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Is Our Solar System Shaped Like a Croissant or a Jumbo Shrimp?

Photo credit: Opher, et al
Photo credit: Opher, et al

From Popular Mechanics

  • Astronomers have long tried to define the shape of our solar system.

  • Researchers used readings from various NASA missions to plot the contents of the solar system and, subsequently, its shape.

  • New research reveals our solar system may actually be shaped like a deflated croissant or, depending on how you look at it, a jumbo shrimp.


Our sun emits powerful solar winds that wrap around the planets in our solar system like a giant bubble. This magnetic bubble, called the heliosphere, protects the planets from harmful cosmic radiation jettisoned out in the wake of powerful cosmic events like supernovae.

Scientists have long suspected the heliosphere might be shaped like a comet, with a distinct, pointed "nose" and a long, sweeping tail. But according to new research published in the journal Nature Astronomy, that's not the case. The truth is much tastier.

You love our badass universe. So do we. Let's nerd out over it together.

After conducting a series of simulations using data from various NASA missions, a team of astronomers now believes our solar system's heliosphere may be shaped like a "deflated croissant." Personally, we see a jumbo shrimp.

Photo credit: Getty/Opher, et al
Photo credit: Getty/Opher, et al

Scientists recently pinpointed the location of the center of the solar system, but defining its shape from within is a tricky task. To get a sense of what shape the solar system takes, researchers first need to identify all of the materials inside it. Obviously, we have planets and moons, asteroids and comets, tiny bacteria, and Steve Buscemi. But there's a whole lot of other stuff in there, too.

Data from the boundary between the solar system and the rest of space—known as the heliopause—is sparse. The Voyager spacecraft, which launched in 1977, reached the edge of the solar system only a few years ago. That brings the total in-situ edge-of-solar-system data points to, well, two.

Fortunately, other missions provide helpful clues that allow scientists to create a rough outline of our bubble-like home.

NASA's Interstellar Boundary Explorer (IBEX) mission studies cosmic rays that speed toward Earth from the distant reaches of the galaxy, as well as another type of particle called an energetic neutral atom, which originates here in the solar system. They zip around, bumping into the heliopause—a whopping 10 billion miles from Earth—and zoom back toward our planet. The Cassini mission, which swirled around Saturn and its many moons between 2004 and 2017, also had an instrument that studied these particles.

The New Horizons mission has been particularly helpful. As the spacecraft has swept through the solar system—past Pluto, Charon, and Arrokoth—it has gathered readings on a special type of particle carried by solar winds called a pick-up ion. These Frankensteinian pick-up ions are way, way hotter than other, much-chillier charged particles found in solar wind because they've been ionized out in space.

“If you have some cold fluid and hot fluid, and you put them in space, they won’t mix — they will evolve mostly separately," astronomer Merav Opher, of Boston University, said in a statement. "What we did was separate these two components of the solar wind and model the resulting 3D shape of the heliosphere.”

If we plan to venture farther out into the solar system, understanding its shape will be critical. It could help us prepare our astronauts and their future living spaces for the onslaught of radiation they'll face on the moon, Mars, and beyond.

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