It is increasingly clear that comets exist, with very specific characteristics, which are not like the others. This minority class of comets is characterized above all because, unlike the more common comets, the dark ones, as the name suggests, do not shine at all. These dark comets look like asteroids but move like comets. Now, a new study indicates the existence of two subtypes of dark comets.
The study is the work of a team that includes, among others, Darryl seligman, of Michigan State University, and Davide Farnocchia, of NASA’s Jet Propulsion Laboratory (JPL), both institutes in the United states.
Seven more were discovered in the new study, doubling the number of known dark comets. The authors of the study also realized that dark comets belong to one or the other of two populations: the large one (hundreds of meters or more from end to end) that reside on the outskirts of the solar system and the of the small ones (tens of meters) that reside in the central region of the solar system (the orbital belt that includes Mercury, Venus, Earth and Mars).
The first indication of the existence of dark comets was obtained by observing, in a 2016 study, that the trajectory of the “asteroid” 2003 RM had deviated from its expected orbit without any object disturbing it with its gravity. This deviation cannot be explained by the non-gravitational forces that typically influence asteroids, such as the Yarkovsky effect. This effect is the small push provided by the Sun when it heats an asteroid, which absorbs its light and re-emits it as heat. Over time, this effect can influence the asteroid’s trajectory.
The deviation observed in the 2003 RM orbit was in line with what we would expect from a comet, with volatile material ejected in the form of gas from its surface, giving it considerably more push than asteroids received from the Yarkovsky effect.
In the new study, Seligman, Farnocchia and their colleagues resolute that the subtype of dark comets characterized by large dimensions and residing on the outskirts of the solar system have characteristics similar to those of comets of the Jupiter family: the main one is that both have very elliptical orbits.
Dark comets move like comets, but due to their dim light they are more similar to asteroids than comets. (Image: NASA)
As regards the subtype of dark comets characterized by small dimensions and residing in the central area of the solar system, they verified that their orbits are almost perfectly circular.
The study is titled “Two Distinct Dark Comet Populations Delineated by Orbits and Size.” And it was published in the academic journal Proceedings of the National Academy of Sciences (PNAS). (Fountain: NCYT by Amazings)
How do dark comets contribute to our understanding of the solar system’s evolution?
Interview with Darryl seligman: Unveiling the Mysteries of Dark Comets
Time.news Editor (TNE): Welcome, Dr. Seligman, and thank you for joining us today to discuss your groundbreaking research on dark comets. Can you start by explaining what dark comets are and how they differ from customary comets?
Darryl Seligman (DS): thank you for having me! Dark comets represent a interesting minority within the broader classification of comets. Unlike traditional comets that are luminous and luminous when they approach the Sun, dark comets do not shine at all. They resemble asteroids visually but have unique orbital movements akin to those of comets, which makes them especially intriguing in our studies.
TNE: Fascinating! So, your recent study has uncovered two distinct subtypes of dark comets. Could you elaborate on those findings?
DS: Certainly! We discovered that dark comets can be categorized into two populations based on their sizes and orbits. The first group consists of larger dark comets, measuring hundreds of meters or more, which reside on the outskirts of our solar system. Their elliptical orbits are reminiscent of comets from the Jupiter family. The second group comprises smaller dark comets, which are tens of meters in size and orbit in a more circular path located in the central part of the solar system, including the orbital belt of Mercury, Venus, Earth, and Mars.
TNE: That’s fascinating! Can you share the significance of these discoveries for the field of astronomy?
DS: Yes, the identification of dark comets contributes significantly to our understanding of solar system dynamics and evolution. By studying these objects, we can gain insights into the conditions and materials present during the early years of our solar system. The behaviour of dark comets may also provide clues about the formation and advancement of other celestial bodies.Given their distinct characteristics, they could help us understand better the conditions that lead to comet or asteroid formation.
TNE: your study started from the observation of asteroid 2003 RM. What prompted you to investigate further into this mysterious object’s trajectory?
DS: The trajectory of 2003 RM showed a deviation from what we expected, which raised questions. This kind of deviation can’t be explained by the usual forces affecting asteroids, like the Yarkovsky effect. The unusual behavior suggested that this object might actually be more comet-like, especially since it exhibited signs of volatiles being released from it’s surface, which provides a greater push compared to any asteroid. this initial finding was an vital clue that led to our expanded investigations into dark comets.
TNE: Many of our readers are space enthusiasts. What practical advice can you offer them regarding observing or studying comets and asteroids?
DS: For anyone interested in observing comets and asteroids, I would suggest keeping an eye on space agency alerts or dedicated astronomical organizations. There’s often new information about upcoming comets, especially as new technology enhances our ability to spot them. Additionally, joining local astronomy clubs can provide great opportunities for stargazing and learning with experienced astronomers. Knowledge of the different types of celestial bodies and their behaviors will enhance understanding and recognition of the cosmos.
TNE: Thank you, Dr. Seligman! Your insights into dark comets and their implications for astronomy are truly enlightening.
DS: Thank you for having me.It’s an exciting time for our field, and I’m glad to share our findings with your readers!