July 17, 2024
1 Solar System Way, Planet Earth, USA

Scientists want to study the heliosphere: here's how they could do it

The Sun warms the Earth, making it habitable for people and animals. But that's not all it does, as it affects a much larger area of ​​space. The heliospherethe area of ​​space influenced by the Sun, It is a hundred times bigger than the distance from the Sun to the Earth.

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 steady solar windThe Sun also occasionally releases plasma eruptions called coronal mass ejectionswhich can contribute to the dawnand bursts of light and energy, called flares.

Plasma leaving 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 liked it I want to understand the heliosphere and how it interacts with the interstellar medium.

The eight known planets of the solar system, the asteroid belt between Mars and Jupiter, and the Kuiper Belt (the band of celestial objects beyond Neptune that includes the planetoid Pluto) all lie within the heliosphere. The heliosphere is so large that objects in the Kuiper Belt orbit closer to the Sun than they do to the Sun. the closest limit of the heliosphere.

Credit: JHU/APL

Protection of the heliosphere

As distant stars explode, expel large amounts of radiation into interstellar space in the form of highly energized 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. from the effects of cosmic radiation, but even before that, the heliosphere itself acts as a cosmic shield against most interstellar radiation.

In addition to cosmic radiation, neutral particles and dust constantly flow into the heliosphere from the local interstellar medium. These particles can It affects the space around the Earth and can even alter How the solar wind reaches Earth.

Supernovae and the interstellar medium may also have played a role The origins of life and The evolution of humans on Earth. Some researchers predict that millions of years ago, the heliosphere came into contact with a cloud of dense, cold particles in the interstellar medium that caused the heliosphere to shrinkexposing Earth to the local interstellar medium.

An unknown form

But scientists don't really know what shape the heliosphere is. Models vary in shape From spherical shapes to comet-shaped or croissant-shaped shapes. These predictions vary in size hundreds to thousands of times the distance from the Sun to 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 spacecraft has been able to accurately observe the heliosphere from the outside or take adequate samples of the local interstellar medium. This could provide scientists with more information about the shape of the heliosphere and its interaction with the local interstellar medium, the space environment beyond the heliosphere.

Crossing the heliopause with Voyager

In 1977, NASA launched the Voyager Mission:Their two spacecraft flew by Jupiter, Saturn, Uranus and Neptune in the outer solar system. Scientists have determined that after observing these gas giants, the probes separately It crossed the heliopause and entered interstellar space. in 2012 and 2018, respectively.

While Voyager 1 and 2 are the only probes to have potentially crossed the heliopause, they have already far exceeded their expected lifetimes. no longer returns the necessary data as their instruments fail or slowly shut down.

These spacecraft were designed to study planets, not the interstellar medium, which means they don't have the right instruments to take all the measurements of the interstellar medium or heliosphere that scientists need.

That's where a potential interstellar probe mission could come in handy. A probe designed to fly beyond the heliopause would help scientists understand the heliosphere by observing it from the outside.

An interstellar probe for the heliosphere

Since the heliosphere is so large, It would take decades for a probe to reach the limiteven using a gravity assist of a massive 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 launched, the probe will take 50 years or more, depending on the trajectory, to reach the interstellar medium. This means that the longer NASA waits to launch a probe, the longer scientists will be left without missions operating in the outer heliosphere or the local interstellar medium.

NASA is considering developing a interstellar probeThe probe would take measurements of plasma and magnetic fields in the interstellar medium and image the heliosphere from the outside. To prepare for it, NASA asked more than 1,000 scientists to come up with a mission concept.

The initial report It was recommended that the probe travel on a trajectory that was about 45 degrees away from the direction of the nose of the heliosphere. This trajectory would again follow part of Voyager's path, but would reach some new regions of space. In this way, scientists would be able to study new regions and revisit some partially known regions of space.

This trajectory would only give the probe a partially angled view of the heliosphere and would not be able to see the heliotail, the region about which scientists know the least.

In the heliotail, scientists predict that the plasma that makes up the heliosphere mixes with the plasma that makes up the interstellar medium. This happens through a process called magnetic reconnectionwhich allows charged particles to flow from the local interstellar medium into the heliosphere. Like neutral particles entering through the nose, these particles affect the space environment within the heliosphere.

In this case, however, the particles are charged and can interact with solar and planetary magnetic fields. While these interactions occur at the edges of the heliosphere, far from Earth, they affect the composition of the interior of the heliosphere.

in a New study In a paper published in Frontiers in Astronomy and Space Sciences, my colleagues and I evaluated six possible launch directions spanning from tip to tail. We found that rather than departing near the tip, a trajectory that intersected the flank of the heliosphere toward the tail would give the best perspective of the heliosphere's shape.

A trajectory in this direction would offer scientists a unique opportunity to study an entirely new region of space within the heliosphere. As the probe exits the heliosphere into interstellar space, it would get a view of the heliosphere from the outside at an angle that would give scientists a more detailed idea of ​​its shape, especially in the contested tail region. In the end, whatever direction an interstellar probe is launched, the science it gains will be invaluable — and, quite literally, astronomical.

This article first appeared in The conversationRepublished here under a Creative Commons license.

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