Fresh from the clogged tubes of teh intarwubs…
“The Sun does not seem like the perfect star for a system where life might arise. Although it is hard to argue with the Sun’s ‘success’ as it so far is the only star known to host a planet with life, our studies indicate that the ideal stars to support planets suitable for life for tens of billions of years may be a smaller slower burning ‘orange dwarf’ with a longer lifetime than the Sun â€• about 20-40 billion years. These stars, also called K stars, are stable stars with a habitable zone that remains in the same place for tens of billions of years. They are 10 times more numerous than the Sun, and may provide the best potential habitat for life in the long run.”
"Built out of relatively more carbon than oxygen, such a planet would still have a metallic iron core, but the outer layers could be composed of ceramics – silicon and titanium carbides – with a shell of pure carbon on top.
These ceramics and graphite would make the entire planet extremely hard and heat-resistant, and it could survive much closer to its star. Even more bizarre is that the high pressure beneath the surface would convert the bottom of the graphite layer into an entire shell of diamond that would be many kilometres thick."