# AP Librae

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Active galactic nucleus in the constellation Libra

AP Librae Light curves for AP Librae. Top panel: The long-term variability, plotted from data published by Fan & Lin (2000).[1] Bottom panel: short-timescale variability, adapted from Carini et al. (1991)[2] Observation data (Epoch J2000) Constellation Libra Right ascension 15h 17m 41.814s[3] Declination −24° 22′ 19.48″[3] Redshift 0.049[4] Distance 700 Mly (215 Mpc)[5] Type BL Lac[6] Apparent dimensions (V) 0′.323 × 0′.278[7] Apparent magnitude (V) 14.0[8] Notable features Highly active; emits a one-sided radio jet Other designations AP Lib, LEDA 54592, PKS 1514-24, QSO B1514-24[9] See also: Quasar, List of quasars

**AP Librae** is a [BL Lacertae object](/source/BL_Lacertae_object)[6] located at a distance of 700 million [light years](/source/Light_year)[5] in the southern [constellation](/source/Constellation) of [Libra](/source/Libra_(constellation)). In the visual [band](/source/Electromagnetic_band) it is one of the most active [blazars](/source/Blazar) known.[10] AP Lib is surrounded by an extended source with a [spectrum](/source/Stellar_spectrum) characteristic of a [red-shifted](/source/Redshift) [giant elliptical galaxy](/source/Giant_elliptical_galaxy). The derived [visual magnitude](/source/Visual_magnitude) of this region is 15.0, and it follows a radially decreasing brightness that is characteristic of an elliptical. Seven fainter galaxies are visible within an angular radius of 9[′](/source/Minute_of_arc), suggesting it is the brightest member of a [galactic cluster](/source/Galactic_cluster).[6]

This object was first identified as an optical [variable](/source/Variable_star) by Martha D. Ashbrook in 1942, who noted the brightness changed irregularly from magnitude 15.0 down to 16.0.[11] The source was found to vary chaotically on time scales of days and even hours.[12] Howard E. Bond and Francois Biraud in 1971 noted the coincidence of this object with the position of the [radio source](/source/Astronomical_radio_source) PKS 1514–24.[13] In 1965, [John G. Bolton](/source/John_Gatenby_Bolton) and associates identified the latter as a sixteenth magnitude [elliptical galaxy](/source/Elliptical_galaxy).[11] Glenn M. Frye and associates in 1971 suggested that it may be a [gamma-ray](/source/Gamma-ray_astronomy) source.[13] The similarity of this object to [BL Lacertae](/source/BL_Lacertae) was noted, leading to it being designated as a BL Lac object.[14]

AP Librae emits a [synchrotron radiation](/source/Synchrotron_radiation) component to its [spectral energy distribution](/source/Spectral_energy_distribution) (SED). The peak component of this radiation lies in the [infrared](/source/Infrared_astronomy) band, making this a low-frequency peaked BL Lac (LBL). It is one of the few LBLs known to emit gamma rays. The width of the high energy component of the SED is considered extremely broad for objects of this class, ranging in energy from around 0.1 [keV](/source/Electronvolt) up to the TeV level.[15] In 1998–99, extended radio emission was detected from a one-sided [jet](/source/Astrophysical_jet) that starts in a south-easterly direction from the source before bending to the northeast.[16] This non-thermal jet extends 15[″](/source/Second_of_arc) from AP Lib (equivalent to ~46 [kly](/source/Light-year#Definitions)), and in 2013 was found to emit [X-rays](/source/X-ray_astronomy).[10] The jet may be the source for the gamma-ray emission in the TeV range.[17]

## References

1. **[^](#cite_ref-Fan_2000_1-0)** Fan, J. H.; Lin, R. G. (July 2000). ["Optical Variability and Periodicity Analysis for Blazars. I. Light Curves for Radio-selected BL Lacertae Objects"](https://iopscience.iop.org/article/10.1086/308996/pdf). *The Astrophysical Journal*. **537** (1): 101–122. [Bibcode](/source/Bibcode_(identifier)):[2000ApJ...537..101F](https://ui.adsabs.harvard.edu/abs/2000ApJ...537..101F). [doi](/source/Doi_(identifier)):[10.1086/308996](https://doi.org/10.1086%2F308996). [S2CID](/source/S2CID_(identifier)) [121252846](https://api.semanticscholar.org/CorpusID:121252846). Retrieved 19 September 2022.

1. **[^](#cite_ref-Carini_1991_2-0)** Carini, M. T.; Miller, H. R.; Noble, J. C.; Sadun, A. C. (April 1991). ["The Timescales of the Optical Variability of Blazars. II. AP Librae"](https://articles.adsabs.harvard.edu/pdf/1991AJ....101.1196C). *Astronomical Journal*. **101** (4): 1196–1201. [Bibcode](/source/Bibcode_(identifier)):[1991AJ....101.1196C](https://ui.adsabs.harvard.edu/abs/1991AJ....101.1196C). [doi](/source/Doi_(identifier)):[10.1086/115756](https://doi.org/10.1086%2F115756). Retrieved 19 September 2022.

1. ^ [***a***](#cite_ref-GaiaEDR3_3-0) [***b***](#cite_ref-GaiaEDR3_3-1) [Brown, A. G. A.](/source/Anthony_Brown_(scientist)); et al. (Gaia collaboration) (2021). ["*Gaia* Early Data Release 3: Summary of the contents and survey properties"](https://doi.org/10.1051%2F0004-6361%2F202039657). *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*. **649**: A1. [arXiv](/source/ArXiv_(identifier)):[2012.01533](https://arxiv.org/abs/2012.01533). [Bibcode](/source/Bibcode_(identifier)):[2021A&A...649A...1G](https://ui.adsabs.harvard.edu/abs/2021A&A...649A...1G). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202039657](https://doi.org/10.1051%2F0004-6361%2F202039657). [S2CID](/source/S2CID_(identifier)) [227254300](https://api.semanticscholar.org/CorpusID:227254300). (Erratum: [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202039657e](https://doi.org/10.1051%2F0004-6361%2F202039657e)). [Gaia EDR3 record for this source](https://vizier.u-strasbg.fr/viz-bin/VizieR-S?Gaia%20EDR3%206227221306646924928) at [VizieR](/source/VizieR).

1. **[^](#cite_ref-Roychowdhury_et_al_2022_4-0)** Roychowdhury, Agniva; et al. (January 2022), "Circumnuclear Dust in AP Librae and the Source of Its VHE Emission", *The Astrophysical Journal*, **924** (2): 19, [arXiv](/source/ArXiv_(identifier)):[2110.12016](https://arxiv.org/abs/2110.12016), [Bibcode](/source/Bibcode_(identifier)):[2022ApJ...924...57R](https://ui.adsabs.harvard.edu/abs/2022ApJ...924...57R), [doi](/source/Doi_(identifier)):[10.3847/1538-4357/ac34f1](https://doi.org/10.3847%2F1538-4357%2Fac34f1), [S2CID](/source/S2CID_(identifier)) [239769140](https://api.semanticscholar.org/CorpusID:239769140), 57.

1. ^ [***a***](#cite_ref-Sanchez_et_al_2015_5-0) [***b***](#cite_ref-Sanchez_et_al_2015_5-1) Sanchez, D. A.; et al. (December 2015), "From radio to TeV: the surprising spectral energy distribution of AP Librae", *Monthly Notices of the Royal Astronomical Society*, **454** (3): 3229–3239, [arXiv](/source/ArXiv_(identifier)):[1506.00965](https://arxiv.org/abs/1506.00965), [Bibcode](/source/Bibcode_(identifier)):[2015MNRAS.454.3229S](https://ui.adsabs.harvard.edu/abs/2015MNRAS.454.3229S), [doi](/source/Doi_(identifier)):[10.1093/mnras/stv2151](https://doi.org/10.1093%2Fmnras%2Fstv2151).

1. ^ [***a***](#cite_ref-Visvanathan_Griersmith_1977_6-0) [***b***](#cite_ref-Visvanathan_Griersmith_1977_6-1) [***c***](#cite_ref-Visvanathan_Griersmith_1977_6-2) Visvanathan, N.; Griersmith, D. (August 1977), "The extended source in AP Librae.", *Astrophysical Journal*, **215**: 759–764, [Bibcode](/source/Bibcode_(identifier)):[1977ApJ...215..759V](https://ui.adsabs.harvard.edu/abs/1977ApJ...215..759V), [doi](/source/Doi_(identifier)):[10.1086/155410](https://doi.org/10.1086%2F155410).

1. **[^](#cite_ref-Skrutskie_et_al_2006_7-0)** Skrutskie, Michael F.; et al. (February 1, 2006), "The Two Micron All Sky Survey (2MASS)", *The Astronomical Journal*, **131** (2): 1163–1183, [Bibcode](/source/Bibcode_(identifier)):[2006AJ....131.1163S](https://ui.adsabs.harvard.edu/abs/2006AJ....131.1163S), [doi](/source/Doi_(identifier)):[10.1086/498708](https://doi.org/10.1086%2F498708), [ISSN](/source/ISSN_(identifier)) [0004-6256](https://search.worldcat.org/issn/0004-6256), [S2CID](/source/S2CID_(identifier)) [18913331](https://api.semanticscholar.org/CorpusID:18913331).

1. **[^](#cite_ref-Ducati2002_8-0)** Ducati, J. R. (2002), "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system.", *CDS/ADC Collection of Electronic Catalogues*, vol. 2237, no. 2237, [Bibcode](/source/Bibcode_(identifier)):[2002yCat.2237....0D](https://ui.adsabs.harvard.edu/abs/2002yCat.2237....0D).

1. **[^](#cite_ref-SIMBAD_9-0)** ["QSO B1514-24"](http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=QSO+B1514-24). *[SIMBAD](/source/SIMBAD)*. [Centre de données astronomiques de Strasbourg](/source/Centre_de_donn%C3%A9es_astronomiques_de_Strasbourg). Retrieved 2022-01-24..

1. ^ [***a***](#cite_ref-Kaufmann_et_al_2013_10-0) [***b***](#cite_ref-Kaufmann_et_al_2013_10-1) Kaufmann, S.; et al. (October 2013), "Discovery of an Extended X-Ray Jet in AP Librae", *The Astrophysical Journal*, **776** (2): 7, [arXiv](/source/ArXiv_(identifier)):[1309.6893](https://arxiv.org/abs/1309.6893), [Bibcode](/source/Bibcode_(identifier)):[2013ApJ...776...68K](https://ui.adsabs.harvard.edu/abs/2013ApJ...776...68K), [doi](/source/Doi_(identifier)):[10.1088/0004-637X/776/2/68](https://doi.org/10.1088%2F0004-637X%2F776%2F2%2F68), [S2CID](/source/S2CID_(identifier)) [118538869](https://api.semanticscholar.org/CorpusID:118538869), 68.

1. ^ [***a***](#cite_ref-Bond1971_11-0) [***b***](#cite_ref-Bond1971_11-1) Bond, Howard E. (July 1971), "The Optically Variable Radio Source PKS 1514-24 = AP Librae", *Astrophysical Journal*, **167**: L79, [Bibcode](/source/Bibcode_(identifier)):[1971ApJ...167L..79B](https://ui.adsabs.harvard.edu/abs/1971ApJ...167L..79B), [doi](/source/Doi_(identifier)):[10.1086/180764](https://doi.org/10.1086%2F180764).

1. **[^](#cite_ref-Hunstead1971_12-0)** Hunstead, R. W. (October 1971), "Further Data on the Optical Variable PKS 1514-24", *Nature*, **233** (5319): 401–402, [Bibcode](/source/Bibcode_(identifier)):[1971Natur.233..401H](https://ui.adsabs.harvard.edu/abs/1971Natur.233..401H), [doi](/source/Doi_(identifier)):[10.1038/233401a0](https://doi.org/10.1038%2F233401a0), [PMID](/source/PMID_(identifier)) [16063399](https://pubmed.ncbi.nlm.nih.gov/16063399), [S2CID](/source/S2CID_(identifier)) [4282407](https://api.semanticscholar.org/CorpusID:4282407).

1. ^ [***a***](#cite_ref-Andrews_et_al_1974_13-0) [***b***](#cite_ref-Andrews_et_al_1974_13-1) Andrews, P. J.; et al. (July 1974), "Photometry of AP Lib and PKS 0521-36", *Monthly Notices of the Royal Astronomical Society*, **168**: 7P–11P, [Bibcode](/source/Bibcode_(identifier)):[1974MNRAS.168P...7A](https://ui.adsabs.harvard.edu/abs/1974MNRAS.168P...7A), [doi](/source/Doi_(identifier)):[10.1093/mnras/168.1.7P](https://doi.org/10.1093%2Fmnras%2F168.1.7P).

1. **[^](#cite_ref-Peterson_et_al_1976_14-0)** Peterson, B. A.; et al. (July 1976), "The BL Lacertae object AP Librae in 1975", *Astrophysical Journal*, **207**: L17–L19, [Bibcode](/source/Bibcode_(identifier)):[1976ApJ...207L..17P](https://ui.adsabs.harvard.edu/abs/1976ApJ...207L..17P), [doi](/source/Doi_(identifier)):[10.1086/182168](https://doi.org/10.1086%2F182168).

1. **[^](#cite_ref-Fortin_et_al_2010_15-0)** Fortin, P.; et al. (2010), Rieger, Frank M.; et al. (eds.), "Gamma-ray emission from AP Librae (PKS1514-241)", *Proceedings of the 25th [Texas Symposium on Relativistic Astrophysics](/source/Texas_Symposium_on_Relativistic_Astrophysics). December 6-10, 2010. Heidelberg, Germany*, p. 199, [Bibcode](/source/Bibcode_(identifier)):[2010tsra.confE.199F](https://ui.adsabs.harvard.edu/abs/2010tsra.confE.199F), [doi](/source/Doi_(identifier)):[10.22323/1.123.0199](https://doi.org/10.22323%2F1.123.0199), [hdl](/source/Hdl_(identifier)):[11858/00-001M-0000-0012-5C76-4](https://hdl.handle.net/11858%2F00-001M-0000-0012-5C76-4).

1. **[^](#cite_ref-Cassaro_et_al_1999_16-0)** Cassaro, P.; et al. (November 1999), "Extended radio emission in BL Lac objects. I. The images", *Astronomy and Astrophysics Supplement*, **139** (3): 601–616, [arXiv](/source/ArXiv_(identifier)):[astro-ph/9910209](https://arxiv.org/abs/astro-ph/9910209), [Bibcode](/source/Bibcode_(identifier)):[1999A&AS..139..601C](https://ui.adsabs.harvard.edu/abs/1999A&AS..139..601C), [doi](/source/Doi_(identifier)):[10.1051/aas:1999511](https://doi.org/10.1051%2Faas%3A1999511), [S2CID](/source/S2CID_(identifier)) [17687679](https://api.semanticscholar.org/CorpusID:17687679).

1. **[^](#cite_ref-Zacharias_et_al_2016_17-0)** Zacharias, Michael; Wagner, Stefan (November 2016), "AP Librae: The Extended Jet as the Source of VHE Emission?", *Galaxies*, **4** (4): 63, [Bibcode](/source/Bibcode_(identifier)):[2016Galax...4...63Z](https://ui.adsabs.harvard.edu/abs/2016Galax...4...63Z), [doi](/source/Doi_(identifier)):[10.3390/galaxies4040063](https://doi.org/10.3390%2Fgalaxies4040063).

## Further reading

- Meyer, E.; et al. (January 2021), "What is the origin of the VHE emission in AP Librae?", *Bulletin of the American Astronomical Society*, **53** (1), [Bibcode](/source/Bibcode_(identifier)):[2021AAS...23723805M](https://ui.adsabs.harvard.edu/abs/2021AAS...23723805M), 2021n1i238p05.

- Pratim Basumallick, Partha; Gupta, Nayantara (July 2017), "Constraints on a Proton Synchrotron Origin of VHE Gamma Rays from the Extended Jet of AP Librae", *The Astrophysical Journal*, **844** (1): 9, [arXiv](/source/ArXiv_(identifier)):[1706.04895](https://arxiv.org/abs/1706.04895), [Bibcode](/source/Bibcode_(identifier)):[2017ApJ...844...58P](https://ui.adsabs.harvard.edu/abs/2017ApJ...844...58P), [doi](/source/Doi_(identifier)):[10.3847/1538-4357/aa7a12](https://doi.org/10.3847%2F1538-4357%2Faa7a12), [S2CID](/source/S2CID_(identifier)) [119480675](https://api.semanticscholar.org/CorpusID:119480675), 58.

- Zacharias, Michael; Wagner, Stefan J. (January 2017), "The extended jet in AP Librae as the source of the VHE γ-ray emission", *6th International Symposium on High Energy Gamma-Ray Astronomy*, AIP Conference Proceedings, vol. 1792, p. 050014, [arXiv](/source/ArXiv_(identifier)):[1611.02103](https://arxiv.org/abs/1611.02103), [Bibcode](/source/Bibcode_(identifier)):[2017AIPC.1792e0014Z](https://ui.adsabs.harvard.edu/abs/2017AIPC.1792e0014Z), [doi](/source/Doi_(identifier)):[10.1063/1.4968960](https://doi.org/10.1063%2F1.4968960), [S2CID](/source/S2CID_(identifier)) [9135990](https://api.semanticscholar.org/CorpusID:9135990).

- Petropoulou, M.; et al. (January 2017), "The TeV emission of Ap Librae: a hadronic interpretation and prospects for CTA", *Monthly Notices of the Royal Astronomical Society*, **464** (2): 2213–2222, [arXiv](/source/ArXiv_(identifier)):[1608.07300](https://arxiv.org/abs/1608.07300), [Bibcode](/source/Bibcode_(identifier)):[2017MNRAS.464.2213P](https://ui.adsabs.harvard.edu/abs/2017MNRAS.464.2213P), [doi](/source/Doi_(identifier)):[10.1093/mnras/stw2453](https://doi.org/10.1093%2Fmnras%2Fstw2453).

- Ciprini, Stefano (August 2016), "Fermi LAT detection of a GeV gamma-ray flare from the BL Lac object AP Librae", *The Astronomer's Telegram*, **9442** (9442): 1, [Bibcode](/source/Bibcode_(identifier)):[2016ATel.9442....1C](https://ui.adsabs.harvard.edu/abs/2016ATel.9442....1C).

- Zacharias, Michael; Wagner, Stefan J. (April 2016), "The extended jet of AP Librae: Origin of the very high-energy γ-ray emission?", *Astronomy & Astrophysics*, **588**: 13, [arXiv](/source/ArXiv_(identifier)):[1602.03430](https://arxiv.org/abs/1602.03430), [Bibcode](/source/Bibcode_(identifier)):[2016A&A...588A.110Z](https://ui.adsabs.harvard.edu/abs/2016A&A...588A.110Z), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201526698](https://doi.org/10.1051%2F0004-6361%2F201526698), [S2CID](/source/S2CID_(identifier)) [119279663](https://api.semanticscholar.org/CorpusID:119279663), A110.

- Hervet, O.; et al. (June 2015), "Linking radio and gamma-ray emission in Ap Librae", *Astronomy & Astrophysics*, **578**: 11, [arXiv](/source/ArXiv_(identifier)):[1503.01377](https://arxiv.org/abs/1503.01377), [Bibcode](/source/Bibcode_(identifier)):[2015A&A...578A..69H](https://ui.adsabs.harvard.edu/abs/2015A&A...578A..69H), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201425330](https://doi.org/10.1051%2F0004-6361%2F201425330), [S2CID](/source/S2CID_(identifier)) [53522733](https://api.semanticscholar.org/CorpusID:53522733), A69.

- [H. E. S. S. Collaboration](/source/High_Energy_Stereoscopic_System); et al. (January 2015), "The high-energy γ-ray emission of AP Librae", *Astronomy & Astrophysics*, **573**: 7, [arXiv](/source/ArXiv_(identifier)):[1410.5897](https://arxiv.org/abs/1410.5897), [Bibcode](/source/Bibcode_(identifier)):[2015A&A...573A..31H](https://ui.adsabs.harvard.edu/abs/2015A&A...573A..31H), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201321436](https://doi.org/10.1051%2F0004-6361%2F201321436), [S2CID](/source/S2CID_(identifier)) [207807491](https://api.semanticscholar.org/CorpusID:207807491), 31.

- H.E.S.S. Collaboration; et al. (January 2015), "The high-energy γ-ray emission of AP Librae", *Astronomy & Astrophysics*, **573**: 7, [arXiv](/source/ArXiv_(identifier)):[1410.5897](https://arxiv.org/abs/1410.5897), [Bibcode](/source/Bibcode_(identifier)):[2015A&A...573A..31H](https://ui.adsabs.harvard.edu/abs/2015A&A...573A..31H), [doi](/source/Doi_(identifier)):[10.1051/0004-6361/201321436](https://doi.org/10.1051%2F0004-6361%2F201321436), [S2CID](/source/S2CID_(identifier)) [207807491](https://api.semanticscholar.org/CorpusID:207807491), A31.

- Sanchez, David; et al. (August 2012), "The challenging SED of AP Librae", *The Spectral Energy Distribution of Galaxies, Proceedings of the International Astronomical Union, IAU Symposium*, vol. 284, pp. 411–413, [Bibcode](/source/Bibcode_(identifier)):[2012IAUS..284..411S](https://ui.adsabs.harvard.edu/abs/2012IAUS..284..411S), [doi](/source/Doi_(identifier)):[10.1017/S1743921312009532](https://doi.org/10.1017%2FS1743921312009532).

- Gudkova, Diana; et al. (November 2009), "The Optical Variability of PKS 1510-089, PKS 1622-297 and AP Librae", *American Physical Society, 76th Annual Meeting of the Southeastern Section of APS, November 11-13, 2009*, vol. 76, [Bibcode](/source/Bibcode_(identifier)):[2009APS..SES.PB002G](https://ui.adsabs.harvard.edu/abs/2009APS..SES.PB002G), PB.002.

- Baxter, D. A.; et al. (September 1987), "Photometric analysis and decomposition of AP Librae (PKS 1514-24).", *Monthly Notices of the Royal Astronomical Society*, **228** (2): 313–327, [Bibcode](/source/Bibcode_(identifier)):[1987MNRAS.228..313B](https://ui.adsabs.harvard.edu/abs/1987MNRAS.228..313B), [doi](/source/Doi_(identifier)):[10.1093/mnras/228.2.313](https://doi.org/10.1093%2Fmnras%2F228.2.313).

- Westerlund, B. E.; et al. (January 1982), "The properties of AP Lib from UBV photoelectric photometry", *Astronomy and Astrophysics*, **105**: 284–292, [Bibcode](/source/Bibcode_(identifier)):[1982A&A...105..284W](https://ui.adsabs.harvard.edu/abs/1982A&A...105..284W).

- Capps, R. W.; Knacke, R. F. (1978), "Polarization of 3C 371 and AP Librae at 2.2μm", *Astrophysical Letters*, **19**: 113, [Bibcode](/source/Bibcode_(identifier)):[1978ApL....19..113C](https://ui.adsabs.harvard.edu/abs/1978ApL....19..113C).

- Rodgers, A. W.; Peterson, B. A. (February 1977), "Emission lines in AP Librae in 1976", *Astrophysical Journal*, **212**: L9–L12, [Bibcode](/source/Bibcode_(identifier)):[1977ApJ...212L...9R](https://ui.adsabs.harvard.edu/abs/1977ApJ...212L...9R), [doi](/source/Doi_(identifier)):[10.1086/182363](https://doi.org/10.1086%2F182363).

- Disney, M. J.; et al. (December 1974), "The Redshift and Composite Nature of AP Librae (pks 1514-24)", *Astrophysical Journal*, **194**: L79, [Bibcode](/source/Bibcode_(identifier)):[1974ApJ...194L..79D](https://ui.adsabs.harvard.edu/abs/1974ApJ...194L..79D), [doi](/source/Doi_(identifier)):[10.1086/181673](https://doi.org/10.1086%2F181673).

- Miller, H. R.; Clonts, S. L.; Folsom, G. H. (December 1974), "Rapid optical variability of the extragalactic radio source PKS 1514-24", *Astronomical Journal*, **79**: 1352, [Bibcode](/source/Bibcode_(identifier)):[1974AJ.....79.1352M](https://ui.adsabs.harvard.edu/abs/1974AJ.....79.1352M), [doi](/source/Doi_(identifier)):[10.1086/111685](https://doi.org/10.1086%2F111685)

v t e Constellation of Libra List of stars in Libra Libra in Chinese astronomy Stars Bayer α1 α2 (Zubenelgenubi) β (Zubeneschamali) γ (Zubenelhakrabi) δ ε ζ1 ζ2 ζ3 ζ4 η θ ι1 ι2 κ λ μ ν ξ1 ξ2 ο σ (Brachium) τ υ Flamsteed 2 3 4 5 10 11 12 16 17 18 22 23 26 28 30 36 37 41 42 47 48 49 50 Variable HN HO KU KX HR 5504 5455 HD 133131 134439 134440 135485 137010 139139 140283 141569 141937 Other 2M1510 2MASS 1507−1627 CWISEP J1446−2317 HE 1523−0901 WASP-57 WISE 1534−1043 WISE 1541−2250 Exoplanets 23 Librae b c Gliese 581b c e HD 137010 b (unconfirmed) K2-315b WASP-189b Star clusters NGC 5897 Galaxies NGC 5597 5605 5716 5728 5792 5793 5861 5885 5890 5898 5915 5917 Other AP Librae IC 1059 IRAS 14348−1447 PKS 1510−089 PKS 1519−273 QSO B1524−136 RXC J1504.1−0248 BCG Category

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Adapted from the Wikipedia article [AP Librae](https://en.wikipedia.org/wiki/AP_Librae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/AP_Librae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.