Astronomy and Space
7 Sagittarii
7 Sagittarii is a massive star in the southern zodiac constellation of Sagittarius which is located in the Lagoon Nebula (NGC 6530), although multiple sources have considered it a foreground star. It is a dim star but visible to the naked eye with an apparent visual magnitude of 5.37. The distance to this star can be determined from the annual parallax shift of 3.02±0.28 mas, 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. Gray and Garrison (1989) listed a stellar classification of F2 II/III 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. 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. It is a suspected chemically peculiar star. 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. This peculiarity is now considered doubtful. 7 Sagittarii has an estimated 18 times the Sun's radius and is radiating 658 times the Sun's luminosity from its photosphere at an effective temperature of around 6,800 K.
Also on this shelf
Byblus Sulcus.
AE Phoenicis.
See also
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