81 Aquarii

Short description: Star in the constellation Aquarius

81 Aquarii  Observation data
Equinox J2000.0]] (ICRS)

Constellation | Aquarius
Right ascension |  23h 01m 23.64174s[1]
Declination | −07° 03′ 40.1556″[1]
Apparent magnitude (V) | 6.23[2]
Characteristics
Spectral type | K5 III[3]
B−V color index | 1.418±0.005[2]
Astrometry
Radial velocity (Rv)| +1.59±0.14[1] km/s
Proper motion (μ)|  RA: −16.221±0.139[1] mas/yr
Dec.: −7.911±0.087[1] mas/yr
Parallax (π)| 7.2372 ± 0.0691[1] mas
Distance| 451 ± 4 ly
(138 ± 1 pc)
Absolute magnitude (MV)| 0.34[2]
Details
Radius| 18.02+1.36
−2.45[1] R☉
Luminosity| 102.3+1.3
−0.6[1] L☉
Temperature| 4,324+329
−154[1] K
Other designations

81 Aqr, BD−07° 5910, HD 217531, HIP 113674, HR 8757, SAO 146447[4]

Database references
SIMBAD| data

81 Aquarii is a star in the constellation of Aquarius. It has an orange hue and is barely visible to the naked eye with an apparent visual magnitude of 6.23.[2] 81 Aquarii is its Flamsteed designation. The star is located at a distance of approximately 451 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +1.6 km/s.[1] It is positioned near the ecliptic and thus is subject to lunar occultations.[5]

This is an aging giant star with a stellar classification of K5 III,[3] indicating it has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. The stellar spectrum displays strong lines of cyanogen.[6] It presently has 18 times the radius of the Sun and is radiating 102 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,324 K.[1]

## References

1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 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.
2. ↑ 2.0 2.1 2.2 2.3 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
3. ↑ 3.0 3.1 Houk, N.; Swift, C. (1999), "Michigan catalogue of two-dimensional spectral types for the HD Stars", Michigan Spectral Survey 5, Bibcode: 1999MSS...C05....0H.
4. ↑ "81 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=81+Aqr.
5. ↑ Evans, D. S.; Edwards, D. A. (August 1981), "Photoelectric observations of lunar occultations. XII", Astronomical Journal 86: 1277−1287, doi:10.1086/113008, Bibcode: 1981AJ.....86.1277E.
6. ↑ Janes, K. A.; McClure, Robert D. (May 1971), "Strong-Cyanogen Stars: Photometry and Kinematics", Astrophysical Journal 165: 561, doi:10.1086/150921, Bibcode: 1971ApJ...165..561J.

* v
* t
* e

Constellation of Aquarius

* Aquarius in Chinese astronomy
* Aquarius Stream
* List of stars in Aquarius

Stars|

| Bayer|

* α
* β
* γ
* δ
* ε
* ζ
* η
* θ
* ι
* κ
* λ
* μ
* ν
* ξ
* ο
* π
* ρ
* σ
* τ1
* τ2
* υ
* φ
* χ
* ψ2
* ψ3
* ω1
* ω2

|

Flamsteed|

* 1
* 3
* 4
* 5
* 7
* 8
* 9
* 10
* 11
* 12
* 14
* 15
* 16
* 17
* 18
* 19
* 20
* 21
* 24
* 25
* 26
* 28
* 29
* 30
* 32
* 35
* 36
* 37
* 38
* 39
* 40
* 41
* 42
* 44
* 45
* 47
* 49
* 50
* 51
* 53
* 54
* 56
* 58
* 60
* 61
* 64
* 65
* 66
* 67
* 68
* 70
* 72
* 74
* 75
* 77
* 78
* 81
* 82
* 83
* 84
* 85
* 86
* 87
* 88
* 89
* 91
* 94
* 96
* 97
* 98
* 99
* 100
* 101
* 103
* 104
* 106
* 107
* 108

Variable|

* R
* U
* AE
* DV
* EW
* EZ
* FO
* HK
* HU
* IZ
* LP

HD|

* 199442
* 200375
* 202259
* 205765
* 208177
* 210277
* 210434
* 211392
* 211575
* 213429
* 214448
* 214810
* 215114
* 215152
* 216718
* 218061
* 219279
* 220035
* 220466
* 220689
* 220766
* 221148
* 222093
* 222582
* 223311

Other|

* 2MASS J21392676+0220226
* BD−22 5866
* Fomalhaut C
* Gliese 849
* Gliese 876
* K2-28
* K2-72
* K2-138
* LS IV-14 116
* Sneden's Star
* TRAPPIST-1
* WASP-6
* WASP-47

| Exoplanets|

* 91 Aquarii b
* Gliese 849 b
* Gliese 876 b
* c
* d
* e
* HD 206610 b
* HD 210277 b
* HD 212771 b
* HD 222582 b
* K2-21b
* c
* K2-72b
* c
* d
* e
* K2-138b
* TRAPPIST-1b
* c
* d
* e
* f
* g
* h
* WASP-6b

|

| Star clusters|

* Messier 2
* Messier 72
* Messier 73

|

| Nebulae|

* Helix
* Saturn

|

Galaxies|

| NGC|

* 6975
* 7001
* 7010
* 7047
* 7051
* 7065
* 7069
* 7077
* 7081
* 7184
* 7252
* 7257
* 7301
* 7302
* 7600
* 7606
* 7723
* 7727
* 7759

|

Other|

* Aquarius Dwarf
* Lyman-alpha blob 1
* SMM J2135-0102
* WISE J224607.57−052635.0

| Galaxy clusters|

* Abell 2597
* XMMXCS 2215-1738

|

| Astronomical events|

* SN 2213-1745

|

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