Detecting Transiting Exoplanets in Crowded Fields

Sammanfattning

The first planet orbiting a main-sequence star was discovered in 1995. Since then more than 4000 additional exoplanets have been discovered. This is a rapidly evolving field in astrophysics. One of the most common ways to detect an exoplanet is through transit, as the brightness of the host star decreases. The transit method is suitable for surveying a large number of stars at the same time and most of the exoplanets discovered so far are from this particular method. In this study, it was investigated if it would be feasible to detect transiting exoplanets in globular clusters. So far globular clusters have been surveyed but no exoplanets have been detected in these environments. The possibility of finding exoplanets in globular clusters was investigated by simulating an observation of a globular cluster once every half an hour for the span of five days with a simulated telescope and detector. Light curves were measured from the stars with simulated photon noise and read-out noise. The box least squares method was then used to detect transiting exoplanets from extracted light curves. The efficiency for finding exoplanets was 31% in a cluster with 20 000 stars, 17% in a cluster with 50 000 stars, 1.5% in a globular cluster with 100 000 stars, and 0% in a globular cluster with 150 000 stars. This leads to the conclusion that surveys for exoplanets are limited by how close the stars are to each other as they can not be resolved and this diminishes the efficiency. However, in clusters with a smaller number of stars exoplanets can be detected as it is less crowded.