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Jupiter’s mysterious “energy crisis” that has puzzled astronomers for 50 years could be caused by auroras, new observations suggest.
The largest planet in our solar system has long been known to be remarkably hot, despite its great distance from the sun. Jupiter is more than 5 astronomical units, or Sun-Earth distances (1 AU is one million miles (150 million kilometers).
There is so little sunlight that far from the sun Jupiter’s upper atmosphere should be freezing cold, scientists estimate it should be around -100 degrees Fahrenheit (-73 degrees Celsius), according to a NASA press release. However, the average temperature in Jupiter’s upper atmosphere is 800 degrees F (426 C) – almost as hot as the surface of the hell planet Venus.
Pictures: NASA’s Juno mission to Jupiter
For decades, astronomers have debated the cause of this “energy crisis,” as they called it, on Jupiter. Today, a new study has revealed that the planet’s intense auroras, fueled by the planet’s strong magnetic field, are causing the soaring temperatures.
Auroras are common phenomena in our solar system, occurring on planets with strong magnetic fields like Earth and Jupiter. (Mars and Venus have their own aurora flavors, but these lights work differently on these planets due to the uneven magnetic environment in these regions.)
In worlds with strong magnetic fields like Earth and Jupiter, auroras occur when electrically charged particles are trapped in the magnetic field and spiral toward the poles. On the way to the poles, particles collide with atoms and molecules in the atmosphere, producing light.
Jupiter’s auroral warming conclusion comes, in part, from new NASA observations Juno spaceship, which dives in and out of the intense radiation field to study the planet up close. Juno’s close-up view allows scientists to track global warming in unprecedented detail.
“Imagine this as a beach: if the warm atmosphere is water, the magnetic field mapped by Juno is the shore and the dawn is the ocean. We have found that the water has left the ocean and has flooded the land, and Juno revealed where that shore was to help us understand the degree of flooding, ”said James O’Donoghue, lead author of the research, in a statement from Keck Observatory.
The team used observations from Juno and the Hisaki satellite from the Japan Aerospace Exploration Agency (JAXA), both of which tracked the planet’s magnetic field. They also used data from the Keck II telescope, which provided high-resolution temperature maps. These combined observations allowed scientists to watch an aurora shoot a pulse of heat toward Jupiter’s equator. Hisaki’s long-term observations since 2013 have also shown the importance of the solar wind – the constant flow of particles from the sun – which brings its own magnetic field to Jupiter and likely enhanced the observed auroras.
“It is pure luck that we captured this potential heat release event,” added O’Donoghue, who is a planetary space scientist at JAXA’s Institute for Space and Astronautical Sciences. “If we had observed Jupiter on a different night, when the solar wind pressure had not recently been high, we would have missed it.”
Using a near infrared spectrograph, Keck plotted the heat of the planet during two observation sessions – in April 2016 and January 2017 – from electrically charged hydrogen molecules as they were moving the poles of the planet to the equator. Keck II has also been configured to improve the resolution of its images by taking more temperature measurements and only including those with a high degree of certainty addressed to the value. This work took years, but the result was new temperature maps with over 10,000 individual data points, greatly improving previous efforts at resolution.
However, the high definition view also showed another heating mystery that has yet to be solved.
“We also revealed a strange and localized heating region far from dawn – a long bar of heating like we’ve never seen before,” said Tom Stallard, co-author of the article at the University of Leicester, in the Keck Declaration. “Although we cannot be sure of this characteristic, I am convinced that this is a heat wave flowing towards the equator from the aurora.”
Jupiter’s magnetic field is much stronger than that of Earth. A nearby Jovian volcanic moon – Io – dumps a lot of material into the region through eruptions, providing many particles that enter Jupiter’s atmosphere. Jupiter’s size and strong winds also play a role in how the available heat from the aurora circulates around the planet.
Although auroral heating is not a new idea, scientists have not been able to confirm this hypothesis so far.
Previously, models examining the planet’s upper atmosphere suggested that auroral winds would not reach the equator. Instead, the theory suggested that the winds would be pushed westward due to Jupiter’s rapid rotation, which lasts almost 10 hours and varies slightly in latitude because the planet is gaseous. The new observations refute this old thought and also suggest that the westerly winds may be weaker than the equatorial winds causing the auroral heat.
An article based on the new findings was published in Nature on Wednesday (August 4).
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