Recent research has provided new insights into the icy planetesimals of the early solar system, particularly trans-Neptunian objects (TNOs) and centaurs. These small celestial bodies formed during the initial stages of planetary development, composed of dust and gas particles in a protoplanetary disk surrounding a young star.
The study sheds light on the distribution and evolution of these intriguing objects, enhancing our understanding of the formation of the outer solar system. Trans-Neptunian objects orbit the Sun beyond Neptune, residing in regions like the Kuiper Belt and possibly extending into the Oort Cloud. They vary in size, with some comparable to dwarf planets, while others are merely fragments of rock and ice.
Notable examples include Pluto and Eris, which share similar dimensions, alongside Haumea, recognized for its elongated shape. The surfaces of these objects often appear reddish or dark due to chemical compounds called tholins, formed through the interaction of ultraviolet light with their icy compositions.
Due to their significant distance from the Sun, TNOs remain extremely cold and travel slowly in their orbits, preserving vital clues about the solar system's ancient past. Astronomers regard these objects as time capsules, offering insights into the formation processes of planets and smaller bodies billions of years ago.
The University of Central Florida (UCF) researchers conducted extensive analyses of TNOs and centaurs using the James Webb Space Telescope (JWST). They identified three distinct compositional groups of TNOs defined by ice retention lines present at the solar system's formation.
The JWST's capabilities enabled scientists to pinpoint specific molecules responsible for the diverse spectra, colors, and albedo observed in TNOs. This research establishes a direct connection between the spectral features of TNOs and their chemical compositions, linking the formation conditions of planetesimals to their present-day characteristics.
Additionally, the study explored centaurs, which are TNOs that have shifted their orbits due to gravitational interactions with Neptune. As TNOs approach the Sun, they may develop comet-like tails, transitioning into centaurs that are often unstable in their current positions.
Unique spectral signatures from centaurs revealed dusty regolith mantles, indicating adaptations during their journey into the inner solar system. The researchers identified three distinct groups based on surface compositions, providing insights into the protoplanetary disk's structure.
This research not only enhances our understanding of TNOs and centaurs but also opens avenues for future exploration. With initial findings on compositional groups established, further investigations are anticipated to uncover the origins of these celestial bodies.
The study was supported by a grant from the Space Telescope Science Institute.