Dwarf planet Makemake an airless world of ice and rock
Ars Technica » Scientific Method 2012-11-21
The outer reaches of the Solar System are home to many small bodies, of which Pluto is the most famous. Due to their distance from Earth and relatively small sizes, these trans-Neptunian objects are somewhat difficult to study: even our most powerful telescopes can't image their surfaces in any detail, leaving astronomers either waiting impatiently for the New Horizons space probe to reach Pluto or resorting to more indirect methods. One such method is occultation, where one of these bodies briefly blocks (or occults) the light of a star.
A group of astronomers used 7 different telescopes in South America to track the occultation of a star by the dwarf planet Makemake (pronounced MAHkayMAHkay) and measured many of its properties for the first time. They concluded Makemake is noticeably non-spherical and may consist of two distinct types of terrain to explain the surface brightness.
When a Solar System object passes directly in front of a star, astronomers can measure both how much light that object blocks and how quickly that blocking occurs. And it's possible to combine data obtained by different telescopes in different locations on Earth (or ideally between multiple occultation events). Combined, these make it possible to reconstruct both the size—via the average length of the light blocking—and the shape of the body. In the absence of direct imaging, this is often the best we can do for a small, distant body.
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