NSF Award
1616115
Solar System objects pass in front of bright stars from time to time, cutting out the starlight. The amount of light that is cut coupled with the amount of time during these passages tells us about the size, shape, whether the object has an atmosphere, and how thick the atmosphere might be. These events are called occultations. This project will observe occultations of stars by the Trans-Neptunian Objects Pluto, Triton, Makemake, Quaoar, and Salacia. Since 1988, Pluto's atmosphere has been tracked by occultations. Its atmosphere has gotten thicker during this time. It is now expected to get thinner as Pluto moves farther away from the Sun in its orbit, and its temperature gets cooler. Two occultations by Pluto will be observed over the next three years to record changes in the thickness of Pluto's atmosphere. These changes will be modeled with data that we already have to describe how Pluto's atmosphere changes. The other large TNOs, covered with bright ice, could also have changing atmospheres like Pluto. Observations of one occultation are planned for each of the other objects listed above. Many amateur astronomers and students will be trained to be part of the occultation observations.<br/><br/><br/>Occultations of reasonably bright stars by Trans-Neptunian Objects (TNOs) provide an opportunity to learn their sizes, shapes and densities, and presence and details of any thin atmospheres. This project will observe occultations of stars by the TNOs Pluto, Triton, Makemake, Quaoar, and Salacia, resulting in data that are crucial to building accurate atmospheric models for these objects. Pluto's atmosphere has been monitored by occultations since its discovery in 1988. It has been doubling in size roughly every ten years, despite the fact that Pluto itself has move farther from the Sun in its orbit. Images of Pluto's surface from the New Horizons spacecraft show large ice reservoirs that are the source of Pluto's atmosphere. These reservoirs have been getting slightly warmer as Pluto has moved away from the Sun, suggesting that Pluto's subsurface stores heat. Models predict, however, that Pluto's frost temperatures will soon start to fall. Two occultations by Pluto will be observed over the next three years to monitor changes in the amount of Pluto's atmosphere. Other large TNOs, covered with bright ice, potentially have changing atmospheres like Pluto. Observations of one occultation are planned for each of the other objects listed above. The planned observations will be sensitive to very thin atmospheres and will refine the size and shape estimates for all objects. Many amateur astronomers and student researchers will be trained and added to support the occultation observations.
