Use of a Stellar Wobble to Locate Planets around Other Stars

       I have done a quick survey of some of the bodies in our solar system that could of harboured life or that is promising to harbour life. I am going to take a break from the survey of our solar system. Today I am going to talk about one method that is useful in finding planets indirectly. The method that I am going to discuss is called the Stellar Wobble. This model is useful in finding large planets that are close to the star.  The Stellar wobble is a measure of the variation in position of a star. This is because the force of gravity of the planet acts upon the star. The diagram below shows this interaction. This interaction causes the star and the planet to orbit the center of mass and thus the star appears to wobble. If the planet did not have a large gravitational effect on the sun then the center of mass would be located in the star and would not appear to wobble. Therefore, this method is only useful when trying to locate large planet that are also close enough as mentioned above. 

Figure obtained from: http://www.astro.wisc.edu/~townsent/static.php?ref=diploma-2

        This wobble is visible when looking at the Doppler shift in the star’s spectrum. This Doppler shift can be seen when the star is moving towards or away from the observer. When the star is moving toward the observer then one will observe a blue shift in the spectrum. This will shift the features of the spectrum to shorter wavelengths. If the star was moving away it would be red shifted and the spectral lines will be shifted to longer wavelengths. From this information we can concluded that there is at least one planet orbiting the star, one can also determine the mass of the planet and its distance away from the star. It gets more complicated when there are multiple planets that are acting on the star but with mathematical modeling one can determine how many and their mass, and distances.

Figure Obtained from:http://spiff.rit.edu/classes/phys230/lectures/planets/planets.html

        In order to determine if the star is in fact moving or wobbling there has to be tons of observations that have to be conducted. One has to check every few days and see how the star is moving. This method to find stars is tedious but I found that it was a very interesting way in which extra solar planets could be found.

Information obtained from http://www.grantchronicles.com/astro43.htm