The Total solution for NCERT class 6-12
The principle of тАШparallaxтАЩ in section 2.3.1 is used in thedetermination of distances of very distant stars. The baseline┬аAB┬аisthe line joining the EarthтАЩs two locations six months apart in its orbit aroundthe Sun. That is, the baseline is about the diameter of the EarthтАЩs orbit тЙИ 3 ├Ч1011m. However, even the nearest stars are so distant that with sucha long baseline, they show parallax only of the order of 1тАЭ (second) of arc orso. A┬аparsec┬аis a convenient unit of length on theastronomical scale. It is the distance of an object that will show a parallaxof 1тАЭ (second) of arc from opposite ends of a baseline equal to the distancefrom the Earth to the Sun. How much is a parsec in terms of meters?
Diameter of EarthтАЩs orbit = 3 ├Ч 1011┬аm
Radius of EarthтАЩs orbit,┬аr┬а= 1.5 ├Ч 1011┬аm
Let the distance parallax angle be= 4.847 ├Ч 10тАУ6┬аrad.
Let the distance of the star be┬аD.
Parsec is defined as the distance at which the average radius ofthe EarthтАЩs orbit subtends an angle of.
Hence, 1 parsec тЙИ 3.09 ├Ч 1016┬аm.