Swiss space telescope makes enigmatic discovery

This artist's impression released by NASA in 2002 depicts the icy Kuiper belt asteroid dubbed "Quaoar" by its discoverers. Keystone / Nasa

A Swiss-designed telescope travelling on board the CHEOPS space satellite has discovered a new ring around the asteroid Quaoar, presenting astronomers with an enigma.

Located more than 4,000 km from the centre of the asteroid, the ring is at an unusually high distance. “When the ring of an asteroid is so far away, we would expect its components to melt within a few decades to form a small moon,” says Willy Benz, professor of astrophysics at the University of Bern, who participated in the discovery with the CHEOPS team. But this has not happened.

The rings around planets or asteroids are made of rock and ice debris. They are generally found below a “theoretical distance” from the planet, known as the Roche limit. This represents the limit of fragmentation under the effect of gravitational forces.

The discovery goes against the idea that the rings can only survive within this Roche limit, established at 1,780 km. “This understanding must now be reviewed entirely,” the European Space Agency (ESA) said in a statement on Wednesday. In this case, the ring is located at about 4,100 km from the planet.

The CHEOPS telescope was developed jointly by the University of Bern and ESA, with collaboration from the University of Geneva. It “patrols” at a height of 700 km above the Earth and has the mission to study closely the already known exoplanets (planets that orbit around stars other than the sun). Astronomers are trying to assess whether conditions exist for life on one of the planets.