Nu Horologii

Nu Horologii, Latinized from ν Horologii, is the Bayer designation for a single[12] star in the southern constellation of Horologium. It was catalogued by the Dutch explorer Frederick de Houtman in 1603.[13] With an apparent visual magnitude of 5.3,[2] this star can be seen with the naked eye from the southern hemisphere. (According to the Bortle scale, it can be seen at night from bright suburban skies.) Based upon parallax measurements made by the Gaia space observatory, Nu Horologii lies at a distance of 169 ± 1 light-years from Earth.[6]

ν Horologii
Location of ν Fornacis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Horologium
Right ascension 02h 49m 01.48701s[1]
Declination −62° 48′ 23.4774″[1]
Apparent magnitude (V) 5.253±0.006[2]
Characteristics
Spectral type A2 V[3]
U−B color index +0.06[4]
B−V color index +0.10[4]
Astrometry
Radial velocity (Rv)30.90[5] km/s
Proper motion (μ) RA: 94.374 ± 0.260[6] mas/yr
Dec.: 29.013 ± 0.223[6] mas/yr
Parallax (π)19.3368 ± 0.1212[6] mas
Distance169 ± 1 ly
(51.7 ± 0.3 pc)
Absolute magnitude (MV)+1.74[7]
Details
Mass1.90±0.02[8] M☉
Radius1.88[9] R☉
Luminosity16.7[8] L☉
Surface gravity (log g)3.96[3] cgs
Temperature8,308[3] K
Metallicity [Fe/H]−0.05[3] dex
Rotational velocity (v sin i)143.7±1.4[10] km/s
Age540±90[8] Myr
Other designations
ν Hor, CPD−63° 188, FK5 2196, HD 17848, HIP 13141, HR 852, SAO 248656.[11]
Database references
SIMBADdata

The stellar classification of A2 V[3] indicates that it is an A-type main sequence star that is generating energy through thermonuclear fusion of hydrogen into helium at its core. Nu Horologii is larger and hotter than the Sun, with 190%[8] of the Sun's mass, 188%[9] of the radius of the Sun, and it shines with 16.7[8] times the solar luminosity. This is a young star with an estimated age of 540[8] million years, and it is spinning rapidly with a projected rotational velocity of 144 km/s along the equator.[10] The effective temperature of the photosphere is 8,308 K,[3] giving it the white-hued glow of an A-type star.[14]

No orbiting companions down to the mass of a brown dwarf have been discovered within a radius of 150 AU of Nu Horologii. However, it is emitting an infrared excess that suggests it is being orbited by a debris disk of dust particles. The mean temperature of this disk is 56 K and it appears to have two components: an inner disk is orbiting at a distance of 96+9
−37 AU, while an outer disk lies 410+24
−96 AU from the star. The estimated mass of the disks is (1.3±0.7)×10−3 times the mass of the Earth. The disks may be viewed edge on, which limits the amount of detail that can be discerned.[8]

Based upon their respective motions through space, ν Horologii had a close encounter with the star Alpha Fornacis some 351,200 years ago. The two stars came within 0.081+0.6250
−0.0488 pc of each other; close enough to disrupt their respective (hypothetical) Oort clouds. Potentially, the interaction may have produced asymmetries in the Nu Horologii debris disk, and could cause comet showers that increase the dust content.[15] However, it is unlikely that the encounter was the cause of the disk itself.[16]

References
  1. van Leeuwen, F. (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.
  2. Paunzen, E. (August 2015), "A new catalogue of Strömgren-Crawford uvbybeta photometry", Astronomy & Astrophysics, 580: 3, arXiv:1506.04568, Bibcode:2015A&A...580A..23P, doi:10.1051/0004-6361/201526413, S2CID 73623700, A23.
  3. Saffe, C.; et al. (October 2008), "Spectroscopic metallicities of Vega-like stars", Astronomy and Astrophysics, 490 (1): 297–305, arXiv:0805.3936, Bibcode:2008A&A...490..297S, doi:10.1051/0004-6361:200810260, S2CID 15059920.
  4. Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data. SIMBAD, Bibcode:1986EgUBV........0M.
  5. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
  6. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  7. 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.
  8. Meshkat, Tiffany; et al. (February 2015), "Searching for Planets in Holey Debris Disks with the Apodizing Phase Plate", The Astrophysical Journal, 800 (1): 5, arXiv:1412.5179, Bibcode:2015ApJ...800....5M, doi:10.1088/0004-637X/800/1/5, S2CID 119211833, 5.
  9. Rhee, Joseph H.; et al. (May 2007), "Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs", The Astrophysical Journal, 660 (2): 1556–1571, arXiv:astro-ph/0609555, Bibcode:2007ApJ...660.1556R, doi:10.1086/509912, S2CID 11879505.
  10. Díaz, C. G.; et al. (July 2011), "Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum", Astronomy & Astrophysics, 531: A143, arXiv:1012.4858, Bibcode:2011A&A...531A.143D, doi:10.1051/0004-6361/201016386, S2CID 119286673
  11. "nu. Hor -- High proper-motion Star", SIMBAD Astronomical Database, Centre de Données astronomiques de Strasbourg, retrieved 2015-12-22.
  12. Rodriguez, David R.; Zuckerman, B. (February 2012), "Binaries among Debris Disk Stars", The Astrophysical Journal, 745 (2): 13, arXiv:1111.5618, Bibcode:2012ApJ...745..147R, doi:10.1088/0004-637X/745/2/147, S2CID 73681879, 147.
  13. Verbunt, F.; van Gent, R. H. (June 2011), "Early star catalogues of the southern sky. De Houtman, Kepler (second and third classes), and Halley", Astronomy & Astrophysics, 530: 26, arXiv:1104.0946, Bibcode:2011A&A...530A..93V, doi:10.1051/0004-6361/201116795, S2CID 53555175, A93.
  14. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on December 3, 2013, retrieved 2012-01-16.
  15. Deltorn, J.-M.; Kalas, P. (2001), Jayawardhana, Ray; Greene, Thomas (eds.), "Search for Nemesis Encounters with Vega, ε Eridani, and Fomalhaut", Young Stars Near Earth: Progress and Prospects, ASP Conference Series, San Francisco: Astronomical Society of the Pacific, 244: 227, arXiv:astro-ph/0105284, Bibcode:2001ASPC..244..227D, ISBN 1-58381-082-X.
  16. Moór, A.; et al. (February 2015), "Stirring in massive, young debris discs from spatially resolved Herschel images", Monthly Notices of the Royal Astronomical Society, 447 (1): 577–597, arXiv:1411.5829, Bibcode:2015MNRAS.447..577M, doi:10.1093/mnras/stu2442, S2CID 56125208.
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