Exomoon Detection: Transit Timing Variations скачать в хорошем качестве

Exomoon Detection: Transit Timing Variations

Exomoons are moons that orbit planets around stars other than our Sun, also know as exoplanets. However, only a handful of candidates have been identified despite thousands of exoplanets being discovered. One method of detecting exomoons is by looking for variations in the timing of the transit of the host exoplanet. As the exoplanet and exomoon orbit a common centre of mass the exoplanet is in a different orientation each transit. This can cause the transit to occur early or late. Unfortunately other astrophysical processes can cause a transit timing variation similar to an exomoon. However, a second technique can offer a more robust way of detecting an exomoon and is known as transit duration variation. Here the velocity of the exoplanet consists of two components. The first is the orbital velocity of the exomoon system around the star, the second is the orbital velocity of the exoplanet about the exomoon - exoplanet centre of mass. Again the orientation of the exomoon - exoplanet system as it transits the star causes variations. If both velocities are in the same direction the exoplanet has a higher velocity across the star, which reduces the transit duration. The opposite is true when the velocities are in different directions and causes the transit duration to increase.