An asteroid dubbed ‘Lucy’s baby’ after a NASA spacecraft discovered it is orbiting another asteroid last November is only 2 to 3 million years old.
Using novel statistical calculations, a Cornell University team derived the age of Selam, a ‘moon’ surrounding the small asteroid Dinkinesh in the main asteroid belt between Mars and Jupiter, based solely on the dynamics, or how the pair interacts. moves in space. Their calculation agrees with one from NASA’s Lucy mission based on an analysis of surface craters, the most traditional method for dating asteroids.
The new method complements that work and has some advantages: it does not require an expensive spacecraft to capture close-up images, it could be more accurate in cases where asteroid surfaces have undergone recent changes, and it can be applied to secondary bodies in dozens. from other known binary systems, which account for 15% of near-Earth asteroids, the researchers said.
“Finding the ages of asteroids is important to understanding them, and this one is remarkably young compared to the age of the solar system, meaning it formed recently,” Colby Merrill, a doctoral student in the field of science, said in a statement. Aerospace engineering. “Obtaining the age of this body can help us understand the population as a whole,” added Merrill, first author of the new study, published in Astronomy & Astrophysics.
Binary asteroids are dynamically complex and fascinating objects that engage in a kind of tug-of-war, the researchers said. Gravity acting on objects causes them to physically bulge and produces tides, which slowly reduce the energy of the system. Meanwhile, radiation from the sun also alters the energy of the binary system with an effect called the binary Yarkovsky-O’Keefe-Radzievskii-Paddack (BYORP) effect.
Over time, the system will reach an equilibrium in which the tides and the BYORP are equally strong: a stalemate in the tug-of-war.
Assuming those forces were in balance and plugging into asteroid data shared publicly by the Lucy mission, the researchers calculated how long it would have taken for Selam to reach its current state after forming from surface material ejected by a spinning Dinkinesh. quickly. Along the way, the team said it improved pre-existing equations that assumed both bodies were equally dense and ignored the mass of the secondary body.
By performing approximately 1 million calculations with different parameters, the results produced an average age for Selam of 3 million years, with 2 million being the most likely result.
YOUNGER THAN THE FOSSIL REMAINS THAT GIVE IT THE NAME
Determining Selam’s age advances comparisons with Didymos and Dimorphos, the even younger system targeted by NASA’s DART mission, and contributes to the understanding that binary systems are continually being created. The researchers now hope to apply their new aging method to other binary systems where the dynamics have been well characterized, even without close flybys.
“Used in conjunction with crater counting, this method could help better constrain the age of a system,” Kubas said. “If we use two methods and they match each other, we can be more confident that we are getting a meaningful age that describes the current state of the system.”
Calculations suggest that the asteroid Selam is younger than the fossil of the human ancestor on Earth for which it is named: the skeletal remains of a 3-year-old girl found in Ethiopia, which was determined to be 3.3 million years old. Selam means “peace” in the Ethiopian language and has also been nicknamed “Lucy’s baby”, in reference to the famous remains of a human ancestor found in 1974 and nicknamed Lucy or Dinkinesh. The NASA mission named after Lucy is on track to study the Trojan asteroids in Jupiter’s orbit in 2027.
