NASA’s 2017 discovery of the first interstellar object, ‘Oumuamua, sparked excitement and raised questions about its nature. This unusual visitor, nicknamed “the scout” due to its Hawaiian name, has erratic motions consistent with gas escaping from its surface. Unlike typical asteroids or comets, ‘Oumuamua lacks a bright tail or nucleus.
Since then, more mysterious objects have been discovered, including 3200 Phaethon, the parent body of the famous Geminid meteor shower. These dark comets challenge our understanding of traditional comets. They appear as faint points of light and lack the glowing tails typically seen in brighter comets.
Dark comets are characterized by their size (often small), spin rate, and composition or age. Their small size limits surface area for material to escape, making them less visible. Rapid spinning also disperses escaping gas and dust, further reducing visibility.
Astronomers can identify dark comets using reflected sunlight from our Sun. Large telescopes around the world have successfully discovered these objects, with recent discoveries made possible by instruments like the Dark Energy Camera in Chile.
A new mega camera, the Vera C. Rubin Observatory, is set to launch in 2025. This will enable faster and more detailed observations of dark comets, potentially doubling or tripling the known number of these mysterious visitors in the next decade.
Source: https://theconversation.com/what-is-a-dark-comet-a-quick-guide-to-the-new-kids-in-the-solar-system-245763