Spaceflight Insider

New Horizons is still doing science in the Kuiper Belt

An artist's rendering of New Horizons at Pluto. Credit: NASA

An artist’s rendering of New Horizons at Pluto. Credit: NASA

Now traveling far into the Kuiper Belt, NASA’s New Horizons spacecraft continues to conduct science observations more than four years after flying by its second target, Kuiper Belt Object (KBO) Arrokoth, in 2019.

At the 2023 Lunar and Planetary Science Conference, mission scientists discussed the range of projects the probe is currently studying.

The spacecraft is now more than 55 astronomical units (AU, with one AU equal to the average Earh-Sun distance, or 93 million miles) from Earth.

Mission scientists are currently searching for a third flyby target and are studying various KBOs and dwarf planets from a distance, using a combination of ground-based telescopes and machine learning artificial intelligence software.

“We’re twice as far out from Earth as when we found Arrokoth, which makes the targets we search for 16 times farther,” said mission principal investigator Alan Stern of the Southwest Research Institue in Boulder, Colorado.

Another project is looking back at Uranus and Neptune and imaging them from deep in the Kuiper Belt.

NASA’s Hubble Space Telescope will image the two ice giants at the same time New Horizons does, so scientists can view them from two very different perspectives.

“The advantage of this is that what Hubble will see is what the cloud patterns are doing that day, and at the same time as New Horizons is seeing them vary as they rotate,” said mission co-investigator Will Grundy of the Lowell Observatory in Flagstaff, Arizona.

“We’re seeing light scattered in a direction that you could not possibly see from Earth or the inner solar system,” Grundy said regarding the spacecraft’s unique perspective. “We’re going to take pictures as the planets rotate, so that we can see their evolving cloud structures coming onto the part that’s lit…and rotating out as the atmosphere evolves.”

Team scientists are taking advantage of the spacecraft’s unique position to study the outer heliosphere, the farthest reaches of the Sun’s influence before the interstellar medium. This area is far less dusty than the inner solar system, so the probe can detect very faint signals and map the cosmic background in both optical and ultraviolet light.

While Voyagers 1 and 2 are also on trajectories out of the solar system, neither has the instruments to do these observations.

“And then, finally, we’re going to be also mapping the local interstellar medium in hydrogen light to understand the cloud structures and other structures that have never been mapped before,” Stern said.

Eight years after New Horizons‘ Pluto flyby and four years after its Arrokoth flyby, new discoveries are still being made about these two objects.

Data collected in 2015 indicates Pluto’s poles are not in their original positions, having wandered away from those locations. The formation of Sputnik Planitia, the icy left side of Pluto’s heart feature, may be connected to these pole shifts.

Additionally, Pluto’s bladed terrain, made up of methane ice, is noticeably similar to structures seen on Earth in Chile’s Atacama Desert. Surface features on Pluto’s far side suggest it too is covered with these structures.

Arrokoth, which has a composition much like that of other distant KBOs, appears to have formed when tiny ice particles began sticking together, creating a larger object. The KBO is made up of primitive material that dates back to the solar system’s earliest days.

Its two lobes are very similar to one another, suggesting a common origin that could explain the scattering of planetesimals in the outer solar system and possibly the inner as well.


Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

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