A recent discovery of an asteroid, known as Selam, has led researchers to estimate that it is only 2-3 million years old, making it a solar system toddler. This estimation was made using novel statistical calculations by a research team led by Cornell University. The team derived the age of Selam by observing its dynamics, or how it moves in space, as it circles the small asteroid Dinkinesh in the main asteroid belt between Mars and Jupiter. This calculation aligns with a separate analysis done by NASA’s Lucy mission based on surface craters, the traditional method for dating asteroids.
The new method developed by the research team offers some advantages over the traditional approach. It does not require an expensive spacecraft to capture close-up images, could provide more accuracy in cases where asteroid surfaces have undergone recent changes, and can be applied to the secondary bodies in other known binary systems. These binary systems make up 15% of near-Earth asteroids and understanding their ages is crucial to gaining a better grasp of the asteroid population as a whole. This research sheds light on the age of Selam and contributes to a better understanding of asteroid formation and evolution.
Colby Merrill, a doctoral student in aerospace engineering and the first author of the study published in Astronomy & Astrophysics, emphasized the importance of determining the ages of asteroids. Selam’s young age relative to the solar system age indicates that it formed relatively recently, providing valuable insights into the overall population of asteroids. Merrill, who was part of NASA’s Double Asteroid Redirection Test (DART) mission, closely watched as the Lucy spacecraft discovered Selam while exploring Dinkinesh. This finding revealed that Selam is a contact binary, consisting of two lobes formed from rubble piles stuck together, a unique and complex structure seen orbiting another asteroid for the first time.
Binary asteroids like Selam and Dinkinesh are intriguing objects that undergo dynamic and complex interactions due to the gravitational forces between them. These forces cause the objects to physically bulge and create tides, leading to a continual shifting of energy within the system. The researchers used this information to calculate the age of Selam by assuming equilibrium between tides and the Binary Yarkovsky-O’Keefe-Radzievskii-Paddack (BYORP) effect, a phenomenon where the sun’s radiation influences the binary system’s energy. By running numerous calculations, the team estimated the median age of Selam to be 3 million years, with 2 million years being the most likely result.
The research team hopes to apply their new aging method to other binary systems where dynamics have been well characterized, even without close flybys. By combining this method with crater counting, researchers can improve the accuracy of age estimations for asteroid systems. The ability to use multiple methods to confirm ages provides greater confidence in the results and helps to paint a clearer picture of the current state of these systems. Ultimately, this study contributes to the ongoing efforts to understand the formation and evolution of asteroids within our solar system.
