Carbon planet

Artist's concept of a carbon planet. The surface is dark and reddish from hydrocarbon deposits.

A carbon planet, also referred to as a diamond planet or carbide planet,^[1] is a theoretical type of planet proposed by Marc Kuchner that could form if protoplanetary discs are carbon-rich and oxygen-poor. According to planetary science, it would develop differently from Earth, Mars and Venus, planets made up mostly of silicon-oxygen compounds. The theory has gained popularity and is now said by researchers such as Jade Bond^[2] to be built on reasonable ideas, specifically that different systems would have different ratios of carbon to oxygen, and that our own solar system's terrestrial planets actually slant toward being "oxygen planets". The planet PSR J1719-1438 b, discovered on August 25, 2011, could be such a planet.

Definition

Such a planet would probably have an iron or steel-rich core like the known terrestrial planets. Surrounding that would be molten silicon carbide and titanium carbide. Above that, a layer of carbon in the form of graphite, possibly with a kilometers-thick substratum of diamond if there is sufficient pressure. During volcanic eruptions, it is possible that diamonds from the interior could come up to the surface, resulting in mountains of diamonds and silicon carbides. The surface would contain frozen or liquid hydrocarbons (e.g. tar and methane) and carbon monoxide.^[3]

Characteristics

Carbon planets are predicted to be of similar diameter to silicate and water planets of the same mass, potentially making them difficult to distinguish.^[4] The equivalences of geologic features on Earth may also be present, but with different compositions. For instance, the rivers might consist of oils. If the temperature is low enough (below 350 K), then gases may be able to photochemically synthesize into long-chain hydrocarbons, which could rain down onto the surface.

NASA cancelled a mission, called TPF, which was to be an observatory much bigger than Hubble that would have been able to detect such planets. The spectra of carbon planets would lack water, but show the presence of carbonaceous substances, such as carbon monoxide.

Possible planets

The pulsar PSR 1257+12 may possess carbon planets that formed from the disruption of a carbon-producing star. Carbon planets might also be located near the galactic core or globular clusters orbiting the galaxy, where stars have a higher carbon-to-oxygen ratio than the sun does. When old stars die, they spew out large quantities of carbon. As time passes and more and more generations of stars end, the concentration of carbon, and carbon planets, will increase.^[5]

In August 2011, Matthew Bailes and his team of experts from Swinburne University of Technology in Australia reported that the millisecond pulsar PSR J1719-1438 may have a binary companion star that has been crushed into a much smaller planet made largely of solid diamond. They deduced that a small companion planet must be orbiting the pulsar and causing a detectable gravitational pull. Further examination revealed that although the planet is relatively small (60,000 km diameter, or five times bigger than the Earth) its mass is slightly more than that of Jupiter. The high density of the planet gave the team a clue to its likely makeup of carbon and oxygen - and suggested the crystalline form of the elements.^[6] However, this "planet", is theorized to be the remains of an evaporated white dwarf companion, being only the remnant inner core. According to some definitions of planet, this would not qualify, as it formed as a star.^[7]

See also

• Carbon
• Extrasolar planet
• Iron planet
• Ocean planet
• Organic chemistry
• WASP-12b

References

1. ^ http://www.firstpost.com/tag/carbon-planet
2. ^ Bond; Lauretta; O'Brien (2010). "The Diversity of Extrasolar Terrestrial Planets". arXiv:1001.3901 [astro-ph.EP]. 
3. ^ http://www.scientificamerican.com/article.cfm?id=a-large-lump-of-coal
4. ^ Seager, S.; M. Kuchner, C. Hier-Majumder, B. Militzer (2007). "Mass-Radius Relationships for Solid Exoplanets". ApJ 669 (2): 1279. arXiv:0707.2895. Bibcode 2007ApJ...669.1279S. doi:10.1086/521346. 
5. ^ http://www.novacelestia.com/space_art_extrasolar_planets/carbon_planets.html
6. ^ Australian Geographic, "Solid diamond planet found", 26 August 2011
7. ^ Time Magazine, "Scientists Discover a Diamond as Big as a Planet", Michael Lemonick, 26 August 2011

External links

• arXiv:astro-ph/0504214 Marc J. Kuchner, Extrasolar Carbon Planets
• Than, Ker (2006-06-07). "Star's Planets Might Have Mountains of Diamonds". Space.com. http://www.space.com/scienceastronomy/060607_carbon_excess.html. 
• spaceplace.nasa.gov