Dark Comets with Darryl Seligman

Neil deGrasse Tyson and Chuck Nice discuss the excitement surrounding the discovery of dark comets and interstellar objects in the solar system. They interview Daryl Seligman, an expert who explains his research in this field. The conversation highlights how recent findings, like 'Oumuamua', have changed our understanding of space objects and their behavior when they travel between stars. Daryl's transition from a PhD student to a postdoctoral fellow at the National Science Foundation emphasizes the freedom that comes with scientific research. As they explore the physics of these fast-moving objects, the passion for discovery and the joy of sharing new knowledge shines through. Dark comets are a thrilling topic, resembling elements one might find in a Marvel movie, yet they represent genuine advancements in our exploration of the cosmos which prompt further investigation and enthusiasm in astronomy.

PanStars is a telescope in Hawaii designed to find near-Earth objects, which are crucial to detect to avoid potential impacts with Earth. While it primarily searches for these objects, it also has the capability to discover interstellar objects. When these objects enter our solar system with a hyperbolic trajectory, they are not bound to the sun, distinguishing them from comets, which can have elliptical orbits and return occasionally. Comets differ from asteroids in that they contain ice that sublimates into gas when heated by the sun, creating a tail. Once an object is detected, researchers can estimate how many interstellar objects may exist based on statistical limits derived from their observations. Understanding these differences is essential for planetary defense and knowing more about the cosmos.

When studying objects from space, scientists often try to understand whether they are asteroids or comets. Objects that form far from their stars, where it's colder and they contain ice, are expected to be comets. These can be ejected from their systems due to gravitational influences from large planets, like Jupiter. One specific object was initially thought to be a comet but later identified as an asteroid because it lacked a visible tail and showed unusual movement not explained by the sun's gravity alone. This means something else is influencing its path, prompting astronomers to use advanced tools, including infrared telescopes, to gather more information. Learning how these celestial bodies behave helps astronomers decipher their origins and characteristics, which is crucial for understanding the dynamics of our universe.

Many comets and asteroids show non-gravitational acceleration due to sublimating ices or solar pressure. 'Oumuamua, a unique object observed intensively, exhibited strong non-gravitational acceleration without a visible dust coma. This peculiarity led to hypotheses suggesting it was a dark comet, with its acceleration linked to outgassing rather than traditional visible traits. The phenomenon challenges our understanding as it represents an object class previously undetected, prompting ongoing debate and research within the scientific community. Understanding such anomalies helps illuminate the complexities of our solar system and encourages the exploration of potentially unseen objects reacting in similar ways to solar forces.

In space science, the term 'volatiles' refers primarily to ice, which includes water ice, ammonia ice, carbon dioxide ice, and more. These volatiles can sublimate, meaning they transition directly into gas, which can contribute to the acceleration of objects like comets. A recent hypothesis about the object 'Oumuamua suggests that its acceleration is due to trapped hydrogen released from water ice, rather than just water vapor alone. Hydrogen's lighter weight and lower energy requirements for sublimation make it a stronger driver for the object’s movement. Some scientists propose alternative theories, like 'Oumuamua being a very low-density object that can also be influenced significantly by sunlight. Understanding these elements helps clarify the mysterious behaviors of celestial objects and strengthens our knowledge of how they interact with cosmic forces in deep space.

Recently, astronomical discoveries have revealed the existence of multiple objects in our solar system that exhibit unusual accelerations, which cannot be explained by typical forces like gravity. Among these objects are light comets, which may have icy cores hidden beneath insulating layers. Upcoming technologies, such as the Rubin Observatory, will enhance our capacity to detect more moving objects in the night sky, potentially leading to discoveries similar to the interstellar object 'Oumuamua'. The idea that cosmic rays can create insulative surfaces on these comets suggests intriguing possibilities about the nature of these celestial bodies and their origins, stirring excitement among astronomers about future observations.

Comets, particularly dark comets, could play a significant role in the origin of water on Earth. These comets contain hydrogen and oxygen trapped in ice. While studying their non-gravitational effects has been challenging, recent research suggests they could be a major source of Earth’s water, more than other types of comets. Scientific understanding evolves; previously held ideas can change as new data emerges. The dialogue emphasizes the importance of scientists admitting when they are wrong, leading to more accurate explanations. This ongoing research could reshape how we see the relationship between comets and Earth's water supply, showcasing the dynamic nature of scientific inquiry and discovery. As new insights surface, particularly from promising graduate students, our grasp of celestial contributions to Earth's makeup continues to deepen, illustrating science's ever-evolving quest for knowledge.

Scientists are exploring whether comets delivered water to Earth, but recent findings suggest that the water in some comets doesn’t match that in our oceans, particularly in the ratio of deuterium to hydrogen. New dark comets may be a potential source of water, and observations from missions like Hayabusa 2 in 2031 could provide answers. Reflectivity, or albedo, varies among celestial bodies: comets are dark, while Pluto has bright areas. Future research, like from the Rubin Observatory, aims to discover numerous interstellar objects, but findings will come through analyzing incoming data rather than targeted searches.

Scientific exploration is always evolving as our tools and methodologies improve. New telescopes like Ruben are set to generate an enormous amount of data—up to 20 terabytes daily—allowing researchers to identify new celestial objects, particularly dark comets and fast-moving interstellar objects. However, the current algorithms might miss these elusive bodies because they weren’t designed to look for certain characteristics like strong non-gravitational acceleration. This emphasizes the importance of continuously refining our detection methods. We must remain open-minded about what exists in the universe beyond our current understanding. Just as past advancements like the telescope and microscope expanded our perception of reality, the future holds vast potential as technology leads to discovering previously unknown objects and phenomena. This reminds us that the universe is more complex than we can currently comprehend.