VIDEO Back in January, a Spanish-led group of astroboffins turned telescopes skywards to watch an occultation of dwarf planet Haumea, and got a surprise.
With the analysis in, it turns out the space rock that circles the sun beyond Pluto has a ring – the first planet discovered beyond Neptune to sport such cosmic jewellery.
The group, led by José Luis Ortiz Moreno (J L Ortiz), a minor planet specialist at the Sierra Nevada Observatory in Granada, presented its findings today in Nature.
The Planetary Society, who provided access to two of the twelve telescopes used to observe Haumea pass in front of a star, describes the planet: “The frigid world is an ellipsoid about as wide as Pluto, shaped roughly like a flattened egg or river stone. This study found its long axis to be about 1704 km. It has two known moons: Hiʻiaka and Namaka.”
The ring was spotted in the pattern of light from the star Haumea occluded, and the Nature paper says the rings are similar to those that surround Uranus and Neptune.
Two minor planets closer than Neptune have rings: the 250-km-wide Chariklo and Chiron, both orbiting “between the asteroid belt and Kuiper belt”, the Planetary Society says.
Yet another surprise arose from the Ortiz team's measurement: Haumea is dimmer than the 0.7 albedo previously assigned to it. That's because the rock, discovered in 2003 and until 2008 called 2003 EL61, is bigger than previous estimates.
“Haumea’s largest axis is at least 2,322 kilometres, larger than previously thought, implying an upper limit for its density of 1,885 kilograms per cubic metre and a geometric albedo of 0.51, both smaller than previous estimates”, the Nature paper says.
Ortiz's team has put together a YouTube visualisation of the rings, below. ®