IAA-CSIC/UHU

Astronomers spot first ring around a distant dwarf planet

Astronomers have spotted a planetary ring in the outer reaches of our solar system. Or perhaps dwarf planetary ring would be more precise, as the narrow cloud of debris circles the roughly Greenland-sized Haumea, which orbits the sun beyond Neptune. The find comes thanks to a minieclipse that occurred when the dwarf planet (artist’s concept, above) passed in front of a distant star, allowing Earth-bound telescopes to measure it in unprecedented detail. In addition to the ring, the observations reveal that Haumea either has no atmosphere or one that exerts a surface pressure less than 50 billionths of Earth’s atmosphere as measured at sea level, the researchers report today in Nature. The scientists were also able to better estimate Haumea’s size and shape, which is somewhat akin to a squished rugby ball about 2322 kilometers long. That’s about 20% longer than previous observations suggested, lowering the dwarf planet’s density to about 1885 kilograms per cubic meter (about the same as Pluto) and its albedo, or light-reflecting ability, to about 51%. At 70 kilometers wide, Haumea’s ring is puny compared with those that circle Jupiter, Saturn, Uranus, and Neptune, but the find suggests that rings around asteroids and dwarf planets may be more common than previously believed.