One of Jupiter’s most recognizable attributes is its size. With a diameter of more than 88,800 miles, the largest planet in our solar system is 11 times wider than the earth and twice as massive than all its planets of combined brothers and sisters. But according to recent calculations based on some of the smallest moons of the gas giant, astronomers now believe that Jupiter was once more than double of its current size, with a magnetic field 50 times stronger. These gargantuan dimensions are not only impressive – they played a major role in the formation of our solar system as it exists today. The new results are detailed in a study published on May 20 in the journal Natural astronomy.
To better understand the primordial stages of Jupiter, the researchers turned to the smallest of the 92 moons known on the planet. Almathea and Thebe are respectively encircling Jupiter to slightly inclined orbits at around 112,400 and 138,000 miles above the cloud tops on the planet.
By analyzing the dynamics of these orbital differences as well as the conservation of the planet of the angular moment, the team could estimate its radius and its inner state at around 3.8 million years after the solar system formed its first solids. At that time, the sun was surrounded by a disc of material known as the protoplanetary nebula which gradually dissipated while it was based in the planets that we know and love. Based on their calculations, the researchers think that the beginning of Jupiter was 2 to 2.5 times larger than today with a much more powerful magnetic field.
“It is surprising that even after 4.5 billion years, enough clues remain to allow us to rebuild Jupiter’s physical state at the dawn of his existence,” said Fred Adams, one of the co-authors of the study and professor of physics and astronomy of the University of Michigan.
By focusing on the directly measurable information from Jupiter moons and the conservation of its angular moment, the team was able to bypass many current uncertainties that afflict planetary training models. These often require astronomers to make hypotheses on variables such as the opacity of the gas, the accretion rate and the central mass of the heavy element.
According to the team, their new calculations are improving more than the understanding of Jupiter’s experts. These factors can be applied to the evolution of other giant planets when they surround stars. They also suggest that gas giants are generally formed by central accretion – or when a gas quickly gathers around an kernel of ice and rock.
“Our ultimate goal is to understand where we come from, and to pin the first phases of the planet’s formation is essential to solve the puzzle,” said Konstantin Batygin, professor of planetary sciences Caltech and co-author of the study. “It brings us closer to understanding how not only Jupiter, but the whole solar system has taken shape.”
