Sun's Wobbling And Exoplanet Detection

It is common that in the solar system every thing revolves around sun....the common barycenter of all bodies.It is true but  is it as far true as we think of it??

Let's try to understand physics behind this, there is a very common method of solving mechanical problems like this is center of mass (CM) method. Suppose we have n number of bodies M1, M2, M3, M4.....Mn, and they are at X1,X2, X3, X4....Xn distance from the origin. Then the CM of mass of the system can be  find with formula given below (for x, y and x directions) 

If we shift origin on X then (M1.X1)+(M2.X2)+(M2.X2)+(M2.X2)......+(Mn.Xn) will be equal to zero.Now if we put M1>>(M2+M3+M4...+Mn) then M1.X1 will become almost zero ( M1.X1~0 ) which in turn comes out as X1~0. What it physically means?? It means CM is almost at the M1's center.In our solar system M1 is sun and it is almost at the CM and all other bodies are revolving around it.

Here comes the point, sun is "ALMOST" at the center not "ON" the center.If we think of a system made up of only tow bodies sun and Jupiter, with all their characteristics , same mass, same distances, then barycenter will come out to be 743,114 km and sun's radius is 695,800 km., means above the sun's surface.Actually in earth-moon system system it lies 1,710 km below earth's surface.

Now think, a planet can make a star to wobble, wobble means star oscillates just like planets but with very small orbital radius. From Doppler Effect we know if a star is moving toward us, will project blue shift in its light spectrum and if it is moving away from us will project red shift on us.Amount of shift depends upon star and planet's masses and distance between them.

Red and Blue shift 

Scientists  observe star's spectrum and find red and blue shift periodically.From that they find exoplanets planets around other star systems.This method is called Radial Velocity method.This very small idea ,very basic physics lead us towards new worlds.Fascinating, isn't it..??

                                

Radial Velocity method

You can find exoplanets found by this method on this wikipedia page.

This kind of phenomenon has also observed with earth's rotational axis. Because of other celestial near bodies, like moon , mars, earth's rotational axis wobble around and a circular path and changes its polar star time to time.

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