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Title: Jupiter Was Formerly Twice Its Current Size and Had a Much Stronger
Magnetic Field

Link: https://science.slashdot.org/story/25/05/20/2...

A new study reveals that about 3.8 million years after the solar system's
first solids formed, Jupiter was twice its current size with a magnetic field
50 times stronger, profoundly influencing the structure of the early solar
system. Phys.Org reports: [Konstantin Batygin, professor of planetary science
at Caltech] and [Fred C. Adams, professor of physics and astronomy at the
University of Michigan] approached this question by studying Jupiter's tiny
moons Amalthea and Thebe, which orbit even closer to Jupiter than Io, the
smallest and nearest of the planet's four large Galilean moons. Because
Amalthea and Thebe have slightly tilted orbits, Batygin and Adams analyzed
these small orbital discrepancies to calculate Jupiter's original size:
approximately twice its current radius, with a predicted volume that is the
equivalent of over 2,000 Earths. The researchers also determined that
Jupiter's magnetic field at that time was approximately 50 times stronger
than it is today. Adams highlights the remarkable imprint the past has left
on today's solar system: "It's astonishing that even after 4.5 billion years,
enough clues remain to let us reconstruct Jupiter's physical state at the
dawn of its existence." Importantly, these insights were achieved through
independent constraints that bypass traditional uncertainties in planetary
formation models -- which often rely on assumptions about gas opacity,
accretion rate, or the mass of the heavy element core. Instead, the team
focused on the orbital dynamics of Jupiter's moons and the conservation of
the planet's angular momentum -- quantities that are directly measurable.
Their analysis establishes a clear snapshot of Jupiter at the moment the
surrounding solar nebula evaporated, a pivotal transition point when the
building materials for planet formation disappeared and the primordial
architecture of the solar system was locked in. The results add crucial
details to existing planet formation theories, which suggest that Jupiter and
other giant planets around other stars formed via core accretion, a process
by which a rocky and icy core rapidly gathers gas. The findings have been
published in the journal Nature Astronomy.

Read more of this story at Slashdot.

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