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Questions and Answers

What does the Hertzsprung-Russell (H-R) diagram classify stars based on?

  • Luminosity (correct)
  • Size (correct)
  • Surface temperature (correct)
  • Color (correct)

What is the actual brightness of a star called?

Luminosity

What is absolute magnitude?

The apparent magnitude of a star placed 32.6 light years from the sun

How bright does a star appear to an observer on Earth?

<p>Apparent magnitude</p> Signup and view all the answers

Describe a main sequence star.

<p>Average size star that's in the early stage of development</p> Signup and view all the answers

What is a supergiant star?

<p>A large low density star that is hundreds of times more luminous than a red giant</p> Signup and view all the answers

What defines a dwarf star?

<p>Stars of an absolute magnitude of +1 or less</p> Signup and view all the answers

What are the characteristics of the sun according to the H-R diagram?

<p>Absolute magnitude of 4.9, temperature of 5800K, color is yellow, and spectral class is G2</p> Signup and view all the answers

What is the relationship between star temperature and absolute magnitude?

<p>The more increase in temperature, the more luminosity a star has</p> Signup and view all the answers

What would be the absolute magnitude and color of a main sequence star with a temperature?

<p>The absolute magnitude would be 13.2, and the color would be red.</p> Signup and view all the answers

How does a star's color change as its temperature increases?

<p>A star's color changes into a lighter tone as its temperature increases.</p> Signup and view all the answers

Why does a cool distant supergiant star have a high apparent magnitude?

<p>Because it is a supergiant star with significant luminosity despite its distance.</p> Signup and view all the answers

Why do nearby white dwarf stars have low absolute magnitudes?

<p>Because white dwarf stars have an absolute magnitude of +1 or less.</p> Signup and view all the answers

If Deneb and Rigel were at Alpha Centauri's distance, how would they appear?

<p>They would appear less luminous than a normal supergiant due to the differences in absolute magnitudes.</p> Signup and view all the answers

How much brighter is Rigel than the sun?

<p>Rigel is 10,000 times brighter than the sun.</p> Signup and view all the answers

How can stars be classified using the Hertzsprung-Russell diagram?

<p>By spectral class based on color, temperature, and size.</p> Signup and view all the answers

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Study Notes

Hertzsprung-Russell (H-R) Diagram

  • Classifies stars based on luminosity, color, surface temperature, and size.
  • Helps in understanding the relationship between different types of stars.

Luminosity

  • Represents the true brightness of a star, independent of distance.

Absolute Magnitude

  • Defined as the apparent magnitude of a star when placed 32.6 light-years from the sun, provides a standard measure to compare stars.

Apparent Magnitude

  • Measures how bright a star appears to an observer on Earth, influenced by distance and intrinsic luminosity.

Main Sequence Stars

  • Average-sized stars in the early stages of development.
  • They occupy a central band in the H-R diagram.

Supergiant Stars

  • Large, low-density stars that are hundreds of times more luminous than red giants.

Dwarf Stars

  • Stars that have an absolute magnitude of +1 or less, indicating lower luminosity.

The Sun's Characteristics

  • Absolute magnitude of 4.9.
  • Surface temperature of approximately 5,800K.
  • Yellow color and classified as spectral class G2.

Temperature and Absolute Magnitude Relationship

  • Higher star temperatures correlate with greater luminosity, indicating that temperature influences a star's brightness.

Characteristics of a Main Sequence Star

  • A main sequence star at certain temperatures can have an absolute magnitude of 13.2 and appear red in color.

Star Color and Temperature

  • As a star's temperature increases, its color transitions to lighter tones, typically from red to blue.

Apparent Magnitude of Cool Distant Supergiants

  • A cool distant supergiant star like Betelgeuse appears highly luminous due to its significant intrinsic brightness, despite its distance and lower temperature.

White Dwarfs and Absolute Magnitude

  • White dwarf stars, despite having high temperatures, have low absolute magnitudes of +1 or less due to their lower luminosity.

Hypothetical Distances for Deneb and Rigel

  • If Deneb and Rigel were at a distance comparable to Alpha Centauri, they would appear less luminous than typical supergiants due to differences in absolute magnitudes.

Rigel's Brightness Compared to the Sun

  • Rigel is approximately 10,000 times brighter than the Sun, highlighting its immense luminosity.

Classifying Stars with the H-R Diagram

  • Stars can be organized by spectral class based on their color, temperature, and size, allowing for a structured comparison within the H-R framework.

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