Starship Asterisk*

[img3="In this artist's conception, a carbon planet orbits a sunlike star in the early universe. Young planetary systems lacking heavy chemical elements but relatively rich in carbon could form worlds made of graphite, carbides and diamond rather than Earth-like silicate rocks. Blue patches show where water has pooled on the planet's surface, forming potential habitats for alien life. (Credit: Christine Pulliam (CfA). Sun image: NASA/SDO)"]https://www.cfa.harvard.edu/sites/www.c ... 1/base.jpg[/img3][hr][/hr]

Our Earth consists of silicate rocks and an iron core with a thin veneer of water and life. But the first potentially habitable worlds to form might have been very different. New research suggests that planet formation in the early universe might have created carbon planets consisting of graphite, carbides, and diamond. Astronomers might find these diamond worlds by searching a rare class of stars. ...

The primordial universe consisted mostly of hydrogen and helium, and lacked chemical elements like carbon and oxygen necessary for life as we know it. Only after the first stars exploded as supernovae and seeded the second generation did planet formation and life become possible.

Mashian and Loeb examined a particular class of old stars known as carbon-enhanced metal-poor stars, or CEMP stars. These anemic stars contain only one hundred-thousandth as much iron as our Sun, meaning they formed before interstellar space had been widely seeded with heavy elements. ...

Although lacking in iron and other heavy elements compared to our Sun, CEMP stars have more carbon than would be expected given their age. This relative abundance would influence planet formation as fluffy carbon dust grains clump together to form tar-black worlds. ...

• Monthly Notices of the RAS (online 2016 May 01) DOI: 10.1093/mnras/stw1037
  arXiv.org > astro-ph > arXiv:1603.06943 > 22 Mar 2016 (v1), 27 Apr 2016 (v2)