LTT 9779 b

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]

LTT 9779 b / Cuancoá

Discovery
Discovery date	2020
Detection method	Transit
Designations
Alternative names	Cuancoá
Orbital characteristics
Semi-major axis	0.01679 AU
Eccentricity	<0.01
Inclination	76.39 ± 0.43°
Star	LTT 9779
Physical characteristics
Mean radius	4.72 ± 0.23 R🜨
Mass	29.32 M🜨
Albedo	0.8
Temperature	2,305 K (2,032 °C; 3,689 °F) (Dayside)

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.

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.^[5] Cuancoá's star was named Uúba after the word for "star," "seed," and "eye" in the same language.

See also

• LTT 9779

• List of proper names of exoplanets

• Neptunian desert

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

References

1. 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. 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. "2022 Approved Names". NameExoworlds. Retrieved 2023-10-21.