IMAP’s science objective is to discover the fundamental physical processes that control our solar system’s evolving space environment. IMAP achieves this objective by making measurements of the solar wind as well as the heliosphere’s “echo” when this material reaches and interacts the outer boundaries of our solar system. With a comprehensive suite of instruments taking unprecedented new data, IMAP scientists advance our understanding of:
- The composition and properties of the local interstellar medium.
- How magnetic fields interact from the Sun through the local interstellar medium.
- How the solar wind and interstellar medium interact through the boundaries of our heliosphere.
- How particles are accelerated to high energies throughout the solar system.
The solar wind from our Sun blows outward against the material between the stars, called the "interstellar medium", and clears out a bubble-like region. This bubble that surrounds the Sun and the Solar System is called the "heliosphere." It is a definable, measurable region in space. The use of the word "global" above means "as seen around the entire sky." The "termination shock" is the region where the solar wind slows down and begins to interact with the interstellar medium. The "heliotail" is the region of our heliosphere opposite to the direction of travel of our Solar System through the Milky Way Galaxy. The part of our heliosphere in the direction of travel is often called the "nose." The "heliopause" is the outermost boundary, where the solar wind does not travel outward any farther.
All of the planets in our Solar System are within the heliosphere. In the late 1970s and 1980s, the Voyager spacecraft expanded our knowledge of the outer Solar System. Voyager 1 launched September 5, 1977, and Voyager 2 launched August 20, 1977. Voyagers 1 and 2 both explored the planets Jupiter and Saturn, and Voyager 2 explored Uranus and Neptune. After their planetary observations, both spacecraft continued outward in different directions. The Voyagers were only supposed to last a few years, but they have continued to operate for over 30 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. The discrepancy in distances and dates can be explained by the fact that Voyager 1 is traveling faster than Voyager 2, and that the termination shock is not at a uniform distance from the Sun. This distance can vary with the activity level of the Sun.
Today, the Voyager spacecraft are at our Solar System’s boundary region, but they can only sample the conditions at those two specific points. Since 2009, the Interstellar Boundary Explorer (IBEX) has imaged the entire sky, giving us an all–sky view of the boundary. The data from the Voyagers has been combined with IBEX’s data, allowed scientists create a more complete model of the boundary of our Solar System. With IBEX’s ability to peer into our solar system’s boundaries and measure the properties of the local interstellar medium, many critical questions on the nature of our heliosphere and local interstellar medium have been raised, such as:
a) What are the properties of the Interstellar Medium?
b) What are the basic properties of our global heliosphere and how are they physically regulated?
c) What is the physical origin of the Ribbon?
IMAP will build off Voyager’s and IBEX’s successful measurements to provide unparalleled new observations that allow us to connect the Sun’s activity to our solar system’s boundaries.