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Exploration of the Outer Heliosphere by New Horizons

Presentation #215.01 in the session Planetary Space Physics Talks (Oral Presentation)

Published onOct 23, 2023
Exploration of the Outer Heliosphere by New Horizons

Our solar system has evolved through accretion of dust and gas as the Sun and its protective magnetic bubble – “the heliosphere” - have plowed through interstellar space on its journey through the galaxy. Over the course of its evolution, the solar system has encountered dramatically different interstellar properties resulting in a severely compressed heliosphere with periods of full exposures of interstellar gas, plasma, dust and galactic cosmic rays (GCRs) that have helped shaped the system we live in today. Voyagers 1 and 2 are now operating in the Very Local Interstellar Medium (VLISM), where they are expected to make a graceful “sortie” in the mid-2030’s after many pioneering discoveries. After discoveries at Pluto and Arrokoth, New Horizons is currently the only spacecraft in the outer heliosphere and is following the same heliospheric longitude as Voyager 2, but in the ecliptic plane. The New Horizons spacecraft is projected to operate across the heliospheric boundary beyond 2040. Now passing 56 AU, New Horizons continues to break new ground in understanding the formation of our solar system by revealing the properties of distant Kuiper Belt Objects and provide critical constraints on the structure of the Sun’s enormous dust disk. Because of its distant position, New Horizons is also providing the key estimates of the cosmic background. In this outer region of the heliosphere, New Horizons is uniquely positioned to measure interstellar Pick-Up Ions (PUIs) for the first time together with solar wind plasma and energetic particles to help understanding how the Sun interacts with the VLISM to uphold our habitable magnetic bubble. Observations of GCRs offers an opportunity to understand how these scatter strongly in the wavy structure of the “ballerina skirt” of the solar magnetic field, leading to the strong modulation. As New Horizons continues to travel outward, dust measurements may reveal an interstellar component that will provide the strongest constraint to date on how interstellar dust grains interact with the heliosphere. Now beyond the infrared and UV haze of the circumsolar dust and hydrogen gas, the Alice UV spectrograph holds promise to search for signatures of the hydrogen wall and perhaps even signatures of our neighboring interstellar clouds. In this presentation we provide an overview of New Horizons’ heliophysics observations in the context of the exploration by Voyager as well as theoretical models.

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