NASA's Solar Probe IMAP: Solving Mysteries of The Sun’s Influence
The Heliosphere | IMAP Mission
A diagram of a birds-eye cross-section of the solar wind. The solar wind passes linearly out in all directions through the planets towards the termination shock, about twice as far as the last shown planet orbit to be (not to scale). Beyond this, the solar wind leading edge stops at where it meets the interstellar medium, forming a bubble-shape back around the solar system. The trailing edge tails far behind. A small cloud labelled bow shock precedes the leading edge, where it meets the interstellar medium.
A diagram showing IMAP's orbital path at LaGrange point 1 between the Earth and Sun. LaGrange points 2, 3, 4 and 5 are also labeled for reference.
Billions of miles into space, an invisible boundary is formed around our solar system by the interaction between the continual flow of energetic particles from the Sun, the solar wind, and the material found between the stars—the interstellar medium (ISM). The solar wind streams outward from the Sun into space and carves out a protective bubble around our entire solar system in the ISM. We call this protective bubble-region the heliosphere. It provides a shield against the harsh radiation present in the galaxy, creating and maintaining a habitable solar system for us. Understanding the physics of this boundary and its dynamic changes over time can help us comprehend how our solar system can support life as we know it as well as informing us in the search for life beyond the solar system.
The heliosphere is a definable, measurable region in space with a distinct geography of its own. The inner heliosphere is created as the solar wind blows through our solar system in all directions. It slows as it approaches the interstellar medium and begins to interact with it in a region called the termination shock, forming an inner edge of the solar boundary. The outermost edge, or heliopause, is formed where the solar wind no longer reaches into the ISM. The inner edge of this boundary is located approximately an average of 9 billion miles (14 billion km) away from Earth, or around 100 times the distance between the Earth and the Sun. However, this distance from the Sun is not uniform and the average distance varies with the activity level of the Sun (the solar cycle). The solar wind is also not evenly distributed, and coronal mass ejections (solar storms) are directional, and these create a rippled effect in the boundary encompassing our solar system. Parts of the outer edge of the solar system boundary, the heliopause, are 11 billion miles (18 billion kilometers) from Earth, while in other directions the heliopause is much further. Fundamental scientific questions await answers about the essential physical processes occurring in this area and its influence on our solar system’s evolving space environment.
NASA's Interstellar Mapping and Acceleration Probe (IMAP)'s groundbreaking mission takes up these questions by studying the heliosphere boundary from afar. IMAP orbits the Sun at a location which is about one million miles from Earth towards the Sun, called Lagrange Point 1 (L1). As it travels this orbital path, IMAP is free from any magnetic interference from the planets. IMAP spins, once every 15 seconds, allowing the comprehensive suite of 10 sensor instruments to scan every part of the heliosphere. IMAP collects and maps near real-time measurements of the solar wind’s high-energy particles and magnetic fields in interplanetary space, as well as collect, count, measure and map energetic neutral atoms returning from the interactive region of the heliopause towards the Sun. The unprecedented new data is utilized to create a comprehensive map of the Sun's influence, an instrumental piece in resolving the fundamental physical processes that control our solar system’s evolving space environment and advance the understanding of:
1) The compositionThe specific components or “ingredients” that make up a substance or type of matter. and properties of the local interstellar medium.
2) How magnetic fields interact from the Sun through the local interstellar medium.
3) How the solar wind and interstellar medium interact through the boundaries of our heliosphere.
4) How particles are accelerated to high energies throughout the solar system.
The IMAP mission’s scientific goals and objectives build upon a heritage of findings from past missions that have expanded our knowledge of the heliosphere and its dynamics.
Starting in the late 1970s and 1980s, NASA's Voyager spacecraft expanded our knowledge of the outer Solar System. Voyager 1 launched September 5, 1977, and Voyager 2 launched August 20, 1977. After making designated planetary observations, both spacecraft continued outward into space in different directions. Voyager were only supposed to last a few years, but they have continued to operate for almost 50 years, well past their designed lifetimes.
Voyager 1 reached the termination shock on December 16, 2004, at a distance of 8.4 billion miles (14.1 billion kilometers) from the Sun. Voyager 2 reached the termination shock on August 30, 2007, at a distance of 7.8 billion miles (12.6 billion kilometers) from the Sun. This discrepancy in distances and dates is due to the facts that Voyager 1 is traveling faster than Voyager 2 and that the distance of the termination shock from the Sun varies.
Today, the Voyager spacecraft have left the solar system’s boundary region, but they can only sample the conditions at their specific locations—not the entire global heliosphere shielding our solar neighborhood. Since 2009, NASA's Interstellar Boundary Explorer (IBEX) mission(Link is external) (Link opens in new window) has imaged the entire sky, giving us a complete global view of the boundary. The data from Voyager has been combined with IBEX’s data, allowing scientists to create a more complete model of the boundary of our Solar System. With IBEX, critical questions have been raised for IMAP to answer about the nature, properties, and dynamic conditions of our heliosphere and local interstellar medium. This also includes determining the physical origin of the concentrations of energetic neutral atoms (ENA’s) forming “the Ribbon” that IBEX has revealed to wrap across the nose of the heliosphere.
Building off Voyager’s and IBEX’s successful measurements, IMAP provides unparalleled new observations that allow us to connect the Sun’s activity to the observed dynamics in our solar system’s boundaries.
Slated to launch no earlier than September 2025, IMAP will study the heliosphere—the giant magnetic bubble that surrounds and protects our solar system—from a spot called Lagrange Point 1 located approximately 1 million miles towards the Sun from Earth.
Image Credit: NASA/IBEX/Adler Planetarium
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