Astronomical Distances

• What are the units used to measure astronomical distances?

  Astronomical Units, Light-years, Parsecs
• What is defined as one astronomical unit (AU)?

  The mean distance from Earth to the Sun

  
• How far is the Earth from the Sun in January?

  1.471 × 10¹¹ m
• How far is the Earth from the Sun in July?

  1.521 × 10¹¹ m
• What is the mean distance from the Earth to the Sun calculated to be?

  1.496 × 10¹¹ m
• Why is the astronomical unit (AU) useful?

  For studying distances in the solar system
• What is a light-year (ly)?

  The distance light travels in one year
• How is the distance of a light-year calculated?

  Distance = speed × time
• What is the speed of light?

  3 × 10⁸ m/s
• How many seconds are in one year?

  3.15 × 10⁷ s
• What is the distance travelled by light in one year?

  9.46 × 10¹⁵ m
• What is the definition of a parsec (pc)?

  The distance at which 1 AU subtends 1 arcsecond

  
• How many arcseconds are in one degree?

  3600 arcseconds
• What is the relationship between arcminutes and arcseconds?

  1 arcminute = 60 arcseconds
• How can 1 parsec be expressed in meters using trigonometry?

  1 pc = 1 AU / tan(1/3600)
• What is the approximate value of 1 parsec in meters?

  3.1 × 10¹⁶ m
• How do parsecs and light-years compare to astronomical units?

  They are much larger than astronomical units
• How far is Alpha Centauri from Earth in light-years?

  Approximately 4.35 light-years
• How do you convert light-years to meters for Alpha Centauri?

  Distance = 4.35 × (9.5 × 10¹⁵)
• What is the distance to Alpha Centauri in meters?

  4.13 × 10¹⁶ m
• How do you convert the distance from meters to astronomical units for Alpha Centauri?

  Distance (AU) = 4.13 × 10¹⁶ / 1.496 × 10¹¹
• What is the distance to Alpha Centauri in astronomical units?

  2.8 × 10⁵ AU
• How do you convert the distance from meters to parsecs for Alpha Centauri?

  Distance (pc) = 4.13 × 10¹⁶ / 3.1 × 10¹⁶
• What is the distance to Alpha Centauri in parsecs?

  1.3 pc
• What conversion factors for astronomical distances are provided in the data booklet?

  1 AU = 1.50 × 10¹¹ m
• What is the value of 1 light-year in meters?

  9.46 × 10¹⁵ m
• What is the value of 1 parsec in meters?

  3.08 × 10¹⁶ m
• How many astronomical units are in one parsec?

  2.06 × 10⁵ AU
• How many light-years are in one parsec?

  3.26 ly