The Kuiper Belt, the vast region at the edge of our Solar System populated by countless icy objects, is a treasure trove of scientific discoveries. The detection and characterization of Kuiper Belt Objects (KBOs), sometimes referred to as Trans-Neptunian Objects (TNOs), has led to a new understanding of the history of the Solar System. The disposition of KBOs is an indicator of gravitational currents that have shaped the Solar System and reveal a dynamic history of planetary migrations. Since the late 20th century, scientists have been eager to get a closer look at KBOs to learn more about their orbits and composition.
Studying bodies in the outer Solar System is one of the many objectives of the James Webb Space Telescope (JWST). Using data obtained by Webb’s Near-Infrared Spectrometer (NIRSpec), an international team of astronomers observed three dwarf planets in the Kuiper Belt: Sedna, Gonggong, and Quaoar. These observations revealed several interesting things about their respective orbits and composition, including light hydrocarbons and complex organic molecules believed to be the product of methane irradiation.
The research was led by Joshua Emery, an Associate Professor of Astronomy and Planetary Sciences at Northern Arizona University. He was joined by researchers from NASA’s Goddard Space Flight Center (GSFC), the Institut d’Astrophysique Spatiale (Université Paris-Saclay), the Pinhead Institute, the Florida Space Institute (University of Central Florida), the Lowell Observatory, the Southwest Research Institute (SwRI), the Space Telescope Science Institute (STScI), American University. and Cornell University. A preprint of their paper has appeared online and is being reviewed for publication by Icarus.
Since its last flyby of the Kuiper Belt object Arrokoth, the New Horizons mission has been exploring objects in the Kuiper Belt and performing heliospheric and astrophysical observations. Credit: Credit: NASA/JHUAPL/SwRI//Roman Tkachenko
Despite all of the advances in astronomy and robotic explorers, what we know about the Trans-Neptunian Region and the Kuiper Belt is still limited. To date, the only mission to study Uranus, Neptune, and their major satellites was the Voyager 2 mission, which flew past these ice giants in 1986 and 1989, respectively. Moreover, the New Horizons mission was the first spacecraft to study Pluto and its satellites (in July 2015) and the only one to encounter an object in the Kuiper Belt, which occurred on January 1st, 2019, when it flew past the KBO known as Arrokoth.
This is one of the many reasons why astronomers have eagerly awaited the launch of the JWST. In addition to studying exoplanets and the earliest galaxies in the Universe, its powerful infrared imaging capabilities have also been turned toward our backyard, revealing new images of Mars, Jupiter, and its largest satellites. For their study, Emery and his colleagues consulted near-infrared data obtained by Webb of three planetoids in the Kuiper Belt – Sedna, Gonggong, and Quaoar. These bodies are about 1,000 km (620 mi) in diameter, which places them within the IAU designation for Dwarf Planets.
As Emery told Universe Today via email, these bodies are especially interesting to astronomers because of their size, orbits, and compositions. Other Trans-Neptunian bodies – like Pluto, Eris, Haumea, and Makemake – have all retained volatile ices on their surfaces (nitrogen, methane, etc.). The one exception is Haumea, which lost its volatiles in a large impact (apparently). As Emery said, they wanted to see if Sedna, Gonggong, and Quaoar have similar volatiles on their surfaces as well:
“Previous work has shown that they may be able to. While all being roughly similar sizes, their orbits are distinct. Sedna is an inner Oort Cloud object with perihelion of 76 AU and aphelion of nearly 1,000 AU, Gonggong is in a very elliptical orbit also, with perihelion of 33 AU and aphelion ~100 AU, and Quaoar is in a relatively circular orbit near 43 AU. These orbits place the bodies in different temperature regimes and different irradiation environments (Sedna, for instance, spends most of its time outside the Sun’s heliosphere). We wanted to investigate how those different orbits could affect the surfaces. There are also other interesting ices and complex organics on the surfaces.”