Studying our solar system's protective bubble

Is this what the sky looks like? BU-led research suggests so. astrophysicists have debated the size and shape of the magnetic force field that protects our solar system. Credit: Merav Opher.

A multi-institutional team of astrophysicists based at Boston University, led by Merav Opher, has made a breakthrough discovery in our understanding of the Cosmic forces that shape the protective bubble surrounding our solar system.

The final explosions of dying stars throughout the universe are believed to protect the planets in our solar system from the powerful radiation from the supernovas. Despite the huge buffer against radiation that the heliosphere provides, no one really knows the shape of it.
How is this relevant to society? The shape of the bubble that surrounds us, produced by the sun, can affect how the rays get into the heliosphere. The structure of the heliosphere can affect the way that Cosmic rays can get in.

Opher's team has constructed some of the most compelling computer simulations of the heliosphere, based on models built on observable data and theoretical astrophysics. The Center for Space Physics at BU has a NASA DRIVE Science Center that is supported by over one million dollars in NASA funding. The team of experts Opher recruited from 11 other universities and research institutes developed models of the heliosphere in an effort called SHIELD.
Opher's SHIELD team has been looking for answers to several puzzling questions since BU's NASA DRIVE Science Center received funding in 2019. How do the ionized particles affect the heliospheric processes? The matter and radiation that exists between stars are influenced by the heliosphere. How do the rays get through the heliosphere?
Opher says that SHIELD combines theory, modeling, and observations to build comprehensive models. The components work together to understand the puzzles of the heliosphere.

A paper published by Opher and his team in Astrophysical Journal shows that neutral hydrogen particles streaming from outside our solar system play a crucial role in the way our heliosphere takes shape.

Opher's team wanted to understand why heliospheric jets become unstable, similar to other types of jets found throughout the universe. Why do stars and black holes shoot unstable jets? Opher says so. "We see these jets projecting as irregular columns, and we have been wondering for years why these shapes present instabilities."

New research led by BU astrophysicist Merav Opher could explain why the heliosphere, a protective magnetic field from our sun, is likely unstable and irregularly shaped. Opher says that the universe is not quiet. The BU model doesn't try to cut out chaos. Credit: Merav Opher.

SHIELD models predict that the heliosphere, which is traveling in tandem with our sun, doesn't appear to be stable. Other models of the heliosphere tend to depict it as a comet-like shape with a jet behind it. Opher's model suggests that the heliosphere is shaped like a donut.

The reason for that? The neutral hydrogen particles have the same amount of positive and negative charge and net no charge at all.

Opher says that they come through the solar system. She took one ingredient out of the recipe and noticed that the jets coming from the sun became super stable. The center axis starts wiggling when I put them back in, that means something inside the heliospheric jets is becoming unstable.

Instability like that would cause the heliosphere to split into two parts, causing the solar winds and jets to change shape. Opher's model suggests that neutrals slamming into our solar system would make it impossible for the heliosphere to flow uniformly. neutrals are definitely moving through space

Drake says Opher's model is the first clear explanation for why the shape of the heliosphere breaks up in the northern and southern areas. It could affect the risk of radiation to life on Earth and also for astronauts in space or future pioneers attempting to travel to Mars or other planets.

Opher says that the universe is not quiet. The BU model doesn't try to cut out the chaos, which has allowed me to identify the cause of the instability. The hydrogen particles are neutral.

The presence of neutrals colliding with the heliosphere causes a phenomenon known as the Rayleigh-Taylor instability, which occurs when two materials of different densities collide, with the lighter material pushing against the heavier material. When oil is suspended above water and heavier fluids are suspended above lighter fluids, it's what happens. Some wildly irregular shapes are caused by gravity. The drag between the neutral hydrogen particles and charged ion creates a similar effect as gravity. The "fingers" seen in the Horsehead Nebula are caused by the instability of the Rayleigh-Taylor.
Opher says that the finding is a major breakthrough and that it will lead to discovering why other models don't.

M. Opher and her team wrote about a Turbulent Heliosheath driven by the Rayleigh–Taylor Instability in The Astrophysical Journal. There is a book titled "10847/1538-4357/ac2d2e".

The Astrophysical Journal has information.

The protective bubble of the solar system was studied on December 3, 2021.

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