7 Sagittarii

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7 Sagittarii
Sagittarius constellation map.svg
Red circle.svg
Location of 7 Sagittarius (circled)
Observation data
Epoch J2000       Equinox J2000
Constellation Sagittarius
Right ascension 18h 02m 51.09872s [1]
Declination −24° 16′ 56.8825″ [1]
Apparent magnitude  (V)5.37 [2]
Characteristics
Spectral type F2 II/III [3]
U−B color index 0.25 [4]
B−V color index 0.51 [4]
Astrometry
Radial velocity (Rv)−11.2±1.0 [5]  km/s
Proper motion (μ)RA: +1.22 [1]   mas/yr
Dec.: −17.52 [1]   mas/yr
Parallax (π)3.02 ± 0.28 [1]   mas
Distance 1,100 ± 100  ly
(330 ± 30  pc)
Absolute magnitude  (MV)−2.21 [2]
Details
Radius 18 [6]   R☉
Luminosity 658.07 [2]   L☉
Surface gravity (log g)3.54±0.20 [5]   cgs
Temperature 6,800±200 [5]   K
Metallicity [Fe/H]0.0 [5]   dex
Rotational velocity (v sin i)35 [7]  km/s
Other designations
7 Sgr, CD−24° 13793, HD  164584, HIP  88380, HR  6724, SAO  186163 [8]
Database references
SIMBAD data
7 Sagittarii is the brightest star in the region of the Lagoon Nebula, towards the right edge. VST images the Lagoon Nebula.jpg
7 Sagittarii is the brightest star in the region of the Lagoon Nebula, towards the right edge.

7 Sagittarii is a massive star in the southern zodiac constellation of Sagittarius which is located in the Lagoon Nebula (NGC 6530), [9] although multiple sources have considered it a foreground star. [10] It is a dim star but visible to the naked eye with an apparent visual magnitude of 5.37. [2] The distance to this star can be determined from the annual parallax shift of 3.02±0.28  mas , [1] yielding a value of roughly 1,100  light years. It is moving closer to the Sun with a heliocentric radial velocity of −11 km/s. [5]

Gray and Garrison (1989) listed a stellar classification of F2 II/III [3] for this star, suggesting it is a K-type star with a spectrum showing mixed traits of a giant/bright giant. Houk and Smith-Moore (1978) had a similar classification of F2/3 II/III. [11] This may indicate it is not a member of NGC 6530, since it should not have evolved to this class from the O-type stars that still populate this cluster, and hasn't had time to evolve from a less massive cluster star. [10]

It is a suspected chemically peculiar star. [4] [5] The spectral class from the calcium K line has been given as A8 while the class determined from other metallic lines was F4, making it an Am star. [12] This peculiarity is now considered doubtful. [4]

7 Sagittarii has an estimated 18 [6] times the Sun's radius and is radiating 658 [2] times the Sun's luminosity from its photosphere at an effective temperature of around 6,800 K. [5]

Related Research Articles

Epsilon Sagittarii Binary star in the constellation Sagittarius

Epsilon Sagittarii, formally named Kaus Australis, is a binary star system in the southern zodiac constellation of Sagittarius. The apparent visual magnitude of +1.85 makes it the brightest object in Sagittarius. Based upon parallax measurements, this star is around 143 light-years from the Sun.

Xi<sup>2</sup> Sagittarii Star in the constellation Sagittarius

Xi2 Sagittarii, Latinized from ξ2 Sagittarii, is a star in the zodiac constellation of Sagittarius. Data collected during the Hipparcos mission suggests it is an astrometric binary, although nothing is known about the companion. It is visible to the naked eye with a combined apparent visual magnitude of +3.51. Based upon an annual parallax shift of 8.93 mas as seen from Earth, this system is located around 370 light years from the Sun.

Xi<sup>1</sup> Sagittarii Star in the constellation Sagittarius

Xi1 Sagittarii (ξ1 Sagittarii) is a solitary, blue-white hued star in the zodiac constellation of Sagittarius. It is visible to the naked eye with an apparent visual magnitude of +5.06. Based upon a small annual parallax shift of 1.58 mas as seen from Earth, this system is located roughly 2,100 light years from the Sun.

Beta<sup>2</sup> Sagittarii Star in the constellation Sagittarius

Beta² Sagittarii is a star in the zodiac constellation of Sagittarius. It is visible to the naked eye, having an apparent visual magnitude of +4.29. Based upon an annual parallax shift of 24.31 mas as seen from Earth, it is located 134 light-years from the Sun.

X Sagittarii Variable star in the constellation Sagittarius

X Sagittarii is a variable star and candidate binary star system in the southern constellation of Sagittarius, near the western constellation boundary with Ophiuchus. It has a yellow-white hue and is visible to the naked eye with an apparent visual magnitude that fluctuates around 4.54. The star is located at a distance of approximately 950 light years from the Sun based on parallax, and is drifting closer with a radial velocity of −10 km/s. The star has an absolute magnitude of around −2.85.

Chi<sup>1</sup> Sagittarii Star in the constellation Sagittarius

Chi1 Sagittarii (χ1 Sagittarii) is a binary star system in the zodiac constellation of Sagittarius. The pair have a combined apparent visual magnitude of +5.03, which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 12.95 mas as seen from Earth, it is located around 252 light years from the Sun. It is advancing through space in the general direction of the Earth with a radial velocity of −43.4 km/s.

Chi<sup>3</sup> Sagittarii Star in the constellation Sagittarius

Chi3 Sagittarii (χ3 Sagittarii) is a solitary, orange-hued star in the zodiac constellation of Sagittarius. It is faintly visible to the naked eye with an apparent visual magnitude of +5.45. Based upon an annual parallax shift of 6.53 mas as seen from Earth, it is located roughly 500 light years from the Sun. It is receding from the Earth with a radial velocity of 39.6 km/s.

12 Canis Majoris is a variable star located 750 light years away from the Sun in the southern constellation of Canis Major. It has the variable star designation HK Canis Majoris; 12 Canis Majoris is the Flamsteed designation. This body is just barely visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of +6.07. It is moving away from the Earth with a heliocentric radial velocity of +16 km/s. This is the brightest star in the vicinity of the open cluster NGC 2287, although it is probably not a member based on its proper motion.

HD 93250 Star in the constellation Carina

HD 93250 is a highly luminous hot blue binary star in the Carina Nebula in the constellation Carina.

HD 74180 Star in the constellation Vela

HD 74180 is a binary star in the constellation Vela. It is approximately 3,200 light years from Earth. The primary component is a yellow-white F-type supergiant with a mean apparent magnitude of +3.81, with a 10th magnitude companion 37.5 arcseconds distant.

V1401 Aquilae is a single, semi-regular pulsating star in the equatorial constellation of Aquila. It has the designation HD 190390 from the Henry Draper Catalogue, and was formerly designated 64 Sagittarii. The evolutionary status of the star is unclear, and it has been classified as a post-AGB object, a UU Herculis variable, or belonging to the W Virginis variable subclass of the type II Cepheids. It is dimly visible to the naked eye with an apparent visual magnitude that fluctuates around 6.38. Based on parallax measurements, it is located at a distance of approximately 2,380 light years. It lies 21.5° from the galactic plane.

V4381 Sagittarii is a variable star in the constellation Sagittarius. A white supergiant of spectral type A2/A3Iab, it is an Alpha Cygni variable that varies between apparent photographic magnitudes 6.57 and 6.62. Its visual apparent magnitude is about 6.54.

HD 165516 Star in the constellation Sagittarius

HD 165516 is a blue supergiant star in the constellation Sagittarius. It is part of the Sagittarius OB1 association and appears against a rich Milky Way starfield near the Triffid Nebula and Lagoon Nebula.

9 Sagittarii Star in the constellation Sagittarius

9 Sagittarii is a massive binary star in the constellation Sagittarius. It has an apparent magnitude of 5.97.

V518 Carinae Star in the constellation Carina

V518 Carinae is a naked-eye variable star in the constellation Carina. It is a member of the bright open cluster IC 2602 near the Carina Nebula.

HD 93194 Star in the constellation Carina

HD 93194 is a star in the constellation Carina. Its apparent magnitude is 4.79. Its parent cluster is IC 2602.

HD 93607 Star in the constellation Carina

HD 93607 is a star in the constellation Carina. Its apparent magnitude is 4.87. Its parent cluster is IC 2602.

Chi Puppis Star in the constellation Puppis

χ Puppis, Latinised as Chi Puppis, is a single star in the southern constellation of Puppis. It has a white hue and is faintly visible to the eye at night with an apparent visual magnitude of 4.79. The star is located at a distance of approximately 1,800 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +30 km/s. O. J. Eggen listed this star as a member of the Hyades Stream based on its space motion.

52 Sagittarii Star in the constellation Sagittarius

52 Sagittarii is a binary star system in the southern constellation of Sagittarius. It has the Bayer designation h2 Sagittarii, while 52 Sagittarii is the Flamsteed designation. This system is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude of 4.59. It is located approximately 190 light years away based on parallax, but is drifting closer with a radial velocity of −19 km/s.

π2 Gruis, Latinised as Pi2 Gruis, is a binary star system in the southern constellation of Grus. It is faintly visible to the naked eye as a yellow-white hued star with an apparent visual magnitude of 5.622. Based upon an annual parallax shift of 25.1 mas as seen from the Earth, the system is located 130 light years from the Sun.

References

  1. 1 2 3 4 5 6 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. 1 2 3 4 5 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.
  3. 1 2 Gray, R. O.; Garrison, R. F. (February 1989), "The early F-type stars: refined classification, confrontation with Stroemgren photometry, and the effects of rotation", Astrophysical Journal Supplement, 69: 301, Bibcode:1989ApJS...69..301G, doi:10.1086/191315.
  4. 1 2 3 4 Renson, P.; Manfroid, J. (May 2009), "Catalogue of Ap, HgMn and Am stars", Astronomy and Astrophysics, 498 (3): 961–966, Bibcode:2009A&A...498..961R, doi: 10.1051/0004-6361/200810788
  5. 1 2 3 4 5 6 7 Khalack, V.; LeBlanc, F. (July 2015), "Project VeSElkA: Analysis of Balmer Line Profiles of Slowly Rotating Chemically Peculiar Stars", The Astronomical Journal, 150 (1): 10, arXiv: 1505.08158 , Bibcode:2015AJ....150....2K, doi:10.1088/0004-6256/150/1/2, S2CID   118283214, 2.
  6. 1 2 Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS)", Astronomy and Astrophysics (Third ed.), 367: 521–524, arXiv: astro-ph/0012289 , Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID   425754.
  7. ↑ Rutten, R. G. M.; Pylyser, E. (February 1988), "Magnetic structure in cool stars. XV. The evolution of rotation rates and chromospheric activity of giants", Astronomy and Astrophysics, 191: 227−236, Bibcode:1988A&A...191..227R.
  8. ↑ "7 Sgr". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 2018-03-14.
  9. ↑ Damiani, F.; et al. (August 2017), "The Gaia-ESO Survey: dynamics of ionized and neutral gas in the Lagoon nebula (M 8)", Astronomy & Astrophysics, 604: 25, arXiv: 1705.08194 , Bibcode:2017A&A...604A.135D, doi:10.1051/0004-6361/201730986, S2CID   119488696, A135.
  10. 1 2 Sowell, James R. (May 1987), "Yellow evolved stars in open clusters", Astrophysical Journal Supplement Series, 64: 241−267, Bibcode:1987ApJS...64..241S, doi:10.1086/191196. See NGC 6530 on p. 257.
  11. ↑ Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
  12. ↑ Hauck, B. (June 1973), "Catalogue of AM stars with known spectral types", Astronomy and Astrophysics Supplement, 10: 385, Bibcode:1973A&AS...10..385H.
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