Carbon planet

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

A carbon planet is a hypothetical type of planet that contains more carbon than oxygen. [1] Carbon is the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen.

Contents

Marc Kuchner and Sara Seager coined the term "carbon planet" in 2005 and investigated such planets following the suggestion of Katharina Lodders that Jupiter formed from a carbon-rich core. [2] Prior investigations of planets with high carbon-to-oxygen ratios include Fegley & Cameron 1987. [3] Carbon planets could form if protoplanetary discs are carbon-rich and oxygen-poor. They would develop differently from Earth, Mars, and Venus, which are composed mostly of silicon–oxygen compounds. Different planetary systems have different carbon-to-oxygen ratios, with the Solar System's terrestrial planets closer to being "oxygen planets" with C/O molar ratio of 0.55. [4] In 2020, survey of the 249 nearby solar analog stars found 12% of stars have C/O ratios above 0.65, making them candidates for the carbon-rich planetary systems. [5] The exoplanet 55 Cancri e, orbiting a host star with C/O molar ratio of 0.78, [6] is a possible example of a carbon planet.

Definition

Such a planet would probably have an iron-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. [7] A weather cycle is hypothetically possible on carbon planets with an atmosphere, provided that the average surface temperature is below 77 °C.

However, carbon planets will probably be devoid of water, which cannot form because any oxygen delivered by comets or asteroids will react with the carbon on the surface. The atmosphere on a relatively cool carbon planet would consist primarily of carbon dioxide or carbon monoxide with a significant amount of carbon smog. [8]

Composition

Comparison of sizes of planets with different compositions Planet sizes.svg
Comparison of sizes of planets with different compositions

Carbon planets are predicted to be of similar diameter to silicate and water planets of the same mass, potentially making them difficult to distinguish. [10] The equivalents 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 gasses may be able to photochemically synthesize into long-chain hydrocarbons, which could rain down onto the surface.

In 2011, NASA cancelled a mission, called TPF, which was to be an observatory much bigger than the Hubble Space Telescope 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 candidates

Draugr, Poltergeist and Phobetor

The pulsar planets Draugr , Poltergeist and Phobetor may be carbon planets that formed from the disruption of a carbon-producing star. Carbon planets might also be located near the Galactic Center or globular clusters orbiting the galaxy, where stars have a higher carbon-to-oxygen ratio than the Sun. 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. [11]

Janssen

In October 2012, it was announced that Janssen showed evidence for being a carbon planet. It has eight times the mass of Earth and twice the radius. Research indicates that the 2,150 °C (3,900 °F) planet is "covered in graphite and diamond rather than water and granite". It orbits the star Copernicus once every 18 hours. [12]

Other carbon-rich objects

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. [13] However, this "planet" is hypothesized 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 because it formed as a star. [14]

At a distance of 267+1.2
−0.9 pc (approximately 870 light-years), [15] PSR J2222−0137 is a nearby intermediate-mass binary pulsar whose low-mass neutron star's companion is a white dwarf (PSR J2222−0137 B). The white dwarf has a relatively large mass of 1.319 ± 0.004  M☉ [16] and a temperature less than 3,000 K, [15] meaning it is likely crystallized, leading to this Earth-sized white dwarf being described as a "diamond-star". [17]

Brown dwarfs

Planets around brown dwarfs are likely to be carbon planets depleted of water. [18]

See also

Related Research Articles

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<span class="mw-page-title-main">White dwarf</span> Type of stellar remnant composed mostly of electron-degenerate matter

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<span class="mw-page-title-main">Brown dwarf</span> Type of substellar object larger than a planet

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<span class="mw-page-title-main">Exomoon</span> Moon beyond the Solar System

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The Black Widow Pulsar is an eclipsing binary millisecond pulsar in the Milky Way. Discovered in 1988, it is located roughly 6,500 light-years away from Earth. It orbits with a brown dwarf or Super-Jupiter companion with a period of 9.2 hours with an eclipse duration of approximately 20 minutes. When it was discovered, it was the first such pulsar known. The prevailing theoretical explanation for the system implied that the companion is being destroyed by the strong powerful outflows, or winds, of high-energy particles caused by the neutron star; thus, the sobriquet black widow was applied to the object. Subsequent to this, other objects with similar features have been discovered, and the name has been applied to the class of millisecond pulsars with an ablating companion, as of February 2023 around 41 black widows are known to exist.

<span class="mw-page-title-main">PSR J1719−1438</span> Millisecond pulsar in the constellation Serpens

PSR J1719-1438 is a millisecond pulsar with a spin period of 5.8 ms located about 4,000 ly from Earth in the direction of Serpens Cauda, one minute from the border with Ophiuchus. Millisecond pulsars are generally thought to begin as normal pulsars and then spin up by accreting matter from a binary companion.

<span class="mw-page-title-main">PSR J1719−1438 b</span> Extrasolar pulsar planet

PSR J1719−1438 b is an extrasolar planet that was discovered on August 25, 2011, in orbit around PSR J1719−1438, a millisecond pulsar. The pulsar planet is most likely composed largely of crystalline carbon but with a density far greater than diamond. PSR J1719-1438 b orbits so closely to its host star that its orbit would fit inside the Sun. The existence of such carbon planets had been theoretically postulated.

<span class="mw-page-title-main">PSR J0348+0432</span> Pulsar–white dwarf binary system in Taurus constellation

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<span class="mw-page-title-main">Pulsar planet</span> Planets found orbiting pulsars

Pulsar planets are planets that are orbiting pulsars. The first such planets to be discovered were around a millisecond pulsar in 1992 and were the first extrasolar planets to be confirmed as discovered. Pulsars are extremely precise clocks and even small planets can create detectable variations in pulsar traits; the smallest known exoplanet is a pulsar planet.

PSR J2222−0137 is a nearby intermediate-mass binary pulsar at a distance of 267+1.2
−0.9 pc, whose low-mass neutron star's companion is a white dwarf. The white dwarf has a relatively large mass of 1.319 ± 0.004 M☉ and a temperature less than 3,000 K, meaning it is likely crystallized, leading to this Earth-sized white dwarf being described as a "diamond-star".

References

  1. ↑ Kuchner, Marc J.; Seager, S. (2005). "Extrasolar Carbon Planets". arXiv: astro-ph/0504214 .
  2. ↑ Lodders, Katharina (2004). "Jupiter Formed with More Tar than heat" (PDF). The Astrophysical Journal . 611 (1): 587–597. Bibcode:2004ApJ...611..587L. doi:10.1086/421970. S2CID   59361587.
  3. ↑ Fegley, Bruce Jr.; Cameron, A. G. W. (April 1987). "A vaporization model for iron/silicate fractionation in the Mercury protoplanet" (PDF). Earth and Planetary Science Letters . 82 (3–4): 207–222. Bibcode:1987E&PSL..82..207F. CiteSeerX   10.1.1.667.7941 . doi:10.1016/0012-821X(87)90196-8.
  4. ↑ P. E. Nissen, The carbon-to-oxygen ratio in stars with planets
  5. ↑ Stonkutė, E.; Chorniy, Y.; Tautvaišienė, G.; Drazdauskas, A.; Minkevičiūtė, R.; Mikolaitis, Š.; Kjeldsen, H.; Essen, C. von; Pakštienė, E.; Bagdonas, V. (2020). "High-resolution Spectroscopic Study of Dwarf Stars in the Northern Sky: Lithium, Carbon, and Oxygen Abundances". The Astronomical Journal. 159 (3): 90. arXiv: 2002.05555 . Bibcode:2020AJ....159...90S. doi: 10.3847/1538-3881/ab6a19 . S2CID   211096705.
  6. ↑ Teske, Johanna K.; Cunha, Katia; Schuler, Simon C.; Griffith, Caitlin A.; Smith, Verne V. (2013). "Carbon and Oxygen Abundances in Cool Metal-Rich Exoplanet Hosts: A Case Study of the C/O Ratio of 55 Cancri". The Astrophysical Journal. 778 (2): 132. arXiv: 1309.6032 . Bibcode:2013ApJ...778..132T. doi:10.1088/0004-637X/778/2/132. S2CID   119291907.
  7. ↑ Musser, George (January 2010). "Earth-Like Planets May Be Made of Carbon". Scientific American . Retrieved 3 January 2013.
  8. ↑ "Kohlenstoffplaneten", Space Magazin April 2014 (p. 35, in German)
  9. ↑ Naeye, Bob (24 September 2007). "Scientists Model a Cornucopia of Earth-sized Planets". Goddard Space Flight Center.
  10. ↑ Seager, Sara; Kuchner, Marc; Hier-Majumder, Catherine; Militzer, Burkhard (2007). "Mass-Radius Relationships for Solid Exoplanets". The Astrophysical Journal . 669 (2): 1279. arXiv: 0707.2895 . Bibcode:2007ApJ...669.1279S. doi:10.1086/521346. S2CID   8369390.
  11. ↑ "Carbon Planets - Space Art and Astronomical Illustrations". Novacelestia.com. Retrieved 3 January 2013.
  12. ↑ Wickham, Chris (15 October 2012). "A diamond bigger than Earth?". Reuters . Archived from the original on 5 March 2016. Retrieved 3 January 2013.
  13. ↑ "Solid diamond planet found". Australian Geographic . 26 August 2011. Archived from the original on 6 October 2011.
  14. ↑ Lemonick, Michael (26 August 2011). "Scientists Discover a Diamond as Big as a Planet". Time . Archived from the original on 26 August 2011.
  15. 1 2 Kaplan, David L.; Boyles, Jason; Dunlap, Bart H.; Tendulkar, Shriharsh P.; Deller, Adam T.; Ransom, Scott M.; McLaughlin, Maura A.; Lorimer, Duncan R.; Stairs, Ingrid H. (2014). "A 1.05M☉Companion to PSR J2222–0137: The Coolest Known White Dwarf?". The Astrophysical Journal. 789 (2): 119. arXiv: 1406.0488v1 . Bibcode:2014ApJ...789..119K. doi:10.1088/0004-637X/789/2/119. ISSN   0004-637X. S2CID   19986066.
  16. ↑ Guo, Y. J.; Freire, P. C. C.; Guillemot, L.; Kramer, M.; Zhu, W. W.; Wex, N.; McKee, J. W.; Deller, A.; Ding, H.; Kaplan, D. L.; Stappers, B.; Cognard, I.; Miao, X.; Haase, L.; Keith, M.; Ransom, S. M.; Theureau, G. (2021). "PSR J2222−0137. I. Improved physical parameters for the system". Astronomy & Astrophysics. 654: A16. arXiv: 2107.09474 . Bibcode:2021A&A...654A..16G. doi:10.1051/0004-6361/202141450. S2CID   236134389.
  17. ↑ Drake, Nadia (24 June 2014). "Astronomers Find Slow-Cooked Diamond the Size of Earth". National Geographic. Archived from the original on 21 March 2021.
  18. ↑ Pascucci, Ilaria; Herczeg, Greg; Carr, John S.; Bruderer, Simon (December 2013). "The atomic and molecular content of disks around very low-mass stars and brown dwarfs" (PDF). The Astrophysical Journal . 779 (2): 178. arXiv: 1311.1228 . Bibcode:2013ApJ...779..178P. doi:10.1088/0004-637X/779/2/178. hdl:11858/00-001M-0000-0017-AAEA-0. S2CID   119001471.
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