Saturn’s northern lights to be probed by Reading astronomer

A University of Reading astronomer will use the most powerful space telescope ever created to work out what is causing Saturn’s very own northern lights. 

Dr James O’Donoghue and a research team led by the University of Leicester have been awarded observation time with the James Webb Space Telescope (JWST) by the Space Telescope Science Institute (STScI) for two programmes that will focus on the mysterious aurorae of the gas giants Saturn and Uranus. Their successful proposals were among 1,931 submissions for the James Webb Space Telescope (JWST) Cycle 3 General Observer Program.

Like on Earth, both planets have their own northern lights - also known as auroral emissions. These aurorae are caused by highly energetic charged particles, which are funnelled down and collide with a planet's atmosphere via the planet's magnetic field lines. Dr James O’Donoghue, a planetary scientist at the University of Reading, will be looking into Saturn’s aurora as a co-investigator in the study. 

He said: “This is an extremely rare opportunity to use the most powerful and most complex telescope ever launched into space. 

“We will be investigating Saturn’s own version of the northern lights, which seem to be caused by winds that flow in what looks like a figure-of-eight. We don’t know what is causing these winds, but we suspect hot spots in the upper atmosphere might be behind them. 

“We will use the James Webb Space Telescope to map the temperatures across Saturn’s northern lights and figure out how weather is creating this spectacular light show.” 

Investigating Saturn and Uranus 

The team, led by Dr Henrik Melin from the University of Leicester School of Physics and Astronomy, will work on two projects. The first project that Dr Melin’s team will use the JWST for will observe the aurora of Uranus, of which very little is known. The conduit of the auroral currents is the magnetic field, which at Uranus is full of strange complexity.

The project will capture images over the course of a single Uranian day, or one full rotation of the planet, in the early months of 2025. This way, the team will be able to map the auroral emissions across a whole rotation Uranus’s magnetic field to answer their key question: are the emissions produced via the interaction with the solar wind (like the Earth), or are there internal sources within the system (like Jupiter), or somewhere in-between (like Saturn)?

For the second project, led by Professor Luke Moore at the Boston University Center for Space Physics, the astronomers will observe Saturn’s northern auroral region through an entire Saturnian day, 10.6 hours in length, to observe the changing temperature of this region as the planet rotates. In revealing the atmospheric auroral energies for the first time we can hunt for a source of Saturn’s atmospherically driven aurora, and thus contextualise this new process more widely, allowing us to understand whether the process is important at Earth, other planets in the solar system, and within astrophysical objects across the universe.

Both projects will use the JWST NIRSpec instrument.

Dr Henrik Melin from the University of Leicester School of Physics and Astronomy said: “JWST is already changing how we perceive the Universe, from the Solar System, our very own cosmic backyard, to the first galaxies formed at the beginning of time. I am thrilled to have been awarded time on this remarkable observatory, and this data will fundamentally shape our understanding of both Saturn and Uranus.”