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 |
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.
A compact model of the heliosphere. Image credit: Dialynas et al. |
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.”
Original Study
Original Study
No comments