On 2005-05-12, wrote:

V? Might refer to Vesta, the brightest asteroid, and thought to be the
seventh planet of Hindu mythology. Or perhaps "Worlds in Collision",
Velikovsky's idea that in historical times Venus was ejected by Jupiter
and had several near collisions with Earth.

Oh, god, yes. Velikovsky. Pronounced in such a way as it might sound
like an F, and

I haven't run across Theia or Orpheus in any usage that I recall. Might
be a term that a particular writer used and it never caught on, or from
a science fiction source.

I get the impression Orpheus was more likely to be from sf than Theia.

My entirely unscientific corpus searching in a citation index gives five
hits for Theia as the protoplanet out of thirteen hits on the word; none
for Orpheus as a protoplanet out of fifty-three. Of those five hits,
they're recent - one 2000, three 2001, one 2004. One in Science, one in
Nature, reasonably well-regarded looking papers.

(However, they all have one Halliday AN, from Zurich, as an author. He
probably likes the name)

"This observation is consistent with the Giant Impact model, provided
that the proto-Earth and the smaller impactor planet (named Theia)
formed from an identical mix of components."

"The data are consistent with the proto-Earth and Theia (the impactor)
having Rb/Sr ratios that were not very different from that of present
day Mars."

"...consistent with a precursor planet (Theia) that was even less
volatile element-depleted than the present Earth (Rb/Sr = 0.03)"

"A collision at or before 50 Myr between a near Earth-sized proto-Earth
and a Mars-sized impactor, here named Theia, would not yield chondritic
W for the present day BSE, unless there was also significant subsequent:
accretion."

"Furthermore, tungsten and strontium isotope compositions of lunar
samples provide evidence that the Moon-forming impacting protoplanet
Theia was probably more like Mars, with a volatile-rich, oxidized
mantle."

So at least one guy uses it, but he writes a decent amount and doesn't
seem to be a crank (unless you're a geologist who doesn't believe in the
giant impact theory, I guess g)

There is a book, titled something like "The
12th Planet", that if I recall acurately, has 2 bodies collide to form
the asteroids and Luna another independant planet. The names it uses
are from Babylonian mythology.

Yup, run across those two; a third Babylonian name gets kicked around as
well, occasionally, though I think the theory behind that one is even
shakier.

--
-Andrew Gray