[wendy1946]

Neptune's own existence was a puzzle until recently. The dusty cloud that gave birth to the planets probably thinned out further from the sun. With building material so scarce, it is hard to understand how Uranus and Neptune, the two outermost planets, managed to get so big.

The best information at present is that there is no way a planet would ever arise from a dusty cloud; and that all agglomerations of matter whether stars, planets, galaxies, or strings of galaxies, arise from the z-pinch effect associated with currents moving through plasma.

[SunkenCiv]

Rogue Planet Find Makes Astronomers Ponder Theory
by Maggie Fox
October 5, 2000

Eighteen rogue planets that seem to have broken all the rules about being born from a central, controlling sun may force a rethink about how planets form, astronomers said on Thursday... "The formation of young, free-floating, planetary-mass objects like these is difficult to explain by our current models of how planets form," Zapatero-Osorio said... They are not linked to one another in an orbit, but do move together as a cluster, she said... Many stars in our own galaxy, the Milky Way, may have formed in a similar manner to the Orion stars, she said. So there could be similar, hard-to-see planets floating around free near the Solar System.