Studying the protective bubble of our solar system – archyde

Is this what the heliosphere looks like? BU-led research suggests this. The size and shape of the magnetic “force field” that protects our solar system from deadly cosmic rays has long been discussed by astrophysicists. Source: Merav Opher, et. al

A multi-agency team of astrophysicists headquartered at Boston University, led by BU astrophysicist Merav Opher, made a groundbreaking discovery in our understanding of the cosmic forces that form the protective bubble around our solar system – a bubble that defines life on earth protects and is known by space researchers as the heliosphere.

Astrophysicists believe that the heliosphere protects the planets in our solar system from the strong radiation emitted by supernovae, the final explosions of dying stars in the entire universe. They believe that the heliosphere extends far beyond our solar system, but despite the massive buffer against cosmic radiation that the heliosphere provides to life forms on earth, nobody knows the shape of the heliosphere – or its size.

“To what extent is this relevant for society? The bubble that surrounds us, produced by the sun, provides protection from galactic cosmic rays, and its shape can affect how those rays get into the heliosphere, ”said James Drake, University of Maryland astrophysicist who works with Opher. “There are many theories, but of course the way galactic cosmic rays enter can be influenced by the structure of the heliosphere – does it have folds and something?”

Opher’s team has created some of the most compelling computer simulations of the heliosphere based on models based on observable data and theoretical astrophysics. At the BU, in the Center for Space Physics, Opher, a professor of astronomy at the College of Arts & Sciences, heads a NASA DRIVE (Diversity, Realize, Integrate, Venture, Educate) science center that is worth $ 1.3 million is supported in NASA funds. This team, made up of Opher experts 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).

Since the BU’s NASA DRIVE Science Center first received funding in 2019, Opher’s SHIELD team has been looking for answers to several puzzling questions: What is the overall structure of the heliosphere like? How do its ionized particles develop and how do they influence heliospheric processes? How does the heliosphere interact and influence the interstellar medium, matter and radiation between the stars? And how is cosmic radiation filtered by the heliosphere or transported through it?

“SHIELD combines theory, modeling, and observations to create comprehensive models,” says Opher. “All of these different components work together to understand the mysteries of the heliosphere.”

And now a paper published by Opher and co-workers in Astrophysikalisches Journal shows that neutral hydrogen particles flowing from outside our solar system most likely play a crucial role in shaping our heliosphere.

In their latest study, Opher’s team wanted to understand why heliospheric jets – blooming columns of energy and matter that resemble other types of cosmic jets throughout the universe – are becoming unstable. “Why do stars and black holes – and our own sun – eject unstable jets?” says Opher. “We see these jets projecting as irregular pillars, and [astrophysicists] have been wondering for years why these forms are unstable. “

New research led by BU astrophysicist Merav Opher could explain why the heliosphere, a protective magnetic “force field” that emanates from our sun and surrounds our solar system, is likely to be unstable and irregularly shaped. “The universe is not calm,” says Opher. “Our BU model doesn’t try to clean up the mess.” Source: Merav Opher, et. al

Similarly, SHIELD models predict that the heliosphere, which travels with our sun and encompasses our solar system, does not appear to be stable. Other models of the heliosphere developed by other astrophysicists tend to depict the heliosphere as a comet-like shape, with a jet – or “tail” – flowing behind it. In contrast, Opher’s model suggests that the heliosphere is shaped more like a croissant or even a donut.

The reason for this? Neutral hydrogen particles, so named because they have equal amounts of positive and negative charge that have no charge at all.

“They come pouring across the solar system,” says Opher. Using a computational model like a recipe to test the effect of ‘neutrals’ on the shape of the heliosphere, she “took an ingredient from the cake – the neutrals – and noticed that it was the rays of the sun that shape the heliosphere super stable. When I put them back in, things bend, the central axis starts shaking, and that means something inside the heliospheric jets becomes very unstable. “

Such instability would, in theory, cause perturbations in the solar winds and jets emanating from our sun and cause the heliosphere to split its shape – into a croissant-like shape. Although astrophysicists have not yet developed methods of observing the actual shape of the heliosphere, Opher’s model suggests that neutrals are in ours Solar- System would make it impossible for the heliosphere to flow uniformly like a shooting comet. And one thing is certain – neutrals are definitely racing through space.

Drake, a co-author of the new study, says that Opher’s model “provides the first clear explanation of why the shape of the heliosphere is breaking up in the northern and southern areas, which could affect our understanding of how galactic cosmic rays hit Earth and in the closer environment arrives – earth environment. ” That could undermine the radiation threat to life on Earth and also to astronauts in space or future pioneers trying to travel to Mars or other planets.

“The universe is not calm,” says Opher. “Our BU model doesn’t try to clean up the mess, which has allowed me to pinpoint the cause [of the heliosphere’s instability]…. The neutral hydrogen particles. “

In particular, the presence of the neutrals colliding with the heliosphere triggers a phenomenon well known to physicists called Rayleigh-Taylor instability, which occurs when two materials of different densities collide, with the lighter material pressing against the heavier material. This happens when oil floats over water and heavier liquids or materials float over lighter liquids. Gravity plays a role and leads to wildly irregular shapes. In cosmic jets, the resistance between the neutral hydrogen particles and charged ions creates an effect similar to that of gravity. The “fingers” seen in the famous Horsehead Nebula, for example, are caused by the Rayleigh-Taylor instability.

“This finding is a really big breakthrough, it really got us to figure out why our model has its distinct croissant-shaped heliosphere and why other models don’t,” says Opher.

Uncover the shape of our solar system

More information:

M. Opher et al., A Turbulent Heliosheath Powered by the Rayleigh-Taylor Instability, The Astrophysical Journal (2021). DOI: 10.3847 / 1538-4357 / ac2d2e

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Quote: Investigation of the protective bubble of our solar system (2021, December 3), accessed on December 3, 2021 from

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