The Search for Exoplanets

Until a few decades ago, ours was the only known solar system in the entire universe.  In fact, our solar system is just one of many, but finding other systems is incredibly difficult. The complexity arises from how bright stars are: they simply cause too much glare to be able to easily detect whether a smaller body such as a planet is orbiting it. Looking for a planet next to a star is like attempting to spot a pinhead next to a floodlight at a great distance.

Looking for other solar systems comes down to searching for exoplanets (planets that are not part of our solar system).  But how do you find exoplanets? The Anglo-Australian Planet Search (AAPS), started in 1998, uses a basic physical principle to detect bodies orbiting stars: even a small planet will exert a gravitational pull on the parent star. This pull will result in the star wobbling on a regular basis as the planet orbits it. A regular wobble can then be detected using the Doppler Effect, as light emitted from the star is shifted blue (as the star wobbles toward the earth) or red (as the star wobbles away from the earth). The AAPS only needs to observe one or two orbital periods before it can ascertain at what distance the exoplanet is orbiting and its mass.

As of August 2015, the AAPS has achieved the highest precision search in the Southern Hemisphere, and has identified over 40 exoplanets using the Anglo-Australian Telescope and UCLES spectrograph.

Finding exoplanets will also aid the search for other life in our universe, as some of the exoplanets that have been found orbit at just the right distance from their parent star to have liquid water. The globular cluster Omega CentauriThis is the Omega Centauri cluster, a stellar globular cluster. Will we find planets orbiting some of these stars? Image: AAO

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