Contrary to earlier visualisations, the sun's heliosphere is dominated by two giant jets of material shooting backwards over the north and south poles of the sun.
The heliosphere is created by the solar wind, the changed particles emitted by the sun. The heliosphere extends far beyond the planets of the solar system. These two jets are confined by the interaction of the sun's magnetic field with the interstellar magnetic field.
"Everyone's assumption has been that the shape of the heliosphere was molded by the flow of interstellar material passing around it," said Merav Opher, astronomer at Boston University and lead author of the NASA-funded study.
Scientists have for decades visualised the heliosphere in the shape of a comet, with a very long tail extending some 464 billion miles. The two jets are similar to other astrophysical jets seen in space, so studying them locally could open doors to understanding such jets throughout the universe.
"Scientists thought the solar wind flowing down the tail could easily pull the magnetic fields in the heliosphere along as it flowed by, creating this long tail. But it turns out that the magnetic fields are strong enough to resist that pull - so instead they squeeze the solar wind and create these two jets," said Opher.
The team could determine the new shape when they adjusted simulations of the heliosphere based on observations collected from NASA's Voyager 1 spacecraft.
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The spacecraft recently moved outside of the heliosphere into interstellar space. "If there were no interstellar flow, then the magnetic fields around the sun would shape the solar wind into two jets pointing straight north and south," said Jim Drake at the University of Maryland in College Park.
"If we're right about all of this, it gives us a local test bed for exploring some very important physics," Drake concluded.
The study findings were detailed in the Astrophysical Journal Letters.