Lesson 10.1.2

10.1.2 Measuring astronomical distances Quiz: Pearson Edexcel Physics, Unit 10

20 questions

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Lesson 10.1.2, Measuring astronomical distances: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 10: Space, written with Revision Ninja.

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The 20 questions

  1. Which equation relates the parallax angle p in arcseconds to distance d in parsecs?

    • d = p
    • d = 1 / p in degrees
    • d = p^2
    • d = 1 / p

  2. What is a parsec?

    • The distance at which a star's parallax angle is 1 arcsecond, about 3.26 light years.
    • The distance light travels in one year, which is about one parsec in length.
    • The distance from the Earth to the Sun, measured along the ecliptic plane of orbit.
    • The distance light travels in one second, measured in a vacuum at standard conditions.

  3. Why can trigonometric parallax only be used for relatively nearby stars?

    • Parallax only works for stars in the Solar System.
    • Parallax depends on the star's temperature, which is unknown for distant stars.
    • The parallax angle becomes too small to measure reliably for distant stars.
    • Distant stars stop emitting light in all directions.

  4. What is a standard candle?

    • An object whose luminosity is known, so its distance can be found from its measured intensity.
    • An object whose parallax is always 1 arcsecond.
    • A lamp used in the laboratory to calibrate detectors.
    • A star whose intensity is always equal to that of the Sun.

  5. A star has parallax 0.50 arcsec. What is its distance?

    • 0.5 pc
    • 5 pc
    • 2 pc
    • 0.2 pc

  6. A star has parallax 0.25 arcsec. What is its distance?

    • 4.0 pc
    • 0.8 pc
    • 0.25 pc
    • 13 pc

  7. A star is at 10 pc. What is its distance in metres, using 1 pc = 3.09 x 10^16 m?

    • 3.1 x 10^18 m
    • 1.0 x 10^17 m
    • 3.1 x 10^16 m
    • 3.1 x 10^17 m

  8. A Cepheid-type standard candle has luminosity 4.0 x 10^26 W and intensity 2.0 x 10^-9 W m^-2 at Earth. What is its distance?

    • 1.3 x 10^14 m
    • 6.3 x 10^16 m
    • 2.5 x 10^17 m
    • 1.3 x 10^17 m

  9. A parallax of 0.05 arcsec gives a distance of 20 pc. If the measurement uncertainty in parallax is 0.01 arcsec, what is the fractional uncertainty in the parallax?

    • 20%
    • 5%
    • 0.2%
    • 2%

  10. How many light years is 10 pc, using 1 pc = 3.26 light years?

    • 326 light years
    • 3.26 light years
    • 32.6 light years
    • 1.0 light year

  11. Two stars have the same luminosity. The brighter star has nine times the intensity of the fainter star at Earth. What is the ratio of the brighter star's distance to the fainter star's distance?

    • 9:1
    • 1:9
    • 3:1
    • 1:3

  12. Why might distances from standard candles be overestimated if interstellar dust is ignored?

    • Dust changes the luminosity of the object, so the inferred distance is too small.
    • Dust makes objects appear brighter, so the inferred distance is too small.
    • Dust dims the light, so the object appears fainter and the inferred distance is too large.
    • Dust removes the parallax angle, so no distance can be found.

  13. A star has parallax 0.10 arcsec and apparent intensity 1.0 x 10^-10 W m^-2 at Earth. What is its luminosity?

    • 1.2 x 10^24 W
    • 1.2 x 10^26 W
    • 3.0 x 10^26 W
    • 9.5 x 10^25 W

  14. If the parallax angle of a star is halved, what happens to its distance?

    • It stays the same.
    • It doubles.
    • It quadruples.
    • It halves.

  15. Why are standard candles useful when the parallax angle of a distant object is too small to measure?

    • They have zero intensity so their distance can be calculated directly.
    • They emit light only in one direction, which makes them easier to measure.
    • Their parallax is always larger than that of nearby stars.
    • Their luminosity is known, so distance can be found from intensity even when parallax cannot be measured.

  16. Which quantity is measured directly by a parallax measurement?

    • The luminosity of the star.
    • The apparent shift in a star's position as Earth moves around the Sun.
    • The peak wavelength of the star's spectrum.
    • The redshift of the star's light.

  17. Which measurement is used directly to find the distance to a nearby star using trigonometry?

    • Its parallax angle, measured from two positions of Earth in its orbit.
    • Its surface temperature, measured from its colour.
    • Its apparent magnitude, measured on a single night.
    • Its redshift, measured from its spectrum.

  18. A star is at 2.5 pc. What is its parallax angle in arcseconds?

    • 4.0 arcsec
    • 2.5 arcsec
    • 0.40 arcsec
    • 0.025 arcsec

  19. What is the advantage of a standard candle over parallax for very distant objects?

    • It does not need a tiny angle, so it works at much greater distances.
    • A standard candle shows the object's exact temperature and chemical composition.
    • A standard candle always gives a more accurate distance than parallax does for stars.
    • A standard candle works without knowing the object's luminosity or its intensity value.

  20. A standard candle has luminosity 2.0 x 10^27 W. Its measured intensity is 2.0 x 10^-8 W m^-2. What is its approximate distance?

    • about 4.0 x 10^18 m
    • about 1.3 x 10^18 m
    • about 6.3 x 10^17 m
    • about 1.3 x 10^16 m

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