However, this is not the first technique used by scientists. Previous attempts have attempted to use the common technique of photometry to detect oscillations on the planet’s surface. These oscillations can then be correlated with the density of specific parts of the planet’s interior. While the technique worked well for Jupiter, the photometric data we have for the ice giants so far have proved insufficient to determine the same density profiles.
An alternative is to use gravitational oscillations on the planet’s surface. In particular, there is a type of oscillation pattern known as the “normal way”. This oscillation pattern occurs when all parts of a system begin to oscillate at the same sine frequency. And the gravitational effects of normal-mode oscillations inside the planet can be felt outside and reflected in the rings themselves.
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UT video discussing planetary rings in the solar system
It is also not the first time that patterns on a planet’s rings have been used to calculate its internal density. Saturn has a more comprehensible ring system than Uranus or Poseidon, the two ice giants with known ring systems. Scientists have been conducting seismic analyzes of Saturn’s ring system for years using data from Voyager and Cassini. The result is a better understanding of some of the normal ways of the planet’s interior and, therefore, an estimate of the composition of the planet’s core and the rate of rotation of most of its material.
Neptune and Uranus each have a number of different rings, although they are not as well studied as Saturn. Some of those rings are associated with shepherds’ moons. But according to the new document, the same density reflections of resonant waves that are visible in Saturn’s rings are likely to be present in the ice giant’s ring systems.
In addition, the inner moons themselves can be affected by the same tunings. Some of the moons can even create their own tunings, such as what is known as the Lindblad tuning. More typically observed at the galaxy scale, Lindblad resonances are known to drive spiral density waves, which cause the “arms” that can be seen in many spiral galaxies. But on a much smaller scale, the same effect occurs in planetary ring systems, including Saturn, and most likely Poseidon and Uranus.
UT video describing the Trident mission, which would return to Poseidon.
The problem with using these tunings reflected in the rings is a problem that is often encountered by science – there is not enough data. So far, no detector has been left to map the details needed to see the full range of the ring system. The authors of the paper and many other researchers suggest that it is time to send a detector to the ice giants to effectively map ring systems, moons and myriads of other recently discovered objects that are so difficult to observe from Earth. But for now, this mission is still in the plan, so we will have to wait to fully understand the interior and ring system of these cold, barren worlds. At least when we finally send a detector this way, we will have the mathematical framework to help shed light on these dark places.
Learn more: A’Hearn et al – Ring Seismology of the Ice Giants Uranus and NeptuneUT – NeptuneUT Rings – Which Planets Have Rings? UT – How Many Rings Does Uranus Have?
Head image: Artistic impression of Uranus and its rings. Appropriations – NRAO / AUI / NSF / S. Dagnello
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