Sidus Ludoviciana

Sidus Ludoviciana /ˈsaɪdəs ˌljuːdoʊˌvɪsiˈeɪnə/, also known as HD 116798[6] is an 8th-magnitude giant star in the asterism of the Big Dipper in the constellation Ursa Major, halfway between Mizar and Alcor. It was discovered on 2 December 1722 by Johann Georg Liebknecht, who mistook it for a planet and named it after Louis V, Landgrave of Hesse-Darmstadt. A line-of-sight companion with Mizar and Alcor (with a spectral type similar to the latter), it is roughly four times more distant. It has the spectral type A8/F0 III.[4]

Sidus Ludoviciana

Location of Sidus Ludoviciana between Alcor and Mizar
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 13h 24m 51.8516s[1]
Declination +54° 53′ 50.839″[1]
Apparent magnitude (V) +7.58[2]
Characteristics
Spectral type A5-F0[3][4]
Astrometry
Radial velocity (Rv)−4.9[4] km/s
Proper motion (μ) RA: −19.910[1] mas/yr
Dec.: −5.202[1] mas/yr
Parallax (π)10.8536 ± 0.0280 mas[1]
Distance300.5 ± 0.8 ly
(92.1 ± 0.2 pc)
Details
Radius1.6[5] R☉
Luminosity6.2[5] L☉
Temperature7,200[5] K
Other designations
Sidus Ludoviciana, HD 116798, SAO 28748, BD+55°1602, GC 18150, TYC 3850-257-1, 2MASS J13245185+5453509
Database references
SIMBADdata

The star is six times more luminous than the Sun, 1.6 times its radius, and has an surface temperature of 7,200 K. Spectral classification based on a spectrum taken for radial velocity measurement tentatively determined a spectral and luminosity class of A8/F0III,[4] which would indicate that it has exhausted its core hydrogen and started to evolve away from the main sequence, however giant stars of this type should be at least ten times more luminous than measured for Sidus Ludoviciana.

References
  1. 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.
  2. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27. Bibcode:2000A&A...355L..27H.
  3. Henry Draper Catalogue and Extension, A. J. Cannon and E. C. Pickering, CDS ID III/135A.
  4. Grenier, S.; Baylac, M.-O.; Rolland, L.; Burnage, R.; Arenou, F.; Briot, D.; Delmas, F.; Duflot, M.; Genty, V.; Gómez, A. E.; Halbwachs, J.-L.; Marouard, M.; Oblak, E.; Sellier, A. (1999). "Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS" (PDF). Astronomy and Astrophysics Supplement. 137 (3): 451. Bibcode:1999A&AS..137..451G. doi:10.1051/aas:1999489.
  5. Andrae, R.; Fouesneau, M.; Creevey, O.; Ordenovic, C.; Mary, N.; Burlacu, A.; Chaoul, L.; Jean-Antoine-Piccolo, A; Kordopatis, G.; Korn, A.; Lebreton, Y.; Panem, C.; Pichon, B.; Thévenin, F.; Walmsley, G.; Bailer-Jones, C. A. L. (2018). "Gaia Data Release 2 – First stellar parameters from Apsis". Astronomy & Astrophysics. 616 (A8): A8. Bibcode:2018A&A...616A...8L. doi:10.1051/0004-6361/201732516.
  6. "The Big Dipper Adds a Star". Sky & Telescope. 2009-12-11. Retrieved 2021-07-28.
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