Webb observes three dwarf planets in the Kuiper Belt

In this artist’s conception, the newly discovered planet-like object, called Sedna, is located on the outer edges of the known solar system. Image source: NASA/JPL-Caltech

using James Webb Space TelescopeAstronomers observed three dwarf planets in… Kuiper beltAnd the discovery of light hydrocarbons and complex molecules. These results advance our understanding of objects in the outer solar system and highlight the capabilities of the James Webb Space Telescope for space exploration.

the Kuiper beltThe vast region at the edge of our solar system, populated by countless icy bodies, is a treasure trove of scientific discoveries. Detection and characterization Kuiper belt objects (KBOs), sometimes referred to as Trans-Neptunian objects (TNO bodies) led to a new understanding of the history of the solar system. The shedding of Kuiper belt objects is an indicator of the gravitational currents that shaped the solar system and reveals a dynamic history of planetary migrations. Since the late 20th century, scientists have been keen to take a closer look at Kuiper Belt objects to learn more about their orbits and composition.

James Webb Space Telescope observations

Studying objects in the outer solar system is one of the many goals of the James Webb Space Telescope (JWST). Using data obtained by Webb Near infrared spectrometer (NIRSpec), an international team of astronomers has observed three dwarf planets in the Kuiper Belt: Sedna, Jungjung, and Kwar. These observations revealed many interesting things about their orbits and composition, including light hydrocarbons and complex organic molecules that are thought to be the products of methane irradiation.

The research was led by Joshua Emery, a professor of astronomy and planetary science at Northern Arizona University. He was joined by researchers from NASAGoddard Space Flight Center (GSFC). Institute of Spatial Astrophysics (Université Paris-Saclay). Pinhead Institutethe Florida Space Institute (University of Central Florida). Lowell Observatorythe Southwest Research Institute (Swei), and 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 Arrokoth object in the Kuiper Belt, the New Horizons mission has been exploring objects in the Kuiper Belt and making heliospheric and astrophysical observations. Image credit: NASA/JHUAPL/SwRI//Roman Tkachenko

History of Kuiper Belt exploration

Despite all the advances in astronomy and robotic explorers, what we know about Trans-Neptune and the Kuiper Belt is still limited. So far, the only task of study Uranus, NeptuneTheir main satellites were Voyager 2 The mission flew by these two ice giants in 1986 and 1989, respectively. Moreover, the new Horizons The mission was the first spacecraft to study Pluto and its satellites (in July 2015) and the only one to have encountered a Kuiper Belt object, which happened on January 1, 2019, when it flew close to the Kuiper Belt known as Arrokoth.

Astronomers’ forecasts from JWST

This is one of the many reasons astronomers have been eagerly awaiting the launch of the James Webb Space Telescope. In addition to studying exoplanets and the oldest galaxies in the universe, powerful infrared imaging capabilities have also been directed toward our backyard, revealing new images of… Mars, Jupiterand her The largest satellite. For their study, Emery and his colleagues relied on near-infrared data obtained by Webb for three planets in the Kuiper Belt — Sedna, Gungong, and Kuar. These objects are about 1,000 km (620 mi) in diameter, which puts them within International Astronomical Union classification of dwarf planets.

Insights about dwarf planets

As Emery told Universe Today via email, these objects are particularly interesting to astronomers because of their size, orbits, and compositions. Other trans-Neptunian objects – such as Pluto, Eris, Haumea, and Makemake – have retained volatile ices on their surfaces (nitrogen, methane, etc.). The only exception is Haumea, which lost its volatiles in (apparently) significant effect. As Emery said, they wanted to know if Sedna, Goonggong, and Quaoar had similar volatiles on their surfaces as well:

“Previous work has shown they might be able to. While they are all roughly similar sizes, their orbits are different. Sedna is an object from the inner Oort Cloud with a perihelion of 76 AU and apogee of about 1,000 AU. Gunggung is in an elliptical orbit Also extremely, with a perihelion of 33 AU and apogee of ~100 AU, Kwar is in a relatively circular orbit near 43 AU. These orbits place objects in different temperature regimes and different radiation environments (Sedna, for example, “It spends most of its time outside the Sun’s heliosphere. We wanted to investigate how these different orbits affect the surfaces. There are also other interesting ices and complex organic materials on the surfaces.”

Images from one of the two PRISM observations of Sedna, Goonggong, and Quoar. Credit: Emery, J.P. et al. (2023)

Using data from the Webb NIRSpec instrument, the team observed all three objects in low-resolution prism mode at wavelengths spanning 0.7 to 5.2 micrometres (µm) – placing them all in the near-infrared spectrum. Additional Quaoar observations were made from 0.97 to 3.16 μm using medium-resolution grids with ten times the spectral resolution. The resulting spectra revealed some interesting things about these TNO objects and their surface compositions, Emery said:

“We found an abundance of ethane (C2H6) on the three bodies, most notably on Sedna. Sedna also shows acetylene (C2H2) and ethylene (C2H4). The abundance is related to the orbit (most on Sedna, less on Gunggung, and least on Kuwar), which is consistent with Relative temperatures and radiation environments. These molecules are products of direct irradiation of methane (CH4). If ethane (or other) had been present on surfaces for a long time, it would have been transformed into more complex molecules by irradiation. Since we still see them, we doubt Rooftops must be refueled with methane (CH4) on a fairly regular basis.

These findings are consistent with those presented in two recent studies led by Dr. Will Grundy, an astronomer at Lowell Observatory and a NASA associate investigator. new Horizons mission, and Chris Glenn, a planetary scientist and geochemist at SwRI. In both studies, Grundy, Glenn and their colleagues measured deuterium/hydrogen (D/H) ratios in methane on Iris and Makemake and concluded that the methane was not primitive. Instead, they argue, the ratios result from methane being processed inside and delivered to the surface.

“We suggest that the same may be true for Sedna, Gonggong and Quaoar,” Emery said. “We also see that the spectra of Sedna, Goonggong, and Quaoar differ from those of the smaller KBOs. There were talks at two recent conferences that showed that the James Webb Space Telescope data for the smaller KBOs cluster in three groups, none of which resemble Sedna, Gonggong, and Quaoar. They agree This is a result even though our three larger bodies have different geothermal histories.

Comparison of the eight largest TNOs with Earth (all to scale). Credit: NASA/Lexicon

Implications of the results

These results could have important implications for the study of Kuiper Belt objects, TNOs, and other objects in the outer solar system. This includes new insight into the formation of objects beyond the frost line in planetary systems, which refers to the line beyond which volatile compounds freeze. In our solar system, the trans-Neptunian region corresponds to the nitrogen line, where objects retain large amounts of volatile materials with very low freezing points (such as nitrogen, methane, and ammonia). Emery said these findings also illustrate the type of evolutionary processes occurring in bodies in this region:

“The primary impact may be to find the volume at which Kuiper Belt objects became warm enough for internal reprocessing of primordial ice, and perhaps even differentiation. We should also be able to use these spectra to better understand the radiation processing of surface ice in the outer solar system.” Future studies will also be able to look in more detail at the volatile stability and the possibility of atmospheres in these objects above any part of their orbits.

The results of this study also demonstrate the capabilities of the James Webb Space Telescope, which has proven its worth several times since it became operational early last year. It also reminds us that in addition to enabling new insights and new discoveries into distant planets, galaxies and the large-scale structure of the universe, Webb can also reveal things about our own little corner of the universe.

“The James Webb Space Telescope data is amazing,” Emery added. “It enabled us to obtain spectra at longer wavelengths than we could from Earth, which enabled us to detect these ices. Often, when observing in a new wavelength range, the raw data can be of very poor quality. The James Webb Telescope was not opened Not only did the space probe provide a new range of wavelengths, but it also provided fantastically high-quality and sensitive data for a range of surface materials in the outer solar system.

Adapted from an article originally published on The universe today.

Reference: “A Tale of Three Dwarf Planets: Ice and Organics in Sedna, Gunggong, and Kuwar from JWST Spectroscopy” by J.P. Emery, I. Wong, R. Brunetto, J.C. Cook, N. Pinilla-Alonso, J. A. Stansbury, B. J. Holler, W. M. Grundy, S. Protopapa, A. C. Souza-Feliciano, E. Fernández-Valenzuela, J. I. Lunine and D. C. Hines, September 26, 2023, Astrophysics > Earth and planetary physics Astrophysics.
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