Short description: Star in the constellation Pegasus

WASP 21

Size comparison between Sun and WASP-21

Observation data
Equinox J2000.0]] (ICRS)
Constellation | Pegasus
Right ascension |  23h 09m 58.25s[1]
Declination | +18° 23′ 45.9″[1]
Apparent magnitude (V) | 11.58 ± 0.08[1]
Characteristics
Spectral type | G3V
Astrometry
Radial velocity (Rv)| -89.45 [1] km/s
Proper motion (μ)|  RA: 17.597 ± 0.074 [2] mas/yr
Dec.: 18.867 ± 0.05 [2] mas/yr
Parallax (π)| 3.8412 ± 0.0427[2] mas
Distance| 849 ± 9 ly
(260 ± 3 pc)
Absolute magnitude (MV)| 4.97
Details
Mass| 0.89 ± 0.071[3] M☉
Radius| 1.136 ± 0.049[3] R☉
Surface gravity (log g)| 4.277 ± 0.025[3] cgs
Temperature| 5800 ± 100[1] K
Metallicity| -0.4 ± 0.1 [1]
Metallicity [Fe/H]| -0.46 ± 0.11 [1] dex
Rotational velocity (v sin i)| 1.5 ± 0.6 [1] km/s
Age| 12 ± 5[1] Gyr
Other designations

Tangra, GSC 01715-00679, 2MASS J23095825+1823459, Gaia DR2 2831084391023184128

Database references
SIMBAD| data

WASP-21 is a G-type star (spectral type G3V) that is reaching the end of its main sequence lifetime[4][5] approximately 850 light years from Earth in the constellation of Pegasus. The star is relatively metal-poor, having 40% of heavy elements compared to the Sun.[5] Kinematically, WASP-21 belongs to the thick disk of the Milky Way.[1]

The survey in 2012 have failed to find any stellar companions to WASP-21.[6]

## Naming

In 2019 the WASP-21 system was chosen as part of the NameExoWorlds campaign organised by the International Astronomical Union, which assigned each country a star and planet to be named. WASP-21 was assigned to Bulgaria. The winning proposal named the star Tangra after a deity worshipped by the early Bulgars, and the planet Bendida after a deity worshipped by the Thracians.[7]

## Planetary System

In 2010 WASP-21 was discovered to host a hot Jupiter type planet by the Wide Angle Search for Planets (WASP).[1] and confirmed by radial velocity by the WASP team in 2010.

Transit-timing variation analysis in 2015 did not find an additional planets in the system.[5]

In 2020, spectroscopic analysis has found the WASP-21 b atmosphere is mostly cloudless and contains sodium.[8]

The WASP-21 planetary system[3][5] Companion
(in order from star) | Mass | Semimajor axis
(AU) | Orbital period
(days) | Eccentricity | Inclination | Radius

|
|
|
|
|
|

b | 0.276 ± 0.018 MJ | 0.0499 ± 0.0013  | 4.322482  | 0.0 [1] | 86.97 ± 0.33° | 1.162 RJ

## References

1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 Bouchy, F.; Hebb, L.; Skillen, I.; Collier Cameron, A.; Smalley, B.; Udry, S.; Anderson, D. R.; Boisse, I. et al. (2010). "WASP-21b: A hot-Saturn exoplanet transiting a thick disc star". Astronomy and Astrophysics 519: A98. doi:10.1051/0004-6361/201014817. Bibcode: 2010A&A...519A..98B.
2. ↑ 2.0 2.1 2.2 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
3. ↑ 3.0 3.1 3.2 3.3 Ciceri, S.; Mancini, L.; Southworth, J.; Nikolov, N.; Bozza, V.; Bruni, I.; Calchi Novati, S.; d'Ago, G. et al. (2013). "Simultaneous follow-up of planetary transits: Revised physical properties for the planetary systems HAT-P-16 and WASP-21". Astronomy & Astrophysics 557: A30. doi:10.1051/0004-6361/201321669. Bibcode: 2013A&A...557A..30C.
4. ↑ Barros, S. C. C.; Pollacco, D. L.; Gibson, N. P.; Howarth, I. D.; Keenan, F. P.; Simpson, E. K.; Skillen, I.; Steele, I. A. (2011). "A lower mass for the exoplanet WASP-21b". Monthly Notices of the Royal Astronomical Society 416 (4): 2593–2599. doi:10.1111/j.1365-2966.2011.19210.x. Bibcode: 2011MNRAS.416.2593B.
5. ↑ 5.0 5.1 5.2 5.3 Seeliger, M.; Kitze, M.; Errmann, R.; Richter, S.; Ohlert, J. M.; Chen, W. P.; Guo, J. K.; Göğüş, E. et al. (2015), "Ground-based transit observations of the HAT-P-18, HAT-P-19, HAT-P-27/WASP40 and WASP-21 systems", Monthly Notices of the Royal Astronomical Society 451 (4): 4060–4072, doi:10.1093/mnras/stv1187, Bibcode: 2015MNRAS.451.4060S
6. ↑ Ginski, C.; Mugrauer, M.; Seeliger, M.; Eisenbeiss, T. (2012), "A lucky imaging multiplicity study of exoplanet host stars", Monthly Notices of the Royal Astronomical Society 421 (3): 2498–2509, doi:10.1111/j.1365-2966.2012.20485.x, Bibcode: 2012MNRAS.421.2498G
7. ↑ "Bulgaria | NameExoworlds" (in en). 2019-12-17. http://www.nameexoworlds.iau.org/bulgaria.
8. ↑ Chen, G.; Casasayas-Barris, N.; Pallé, E.; Welbanks, L.; Madhusudhan, N.; Luque, R.; Murgas, F. (2020), "Detection of Na in WASP-21b's lower and upper atmosphere", Astronomy & Astrophysics 642: A54, doi:10.1051/0004-6361/202038661, Bibcode: 2020A&A...642A..54C

Coordinates:  23h 09m 58.25s, +18° 23′ 45.9″

* v
* t
* e

Stars of Pegasus

Bayer|

* α (Markab)
* β (Scheat)
* γ (Algenib)
* ε (Enif)
* ζ (Homam)
* η (Matar)
* θ (Biham)
* ι
* κ
* λ
* μ (Sadalbari)
* ν
* ξ
* ο
* π1
* π2
* ρ
* σ
* τ (Salm)
* υ (Alkarab)
* φ
* χ
* ψ

Flamsteed|

* 1
* 2
* 3
* 4
* 5
* 7
* 9
* 11
* 12
* 13
* 14
* 15
* 16
* 17
* 18
* 19
* 20
* 21
* 23
* 25
* 28
* 30
* 31
* 32
* 33
* 34
* 35
* 36
* 37
* 38
* 39
* 40
* 41
* 45
* 51 (Helvetios)
* 52
* 55
* 56
* 57
* 58
* 59
* 60
* 61
* 63
* 64
* 65
* 66
* 67
* 69
* 70
* 71
* 72
* 73
* 74
* 75
* 76
* 77
* 78
* 79
* 80
* 82
* 83
* 85
* 86
* 87
* 23 Psc
* 34 Vul

Variable|

* R
* S
* U
* W
* Z
* RU
* RV
* RZ
* SV
* TW
* TY
* AG
* AQ
* AT
* AU
* AV
* AW
* BB
* BH
* BK
* BO
* BP
* BX
* BY
* DH
* DI
* DY
* EE
* EF
* EQ
* EZ
* GT
* GX
* HN
* HO
* HP
* HR
* HX
* II
* IK
* IM
* IP
* KT
* KU
* LL
* LO
* LS
* MS
* MT
* NV
* NZ
* OY
* PT
* V342
* V343
* V354
* V363
* V372
* V376
* V391

HR|

* 19
* 49
* 8116
* 8219
* 8221
* 8231
* 8250
* 8257
* 8258
* 8274
* 8292
* 8325
* 8341
* 8348
* 8358
* 8359
* 8364
* 8372
* 8391
* 8397
* 8412
* 8415
* 8435
* 8441
* 8455
* 8456
* 8458
* 8460
* 8461
* 8466
* 8475
* 8482
* 8491
* 8503
* 8514
* 8543
* 8555
* 8564
* 8587
* 8604
* 8605
* 8608
* 8631
* 8638
* 8642
* 8737
* 8784
* 8788
* 8792
* 8824
* 8831
* 8833
* 8838
* 8839
* 8873
* 8922
* 8942
* 8953
* 8970
* 9039
* 9055
* 9078
* 9109

HD|

* 434
* 204603
* 205011
* 205422
* 205603
* 206689
* 206793
* 208897
* 209709
* 210890
* 211076
* 213025
* 215549
* 215733
* 219196
* 219828
* 220288
* 220773
* 221170
* 221493
* 225292

Gliese|

* Gliese 829
* Gliese 880

Other|

* BD+14 4559
* BD +17 4708
* BD +28 4211
* GD 246
* HAT-P-8
* NGC 8
* NGC 18
* NGC 30
* PG 2131+066
* PG 2303+243
* PSR B2127+11C
* PSR B2303+30
* WASP-10
* WASP-21
* WASP-52
* WASP-59
* WASP-60
* X2127+119

* List

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Original source: https://en.wikipedia.org/wiki/WASP-21. Read more

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