Scientists solve 40-year mystery over Jupiterâs X-ray aurora
9 July 2021
A research team co-led by MyAV·¶ has solved a decades-old mystery as to how Jupiter produces a spectacular burst of X-rays every few minutes.
The X-rays are part of Jupiterâs aurora â bursts of visible and invisible light that occur when charged particles interact with the planetâs atmosphere. A similar phenomenon occurs on Earth, creating the northern lights, but Jupiterâs is much more powerful, releasing hundreds of gigawatts of energy, enough to briefly power all of human civilisation*.
In a new study, published in Science Advances, researchers combined close-up observations of Jupiterâs environment by NASAâs satellite Juno, which is currently orbiting the planet, with simultaneous X-ray measurements from the European Space Agencyâs XMM-Newton observatory (which is in Earthâs own orbit).
The research team, led by MyAV·¶ and the Chinese Academy of Sciences, discovered that X-ray flares were triggered by periodic vibrations of Jupiterâs magnetic field lines. These vibrations create waves of plasma (ionised gas) that send heavy ion particles âsurfingâ along magnetic field lines until they smash into the planetâs atmosphere, releasing energy in the form of X-rays.
Co-lead author Dr William Dunn (MyAV·¶ Mullard Space Science Laboratory) said: âWe have seen Jupiter producing X-ray aurora for four decades, but we didn't know how this happened. We only knew they were produced when ions crashed into the planetâs atmosphere.
âNow we know these ions are transported by plasma waves â an explanation that has not been proposed before, even though a similar process produces Earthâs own aurora. It could, therefore, be a universal phenomenon, present across many different environments in space.â
X-ray auroras occur at Jupiterâs north and south poles, often with clockwork regularity â during this observation Jupiter was producing bursts of X-rays every 27 minutes.
The charged ion particles that hit the atmosphere originate from volcanic gas pouring into space from giant volcanoes on Jupiterâs moon, Io.
This gas becomes ionised (its atoms are stripped free of electrons) due to collisions in Jupiterâs immediate environment, forming a doughnut of plasma that encircles the planet.
Co-author Professor Graziella Branduardi-Raymont (MyAV·¶ Mullard Space Science Laboratory) said: âX-rays are typically produced by extremely powerful and violent phenomena such as black holes and neutron stars, so it seems strange that mere planets produce them too.
âWe can never visit black holes, as they are beyond space travel, but Jupiter is on our doorstep. With the arrival of the satellite Juno into Jupiterâs orbit, astronomers now have a fantastic opportunity to study an environment that produces X-rays up close.â
For the new study, researchers analysed observations of Jupiter and its surrounding environment carried out continuously over a 26-hour period by the Juno and XMM-Newton satellites.
They found a clear correlation between waves in the plasma detected by Juno and X-ray auroral flares at Jupiterâs north pole recorded by X-MM Newton. They then used computer modelling to confirm that the waves would drive the heavy particles towards Jupiterâs atmosphere.
Why the magnetic field lines vibrate periodically is unclear, but the vibration may result from interactions with the solar wind or from high-speed plasma flows within Jupiterâs magnetosphere.
Jupiterâs magnetic field is extremely strong â about 20,000 times as strong as Earthâs â and therefore its magnetosphere, the area controlled by this magnetic field, is extremely large. If it was visible in the night sky, it would cover a region several times the size of our moon.
The work was supported by the Chinese Academy of Sciences, the National Natural Science Foundation of China, and the UKâs Science and Technology Facilities Council (STFC), Royal Society, and Natural Environment Research Council, as well as ESA and NASA.
* Jupiterâs X-ray aurora alone releases about a gigawatt, equivalent to what one power station might produce over a period of days.
Links
- Professor Graziella Branduardi-Raymontâs academic profile
- MyAV·¶ Mullard Space Science Laboratory
- MyAV·¶ Mathematical & Physical Sciences
Image
- Credit: ESA/NASA/Yao/Dunn. Bottom image:ÌęOverlaid imageÌęof Jupiterâs north pole from NASAâs satellite Juno and NASAâs Chandra X-ray telescope.ÌęThe X-ray aurora (purple) is overlaid on a visible Junocam image.
Media contact
Mark Greaves
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E: m.greaves [at] ucl.ac.uk