Scientists have proposed that the Sun may have consumed a planet several times the mass of Earth during its early development, potentially leaving lasting chemical traces within its interior. This hypothesis, detailed in a study published in Monthly Notices of the Royal Astronomical Society, offers a new perspective on longstanding inconsistencies between solar models and observations.
Professor Mutlu Yildiz from Ege University in Turkey led the research, which involved simulating the Sun's evolution and comparing these models with precise measurements of its internal structure. The findings suggest that the ingestion of a super-Earth could account for subtle variations in the Sun's interior and its notably depleted lithium abundance.
The study also indicates that such a planet could pass through the Sun's outer layers with minimal mass loss, implying that planets might leave detectable 'fingerprints' inside stars long after they have been engulfed.
Traditional solar models have struggled to simultaneously explain certain helioseismic observations, such as the sound-speed profile beneath the convection zone and the zone's depth, alongside the Sun's surface lithium depletion. The research team explored whether these issues could share a common origin linked to the Sun's early chemical history.
Using the MESA stellar-evolution code, the researchers tested various accretion scenarios and compared the results against helioseismic data and surface element abundances. Their models favor a scenario where the young Sun absorbed a super-Earth approximately five to ten times Earth's mass.
This approach not only addresses multiple solar modeling challenges but also aligns with independent measurements of the Sun's internal characteristics and lithium levels. Professor Yildiz noted that the convergence on a specific planet mass range was an unexpected but significant outcome.
While definitive proof of such an engulfment event remains elusive, identifying the predicted chemical and structural signatures through future observations could provide strong evidence that the Sun once swallowed a planet. This research also offers insight into why our solar system lacks close-in super-Earths, which are common in other star systems.
The study builds on earlier theoretical work suggesting that super-Earths could have formed inside Mercury's orbit and migrated inward, potentially falling into the young Sun. However, this new research focuses on whether the Sun still retains observable evidence of such an event.
The next step involves searching for these 'fingerprints' within the Sun using helioseismic or other observational techniques, which could deepen our understanding of stellar and planetary evolution.