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WR 121-16
WR 121-16 is a transitional Wolf-Rayet star in the constellation of Scutum, near the Wild Duck Cluster (M11). It is located in the Far 3 kpc Arm of the Milky Way. It is very dim from Earth, having an apparent magnitude of about 14,[2] from being so reddened by interstellar extinction, and its distance of over 23,000 light years.[4] It is one of the dimmest known conventional Wolf-Rayet stars, with a luminosity of less than 76,000 times that of the Sun. WR 121-16 varies irregularly between magnitudes 13.95 and 14.14.[2] WR 121-16 is a recent addition to the Wolf-Rayet Star Catalogue, being the 667th star added. It was discovered in August 2020. DiscoveryWR 121-16 was originally discovered as a ‘by-product’ of the LAMOST testing observations during the full moon nights, when the telescope was pointing to the open cluster M11, with WR 121-16 being about 42′ 24 apart from the centre of M11.[2] FeaturesWR 121-16 is one of a few transitional Wolf-Rayet stars, which display both carbon and nitrogen emission, with a spectral type of WN7o/WC. Modelling the spectrum shows that WR 121-16 is not very luminous at all, with a luminosity of just 75,900 L☉, much less than most Wolf-Rayet stars. WR 121-16 has just over 7 solar masses, nearly all of which is helium. 1.5% of the star is composed of nitrogen, and 0.2% of it is composed of carbon.[2] Strong stellar winds, typical of Wolf-Rayet stars, with a terminal velocity of 1,000 kilometers per second are causing WR 121-16 to lose 10−4.97 M☉/year,[2] much more than the Sun's (2-3) x 10−14 solar masses per year. The winds are so dense that the photosphere of the star is not visible. Its radius is defined for consistency with other Wolf-Rayet stars as being at an optical depth of 20, at about 4 R☉. A "transformed" radius at an optical depth of 2/3, more comparable to other types of star, is at about 6 R☉.[2] References
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