NASA’s New Horizons mission begins again at the edge of the solar system

NASA’s New Horizons mission begins again at the edge of the solar system
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Disclaimer: The author was an undergraduate student researcher and worked with the New Horizons team.

On New Year’s Day in 2003, a small spacecraft passed a chunk ice billions of kilometers away. Scientists on Earth cheered. That was the second time the New Horizons probe got up close and personal with an object in the far-away Kuiper Belt–after capturing images of Pluto, its first target, in unprecedented detail.

Now New Horizons has the chance to change how astronomers view distant parts of the solar system. The spacecraft entered the third phase of its mission on October 1. It was the 2nd Kuiper Belt Extended Mission (or KEM2).

Every few years, each NASA mission–yes, even the 45-year-old Voyager–undergoes a formal review in which administrators decide whether the project should continue. SOFIA, NASA’s observatory-on-an-airplane, was just a victim of this process, shutting down operations on September 30, the end of the administration’s fiscal year. New Horizons was on the other side renewed this summer for a 2-year extension to its operations as the aircraft continues flying further out into the solar system.

In KEM2, since the probe is traveling through an extremely far-out area in space, New Horizons will expand its scope beyond its earlier phases. “New Horizons is now this interdisciplinarious observatory in Kuiper Belt,” states Alan Stern , principal investigator for New Horizons.

The mission is expanding into two additional disciplines: astrophysics, and heliophysics. New Horizons is going to measure the solar wind, particles streaming out from the sun, and the probe will eventually reach the termination shock and heliopause, two places that can be considered outer boundaries of our solar system. Although Voyagers 1 & 2 reached the heliopause and made similar measurements, they did so with far less sophisticated tech.

[Related: NASA’s New Horizons is so far away, it’s seeing stars from new angles]

New Horizons will allow heliophysicists to better understand the shape and limits of the sun’s influence in space. It’s also the “ultimate dark-sky site” for astrophysicists, allowing them to measure the amount of background light in the universe, a key constraint on the history of galaxies.

Although these aims are different from its previous goals it will continue to explore far-off rock and ice bodies. New Horizons has been incredibly successful at exploring the outer solar system, providing the first detailed images of both the dwarf planet Pluto and a smaller Kuiper Belt object (KBO) called 2014 MU69. These icy objects are among the most well-preserved relics from the early days of our solar system. They provide astronomers with a window into the past and allow them to see how they formed.

The spacecraft is currently moving a whopping 32,000 miles per hour, faster than even a rocket launching off Earth. It’s about 54 astronomical units (AU) from the sun, and will move 3 AU further away each year, rapidly approaching the edges of our solar system. It’s in unexplored territory–only four other probes, from the Voyager and Pioneer missions, have made it that far out). And those craft took different paths than New Horizons, carrying the now-outdated technology of the 1970s.

NASA’s New Horizons mission begins again at the edge of the solar system
The spacecraft’s location in the solar system as of October 2022, far beyond Pluto and its second target, 2014 MU69 a.k.a. Arrokoth. New Horizons / JHU APL.

“I am excited about how far out we will be going into the distant parts of the solar system,” says Kelsi Singer, project scientist on New Horizons. In two years, she adds, the probe will be at 60 AU-at an edge of the belt that’s nearly impossible for scientists to explore using Earth-based tools.

Due to the distance of Kuiper Belt objects, even the largest telescopes can’t see them. New Horizons will be able to see the Kuiper Belt from a closer distance. however, will have a more detailed view. In the first extended mission, the team spotted 36 KBOs using the spacecraft’s onboard cameras, the closest from only 0.1 AU away, and they expect similar observations in KEM2. The team also has the opportunity to use New Horizons for unique images of the ice giants, Uranus and Neptune, from an angle we can’t see here on Earth.

[Related: The New Horizons spacecraft just revealed secrets of the most distant object we’ve ever visited]

Plus, New Horizons has an instrument, the Student Dust Counter, to measure how much space dust it encounters, tracing the distribution of dust near the edges of the solar system. While we tend to think of outer space as empty, there is a lot of dust there. This dust, which was left over when the planets formed, gives astronomers key insights into the history of our solar system.

For now, the spacecraft is still in hibernation until it awakens in March 2023. Until then, the team is preparing for the exciting science to come, working tirelessly to hunt for new KBO targets with ground-based observations. If they are lucky, KEM2 could be the second of many extended missions.
“The spacecraft is in perfect health, and it has the fuel and the power to run through sometime in the 2040s,” Stern says. Stern says, “This is not the end of New Horizons .”

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