SPACE DISTANCE
PART-1.
If you ask any Astronomers that, When is the Universe originated? They simply answer that, It originates from 13.8 billion years ago. But, How they can say 13.8 billion years? Let's see about it.
HUBBLE's CONSTANT:
To know more, We'll make a graph of Distance of any object at X-axis and the Velocity of that object at Y-axis. The graph shows to us is, If the distance of the Star increases then the Velocity of the Star also increases. We can conclude that VαD. To remove this Proportionality, We include a constant, which is Hubble's Constant, H˳, V=H˳D. Here, H˳ is the Velocity is divided by Distance. H˳=70km/sec for every one MPC. 1MPC=3.262 Light Years.
In every second MPC, the speed increased by 70km/sec. We all know, TIME=DISTANCE/VELOCITY. This constant is reciprocal to the Time equation. So, T=1/H˳. If we apply all the known values in this equation, We can get 13.97 Billion Years. But, Our Universe is originated from 13.8 Billion Years. Why the calculated value is High? The value we calculated is only by Stars. But, We can calculate with the Help of CMB(Cosmic Microwave Background), It gives the exact value. How can we measure the distance of a Star? How can we calculate it's Velocity?
PARALLAX EFFECT:
By the Parallax Effect, If you raise your thumb finger and see with your two eyes, it is in a Stable position. But, you close and open eyes alternatively, You can notice that the position is changing. This is called Parallax Effect. If we see a Star in January, We can see the one side of a Star. After six months we can see the another side of the same Star. This forms a Triangle.
If we find angle, We can calculate its Distance. This angle is called as Parallax Angle. For example, We can take our nearest Star, Proximal Centauri, The Parallax Angle of that is θ=0.7681 Arc seconds. After the calculations, We can get 1.3 Par second. The final value we get is, 4.24 Light Years. We all notice that, If we travel in night, The Moon follows us. But, The trees, Shops, Street light are Move fast. This is also by the Parallax Effect. The Parallax Angle of tree is a very high when compared to the Parallax Angle of Moon. But, The Parallax Angle is used to find the Objects that present below 32,000 Light Years. But, How can we calculate the distance of the Stars, Galaxies that present away from 32,000 Light Years?
If you travel in night through a road that contains Street Light. Which Light is Far away from You? You will say that The dimmest light is the Farthest. Like this, Each and every Star has different sizes, different mass, different color, different Surface Temperature. If you know all these only we can calculate the distance of a object that present below 32.000 Light Years. How can we find the distance of a Object that present after 32,000 Light Years? Before that, We know about the HR Diagram.
HERTZSPRUNG RUSSEL DIAGRAM:
To draw this diagram, We need two things, One is the Light from a Star at a time, LUMINOSITY. Another one is Color of the Star. We already know to find the Distance of a Star by the Parallax Effect. We need another formula. That is Inverse Square Law. B=L/4πD² B is the Apparent Brightness. The color of the Star is noticed by its Wave Length, λ. The temperature of the Star is calculated using the Wein's Displacement Law.
THE CONCLUSION:
But, How we find the distance of the Object that present away from 32,000 Light Years? We will learn Tomorrow. Stay Tuned.
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