At the ends of the Solar System, beyond the orbit of Neptune, there is a belt of objects composed of ice and rocks, among which four dwarf planets stand out: Pluto, Eris, Makemake and Haumea. The latter is the least well known of the four and was recently the object of an international observation campaign which was able to establish its main physical characteristics.
The study, led by astronomers from the Institute of Astrophysics of Andalusia and published in Nature, reveals the presence of a ring around the planet.
Trans-neptunian objects are difficult to study because of their small size, their low brightness, and the enormous distances that separate us from them. A very efficient but complex method lies in the study of stellar occultations, or the passing of these objects in front of a star (like a small eclipse). It allows astronomers to determine the main physical characteristics of an object (size, shape, and density) and has been successfully applied to dwarf planets Pluto, Eris and Makemake.
“We predicted that Haumea would pass in front of a star on the 21st of January 2017, and twelve telescopes from ten different European observatories converged on the phenomenon,” says José Luis Ortiz, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) in charge of the study. “This deployment of technical means allowed us to reconstruct with a very high precision the shape and size of dwarf planet Haumea, and discover to our surprise that it is considerably bigger and less reflecting than was previously believed. It is also much less dense than previously thought, which answered questions that had been pending about the object.”
Haumea is an interesting object: it rotates around the Sun in an elliptic orbit which takes it 284 years to complete (it presently lies fifty times further from the Sun than the Earth), and it takes 3.9 hours to rotate around its axis, much less than…