Abstract
Super-Earths are the newest class of extra-solar planets with a mass range between about 1–10M ⊕ . With their large masses, they experience very large internal pressures. The central pressure scales proportionately with mass, reaching values that require us to extend our understanding of rock and H2O behavior to such extreme conditions. Pressure also constrains the power law relationship between mass and radius of solid planets R∼M β. The value for the exponent is 0.262≤β≤0.274 as constrained by the different internal structure models for super-Earths, while it is 0.3 for planets between 5–50% the mass of Earth. Despite uncertainties in planetary composition, temperature structure and equation of state, the mass-radius relationship is robust, and thus, useful for inferring the expected signal in transit searches.
In the next few years many super-Earths will be discovered and their masses and radii will be known with some uncertainty. Even without errors in both the data and structure models, a large number of compositions can fit the same average density. However, the follow-up observations with space telescopes will yield very precise radius measurements and even probe the atmospheres of super-Earths. This radius uncertainty will then be comparable to the current error derived from the equation of state used by the structure models. Thus, there is a need for accurate equations of state of solid planetary materials. Furthermore, information on the structure, such as the size and state of the core, crucially depends on the exact behavior of super-Earth materials (i.e. silicates, iron, iron alloy and ices) at high pressures and temperatures. In addition, information about the atmospheric composition of these planets may prove useful in constraining their interiors. Ultimately any inference on the structure of super-Earths, including information from atmospheres, depends on the precision of interior models, which in turn require accurate equations of state.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Adams, E., Seager, S., Elkins-Tanton, L.: Ocean planet or thick atmosphere: On the mass-radius relationship for solid exoplanets with massive atmospheres. Astrophys. J. 673, 1160–1164 (2008)
Beaulieu, J.P., Bennett, D.P., Fouque, P., Williams, A., Dominik, M., Jorgensen, U.G., Kubas, D., Cassan, A., Coutures, C., Greenhill, J., Hill, K., Menzies, J., Sackett, P.D., Albrow, M., Brillant, S., Caldwell, J.A.R., Calitz, J.J., Cook, K.H., Corrales, E., Desort, M., Dieters, S., Dominis, D., Donatowicz, J., Hoffman, M., Kane, S., Marquette, J.B., Martin, R., Meintjes, P., Pollard, K., Sahu, K., Vinter, C., Wambsganss, J., Woller, K., Horne, K., Steele, I., Bramich, D., Burgdorf, M., Snodgrass, C., Bode, M., Udalski, A., Szymanski, M., Kubiak, M., Wieckowski, T., Pietrzynski, G., Soszynski, I., Szewczyk, O., Wyrzykowski, L., Paczynski, B., Collaboration, T.M.: Discovery of a cool planet of 5.5 earth masses through gravitational microlensing. Nature 439, 437–440 (2006)
Bennett, D.P., Bond, I.A., Udalski, A., Sumi, T., Abe, F., Fukui, A., Furusawa, K., Hearnshaw, J.B., Holderness, S., Itow, Y., Kamiya, K., Korpela, A.V., Kilmartin, P.M., Lin, W., Ling, C.H., Masuda, K., Matsubara, Y., Miyake, N., Muraki, Y., Nagaya, M., Okumura, T., Ohnishi, K., Perrott, Y.C., Rattenbury, N.J., Sako, T., Saito, T., Sato, S., Skuljan, L., Sullivan, D.J., Sweatman, W.L., Tristram, P.J., Yock, P.C.M., Kubiak, M., Szymanski, M.K., Pietrzynski, G., Soszynski, I., Szewczyk, O., Wyrzykowski, L., Ulaczyk, K., Batista, V., Beaulieu, J.P., Brillant, S., Cassan, A., Fouque, P., Kervella, P., Kubas, D., Marquette, J.B.: A low-mass planet with a possible sub-stellar-mass host in microlensing event moa-2007-blg-192 (2008)
Borde, P., Rouan, D., Leger, A.: Exoplanet detection capability of the corot space mission. Astron. Astrophys. 405, 1137 (2003)
Borucki, W.J., Koch, D., Basri, G., Brown, T., Caldwell, D., Devore, E., Dunham, E., Gautier, T., Geary, J., Gilliland, R., Gould, A., Howell, S., Jenkins, J.: Kepler mission: a mission to find earth-size planets in the habitable zone. In: Fridlund, M., Henning, T. (eds.) Proceedings of the Conference on Towards Other Earths: DARWIN/TPF and the Search for Extrasolar Terrestrial Planets, ESA SP-539, Noordwijk, pp. 69–81, 2003
Bouchy, F., Mayor, M., Lovis, C., Udry, S., Benz, W., Bertaux, J.-L., Delfosse, X., Mordasini, C., Pepe, F., Queloz, D., Segransan, D.: The HARPS search for southern extra-solar planets. XVII. Super-Earth and Neptune-mass planets in multiple planet systems HD 47 186 and HD 181 433. Astron. Astrophys. 496, 527–531 (2009). doi:10.1051/0004-6361:200810669
Cizkova, H., Oganov, A.R., Yuen, D.A., Cadek, O., Matyska, C.: Why post-perovskite should have a low viscosity, its dynamical consequences. In: AGU Fall Meeting Abstracts, A1742+, 2008
Clampin, M.: The James webb space telescope (jwst). Adv. Space Res. 12, 1983–1991 (2008)
Cohen, R., Gulseren, O., Hemley, R.J.: Accuracy of equations of state formulations. Am. Mineral. 85, 338–344 (2000)
Fortney, J.J., Marley, M.S., Barnes, J.W.: Planetary radii across five orders of magnitude in mass and stellar insolation: application to transits. Astrophys. J. 659(2), 1661–1672, Part 1 APR20 (2007)
Hama, J., Suito, K.: The search for a universal equation of state correct up to very high pressures. J. Phys. Condens. Matter 8, 67–81 (1996)
Ida, S., Lin, D.: Toward a deterministic model of planetary formation. I. A desert in the mass and semimajor axis distributions of extrasolar planets. Astrophys. J. 604, 388–413 (2004)
Lin, J., Gregoryanz, E., Struzhkin, V., Somayazulu, M., Mao, H., Hemley, R.: Melting behavior of H2O at high pressures and temperatures. Geophys. Res. Lett. 32, 11306 (2005)
Lovis, C., Mayor, M., Pepe, F., Alibert, Y., Benz, W., Bouchy, F., Correia, A.C.M., Laskar, J., Mordasini, C., Queloz, D., Santos, N.C., Udry, S., Bertaux, J., Sivan, J.: An extrasolar planetary system with three Neptune-mass planets. Nature 441, 305–309 (2006)
Mao, W.L., Shen, G., Prakapenka, V.B., Meng, Y., Campbell, A.J., Heinz, D.L., Shu, J., Hemley, R.J., Mao, H.-K.: Ferromagnesian postperovskite silicates in the D″ layer of the Earth. Proc. Natl. Acad. Sci. (USA) 101(45), 15867–15869 (2004)
Mashimo, T., Chau, R., Zhang, Y., Kobayoshi, T., Sekine, T., Fukuoka, K., Syono, Y., Kodama, M., Nellis, W.J.: Transition to a virtually incompressible oxide phase at a shock pressure of 120 GPa (1.2 mbar): Gd3ga5o12. Phys. Rev. Lett. 96, 105504:1–4 (2006)
Mayor, M., Udry, S., Lovis, C., Pepe, F., Queloz, D., Benz, W., Bertaux, J.-L., Bouchy, F., Mordasini, C., Segransan, D.: The HARPS search for southern extra-solar planets. XIII. A planetary system with 3 super-Earths (4.2, 6.9, and 9.2 M-Earth). Astron. Astrophys. 493, 639–644 (2009). doi:10.1051/0004-6361:200810451
Murakami, M., Hirose, K., Kawamura, K., Sata, N., Ohishi, Y.: Post-perovskite phase transition in MgSiO3. Science 304(5672), 855–858 (2004)
Rivera, E.J., Lissauer, J.J., Butler, R.P., Marcy, G., Vogt, S.S., Fischer, D.A., Brown, T.M., Laughlin, G., Henry, G.W.: A 7.5 earth-mass planet orbiting the nearby star. gj 876. Astrophys. J. 634, 625–640 (2005)
Schwegler, E., Sharma, M., Gygi, F., Gallir, G.: Melting of ice under pressure. Proc. Natl. Acad. Sci. (USA) 105, 14779–14783 (2008)
Seager, S., Kuchner, M., Hier-Majumder, C., Militzer, B.: Mass-radius relationships for solid exoplanets. Astrophys. J. 669, 1279–1297 (2007)
Sotin, C., Grasset, O., Mocquet, A.: Mass-Radius curve for extrasolar Earth-like planets and ocean planets. Icarus 191, 337–351 (2007)
Udry, S., Bonfils, X., Delfosse, X., Forveille, T., Mayor, M., Perrier, C., Bouchy, F., Lovis, C., Pepe, F., Queloz, D., Bertaux, J.-L.: The HARPS search for southern extra-sola planets. XI. Super-Earths (5 and 8 M-Earth) in a 3-planet system. Astron. Astrophys. 469, L43–L47 (2007)
Valencia, D., O’Connell, R.J., Sasselov, D.D.: Internal structure of massive terrestrial planets. Icarus 181, 545–554 (2006)
Valencia, D., Sasselov, D.D., O’Connell, R.J.: Detailed models of super-earths: How well can we infer bulk properties? Astrophys. J. 665, 1413 (2007a)
Valencia, D., Sasselov, D.D., O’Connell, R.J.: Radius and structure models of the first super-earth planet. Astrophys. J. 656, 545–551 (2007b)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Valencia, D., O’Connell, R.J. & Sasselov, D.D. The role of high-pressure experiments on determining super-Earth properties. Astrophys Space Sci 322, 135–139 (2009). https://doi.org/10.1007/s10509-009-0034-6
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10509-009-0034-6