Swiss space telescope finds unexpected ring around dwarf planet Climate activists occupy Gymi in Zurich today – and call for consultation with education department

The Swiss Cheops space telescope has discovered a new ring around the dwarf planet Quaoar. More than four thousand kilometers from the center of Quaoar, the ring is unusually far from its planet. This surprises astronomers.

“With a ring that far out, we would expect the ring material to merge into a small moon within a few decades.” Willy Benz, professor of astrophysics at the University of Bern, stated this on Wednesday at the request of the Keystone-SDA news agency. Benz was involved in the discovery of the ring together with the Cheops team. The findings were published Wednesday in the renowned journal Nature.

The rings around planets are – just like the well-known Saturn ring – made of pieces of ice and rock. Most planetary rings are within a critical distance from their planet, known as the Roche limit. Inside, gravity prevents the pieces of ice and rock from merging.

The newly discovered ring around Quaoar does not adhere to this rule: it is located 4100 kilometers from the center of Quaoar, while the Roche limit is 1780 kilometers. The previous assumption that rings only survive within the Roche limit should therefore be thoroughly revised, according to a statement from the European Space Agency (ESA).

Young, elastic or fast

Theorists now speculate about how the ring material prevents clumping. “One explanation would be that the ring is still very young,” Benz said. However, that is very unlikely. One possibility, however, is that the ring material is more elastic than is often assumed. “This way, the particles tend to pop apart rather than stick together.”

Another scenario is that the particles move at a very high speed. That would also prevent sticking together. However, further research is needed to definitively solve the mystery.

Difficult assignment

Exploring this dwarf planet was difficult, mainly because of its extreme distance. Quaoar is a so-called trans-Neptunian object – it orbits our sun beyond the orbit of the planet Neptune, 44 times farther from the sun than Earth.

The ring around Quaoar is too small and narrow to be seen directly – even with large telescopes. Instead, the researchers measured the stars’ brightness as Quaoar passed in front of them. The ring material around Quaoar caused a temporary dip in the brightness of the stars by blocking some of the starlight from reaching the telescopes.

Swiss technology

This is where the Swiss Cheops space telescope came into play – it was used to make the measurements of the light. “It was the first time ever such a measurement had been made from space,” Benz said. That has major advantages. Because the telescope doesn’t see through the distorting effects of Earth’s lower atmosphere, the signals were very clear. This brightness proved crucial for detecting Quaoar’s ring system, allowing researchers to rule out the possibility that the light decay was caused by a spurious effect in Earth’s atmosphere.

Cheops is a joint ESA-Swiss mission led by the University of Bern in collaboration with the University of Geneva. Unlike previous missions, the space telescope, which flies at an altitude of 700 kilometers, is not intended to detect new exoplanets, but to investigate the already known exoplanets. Among other things, the researchers want to find out whether life-friendly conditions prevail on one of the planets. After the excursion, Cheops returned to its actual mission.

(sda)