Data from NASA’s Cassini, Voyager and IBEX missions suggest that the solar system is surrounded by a MASSIVE, SPHERICAL shaped magnetic field. In the past, experts thought that the heliosphere was in fact a comet-shaped structure, with a rounded head and an extended tail. But new data covering an entire 11-year cycle of solar activity shows that this may not be the case.
According to scientists, our Sun releases a constant flux of magnetic solar material—called solar wind—that fills the inner solar system, and extends beyond the orbit of Neptune.
Shown in a Hubble Space Telescope image, the “astrosphere” around the star L.L. Orionis approximates the heliosphere around our solar system. IMAGE COURTESY ESA/NASA
This wind creates something that can be explained as a bubble, some 37 million kilometers wide, called the heliosphere. Our entire solar system, including the H, moves through interstellar space. Just as Earth orbits the Sun, our Sun orbits the galactic center –which from our vantage point is located around 25,00 light years— in an elliptic orbit. It completes a revolution every 225 million years approximately—called a Galactic year.
Anyway, getting back on track, this new discovery calls into question the alternate view of the solar magnetic fields trailing behind the sun in the shape of a long comet tail—almost like a kite.
Until now, scientists thought that the heliosphere was in fact a comet-shaped structure, with a rounded head and an extended tail. But new data covering an entire 11-year cycle of solar activity shows that this may not be the case: the heliosphere is most likely rounded at both ends, making its shape almost spherical. An article featuring the results of the study was published in Nature Astronomy.
“Instead of a prolonged, comet-like tail, this rough bubble-shape of the heliosphere is due to the strong interstellar magnetic field—much stronger than what was anticipated in the past—combined with the fact that the ratio between particle pressure and magnetic pressure inside the heliosheath is high,” says Kostas Dialynas of the Academy of Athens in Greece, lead author of the study. Interestingly, Cassini—which has explored Saturn for over a decade—using its Magnetospheric Imaging Instrument discovered surprising new data about the shape of the heliosphere’s trailing end, the heliotail.
“Our Cassini instrument was designed to image the ions that are trapped in the magnetosphere of Saturn,” says coauthor Tom Krimigis, of the Johns Hopkins Applied Physics Laboratory, an instrument lead on the Cassini and Voyager missions. “We never thought that we would see what we’re seeing and be able to image the boundaries of the heliosphere.”
Since these particles move only at a small fraction of the speed of light, their trip from the sun to the edge of the heliosphere and back takes quite a lot. Now, when the number of particles coming from the sun changes, it takes years before that is reflected in the amount of natural atoms shooting back into the solar system. As Cassini was orbiting Saturn, its instruments measured the neutral atoms revealed surprising details—the particles coming from the ‘tail’ of our solar system’s heliosphere reflect the changes in the solar cycle almost exactly as fast as those coming from the nose of the heliosphere.
“If the heliosphere’s ‘tail’ is stretched out like a comet, we’d expect that the patterns of the solar cycle would show up much later in the measured neutral atoms,” said Krimigis.
What does this mean? Well, since patterns of solar activity show just as quickly on one side of the heliosphere as the other, it implies that the tail of the heliosphere is around the same distance from us as the nose. In other words, the comet-like tail that scientists thought existed previously may not be there at all, as the heliosphere that wraps the solar system is nearly round.
Scientists note that a spherical heliosphere may exist due to a number of reasons. First of all, data gathered by the voyager 1 probe shows that the interstellar magnetic field beyond the heliosphere is much stronger than scientists had expected.
“This data that Voyager 1 and 2, Cassini and IBEX provide to the scientific community is a windfall for studying the far reaches of the solar wind,” says Arik Posner, NASA’s Voyager and IBEX program scientist. “As we continue to gather data from the edges of the heliosphere, this data will help us better understand the interstellar boundary that the heliosphere, this data will help us better understand the interstellar boundary that helps shield the Earth environment from harmful cosmic rays.”