The farthest objects in our universe discovered by modern astronomers are so distant that light emitted by them takes billions of years to reach the Earth. These objects (known as quasars) have many puzzing features, which have not yet been satisfactorily explained. What is the distance in km of a quasar from which light takes 3.0 billion years to reach us ?

Explanation

Time taken by light to reach to Earth,
t=3 Billion years
`=3xx10^(9)` years
`=3xx10^(9)xx365.25xx24xx3600s`
`=94672800xx10^(9)`
`~~9.46728xx10^(16)s`
Speed of light `c=3xx10^(8)ms^(-1)`
Distance of quasars from Earth D=ct
`:.D=3xx10^(8)xx9.46728xx10^(16)`
`=28.40184xx10^(24)`
`~~2.84xx10^(25)m`
`~~2.84xx10^(22)km`