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# A star is 1.45 parsec light years away. How much parallax would this star show when viewed from two locations of the earth six months apart in its orbit around the sun?

A
2 Parsec
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B
0.725 Parsec
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C
1.45 Parsec
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D
2.9 Parsec
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Solution

## The correct option is A 2 ParsecOne light year = speed of light × one yearor 1ly=3×108×(24×3600)=94608×1011mSo, 4.29ly=4.29×(94608×1011)=4.058×1016mAs 1 parsec =3.08×1016m(Parsec is a unit of length used to measure large distances to objects outside our Solar System)Thus, 4.29ly=4.058×10163.08×1016=1.32 parsecNow angular displacement , θ=dDwhere d= diameter of earth's orbit =3×1011m and D= distance of star from the earth =4.058×1016mSo, θ=3×10114.058×1016=7.39×10−6 radAs 1sec=4.85×10−6rad so, 7.39×10−6rad=7.39×10−64.85×10−6=1.52sec  Suggest Corrections  0      Similar questions  Related Videos   Order of Magnitude
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