HAT-P-21

Last updated
HAT-P-21
Observation data
Epoch J2000       Equinox J2000
Constellation Ursa Major [1]
Right ascension 11h 25m 05.9859s [2]
Declination +41° 01′ 40.665″ [2]
Apparent magnitude  (V)11.46 [3]
Characteristics
Spectral type G3V [4]
Astrometry
Radial velocity (Rv)−51.87±0.48 [2] km/s
Proper motion (μ)RA: −1.142(17) mas/yr [2]
Dec.: 13.523(24) mas/yr [2]
Parallax (π)3.5190±0.0228  mas [2]
Distance 927 ± 6  ly
(284 ± 2  pc)
Details [5] [6]
Mass 0.947±0.042  M☉
Radius 1.105±0.083  R☉
Luminosity 1.06+0.20
−0.16  L☉
Surface gravity (log g)4.33±0.06  cgs
Temperature 5634±67  K
Metallicity 0.04±0.08
Rotation 15.88±0.02 d [7]
Rotational velocity (v sin i)3.5±0.5 km/s
Age 10.2±2.5  Gyr
Other designations
Mazaalai, HAT-P-21, TOI-1800, TIC 17993892, TYC 3013-1229-1, GSC 03013-01229, 2MASS J11250598+4101406 [3]
Database references
SIMBAD data
Exoplanet Archive data

HAT-P-21, also named Mazaalai, is a G-type main-sequence star about 927 light-years away. The star has amount of metals similar to solar abundance. The survey in 2015 has failed to detect any stellar companions. [8] The star is rotating rapidly, being spun up by the tides of giant planet on close orbit. [6]

Contents

Naming

In 2019, the star HAT-P-21 received the proper name Mazaalai while its planet HAT-P-21b received the name Bambaruush in the international NameExoWorlds contest. These names refer to the Mongolian name for the endangered Gobi bear subspecies, and the Mongolian term for 'bear cub', respectively. Mazaalai was also the name of Mongolia's first satellite. [9] Some IAU publications have misspelled the star's name as Mazalaai, but the latest IAU Catalog of Star Names lists Mazaalai. [10]

Planetary system

In 2010 a transiting hot super-Jovian planet on moderately eccentric orbit was detected. [4] Its equilibrium temperature is 1283±50 K. The transit-timing variation survey in 2011 have failed to rule out or confirm the existence of additional planets in the system, until the orbital parameters of HAT-P-21b are known with better precision. [7]

The planetary orbit is likely aligned with the equatorial plane of the star, misalignment equal to 25±16 degrees. [11]

Size comparison of HAT-P-21 b and Jupiter Exoplanet Comparison HAT-P-21 b.png
Size comparison of HAT-P-21 b and Jupiter
The HAT-P-21 planetary system [4] [12]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (Bambaruush)4.063±0.161  MJ 0.0494±0.00074.124481±0.0000070.228±0.01688.6° 1.08±0.18  RJ

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific . 99 (617): 695. Bibcode:1987PASP...99..695R. doi: 10.1086/132034 . Constellation record for this object at VizieR.
  2. 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv: 2208.00211 . Bibcode:2023A&A...674A...1G. doi: 10.1051/0004-6361/202243940 . S2CID   244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 "HAT-P-21". SIMBAD . Centre de données astronomiques de Strasbourg.
  4. 1 2 3 Bakos, G. Á.; Hartman, J.; Torres, G.; Latham, D. W.; Kovács, Géza; Noyes, R. W.; Fischer, D. A.; Johnson, J. A.; Marcy, G. W.; Howard, A. W.; Kipping, D.; Esquerdo, G. A.; Shporer, A.; Béky, B.; Buchhave, L. A.; Perumpilly, G.; Everett, M.; Sasselov, D. D.; Stefanik, R. P.; Lázár, J.; Papp, I.; Sári, P. (2010), "HAT-P-20b–HAT-P-23b: FOUR MASSIVE TRANSITING EXTRASOLAR PLANETS", The Astrophysical Journal, 742 (2): 116, arXiv: 1008.3388 , Bibcode:2011ApJ...742..116B, doi:10.1088/0004-637X/742/2/116, S2CID   119182075
  5. ↑ Stassun, Keivan G.; Collins, Karen A.; Gaudi, B. Scott (2016), "Accurate Empirical Radii and Masses of Planets and Their Host Stars with Gaia Parallaxes", The Astronomical Journal, 153 (3): 136, arXiv: 1609.04389 , Bibcode:2017AJ....153..136S, doi: 10.3847/1538-3881/aa5df3 , S2CID   119219062
  6. 1 2 Maxted, P. F. L.; Serenelli, A. M.; Southworth, J. (2015), "A comparison of gyrochronological and isochronal age estimates for transiting exoplanet host stars", Astronomy & Astrophysics, 577: A90, arXiv: 1503.09111 , Bibcode:2015A&A...577A..90M, doi:10.1051/0004-6361/201525774, S2CID   53324330
  7. 1 2 Damiani, C.; Lanza, A. F. (2011), "Prospecting transit duration variations in extrasolar planetary systems", Astronomy & Astrophysics, 535: A116, arXiv: 1109.0936 , Bibcode:2011A&A...535A.116D, doi:10.1051/0004-6361/201117207, S2CID   118460941
  8. ↑ Wöllert, Maria; Brandner, Wolfgang; Bergfors, Carolina; Henning, Thomas (2015), "A Lucky Imaging search for stellar companions to transiting planet host stars", Astronomy & Astrophysics, 575: A23, arXiv: 1507.01938 , Bibcode:2015A&A...575A..23W, doi:10.1051/0004-6361/201424091, S2CID   119250579
  9. ↑ "IAU 100 NameExoWorlds Approved Names". Archived from the original on 2019-12-19. Retrieved 2020-07-08.
  10. ↑ "IAU Catalog of Star Names" . Retrieved 23 May 2025.
  11. ↑ Mancini, L.; et al. (2022), "The GAPS Programme at TNG", Astronomy & Astrophysics, 664: A162, arXiv: 2205.10549 , doi:10.1051/0004-6361/202243742, S2CID   248986121
  12. ↑ Davoudi, F.; Jafarzadeh, S.J.; Poro, A.; Basturk, O.; Mesforoush, S.; Fasihi Harandi, A.; Gozarandi, M.J.; Zare Mehrjardi, Z.; Maley, P.D.; Khakpash, S.; Rokni, K.; Sarostad, A. (2020), "Light Curve Analysis of Ground-Based Data from Exoplanets Transit Database", New Astronomy, 76: 101305, arXiv: 1910.11438 , Bibcode:2020NewA...7601305D, doi:10.1016/j.newast.2019.101305, S2CID   202931761
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