Stellar Occultation Events, How Photometry Works on This Topic, and What We Have to Gain with Such Data:

Our current project consists of studying the small bodies orbiting the Sun between the Giant Planets – Centaurs and the ones orbiting the Sun after Neptune’s orbit – Trans-Neptunian Objects (TNOs) by using stellar occultation data. Stellar occultation happens when an asteroid passes in front of a star, blocking its flux for an observer on Earth. Those events usually last only a few seconds; to observe them, we must acquire images as fast as possible to obtain a good data sample. Estela attached a video to the previous email with an example of such data sets. Once we have that data, we will use aperture photometry to obtain individual stellar flux measurements for every image. The stellar flux as a function of time is called a light curve. Once we have a light curve for each star in the image, we use comparison stars to compensate our data for atmospheric interferences, i.e., the light curve obtained for the star to be occulted by the asteroid is divided by a median light curve obtained from the other stars measured in the images. This way, the flux drops that may appear in the data are addressed to the physical characteristics of the TNOs (or Centaur). So far, stellar occultation events enable us to measure the position, limb’s size and shape, and surface topography of dozens of those small bodies. The technique also allowed the discovery and follow-up of structures in objects’ surroundings, such as rings and satellites.

*This information was written by Flavia Lauane Rommel, A Research Member at Florida Space Institute