At the European Geosciences Union (EGU) 2021 Annual Meeting in April, NASA presented a new plan to explore interstellar space beyond our solar system – launching an interstellar probe that is scheduled to fly out of our solar system within 15 years to examine distant space that humans have never visited.
To date NASA’s Voyager 1 and 2 are the longest-operating probes in human history and located in the most distant space. They were launched in 1977 and left the solar system to fly into interstellar space in 2012 and 2018, respectively. The process took three to four decades.
NASA hopes that the next probe to be launched will take much less time to fly out of the solar system than Voyager, which is about 10 times faster. One of its main goals is to examine the heliosphere from the outside of the solar system.
Scientists define the solar system by calling the entire area that the solar wind, the plasma blown by the sun, can reach the heliosphere. The space inside the heliosphere is as far as the Sun’s magnetic field can protect it; outside the heliosphere, it is filled with all kinds of interstellar matter. The boundary zone of the heliosphere is the watershed where these two types of matter meet. Preliminary studies show some kind of interaction between them, such as the production of some high-energy neutral atoms. This is exactly what scientists are now keen to explore.
Furthermore, the shape of the heliosphere is another issue that scientists are not sure about. The sun is a sphere, and the solar wind blows out in all directions, creating a solar circle that should also be a sphere. But the study found that this is not the case. Most physicists believe that the solar system is also moving at high speed within the Milky Way, so the heliosphere is a comet-like shape, with a thin “front” and a long tail at the “back. The study, selected for the cover of Nature Astronomy in July 2020, suggests that the solar sphere does not have such a tail, but is more like the shape of a croissant.
Previously, detecting these issues has been difficult because we have been located in the inner part of the heliosphere. Elena Provornikova of the Johns Hopkins University Applied Physics Laboratory (APL), the leader of this project, said: “This probe will fly to unknown interstellar space – places where humans have never been before. In time, for the first time, we will take pictures from the outside of the heliosphere to see what our solar system looks like.”
Such photos are rare, and 30 years ago, on February 14, 1990, Voyager 1 “turned back” to take a picture of the solar system from a distance of about 6 billion kilometers from the Sun before powering down the camera forever. The famous Earth photo “Pale Blue Dot” (Pale Blue Dot) is one of them, that is a landmark moment in the history of human space exploration.
This new NASA project is still in the early stages of planning, its vehicle is tentatively named Interstellar Probe (Interstellar Probe), no specific name yet.
Provonikova said the new project plans to probe how matter inside the heliosphere interacts with interstellar matter from outer space, from the outside of the heliosphere. The probe will use high-energy neutral atoms to take pictures of the heliosphere and hopefully observe background light from the early days of galaxy formation.
By the end of this year, the project team will submit a formal project proposal report to NASA. The probe is expected to be launched in the early 1930s and is scheduled to operate for at least 50 years.
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