NASA is considering creating a probe to study the heliosphere
- June 9, 2024
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The Sun warms the Earth, making it habitable for humans and animals. But that’s not the only thing it does, and it affects a much wider area of
The Sun warms the Earth, making it habitable for humans and animals. But that’s not the only thing it does, and it affects a much wider area of
The Sun warms the Earth, making it habitable for humans and animals. But that’s not the only thing it does, and it affects a much wider area of space. The heliosphere, the region of space affected by the Sun, is more than a hundred times the distance from the Sun to the Earth.
The Sun is a star that constantly emits a steady stream of plasma, a high-energy ionized gas called the solar wind. In addition to the persistent solar wind, the sun also occasionally produces bursts of light and energy called flares and bursts of plasma called coronal mass ejections that can contribute to the aurora borealis.
Plasma from the Sun expands in space along with the Sun’s magnetic field. Together, they form the heliosphere (plasma, neutral particles, and dust that fill the space between stars and associated astrospheres) in the surrounding local interstellar medium. Heliophysicists like me want to understand the heliosphere and how it interacts with the interstellar medium.
The Solar System’s eight known planets, the asteroid belt between Mars and Jupiter, and the Kuiper belt, a belt of celestial bodies beyond Neptune that includes the planetoid Pluto, are all in the heliosphere. The heliosphere is so large that objects orbiting the Kuiper belt are closer to the Sun than to the nearest boundary of the heliosphere.
When distant stars explode, they release large amounts of radiation into interstellar space in the form of high-energy particles known as cosmic rays. These cosmic rays can be dangerous to living organisms and damage electronic devices and spacecraft.
Earth’s atmosphere protects life on the planet from 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 enter the heliosphere from the local interstellar medium. These particles can affect the space around Earth and even change the path of the solar wind reaching Earth.
Supernovae and interstellar environments may also have influenced the origin of life and the evolution of humans on Earth. Some researchers propose that millions of years ago the heliosphere came into contact with a cold, dense cloud of particles in the interstellar medium, causing the heliosphere to compress, exposing Earth to the local interstellar medium.
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But scientists don’t really know what the shape of the heliosphere is. The shapes of the models vary from spherical to comet-shaped and croissant-shaped. The sizes of these projections vary by hundreds to thousands of times the distance from the Sun to the Earth. However, scientists have defined the direction in which the Sun moves as the “nose” direction, and the opposite direction as the “tail” direction. The nose direction should have the shortest distance to the heliopause, which is the boundary between the heliosphere and the local interstellar medium.
No probe has been able to get a good look at the heliosphere from outside or adequately sample the local interstellar environment. This could give scientists more information about the shape of the heliosphere and how it interacts with the local interstellar medium, the space environment outside the heliosphere.
In 1977, NASA launched the Voyager mission: two spacecraft flew past Jupiter, Saturn, Uranus, and Neptune in the outer solar system. After observing these gas giants, scientists determined that the probes entered interstellar space by separately crossing the heliopause in 2012 and 2018, respectively.
Although Voyager 1 and Voyager 2 were the only probes that could potentially pass the heliopause, they far exceeded their planned lifetime. They can no longer retrieve the data they need as their devices slowly fail or shut down.
This spacecraft was designed to study planets, not the interstellar medium. This means that scientists do not have the right tools to make all the measurements of the interstellar medium, or heliosphere, that they need. This is where a potential interstellar probe mission could come into play. Designed to fly beyond the heliopause, the probe will help scientists understand the heliosphere by observing it from the outside.
Because the heliosphere is so large, it would take decades for the probe to reach the limit, even if it used the gravitational assistance of a massive planet like Jupiter.
The Voyager spacecraft will no longer be able to provide data from interstellar space long before the 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 the orbit. This means that the longer NASA waits to launch a probe, the less likely scientists will be able to perform missions in the outer heliosphere or local interstellar medium.
NASA is considering developing an interstellar probe. This probe will measure plasma and magnetic fields in the interstellar medium and image the heliosphere from the outside. To prepare, NASA asked more than 1,000 scientists for input on the mission concept.
The initial report recommended that the probe proceed in an orbit of approximately 45 degrees from the nose of the heliosphere. This orbit will follow part of Voyager’s path as it reaches some new regions of space. In this way, scientists will be able to explore new regions and revisit some partially known regions of space. This path would give the probe only a partial, angled view of the heliosphere and would not see the helio tail, which scientists in the region know the least about.
In the Heliotail, scientists speculate that the plasma that forms the heliosphere mixes with the plasma that forms the interstellar medium. This occurs through a process called magnetic reconnection, which allows charged particles to flow from the local interstellar medium into the heliosphere. Similar to neutral particles entering the nose, these particles affect the space environment in the heliosphere.
But in this case the particles have a charge and can interact with solar and planetary magnetic fields. Although these interactions occur at the boundaries of the heliosphere, far from Earth, they affect the composition of the heliosphere’s interior.
In a new study published in the journal Frontiers in Astronomy and Space Sciences, my colleagues and I evaluated six potential launch paths, from nose to tail. We found that an orbit passing from the side of the heliosphere towards the tail, rather than exiting near the nose, would give the best perspective on the shape of the heliosphere.
An orbit in this direction will give scientists a unique opportunity to study a completely new area of space in the heliosphere. Once the probe exits the heliosphere and enters interstellar space, it will be able to image the heliosphere from the outside, particularly in the disputed tail region, at an angle that will give scientists a more detailed picture of its shape. Ultimately, no matter which direction the interstellar probe goes, the science it will bring will be priceless and literally astronomical.
Source: Port Altele
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