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First Pluto, now the Kuiper Belt: How the New Horizons Spacecraft is Helping us Picture Interstellar

Written by Josue Navarro ‘25

Edited by Naphat Permpredanun '24

Image 1. New Horizons Spacecraft [1].

The existence of a distant planet similar to Earth has captivated the minds of astronauts and those who study interstellar space. Space exploration is still relatively new, only kicking off during the Cold War with the launch of Sputnik I by the Soviet Union in 1957 (2). Since then, manned exploration has reached the moon, and unmanned exploration has entered interstellar space and beyond. Of course, there have been many bumps along the way with harsh lessons learned, but those bumps have propelled aerospace engineers to work harder to maximize our understanding of the unknown. One of the greatest space expeditions in recent history is Pluto. Pluto was considered a planet until 2006, when it was demoted to a dwarf planet because of size and orbit differences compared to the other 8 planets (3). Though Pluto does not fully fit the profile of a planet, it is the largest Kuiper Belt object to orbit the sun. Perhaps that is why it was incorrectly classified as a planet since it was forced into an orbit around the sun similar to Neptune's. This little known information was clarified in the form of pictures from telescopes that provided fuzzy images of what Pluto looked like. Another fact we learned from Pluto was its number of moons. Scientists thought Pluto had 3 moons until 2015, when an unmanned fly-by mission uncovered 2 additional moons in its orbit. This fly-by mission by the spacecraft New Horizons provided scientists with clarity as they had very little access to it from far away.

On January 9, 2006, the New Horizons spacecraft was launched to search for answers about Pluto and the Kuiper Belt (4). The spacecraft arrived at Pluto on July 14, 2015, eight and a half years later. Upon arrival, the spacecraft used its cameras and technology onboard to study the composition of Pluto fully. Ground-based telescopes showed that Pluto was composed of highly volatile ices containing N2, CO, and CH4 (5). New Horizons confirmed this discovery through infrared spectroscopy and found that water may have existed at some point in the dwarf planet’s life (5). In terms of its moons, New Horizons found that Charon (Pluto’s largest moon) has deposits of NH4 on its surface (5). This is the result of NH4 escaping Pluto’s weak atmosphere. Pluto completes one full revolution around the sun every 248 Earth years (5). This, combined with the fact that Charon has a very elliptical orbit around Pluto makes it susceptible to NH4 deposits, giving it an orange tint on one side (5).

After successfully completing its main mission, New Horizons was approved for an extended five-year-long mission called the Kuiper Belt Extended Mission or KEM (6). During this phase, New Horizons explored the Kuiper Belt–an orbit of celestial objects beyond Pluto–to answer questions about the origins of planet formation (6). Specifically, it did a close fly-by of Arrokoth (formerly 2014 MU69) to look closely for coma activity (gas activity in the atmosphere), satellites, and rings (6). Arrokoth was composed of 2 lobes (smaller rocks), likely formed by a gentle collision between 2 celestial bodies (7). This suggests that Kuiper Belt objects formed around the same time our solar system formed (7).

This extension of the mission was successful, and scientists could gather more information than they were expecting. Now, NASA is looking to add a second extension to the New Horizons mission that is expected to take place between 2023-2025 (8). Scientists hope to survey the heliopause (the terminus of our solar system), and its effects on New Horizons and Kuiper Belt objects during this extension (6). In retrospect, New Horizons is the first spacecraft that will provide concrete data to NASA in regard to the temperature changes and solar winds caused by the changing environment. Upon crossing the termination shock, New Horizons will enter the Heliopause. Though the Pioneer and Voyager spacecraft passed this region before, they did so before it was formally discovered (6). With this extension, New Horizons will be able to give scientists more data on the changes in space as you get as far away as possible from the protection of the Sun and the solar system.

Currently, New Horizons is in hibernation mode until March 1, 2023 to conserve energy (7). After this date, NASA plans to reboot New Horizons’ systems to continue gathering more data. For NASA, this mission has been a success, and it has provided us with data that is otherwise unavailable to us because of the distance of these objects. Previous missions to this region have not provided us with the data we have now. As we await to see what New Horizons will discover next, it is important to remember that the universe is constantly expanding. We are only a speck of dust in the universe, and New Horizons allows us to make our mark beyond the stars.



[1] Pulliam C, New Horizons Spacecraft [Illustration]. 2021. Space Telescope Science Institute. NASA Hubblesite.

[2] Aerospace. A Brief History of Space Exploration: The Aerospace Corporation [Internet]. Aerospace Corporation. 2023 [cited 2023Mar6]. Available from:,orbit%20Earth%20in%20Vostok%201

[3] Hartman S. This Day in History: Pluto Demoted to Dwarf Planet in 2006 [Internet]. KCRA. KCRA; 2022 [cited 2023Mar6]. Available from:,controversy%20both%20scientifically%20and%20culturally

[4] Mars K. 15 Years Ago: New Horizons Launched to Pluto and Beyond [Internet]. NASA. NASA; 2021 [cited 2023Mar6]. Available from:

[5] Cruikshank DP, Pendleton YJ, Grundy WM. Organic Components of Small Bodies in the Outer Solar System: Some Results of the New Horizons Mission. Life. 2020;10(8):126.

[6] Stern SA, Weaver HA, Spencer JR, Elliott HA. The New Horizons Kuiper Belt Extended Mission. Space Science Reviews. 2018;214(4).

[7] Tillman NT. One Year Ago, NASA's New Horizons made the Most Distant Flyby in Space History [Internet]. Space; 2020 [cited 2023Mar6]. Available from:

[8] Bagenal F, New Horizons Team. New Horizons Exploration of the Outer Heliosphere. Flagstaff, AZ: NASA; 2021.

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