A giant impact 4.5 billion years ago could be the reason Jupiter’s core is stranger than astronomers expected.
Astronomers thought that Jupiter began as a rocky and icy planetary embryo that later formed its massive gaseous envelope, drawing in hydrogen and helium from the solar nebula by virtue of its huge gravity. This would mean there was a relatively clear delineation between the solid core and the gas surrounding it.
However, that does not appear to be the case. Over the past few years, NASA’s Juno spacecraft has made measurements of Jupiter’s gravitational field and these suggest the solid core is mixed with hydrogen through a large part of its radius.
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