“The universe is not quiet,” Opher says.
“Our BU model doesn’t try to cut out the chaos.” Credit: Merav Opher, et.A multi-institutional team of astrophysicists headquartered at Boston University, led by BU astrophysicist Merav Opher, has made a breakthrough discovery in our understanding of the cosmic forces that shape the protective bubble surrounding our solar system—a bubble that shelters life on Earth and is known by space researchers as the heliosphere?
They believe the heliosphere extends far beyond our solar system, but despite the massive buffer against cosmic radiation that the heliosphere provides Earth’s life-forms, no one really knows the shape of the heliosphere—or, for that matter, the size of it.
The bubble that surrounds us, produced by the sun, offers protection from galactic cosmic rays, and the shape of it can affect how those rays get into the heliosphere,” says James Drake, an astrophysicist at University of Maryland who collaborates with Opher.
“There’s lots of theories but, of course, the way that galactic cosmic rays can get in can be impacted by the structure of the heliosphere—does it have wrinkles and folds and that sort of thing?”?
That team, made up of experts Opher recruited from 11 other universities and research institutes, develops predictive models of the heliosphere in an effort the team calls SHIELD (Solar-wind with Hydrogen Ion Exchange and Large-scale Dynamics)?
The size and shape of the magnetic “force field” that protects our solar system from deadly cosmic rays has long been debated by astrophysicists?
And how do cosmic rays get filtered by, or transported through, the heliosphere.“SHIELD combines theory, modeling, and observations to build comprehensive models,” Opher says.And now a paper published by Opher and collaborators in Astrophysical Journal reveals that neutral hydrogen particles streaming from outside our solar system most likely play a crucial role in the way our heliosphere takes shape?In their latest study, Opher’s team wanted to understand why heliospheric jets—blooming columns of energy and matter that are similar to other types of cosmic jets found throughout the universe—become unstable.
“Why do stars and black holes—and our own sun—eject unstable jets?” Opher says.Similarly, SHIELD models predict that the heliosphere, traveling in tandem with our sun and encompassing our solar system, doesn’t appear to be stable.
Other models of the heliosphere developed by other astrophysicists tend to depict the heliosphere as having a comet-like shape, with a jet—or a “tail”—streaming behind in its wake.
In contrast, Opher’s model suggests the heliosphere is shaped more like a croissant or even a donut.“They come streaming through the solar system,” Opher says.
Although astrophysicists haven’t yet developed ways to observe the actual shape of the heliosphere, Opher’s model suggests the presence of neutrals slamming into our solar system would make it impossible for the heliosphere to flow uniformly like a shooting comet.Drake, a coauthor on the new study, says Opher’s model “offers the first clear explanation for why the shape of the heliosphere breaks up in the northern and southern areas, which could impact our understanding of how galactic cosmic rays come into Earth and the near-Earth environment.” That could affect the threat that radiation poses to life on Earth and also for astronauts in space or future pioneers attempting to travel to Mars or other planets.“This finding is a really major breakthrough, it’s really set us in a direction of discovering why our model gets its distinct croissant-shaped heliosphere and why other models don’t,” Opher says.
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