Astronomy:KELT-21b

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KELT-21b
Discovery
Discovered byMarshall Johnson et al.[1]
Discovery siteKELT
Discovery date2018
Transit method
Orbital characteristics
0.05224 AU (7,815,000 km)
Orbital period3.6127647[1] d
Inclination86.46[1]
StarKELT-21 A
(HD 332124)
Physical characteristics
Mean radius1.586[1] |♃|J}}}}}}
Mass<3.91[1] |♃|J}}}}}}
Mean density<1.24 g cm−3
Physics2,051 K (1,778 °C; 3,232 °F)[1]


KELT-21b is an extrasolar planet discovered in 2017. It is a hot Jupiter with radius of about 1.586 MJ.[1]

Host star

KELT-21b orbits KELT-21 A (HD 332124). It orbits the primary star in a triple star system, with the other two stars located 1.2 arcseconds away. These two stars, designated KELT-21 B and C, have masses of 0.13 M☉ and 0.11 M☉, respectively.[1] The primary star is heavy at 1.458±0.029M☉, extremely hot at 8210±771 K and rapidly rotating (equatorial velocity equal to 141 km/s).[2] In comparison, the Sun has a temperature of 5772 K[3] and rotates at an equatorial velocity of 1.997 km/s.[4] The planetary orbit is well aligned with the equatorial plane of the host star, with misalignment equal to −5.6+1.7−1.9°.[5]

Transmission planetary spectroscopy was performed in 2021, based on a single transit observation in 2019. High planetary gravity and relatively low planetary temperature made detection of an atmosphere impossible that time.[6]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Johnson, Marshall C; Rodriguez, Joseph E; Zhou, George; Gonzales, Erica J; Cargile, Phillip A; Crepp, Justin R; Penev, Kaloyan; Stassun, Keivan G et al. (2018). "KELT-21b: A Hot Jupiter Transiting the Rapidly Rotating Metal-poor Late-A Primary of a Likely Hierarchical Triple System". The Astronomical Journal 155 (2): 100. doi:10.3847/1538-3881/aaa5af. Bibcode: 2018AJ....155..100J. 
  2. ↑ Garai, Z.; Pribulla, T.; Kovács, J.; Szabó, Gy M.; Claret, A.; Komžík, R.; Kundra, E. (2022), "Rapidly rotating stars and their transiting planets: KELT-17b, KELT-19Ab, and KELT-21b in the CHEOPS and TESS era", Monthly Notices of the Royal Astronomical Society 513 (2): 2822–2840, doi:10.1093/mnras/stac1095 
  3. ↑ Williams, D. R. (1 July 2013). "Sun Fact Sheet". NASA Goddard Space Flight Center. http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html. 
  4. ↑ "Solar System Exploration: Planets: Sun: Facts & Figures". NASA. http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sun&Display=Facts&System=Metric. 
  5. ↑ Rice, Malena; Wang, Songhu; Wang, Xian-Yu; Stefánsson, Guđmundur; Isaacson, Howard; Howard, Andrew W.; Logsdon, Sarah E.; Schweiker, Heidi et al. (2022), "A Tendency Toward Alignment in Single-star Warm-Jupiter Systems", The Astronomical Journal 164 (3): 104, doi:10.3847/1538-3881/ac8153, Bibcode: 2022AJ....164..104R 
  6. ↑ Stangret, M.; Casasayas-Barris, N.; Pallé, E.; Orell-Miquel, J.; Morello, G.; Luque, R.; Nowak, G.; Yan, F. (2022), "High-resolution transmission spectroscopy study of ultra-hot Jupiters HAT-P-57b, KELT-17b, KELT-21b, KELT-7b, MASCARA-1b, and WASP-189b", Astronomy & Astrophysics 662: A101, doi:10.1051/0004-6361/202141799, Bibcode: 2022A&A...662A.101S 




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