Once it seemed Saturn was rather unique with its magnificent ring system. But we’ve since found it is not alone – and now another world has revealed that it too is a ring-bearer.
That world is Haumea, a dwarf planet located 50 times further from the Sun than Earth, beyond the orbit of Neptune. In this position, it is known as a trans-Neptunian object (TNO), one of four dwarf planets in this region we know to exist. It's the first dwarf planet or TNO we've found with a ring.
The discovery, published in Nature and led by Jose Ortiz from the Institute of Astrophysics of Andalusia in Granada, Spain, suggests rings are more commonplace in the Solar System than we thought. We’d already discovered rings on Centaurs (Chariklo was the first known to have one), which are bodies that orbit between Jupiter and Neptune. Now we’ve found one much further out around a TNO.
"It now appears that rings might be common in the outer Solar System," Ortiz told IFLScience. "We think that this ring is probably made of rock and water ice, with some organic material as well."
The ring has a diameter of more than 4,500 kilometers (2,800 miles), but is just 70 kilometers (45 miles) wide. It is located about 1,000 kilometers (620 miles) from the surface of the dwarf planet.
Finding the ring was no mean feat. On January 21, 2017, a team of astronomers used 12 telescopes in 10 locations to watch as the dwarf planet passed in front of a distant star, called URAT1 533-182543. As the star’s light was blocked out, the existence of the ring became apparent.