What is Parsec ? How 1 parsec is measured?
What is Parsec?
Parsec is the acronym to, parallax of one arc-second. It is the longest unit of length, till date.
Now, what is 1 parsec? That is, How much length is covered, in 1 parsec?
To realize 1 parsec, and its Mathematical calculations , consider our solar system. The Average distance, between the sun and the earth, is called, an astronomical unit. Its accepted value is, 149.6 million kilometer.
An object, moving perpendicular to that line, continuously makes variable angles, with respect to the sun, and the earth.
Now, think carefully. Further the object goes from the Earth, smaller the angle it creates. And, closer the object to the earth, the angle is bigger.
For example, at about 86 million kilometer from the earth, the object generates a 60 degree angle.
At a distance of 1 astronomical unit, or 149.6 million kilometer, the angle is 45 degree.
At about 259 million kilometer, the angle is 30 degree.
Again, at 8.57 billion kilometer, the angle is 1 degree.
Going further again, at about 514 billion km away, the angle becomes only 1 arc-minute.
So, we observed that, to get a smaller angle, the object needs to go to a further distance.
If we want the object, to make smaller and smaller angle. That is of 1 arc-second. Or 1 by 3600 degree. Then, the object should go, to some trillion kilometer away from the earth.
This distance is known as, 1 parsec. Thus, 1 parsec is a distant point from the earth, where, the Earth's orbital Radius makes an Angle of, 1 arc-second.
And, it is equal to, 30.86 trillion kilometer. or, 3.26 light years. Or , 3.086 into, 10 to the power 16 meter, in, s i method.
NOW, think Mathematically. If the angle be theta, then, tan theta equals to, distance s-e, divided by, distance o-e. In this very case, the theta is 1 arc-second. And, distance s-e is 149.6 million kilometer. After putting values of theta, and distance s e, we should get, 1 parsec, equal to 3.086 into, 10 to the power 16 meter.
In general, astronomers use this unit, to measure distances to near earth stars, and other objects.
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See you in our next tutorial. Good bye for now.
