Exoplanetology

Exoplanetology, or exoplanetary science, is an integrated field of astronomical science dedicated to the search and study of exoplanets (extrasolar planets). It employs an interdisciplinary approach which includes astrobiology, astrophysics, astronomy, astrochemistry, astrogeology, geochemistry, and planetary science.

Methodology

The first exoplanet was detected on 6 October 1995, and was named 51 Pegasi b.[1] When extrasolar planets are observed to transit their parent stars, astronomers are able to assess some physical properties of the planets from an interstellar distance, including planetary masses and size, which in turn provide fundamental constraints on models of their physical structure.[2] Furthermore, such events afford the opportunity to study the dynamics and chemistry of their atmospheres.[2]

Statistical surveys and individual characterization are the keys to addressing the fundamental questions in exoplanetology.[3] Varying techniques have been used to discover 2,002 planets outside the Solar System.[4] Documenting the properties of a large sample exoplanets at various ages, orbiting their parent stars of various types, will contribute to increased understanding —or better models— of planetary formation (accretion), geological evolution, orbit migration,[3][5] and their potential habitability.[6] Characterizing the atmospheres of extrasolar planets is the new frontier in exoplanetary science.[7]

Detection techniques

About 97% of all the known exoplanets have been discovered by indirect techniques of detection, mainly by radial velocity measurements and transit monitoring techniques.[6] The following methods have proved successful for discovering a new planet or confirming an already discovered planet:[8]

  • Radial velocity
  • Gravitational microlensing
  • Direct imaging
  • Polarimetry
  • Astrometry
  • Transit photometry
    • Reflection/emission modulations
    • Light variations due to relativistic beaming
    • Light variations due to ellipsoidal variations
  • Timing variations
    • Pulsar timing
    • variable star timing
    • Transit timing variation method
    • Transit duration variation method
    • Eclipsing binary minima timing

Habitability potential

As more planets are discovered, the field of exoplanetology continues to grow into a deeper study of extrasolar worlds, and will ultimately tackle the prospect of life on planets beyond the Solar System.[6] At cosmic distances, life can only be detected if it is developed at a planetary scale and strongly modified the planetary environment, in such a way that the modifications cannot be explained by classical physico-chemical processes (out of equilibrium processes).[6] For example, molecular oxygen (O
2) in the atmosphere of Earth is a result of photosynthesis by living plants and many kinds of microorganisms, so it can be used as an indication of life on exoplanets, although small amounts of oxygen could also be produced by non-biological means.[9] Furthermore, a potentially habitable planet must orbit a stable star at a distance within which planetary-mass objects with sufficient atmospheric pressure can support liquid water at their surfaces.[10][11]

See also

References

  1. ↑ Exoplanet Anniversary: From Zero to Thousands in 20 Years. NASA News, 6 October 2015.
  2. 1 2 "The Era of Comparative Exoplanetology." American Astronomical Society. Charbonneau, David. AAS Meeting #212, #54.01; Bulletin of the American Astronomical Society, May 2008, Vol. 40, p.250
  3. 1 2 Desert, Jean-Michel; Deming, Drake; Knutson, Heather; Bean, Jacob; Fortney, Jonathan; Burrows, Adam; Showman, Adam (September 2012). "New Frontiers for Comparative Exoplanetology In the Era of Kepler". NASA. NASA. Retrieved 2015-09-11.
  4. ↑ Interactive Extra-solar Planets Catalog, The Extrasolar Planets Encyclopaedia. Updated November 24, 2015. Accessed November 25, 2015
  5. ↑ Kraus, Adam L.; Ireland, Michael J. (27 December 2012). "LkCa 15: A YOUNG EXOPLANET CAUGHT AT FORMATION?". The Astrophysical Journal 745 (1): 5. arXiv:1110.3808. Bibcode:2012ApJ...745....5K. doi:10.1088/0004-637X/745/1/5. Retrieved 2015-09-11.
  6. 1 2 3 4 Ollivier, Marc; Maurel, Marie-Christine (2014). "Planetary Environments and Origins of Life: How to reinvent the study of Origins of Life on the Earth and Life in the" (PDF). BIO Web of Conferences 2 2: 00001. doi:10.1051/bioconf/20140200001. Retrieved 2015-09-11.
  7. ↑ Madhusudhan, Nikku; Agúndez, Marcelino; Moses, Julianne I.; Hu, Yongyun (20 Apr 2016). "Exoplanetary Atmospheres - Chemistry, Formation Conditions, and Habitability". Space Science Reviews. arXiv:1604.06092. Bibcode:2016arXiv160406092M.
  8. ↑ Ollivier M., Encrenaz T., Roques F., Selsis F., Casoli F., Planetary Systems - Detection, Formation and Habitability of Extrasolar Planets, Springer, Berlin (2008)
  9. ↑ "Oxygen Is Not Definitive Evidence of Life on Extrasolar Planets". NAOJ (Astrobiology Web). 10 September 2015. Retrieved 2015-09-11.
  10. ↑ Kopparapu, Ravi Kumar (2013). "A revised estimate of the occurrence rate of terrestrial planets in the habitable zones around kepler m-dwarfs". The Astrophysical Journal Letters 767 (1): L8. arXiv:1303.2649. Bibcode:2013ApJ...767L...8K. doi:10.1088/2041-8205/767/1/L8.
  11. ↑ Cruz, Maria; Coontz, Robert (2013). "Exoplanets - Introduction to Special Issue". Science 340 (6132): 565. doi:10.1126/science.340.6132.565. Retrieved 18 May 2013.

External links

Exoplanet catalogs and databases
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