51 Ophiuchi

51 Ophiuchi is a single[8] star located approximately 410[1] light years away from the Sun in the equatorial constellation of Ophiuchus, northwest of the center of the Milky Way. It is visible to the naked eye as a faint, blue-white point of light with an apparent visual magnitude of 4.81.[2] The star is moving closer to the Earth with a heliocentric radial velocity of –12 km/s.[4]

51 Ophiuchi
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension 17h 31m 24.95413s[1]
Declination −23° 57′ 45.5136″[1]
Apparent magnitude (V) 4.81[2]
Characteristics
Spectral type B9.5IIIe[3]
U−B color index –0.06[2]
B−V color index +0.00[2]
Astrometry
Radial velocity (Rv)–12[4] km/s
Proper motion (μ) RA: 5.24[1] mas/yr
Dec.: −25.72[1] mas/yr
Parallax (π)8.04 ± 0.24 mas[1]
Distance410 ± 10 ly
(124 ± 4 pc)
Details
Mass3.3±0.1[5] M☉
Radius5.66±0.23[5] R☉
Luminosity3.12[6] L☉
Temperature9,772[6] K
Metallicity [Fe/H]–0.25[6] dex
Rotational velocity (v sin i)267 ± 5[7] km/s
Age0.3[8] Myr
Other designations
c Oph, 51 Oph, CD–23° 13412, GC 23320, HD 158643, HIP 85755, HR 6519, SAO 185470[9]
Database references
SIMBADdata

This object is notable for being "a rare, nearby example of a young planetary system just entering the last phase of planet formation".[10] There is uncertainty about the stellar classification of this star. It has the nominal classification of B9.5IIIe, a B-type giant star with emission lines. However, it has also been classified as an A0 II-IIIe star and as a Herbig Ae/Be star.[11] 51 Ophiuchi is about 300,000[8] years old with 3.3 times the mass of the Sun and a polar radius 5.7 times the Sun's radius.[5] It is radiating three[6] times the Sun's luminosity from its photosphere at an effective temperature of 9,772 K.[6] The star is spinning rapidly with a projected rotational velocity of 267 km/s,[7] close to the critical rotation rate.[5]

Dust and gas disk

51 Ophiuchi has a disk of dust and gas that appears to be a young debris disk and is probably a planetary system in the late stages of formation. This system resembles Beta Pictoris, a well known star with a large debris disk, in several ways: spectral type, the presence of an edge-on disk with both gas and dust, and the presence of variable blue-shifted absorption lines suggesting in-falling comets.[10][12]

The distance to 51 Ophiuchi is much greater than the distance to Beta Pictoris, and its debris disk is relatively compact. As a consequence, the disk around 51 Ophiuchi requires an interferometer to resolve, in contrast to that of Beta Pictoris, which has been observed using visual spectrum imaging.[13] Recent observations of 51 Ophiuchi made with the Keck Interferometer Nuller at the W. M. Keck Observatory show that the disk has two components: a central cloud of large particles (exozodiacal dust) surrounded by a much larger cloud of small silicate particles extending to about 1,000 astronomical units.[12] The inner disk has a radius approximately four times the distance between the sun and the Earth, with a density of around 100,000 times that of the dust in the Solar System.[10]

The spectra taken by 2020 have indicated the circumstellar disc is similar in composition to interstellar medium. The dominant species in atomic numbers are hydrogen, helium, oxygen, nitrogen, silicon and iron. Surprisingly, the disk was found to be strongly depleted of carbon and carbon monoxide.[14]

References
  1. 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
  2. Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
  3. Manoj, P.; et al. (December 2006), "Evolution of Emission-Line Activity in Intermediate-Mass Young Stars", The Astrophysical Journal, 653 (1): 657–674, arXiv:astro-ph/0608541, Bibcode:2006ApJ...653..657M, doi:10.1086/508764, S2CID 17545474
  4. Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium, vol. 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E
  5. Jamialahmadi, N.; et al. (July 2015). "The peculiar fast-rotating star 51 Ophiuchi probed by VEGA/CHARA". Astronomy & Astrophysics. 579: 4. arXiv:1709.04872. Bibcode:2015A&A...579A..81J. doi:10.1051/0004-6361/201425473. S2CID 6213084. A81.
  6. 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
  7. Dunkin, S. K.; Barlow, M. J.; Ryan, Sean G. (April 1997), "High-resolution spectroscopy of Vega-like stars - I. Effective temperatures, gravities and photospheric abundances", Monthly Notices of the Royal Astronomical Society, 286 (3): 604–616, Bibcode:1997MNRAS.286..604D, doi:10.1093/mnras/286.3.604
  8. Roberge, A.; et al. (March 2002). "Far Ultraviolet Spectroscopic Explorer Observations of Possible Infalling Planetesimals in the 51 Ophiuchi Circumstellar Disk". The Astrophysical Journal. 568 (1): 343–351. arXiv:astro-ph/0111154. Bibcode:2002ApJ...568..343R. doi:10.1086/338877. S2CID 15321298.
  9. "c Oph". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-06-22.
  10. "Twin Keck telescopes probe dual dust disks", e! Science News, September 24, 2009, retrieved 2009-10-01
  11. Berthoud, M. G.; et al. (May 2007), "Near-IR CO Overtone Emission in 51 Ophiuchi", The Astrophysical Journal, 660 (1): 461–468, Bibcode:2007ApJ...660..461B, doi:10.1086/512056
  12. Stark, Christopher C.; et al. (2009), "51 Ophiuchus: A Possible Beta Pictoris Analog Measured with the Keck Interferometer Nuller", Astrophysical Journal, 703 (2): 1188–1197, arXiv:0909.1821, Bibcode:2009ApJ...703.1188S, doi:10.1088/0004-637X/703/2/1188, S2CID 17938884
  13. Smith, B. A.; Terrile, R. J. (1984), "A circumstellar disk around Beta Pictoris", Science, 226 (4681): 1421–1424, Bibcode:1984Sci...226.1421S, doi:10.1126/science.226.4681.1421, PMID 17788996, S2CID 120412113
  14. Jenkins, Edward B.; Gry, Cecile (2020). "The Composition, Excitation, and Physical State of Atomic Gas in the Debris Disk Surrounding 51 Oph". Astrophysical Journal. 896: 24. arXiv:2004.10238. doi:10.3847/1538-4357/ab8bdd. S2CID 216056466.
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