Astronomers think that Neptune's largest moon, Triton, once travelled around the Sun accompanied by a planetesimal partner. At some time in the formation of the Solar System, Neptune's gravity captured Triton and ejected its mate. A new analysis details when and how this might have happened.
David Vokrouhlický of Charles University in Prague and his colleagues used the 'Nice' model, which describes how the planets attained their final configuration. According to their simulations, Triton's capture could only have occurred within the first 5–10 million years of the Solar System's formation, when a gas would have been present to slow the relative velocities of the three bodies.
That means that Neptune must have formed much earlier than some astronomers have suggested, the authors say.
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Astronomy: When Triton lost its mate. Nature 455, 434 (2008). https://doi.org/10.1038/455434e
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DOI: https://doi.org/10.1038/455434e
