Astronomers decipher why our solar system is shaped like a crescent

Hydrogen particles hitting the solar system from the outside could play a crucial role in determining the shape of the protective bubble around our Sun and its planets, according to a new study.

Astronomers say that this bubble, known as the heliosphere, shields the planets in our solar system from intense galactic radiation such as that from supernovae – the final explosions of dying stars throughout the universe.

Without this protective layer, scientists say there could be an increased risk to life on Earth and also to astronauts in space due to the powerful cosmic radiation.

While researchers previously argued that this magnetic bubble around the solar system is shaped like a comet, with a rounded leading edge and a long trail behind, data from various NASA missions last year suggests that it looks more like a deflated croissant.

The new study, published in The Journal of Astrophysics Friday, discovered that neutral hydrogen particles – so called because they have equal amounts of positive and negative charges – determine the shape of the heliosphere.

“The bubble around us, produced by the sun, provides protection against galactic cosmic rays, and its shape can affect how these rays enter the heliosphere,” study co-author James Drake, astrophysicist at the University of Maryland, said in a statement.

“There are a lot of theories, but of course the way galactic cosmic rays can enter can be affected by the structure of the heliosphere – does it have wrinkles and folds and that sort of thing?”, Dr Drake added.

In the study, astronomers analyzed twin jets of matter from the Sun’s poles whose paths are shaped by the interaction of the solar magnetic field with the interstellar magnetic field.

These jet streams, say the scientists, are unstable and curved by the interstellar magnetic field like the tips of a crescent.

“We see these jets projecting in the form of irregular columns, and [astrophysicists] I have wondered for years why these shapes show instabilities, ”said BU astrophysicist Merav Opher.

Scientists discovered using a computer model that when neutral hydrogen particles were removed from the simulation, jets from the sun became “super stable.”

But when they were put back in place, “things start to bend, the central axis starts to move, and that means something inside the heliospheric jets is getting very unstable,” said Dr Opher.

This kind of instability could cause disturbances in solar winds and jets emanating from our sun, scientists say, and could cause the heliosphere to split its shape into something more like a crescent.

While astrophysicists have yet to actually observe the actual shape of the heliosphere, Dr Opher’s model suggests that neutral hydrogen projected onto the solar system would prevent the heliosphere from flowing evenly like a burning comet.

Dr Drake believes the model “offers the first clear explanation for the disruption of the shape of the heliosphere in the northern and southern areas, which could impact our understanding of how galactic cosmic rays enter Earth. and in the environment close to Earth “.

“This discovery is a really major breakthrough, it really set us on the path to finding out why our model gets its distinct crescent shaped heliosphere and why other models don’t,” says Dr. Opher.

Arline J. Mercier