This article was originally published on The conversation. The publication contributed the article to Space.com Expert Voices: Opinion Pieces and Insights.
Sarah Spitzer is a researcher in climate and space science and engineering at the University of Michigan.
The sun warms the earth, making it habitable for humans and animals. But that’s not all it does, and it affects a much larger area of space. The heliospherethe area of room influenced by the sun, is more than a hundred times larger then the distance from the sun to the Soil.
The Sun is a star that constantly emits a steady stream of plasma—highly energized ionized gas—called the solar wind. In addition to the constant solar wind, the Sun also occasionally releases bursts of plasma called coronal mass ejections, which can contribute to the aurorae, and bursts of light and energy called flares.
The plasma emanating from the Sun expands through space, along with the Sun’s magnetic field. Together, they form the heliosphere within the surrounding local interstellar medium – the plasma, neutral particles, and dust that fill the space between stars and their respective astrospheres. Heliophysicists like me want to understand the heliosphere and how it interacts with the interstellar medium.
The eight known planets in the solar systemthe asteroid belt between Mars And Jupiterand the Kuiper Belt – the band of celestial bodies beyond Neptune to which the asteroid also belongs Pluto – are all in the heliosphere. The heliosphere is so large that objects in the Kuiper Belt orbit closer to the sun than to the nearest boundary of the heliosphere.
Related: Something spooky is happening at the edge of the solar system
Protection of the heliosphere
As distant stars explode, emit large amounts of radiation in interstellar space in the form of very energetic particles known as cosmic raysThese cosmic rays can be dangerous to living organisms and can damage electronic devices and spacecraft.
The Earth’s atmosphere protects life on the planet against the effects of cosmic rays, but even before that the heliosphere itself acts as a cosmic shield against most interstellar radiation.
In addition to cosmic rays, neutral particles and dust are steadily streaming into the heliosphere from the local interstellar medium. These particles can affect the space around the Earth and can even change how the solar wind reaches earth.
Supernovae and the interstellar medium may also have had an influence the origin of life And the evolution of man on Earth. Some researchers predict that millions of years ago the heliosphere came into contact with a cold, dense cloud of particles in the interstellar medium that caused the heliosphere to shrinkexposing the Earth to the local interstellar medium.
An unknown shape
However, scientists do not know exactly what shape the heliosphere has. Models vary in shape from spherical to comet-shaped to croissant-shaped. These predictions vary in size by hundreds to thousands of times the distance of the sun to the earth.
However, scientists have defined the direction in which the Sun is moving as the “nose” direction and the opposite direction as the “tail” direction. The nose direction should have the shortest distance to the heliopause – the boundary between the heliosphere and the local interstellar medium.
No probe has ever been able to get a good look at the heliosphere from outside or sample the local interstellar medium properly. This could tell scientists more about the shape of the heliosphere and how it interacts with the local interstellar medium, the space environment outside the heliosphere.
Crossing the Heliopause with Voyager
In 1977, NASA launched the Voyager mission:The two spacecraft flew past Jupiter, Saturn, Uranus And Neptune in the outer solar system. Scientists have determined that after observing these gas giantsthe probes crossed the heliopause separately and entered interstellar space in 2012 and 2018 respectively.
While Traveler 1 and 2 are the only probes ever to potentially cross the heliopause, they are well past their intended mission lifetime. They can no longer return the required data while their instruments slowly break or fail.
These spacecraft are designed to study planets, not the interstellar medium. This means they don’t have the right instruments to make all the measurements of the interstellar medium or the heliosphere that scientists need.
That’s where a potential interstellar probe mission could come in. A probe designed to fly beyond the heliopause would help scientists understand the heliosphere by observing it from the outside.
An interstellar probe
Because the heliosphere is so large, it would take decades to reach the bordereven using gravity assist of a large planet like Jupiter.
The Voyager spacecraft will no longer be able to provide data from interstellar space long before an interstellar probe leaves the heliosphere. And once the probe is launched, it will take about 50 years or more to reach the interstellar medium, depending on its orbit. This means that the longer NASA The longer the space journey takes to launch a probe, the longer scientists will be unable to conduct missions into the outer heliosphere or the local interstellar medium.
NASA is considering a interstellar probe. This probe would make measurements of the plasma and magnetic fields in the interstellar medium and image the heliosphere from outside. In preparation, NASA sought input from more than 1,000 scientists on a mission concept.
The first report recommended that the probe travel on a trajectory that is about 45 degrees off the nose of the heliosphere. This trajectory would follow part of Voyager’s path, while reaching some new regions of space. This would allow scientists to study new areas and revisit some partially known regions of space.
This way, the probe would have only a partial view of the heliosphere and would not be able to see the heliotail, the region scientists know the least about.
In the heliotail, scientists predict that the plasma that makes up the heliosphere mixes with the plasma that forms the interstellar medium. This occurs through a process called magnetic reconnectionwhich allows charged particles to flow from the local interstellar medium into the heliosphere. Like the neutral particles entering through the nose, these particles influence the spatial environment within the heliosphere.
In this case, however, the particles have a charge and can interact with magnetic fields from the Sun and planets. Although these interactions occur at the boundaries of the heliosphere, far from Earth, they influence the composition of the interior of the heliosphere.
In a new study published in Frontiers in Astronomy and Space Sciences, my colleagues and I evaluated six possible launch directions, ranging from the nose to the tail. We found that rather than starting close to the nose direction, a trajectory that crosses the flank of the heliosphere toward the tail direction would provide the best perspective on the shape of the heliosphere.
A trajectory in this direction would give scientists a unique opportunity to study an entirely new region of space within the heliosphere. As the probe leaves the heliosphere and enters interstellar space, it would get a view of the heliosphere from outside at an angle that would give scientists a more detailed idea of its shape – particularly in the contested tail region.
Ultimately, the science an interstellar probe returns will be invaluable and literally astronomical in nature, regardless of the direction in which it is launched.