Jupiter shrinks as it reveals secrets of our solar system

In a groundbreaking study, researchers have discovered that Jupiter, the largest planet in our solar system, was significantly larger in its youth, possibly double its current size. This research highlights that approximately 4.5 billion years ago, Jupiter was not only physically larger but also possessed a magnetic field that was fifty times stronger than what we observe today. The study was led by planetary scientist Konstantin Batygin from the California Institute of Technology (Caltech), who collaborated with other researchers to investigate Jupiter's formation and current characteristics. The focus of the study was on the orbits of two of Jupiter’s moons, Amalthea and Thebe, which have retained their slightly tilted orbits since their initial formation. By examining the gravitational interactions involving these moons and Io, another moon known for its volcanic activity, the researchers were able to deduce vital information regarding the size of Jupiter when it first formed. Their findings suggest that for Amalthea and Thebe’s current orbits to exist, Jupiter's radius would have had to range between two and 2.5 times its present size. As Jupiter formed, it was primarily made up of hot gases and ices, leading to a much larger volume due to lower density at that time. Over billions of years, as the planet’s surface has cooled, it has gradually contracted, shrinking at a rate of about 2 centimeters per year. This slow process of shrinkage not only affects the size of the planet but also generates energy, causing Jupiter to emit more energy than it receives from the Sun, highlighting its dynamic and complex geological process. The implications of understanding Jupiter’s formation and changing size are profound, as they offer insights into the processes that shaped not just Jupiter but the broader solar system in which we live. Fred Adams, an astrophysicist from the University of Michigan and co-author of the study, expressed amazement at how clues from the past can still be used to reconstruct the physical state of Jupiter at the dawn of its existence. As scientists continue to unravel the mysteries of Jupiter, it remains an object of fascination that may help illuminate the origins of other celestial bodies and, ultimately, the conditions required for life on Earth and beyond.