LTT 9779 b, officially named Cuancoá, is a Neptune-sized planet orbiting the sunlike star LTT 9779, or Uúba. As of 2023, it has the highest-known albedo of any planet.[1]

Characteristics

LTT 9779 b is one of the few known planets in the Neptunian desert.[2] It is highly reflective, with an albedo of 0.8.[3] This makes it the most reflective exoplanet discovered so far. It completes an orbit around LTT 9779 in less than a day, making temperatures on the day side soar to over 2,000 degrees Celsius.[4] Global climate models of the planet indicate it has a very metal-rich atmosphere, with clouds made of silicate likely being present.[1]

Being in the Neptunian desert, LTT 9779 b is a very rare class of planet, with few like it being known. It is estimated that only 1 in 200 Sun-like stars possess a planet with an orbital period of less than a day,[2] and most of those are Hot Jupiters or rocky planets, with ultra-hot Neptune planets being rare.[2] Because of this, LTT 9779 b has been extensively studied by many space telescopes including Hubble and James Webb.

A study using JWST NIRISS found highly reflective white clouds on the western dayside of LTT 9779b. The researchers suggest an eastwards equatorial jet, leading to a colder western dayside, allowing the formation of silicate clouds. These clouds can be best described with MgSiO3 (enstatite) and Mg2SiO4 (forsterite). The study also detected water vapor in the atmosphere in the form of a dip at 1.4 μm. The dayside temperature was measured to be 2260+40
−50 Kelvin (K) and the nightside temperature was measured to be <1,330 K.[5][6]

Name

LTT 9779 b was officially named Cuancoá in 2022 by the International Astronomical Union, as part of the NameExoWorlds competition. Cuancoá is a word that refers to the morning star in the Uwa language.[7] Cuancoá's star was named Uúba after the word for "star," "seed," and "eye" in the same language.

See also

  • NGTS-4b, another planet in the Neptunian desert

References

  1. ^ a b Hoyer, S.; Jenkins, J. S.; Parmentier, V.; Deleuil, M.; Scandariato, G.; Wilson, T. G.; Díaz, M. R.; Crossfield, I. J. M.; Dragomir, D.; Kataria, T.; Lendl, M.; Ramirez, R.; Rojas, P. A. Peña; Vinés, J. I. (2023-07-01). "The extremely high albedo of LTT 9779 b revealed by CHEOPS - An ultrahot Neptune with a highly metallic atmosphere". Astronomy & Astrophysics. 675: A81. doi:10.1051/0004-6361/202346117. ISSN 0004-6361. S2CID 259715040.
  2. ^ a b c Jenkins, James S.; Díaz, Matías R.; Kurtovic, Nicolás T.; Espinoza, Néstor; Vines, Jose I.; Rojas, Pablo A. Peña; Brahm, Rafael; Torres, Pascal; Cortés-Zuleta, Pía; Soto, Maritza G.; Lopez, Eric D.; King, George W.; Wheatley, Peter J.; Winn, Joshua N.; Ciardi, David R. (2020-09-14). "An Ultra-Hot Neptune in the Neptune desert". Nature Astronomy. 4 (12): 1148–1157. arXiv:2009.12832. doi:10.1038/s41550-020-1142-z. ISSN 2397-3366. S2CID 221883508.
  3. ^ "Cheops shows scorching exoplanet acts like a mirror". www.esa.int. Retrieved 2023-10-21.
  4. ^ Crossfield, Ian J. M.; Dragomir, Diana; Cowan, Nicolas B.; Daylan, Tansu; Wong, Ian; Kataria, Tiffany; Deming, Drake; Kreidberg, Laura; Mikal-Evans, Thomas; Gorjian, Varoujan; Jenkins, James S.; Benneke, Bjoern; Collins, Karen A.; Burke, Christopher J.; Henze, Christopher E. (2020-10-26). "Phase Curves of Hot Neptune LTT 9779b Suggest a High-Metallicity Atmosphere". The Astrophysical Journal. 903 (1): L7. arXiv:2010.12745. doi:10.3847/2041-8213/abbc71. ISSN 2041-8213.
  5. ^ Coulombe, Louis-Philippe; Radica, Michael; Benneke, Björn; D’Aoust, Élyse; Dang, Lisa; Cowan, Nicolas B.; Parmentier, Vivien; Albert, Loïc; Lafrenière, David; Taylor, Jake; Roy, Pierre-Alexis; Pelletier, Stefan; Allart, Romain; Artigau, Étienne; Doyon, René (2025-02-25). "Highly reflective white clouds on the western dayside of an exo-Neptune". Nature Astronomy: 1–14. arXiv:2501.14016. Bibcode:2025arXiv250114016C. doi:10.1038/s41550-025-02488-9. ISSN 2397-3366.
  6. ^ White, Heidi (2025-02-25). "JWST Forecasts Partially Cloudy Skies on Ultra-Hot Neptune LTT 9779 b - Trottier Institute for Research on Exoplanets". exoplanetes.umontreal.ca. Retrieved 2025-02-25.
  7. ^ "2022 Approved Names". NameExoworlds. Retrieved 2023-10-21.
Allikas: http://en.wikipedia.org/wiki/LTT_9779_b
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