Jupiter’s mysterious X-rays shed light on the aurora borealis, ending 40 years of searching for answers. For the first time, astronomers have seen the way in which Jupiter’s magnetic field is compressed, which heats particles and directs them along magnetic field lines into Jupiter’s atmosphere, creating X-ray auroras. The communication was accomplished by combining in-situ data from NASA’s Juno mission with X-ray observations from ESA’s XMM-Newton instrument. Credit: ESA/NASA/Yao/Dunn
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A team of researchers has solved a decades-old mystery about how Jupiter produces stunning X-ray bursts every few minutes.
A research team led by UCL (University College London) has solved a decades-old puzzle about how Jupiter produces stunning X-ray bursts every few minutes.
X-rays are part of Jupiter’s auroras – visible and invisible bursts of light that occur when charged particles interact with the planet’s atmosphere. A similar phenomenon occurs on Earth, where it creates the Northern Lights, but Jupiter is much more powerful, releasing hundreds of gigawatts of energy, which is enough to power an entire human civilization. *
In a new study published in scientific progressThe researchers combined close observations of Jupiter’s surroundings by NASA’s Juno satellite, which is currently orbiting the planet, with simultaneous X-ray measurements from the European Space Agency’s XMM-Newton Observatory (in Earth orbit).
The research team, led by UCL and the Chinese Academy of Sciences, discovered that the X-ray flares are caused by periodic vibrations of Jupiter’s magnetic field lines. These vibrations create waves of plasma (ionized gas) that send heavy ion particles “surfing” along magnetic field lines until they collide with the planet’s atmosphere, releasing energy in the form of X-rays.
Overlay image of Jupiter’s poles from NASA’s Juno satellite and NASA’s Chandra X-ray telescope. The left image shows an X-ray projection of Jupiter’s aurora borealis (magenta) on JunoCam’s image at the North Pole. The right shows the southern pair. Credit: NASA Chandra / Juno Walk / Dunn
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Co-lead author Dr. William Dunn (UCLA Mullard Space Science Laboratory) said: “We’ve been watching Jupiter produce X-ray auroras for four decades, but we don’t know how that happens. We know they are only produced when ions hit the planet’s atmosphere.
“We now know that these ions are transported by plasma waves – an explanation that has never been proposed before, although a similar process produces Earth’s own auroras. Therefore, it could be a global phenomenon, present in many different environments in outer space.”
X-ray aurorae occur at Jupiter’s north and south poles, often clockwork regularly—during these observations, Jupiter produced bursts of X-rays every 27 minutes.
The charged ion particles that hit the atmosphere came from volcanic gases that flowed into space from the giant volcano on Jupiter’s moon, Io.
This gas is ionized (the atoms are stripped of electrons) due to collisions in Jupiter’s immediate environment, forming a donut of plasma that surrounds the planet.
For the first time, astronomers have seen the way in which Jupiter’s magnetic field is compressed, which heats particles and directs them along magnetic field lines into Jupiter’s atmosphere, creating X-ray auroras. The communication was accomplished by combining in-situ data from NASA’s Juno mission with X-ray observations from ESA’s XMM-Newton instrument. Credit: ESA/NASA/Yao/Dunn
Co-author Dr Zhonghua Yao (Chinese Academy of Sciences, Beijing) said: “Now that we have identified this fundamental process, there are many possibilities where it can be studied further. A similar process likely occurred around Saturn, Uranus, Neptune, and possibly around exoplanets. Also, with different types of charged particles “surfing” in waves.
Co-author Professor Graziella Brandoardi-Raymont (UCLA Space Science Laboratory), said: “X-rays are usually produced by very strong and violent phenomena such as black holes and neutron stars, so it seems odd that only planets produce them as well.
“We can never visit black holes, because they go beyond space travel, but Jupiter is at our doorstep. With Jupiter orbiting Juno, astronomers now have a fantastic opportunity to study X-ray-generating environments up close.”
For the new study, the researchers analyzed continuous 26-hour observations of Jupiter and its surroundings by the Juno and XMM-Newton satellites.
They found a clear correlation between the waves in the plasma detected by Juno and the X-ray flare of Jupiter’s north pole aurora recorded by XMM-Newton. Then they used computer modeling to confirm that the waves would push heavy particles into Jupiter’s atmosphere.
Why the magnetic field lines periodically vibrate is unclear, but the vibrations may result from interactions with the solar wind or from high-speed plasma flows within Jupiter’s magnetosphere.
Jupiter’s magnetic field is very strong – about 20,000 times stronger than Earth’s – and therefore Jupiter’s magnetosphere, the area controlled by this magnetic field, is very large. If seen in the night sky, it would cover an area several times the size of our Moon.
This work was supported by the Chinese Academy of Sciences, the China National Foundation for Natural Sciences, the British Science and Technology Facility Council (STFC), the Royal Society, the Natural Environment Research Council, as well as the European Space Agency and NASA.
* Jupiter’s X-ray aurora alone emits gigawatts, the equivalent of what a single power plant would produce over several days.
Reference: 9 July 2021, scientific progress.
DOI: 10.1126 / sciadv.abf0851
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