3 Aquarii

3 Aquarii
Observation data Epoch J2000 Equinox J2000
Location of 3 Aquarii (circled)
Constellation	Aquarius
Right ascension	20^h 47^m 44.23898^s^[1]
Declination	–05° 01′ 39.7220″^[1]
Apparent magnitude (V)	4.429^[2]
Characteristics
Spectral type	M3 III^[3]
U−B color index	+1.914^[2]
B−V color index	+1.651^[2]
Variable type	Lb^[4]
Astrometry

Radial velocity (R_v)	−22.0^[5] km/s
Proper motion (μ)	RA: +1.68^[1] mas/yr Dec.: −40.06^[1] mas/yr
Parallax (π)	5.57 ± 0.28 mas^[1]
Distance	590 ± 30 ly (180 ± 9 pc)
Absolute magnitude (M_V)	−1.83^[6]

Details

Mass	1.8^[7] `M`_☉
Radius	117.59+3.98 −4.21^[8] `R`_☉
Luminosity	1,771±128^[8] `L`_☉
Surface gravity (log g)	0.25^[9] cgs
Temperature	3,452±35^[8] K

Other designations
EN Aqr, BD–05°5378, FK5 1543, HD 198026, HIP 102624, HR 7951, SAO 144814^[10]
Database references
SIMBAD	data

A light curve for EN Aquarii, plotted from *Hipparcos* data.^[11] The data were folded with the 4.57 day period reported by Koen and Eyer (2002)^[12]

3 Aquarii (abbreviated 3 Aqr) is a variable star in the equatorial constellation of Aquarius. 3 Aquarii is the Flamsteed designation; it also bears the Bayer designation k Aquarii and the variable star designation EN Aquarii. With a mean apparent visual magnitude of 4.429,^[2] it is visible to the naked eye in dark skies. It has an annual parallax shift of 5.57 milliarcseconds with a 5% margin of error,^[1] which translates to a physical distance of around 590 light-years (180 parsecs) from Earth.

With a stellar classification of M3 III,^[3] this is a red giant star that has exhausted the hydrogen at its core and evolved away from the main sequence of stars like the Sun. The measured angular diameter of this star, after correction for limb darkening, is 5.60±0.70 mas.^[13] At the estimated distance of 3 Aquarii,^[1] this yields a physical size of about 108 times the radius of the Sun.^[14] The effective temperature of the outer atmosphere is 3,450 K,^[8] giving this star the cool, reddish hue of an M-type star.

The apparent magnitude of 3 Aquarii varies by up to 0.06 magnitudes, which was first noted in the 1960s.^[15]^[16] It was formally listed as a variable star in 1973, and given the variable star designation EN Aquarii.^[17] It is classified as an irregular variable,^[4] although detailed analysis shows multiple possible periods.^[18]

Pulsation periods^[18]
Period (days)	20.2	24.9	27.2	35.0	36.9	143.9	197.2
Amplitude (magnitudes)	0.020	0.038	0.027	0.021	0.024	0.022	0.027

References

^ ^a ^b ^c ^d ^e ^f ^g van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
^ ^a ^b ^c ^d Gutierrez-Moreno, Adelina; et al. (1966). "A System of photometric standards". Publ. Dept. Astron. Univ. Chile. 1. Publicaciones Universidad de Chile, Department de Astronomy: 1–17. Bibcode:1966PDAUC...1....1G.
^ ^a ^b Morgan, W. W.; et al. (1973). "Spectral Classification". Annual Review of Astronomy and Astrophysics. 11: 29. Bibcode:1973ARA&A..11...29M. doi:10.1146/annurev.aa.11.090173.000333.
^ ^a ^b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
^ Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W.
^ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644. Vizier catalog entry
^ Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (2022). "Stellar and substellar companions from Gaia EDR3. Proper-motion anomaly and resolved common proper-motion pairs". Astronomy and Astrophysics. 657: 657. arXiv:2109.10912. Bibcode:2022A&A...657A...7K. doi:10.1051/0004-6361/202142146. S2CID 237605138.
^ ^a ^b ^c ^d Baines, Ellyn K.; Thomas Armstrong, J.; Clark, James H.; Gorney, Jim; Hutter, Donald J.; Jorgensen, Anders M.; Kyte, Casey; Mozurkewich, David; Nisley, Ishara; Sanborn, Jason; Schmitt, Henrique R. (November 2021). "Angular Diameters and Fundamental Parameters of Forty-four Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 162 (5): 198. arXiv:2211.09030. Bibcode:2021AJ....162..198B. doi:10.3847/1538-3881/ac2431. ISSN 0004-6256. S2CID 238998021.
^ McDonald, I.; Zijlstra, A. A.; Watson, R. A. (15 June 2017). "Fundamental parameters and infrared excesses of Tycho–Gaia stars". Monthly Notices of the Royal Astronomical Society. 471 (1): 770–791. arXiv:1706.02208. Bibcode:2017MNRAS.471..770M. doi:10.1093/mnras/stx1433. eISSN 1365-2966. ISSN 0035-8711.
^ "* k Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-07-16.
^ "/ftp/cats/more/HIP/cdroms/cats". Centre de Données astronomiques de Strasbourg. Strasbourg astronomical Data Center. Retrieved 15 October 2022.
^ Koen, Chris; Eyer, Laurent (March 2002). "New periodic variables from the Hipparcos epoch photometry". Monthly Notices of the Royal Astronomical Society. 331 (1): 45–59. arXiv:astro-ph/0112194. Bibcode:2002MNRAS.331...45K. doi:10.1046/j.1365-8711.2002.05150.x. S2CID 10505995.
^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
^ Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1.. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(180\cdot 5.60\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 216.8\cdot R_{\bigodot }\end{aligned}}$
^ A. W. J. Cousins (1966). "Fabry photometry of bright southern stars". Royal Greenwich Observatory Bulletins. 122: 59. Bibcode:1966RGOB..122...59C.
^ Eggen, Olin J. (1969). "Narrow-and Broad-Band Photometry of Red Stars.IV. Population Separation in Giant Stars". The Astrophysical Journal. 158: 225. Bibcode:1969ApJ...158..225E. doi:10.1086/150186.
^ Kukarkin, B. V.; Kholopov, P. N.; Kukarkina, N. P.; Perova, N. B. (1973). "59th Name-List of Variable Stars". Information Bulletin on Variable Stars. 834: 1. Bibcode:1973IBVS..834....1K.
^ ^a ^b Tabur, V.; Bedding, T. R.; Kiss, L. L.; Moon, T. T.; Szeidl, B.; Kjeldsen, H. (December 2009). "Long-term photometry and periods for 261 nearby pulsating M giants". Monthly Notices of the Royal Astronomical Society. 400 (4): 1945–1961. arXiv:0908.3228. Bibcode:2009MNRAS.400.1945T. doi:10.1111/j.1365-2966.2009.15588.x.

External links

Image 3 Aquarii

Constellation of Aquarius

Stars

Bayer	α (Sadalmelik) β (Sadalsuud) γ (Sadachbia) δ (Skat) ε (Albali) ζ η θ (Ancha) ι κ (Situla) λ (Hydor) μ ν ξ (Bunda) ο π ρ σ τ¹ τ² υ φ χ ψ¹ (91) ψ² ψ³ ω¹ ω² A¹ A² b¹ b² b³ c¹ c² c³ d e f g¹ g² h i¹ i² i³ k α PsA C
Flamsteed	1 4 5 7 8 9 10 11 12 14 15 16 17 18 19 20 21 24 26 28 29 30 32 35 36 37 39 40 41 42 44 45 47 49 50 51 54 56 58 60 61 64 65 67 70 72 74 75 77 78 81 82 84 85 87 94 96 97 100
Variable	R U AE DV EP EW EZ FO HK IL HU IZ LP
HR	8017 8056 8121 8263 8363 8453 8500 8507 8581 8612 8629 8645 8716 8783 8836 8856 8879 8924 9014
HD	206610 (Bosona) 210277 212771 (Lionrock) 215152 219617 220466 220689 222093 222582
Other	2MASS J21392676+0220226 BD−22 5866 Gliese 849 K2-21 K2-28 K2-58 K2-72 K2-138 LS IV-14 116 Sneden's Star TRAPPIST-1 WASP-6 (Márohu) WASP-47 WASP-69 WASP-75

Exoplanets	ψ¹ Aquarii b Gliese 849 b Gliese 876 b c d e HD 206610 b HD 210277 b HD 212771 b (Victoriapeak) HD 221416 b HD 222582 b K2-66b 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 Nebula Saturn Nebula

Galaxies

NGC	6975 7001 7010 7047 7051 7065 7069 7077 7081 7184 7252 7257 7301 7302 7393 7492 7585 7592 7600 7606 7723 7727 7759
Other	Aquarius Dwarf ESO 603-G21 Lyman-alpha blob 1 PGC 1228197 PHL 293B RX J2129.7+0005 BCG SMM J2135-0102 WISE J224607.57−052635.0

Galaxy clusters	Abell 2597 RXC J2211.7-0350 XMMXCS 2215-1738

Astronomical events	SN 2213-1745

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References

External links