Neptune may have eaten a planet and stolen its moon

New Scientist ^ | March 22, 2010 | David Shiga

[SunkenCiv]

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.

But what if they formed closer in? In 2005, a team of scientists proposed that the giant planets shifted positions in an early upheaval (New Scientist, 25 November 2006, p 40). In this scenario, Uranus and Neptune formed much closer to the sun and migrated outwards, possibly swapping places in the process.

That would have left behind enough material just beyond their birthplace to form a planet with twice the Earth's mass, according to calculations published in 2008 by Steven Desch of Arizona State University in Tempe.

Neptune's peculiar moon Triton may once have been paired with this hypothetical super-Earth, Desch and colleague Simon Porter now say. Triton is larger than Pluto, and it moves through its orbit in the opposite direction to Neptune's rotation, suggesting that it did not form there but was captured instead.

For Neptune to capture Triton, the moon would have had to slow down drastically. One way to do this is for Triton to have had a partner that carried away most of the pair's kinetic energy after an encounter with Neptune. In 2006 researchers argued that Triton was initially paired with another object of similar size that wound up being gravitationally slung into space after the pair ventured near Neptune (New Scientist, 13 May 2006, p 8).

[LiberConservative]

“Mmmm. Planets.”

[rdl6989]

Now that is funny!

[rdl6989]

Earth, Mars and Venus being moons of Saturn...

Very interesting. I hadn’t heard that.

[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.

[SunkenCiv]

Note: this topic is from 4/03/2010.

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