Question

Identify the INCORRECT statement(s) with reference to a Light-year.

1. It is a unit of distance.

2. It is the distance light travels in one Earth year.

3. Its value in kilometres is 5.88 × 10¹².

1. Only 1 and 2
2. Only 3
3. Only 2 and 3
4. Only 1

Answer 1

Correct Answer - Option 3 : Only 2 and 3

The correct answer is Only 2 and 3.

• Light Year:
  • Large distances in outer space are measured in light-years.
  • A light-year is the distance light travels in one year at the speed of 299,792,458 metres per second or roughly 300,000 km per second.
  • No star, apart from the sun, is close enough to Earth to appear as anything but a point of light.
  • 1 light year = 9.46 × 10¹² km.
  •                    =5.88×10¹² miles
  • The first successful measurement of the distance to a star(other than the Sun) was done by Friedrich Bessel​ in 1838.
  • Measurement Units of Space:
    • Astronomical Unit (A.U.): It is the mean distance between the earth and the sun.
      • One Light Year is equal to 60,000 A.U. 1 A.U. = 150 million km.
    • Parsec: One parsec is the distance to a star that subtends an angle of 1 arc second act an arc length of 1 A.U.
      • 1 Parsec = 3.26 light-years. 

• The closest star to our solar system is Proxima Centauri (4.2 light-years away).
• Andromeda is a spiral galaxy and also our closest neighbour.