The Webb Space Telescope will examine planetary remains in the Solar System Graveyard

Illustration of the New Horizons space probe in the Kuiper Belt.

These icy bodies are the remnants of the formation of the planets.

At the edge of the solar system is a region called the Kuiper Belt. beyond the orbit of Neptune, this ring of icy bodies is a remnant of the early days of planet formation. Kuiper Belt objects, often pristine, come in many shapes and sizes. Some reside in pairs or multiples, while others have rings or moons. They exhibit a wide range of colors, which may indicate different formation histories or different exposure to sunlight.

These inhabitants of the Kuiper belt could teach astronomers a lot about the formation of our solar system. " data-gt-translate-attributes="[{" attribute="">Nasait’s James Webb Space Telescopewhich launched on December 25, 2021, will be looking at an assortment of these items shortly after its rollout ends.

Pluto and Charon

Pluto and its largest moon, Charon, are two of the best-known residents of the Kuiper Belt. This composite of enhanced color images of Pluto (bottom right) and Charon (top left), was taken by NASA’s New Horizons spacecraft as it passed through the Pluto system on July 14, 2015. The color and luminosity of Pluto and Charon have been treated identically to allow a direct comparison of their surfaces and to highlight the similarity between the polar red terrain of Charon and the equatorial red terrain of Pluto. Pluto and Charon are shown with approximately correct relative sizes, but their true separation is not to scale. Credit: NASA/JHUAPL/SwRI

Beyond Neptune’s orbit, a diverse collection of thousands of dwarf planets and other relatively small objects inhabit a region called the Kuiper Belt. These often pristine remnants from the time of the formation of planets in our solar system are called Kuiper Belt Objects, or Trans-Neptunian Objects. NASA’s James Webb Space Telescope will examine an assortment of these icy bodies in a series of programs called Time Guaranteed Observations. The goal is to learn more about the formation of our solar system.

“These are objects that are in the graveyard of the formation of the solar system,” explained Jonathan Lunine of Cornell University, a Webb interdisciplinary scientist who will use Webb to study some of these targets. “They’re in a place where they could last for billions of years, and there aren’t many places like that in our solar system. We would like to know what they look like.

Neptune Lunar Triton

This global color mosaic of Neptune’s moon Triton, likely a captured KBO, was taken in 1989 by Voyager 2 during its flyby of the Neptune system. Triton is by far the largest satellite of Neptune. Credit: NASA/JPL/USGS

By studying these bodies, Lunine and his colleagues hope to discover what ices were present in the early solar system. They are the coldest worlds to display geological and atmospheric activity, so scientists are also interested in comparing them with the planets.

Kuiper Belt objects are very cold and faint, but they glow in infrared light, which is wavelengths beyond what our human eyes can see. Webb is specially designed to detect infrared light. To study these distant objects, scientists will primarily use a technique called spectroscopy, which splits light into its individual colors to determine the properties of materials that interact with that light.

A wide assortment

People in the Kuiper Belt come in different shapes and sizes. Some reside in pairs or multiples, while others have rings or moons. They exhibit a wide range of colors, which may indicate different formation histories or different exposure to sunlight.

New Horizons of Arrokoth

Although not on Webb’s list of targets, Arrokoth is likely one example among many Kuiper Belt objects. The most distant object ever visited by a spacecraft, it is made up of two joined planetesimals. Arrokoth was photographed by the New Horizons spacecraft in December 2018 and January 2019. Credit: NASA/JHUAPL/SwRI/Roman Tkachenko

“Some appear to be more red in color, others more blue. Why so?” said Heidi Hammel, Webb Interdisciplinary Scientist for Solar System Observations. She is also vice president for science at the Association of Universities for Research in Astronomy (AURA) in Washington, D.C. why there are these different populations in the Kuiper Belt.

Expelled from the club

Included between Jupiter and Neptune, and crossing the orbit of one or more of the giant planets, is a different population of objects called centaurs. These are small solar system bodies that have been ejected from the Kuiper Belt. In addition to observing present-day Kuiper Belt Objects, these Webb programs will study Solar System bodies that have been “kicked out of the club.” These ancient Kuiper Belt Objects have orbits that have been significantly perturbed, bringing them considerably closer to the Sun.

“Because they cross the orbits of Neptune, " data-gt-translate-attributes="[{" attribute="">Uranusand Saturn, Centaurs are short-lived. So they’ve usually only been around for about 10 million years,” explained John Stansberry of the Space Telescope Science Institute in Baltimore, Maryland. Stansberry leads a different team that will use Webb to study the Kuiper Belt Objects. “At this point they have an interaction with one of the major planets which is very strong, and they are either thrown into the Sun or kicked out of the solar system.”

Another body Webb will study is Neptune’s moon Triton. The largest of the Ice Giant’s 13 moons, Triton shares many similarities with Pluto. “Even though it is Neptune’s moon, we have evidence to suggest it is a Kuiper Belt Object that got too close to Neptune at some point in its past. and it was captured orbiting Neptune,” Hammel said. “Triton was studied by the Voyager 2 spacecraft in 1989. These data from the spacecraft will provide us with very important ‘ground truth’ for our Webb observations of Kuiper Belt objects.”

A sample of the targets

Here is a small sampling of just a few of the dozens of current and ancient Kuiper Belt objects that Webb will observe:

  • Pluto and Charon: The dwarf planet Pluto and its largest moon, Charon, are two of the best-known residents of the Kuiper Belt. Pluto has an atmosphere, haze and seasons. It has geological activity on its surface and may have an ocean inside. In addition to Charon, it is home to four other moons: Nix, Hydra, Styx, and Kerberos. The Webb data will complement observations made by NASA’s New Horizons spacecraft when it flew by the Pluto system in 2015.
  • Eris: Almost the size of Pluto, Eris is the second largest known dwarf planet in the solar system. At its furthest point, the mysterious Eris is more than 97 times farther from the Sun than Earth. Its distance makes it difficult to observe, but Webb will tell scientists a lot about the types of ice on its surface.
  • Sedna: With its deep red hue, Sedna is actually located beyond the main Kuiper Belt. It takes about 11,400 years to complete an orbit, and the furthest point in this very elongated orbit is estimated to be 940 times the distance from Earth to the Sun.
  • Haumea: This large, rapidly rotating body is shaped like an egg, and scientists would like to know why. In addition to moons, it also appears to have a system of rings. With Webb, the scientists hope to learn more about the formation of these rings.
  • Chariklo: The largest centaur, Chariklo is also the first asteroid to possess a ring system. It was the fifth ring system found in our solar system, after Saturn, Jupiter, Uranus and Neptune. The rings are thought to be between two and four miles wide.

Another program, called Target of Opportunity, will observe a Kuiper Belt object passing in front of a star, should such an alignment occur during the first two years of Webb’s life. Called occultation, this type of observation can reveal the size of an object.

The few spacecraft that have flown near the Kuiper Belt Objects have only been able to study these intriguing objects for a very short time. With Webb, astronomers can target more Kuiper Belt objects over an extended period. The result will be new insights into the earliest history of our solar system.

The James Webb Space Telescope will be the world’s first space-based science observatory after its deployment in 2022. Webb will solve the mysteries of our solar system, look beyond distant worlds around other stars, and probe the mysterious structures and origins of our universe. and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

A previous version of this article was published in October 2020.

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