While everyone has been getting excited about exoplanets – distant worlds orbiting stars light years from Earth – the giant of our solar system has shown there are still plenty of surprises left much closer to home. 

The first detailed results from NASA's Juno spacecraft orbiting Jupiter reveal a much larger fuzzy core of metallic hydrogen, enormous chaotic ammonia cyclones at the poles and a stronger magnetic field than expected.

"Everything is weird," said Brad Tucker, an astronomer from the Australian National University who is not connected to the studies.

When the Juno mission was first proposed people said, "Don't we already know stuff about Jupiter", Dr Tucker said. 

"What this shows is the answer to this is 'No, we didn't know much'. 

"Jupiter couldn't be more different from Earth in every way based on what these two papers are saying."

Lucyna Chudczer is an astronomer at the University of NSW. Dr Tucker said she probably knows more about Jupiter than anyone on the planet outside the Juno missions.

Fairfax Media spoke to Dr Chudczer by Skype from Hawaii, where she has been studying Jupiter from the Gemini North observatory at Maunu Kea, comparing ground observations with those from Juno.

"These studies are really exciting," she said. "There is just so much detail. It's going to take us a while to really unpack all the information."

Dr Tucker said: "It's absurd – this amount of information comes from just one pass of the Juno spacecraft around Jupiter on August 27."

Astronomers working on NASA's Juno mission on Friday published two papers. One study, led by Scott Bolton, looks at Jupiter's interior and deep atmosphere; the other, led by John Connerney, looks at the gas giant's magnetosphere and polar aurorae.

Together they show we still have much to learn about Jupiter. 

Planetary weather

Dr Chudczer said that it had been thought that the dynamic layer of Jupiter's atmosphere was relatively shallow, given how quickly the gas of the interior would experience high pressures.

"However, the weather of Jupiter runs deeper than expected – down to more than 400 kilometres, where pressures are greater than 300 Earth atmospheres and temperatures are about 900 Kelvin [627 degrees]," she said.

Within this layer are dynamic swirls of largely ammonia gas and some water vapour. This leads to great bands of variable heat at the surface, with cooler areas being more opaque.

"Zonal weather patterns breakdown towards the poles where we find random vertices and cyclones of ammonia," she said.

This is in distinction from Saturn, which we recently saw had a structured, hexagonal shape at its north polar region.

"The polar dynamics and structures of the atmospheres of these two planets are fundamentally different," said Dr Bolton in his paper.

In its initial pass over the poles, upon which these papers are based, Juno recorded ammonia cyclones up to 1400 kilometres across, which is 10 per cent the width of Earth.

Jupiter's core and gravity

If you wanted to get the measured strength of the magnetic and gravitational fields that Juno has detected, it tells us some new things about the core of the largest planet in the solar system.

"This suggests that Jupiter's core is half the radius of the entire planet," Dr Tucker said based on his reading of the papers. "That's really big."

Dr Bolton's paper states: "A possible interpretation for the Juno data ... requires a core that is dispersed out to perhaps as much as 0.5 planetary radius."

Dr Chudczer said that rather than a single dense core of heavier elements such as iron and nickel, there might be unevenly distributed clumps of such elements within a core of very dense metallic hydrogen, with a fuzzy boundary out to electronically neutral molecular hydrogen.

Magnetic field and auroras

This composite of Hubble Space Telescope images shows auroras at Jupiter's north pole. Photo: NASA

Dr Chudczer said these results show the processes driving the auroras at Jupiter's poles are completely different to Earth.

"On Earth, the solar winds interacting with our atmosphere and magnetic field produce intermittent auroras," she said.

"On Jupiter the magnetosphere is interacting with charged particles all the time. Some of these particles – ionic sulphur and oxygen – are most likely coming from volcanic eruptions on Jupiter's moon, Io," Dr Chudczer said.

Electrons streaming out from inside the planet are also causing the auroras, the paper said.

Dr Tucker said: "Jupiter essentially drives its own aurora ... like, what?

"We knew it had aurora but the fact that there are reactions that we cannot see on Earth, alongside huge radiation, magnetic fields and these cyclones at the poles shows that everything is weird."

Dr Chudczer said she was surprised that the emerging model of the magnetosphere is more haphazard.

"We expected more parallel currents and we haven't seen that in these papers," she said. "We'll need to change our models of the magnetic fields."

Dr Bolton's paper found "the maximum magnetic field observed ... was 7.766 Gauss", more than 10 times the size of Earth's maximum surface magnetic field, which is 0.66 Gauss at the South Pole.

Exploring other worlds

Dr Tucker said in some senses we have to think of Jupiter and its moons as its own system.

"And I like to apply what this tells us about other planetary systems," he said.

Dr Tucker has lately been focusing exoplanets. "We have been finding lots of large Jupiter and Neptune type planets around other stars," he said.

"So if Jupiter is as dynamic as these studies suggest, what does this tell us about other worlds and their formation?

"We had to see that there were so many exoplanets, but to find out more about them in the next decade we'll need to develop more detailed models of much closer planets – in our solar system."

He said that these studies of Jupiter will allow us to find out more about how systems operate and evolve and tell us things about planets around distant stars.

"By studying Jupiter and other planets in our solar system in detail, we can connect them with models of exoplanets ... and this will tell us something useful," he said.