Surface temperature 3,650 K Apparent magnitude (V) 10.82 to 11.35 B−V color index +3.18 | Mass 7.956 × 10^31 kg (40 M☉) Absolute magnitude (MV) -7.57 (variable) | |
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V354 Cephei is a red supergiant star located within the Milky Way. It is an irregular variable located approximately 9,000 light-years away from the Sun, and is currently considered one of the largest known stars, with a radius estimate of 1,520 solar radii (1.06×109 km; 7.1 au). If it were placed in the center of the Solar System, it would extend to between the orbits of Jupiter and Saturn.
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V354 cephei
Identification
V354 Cephei is now clearly identified as a red supergiant variable star and included on surveys such as IRAS and 2MASS, but prior to its inclusion in the General Catalogue of Variable Stars in 1981, it was referred to only by its listings on relatively obscure catalogs. It is too faint to be included in catalogs such as the Henry Draper Catalogue or Bonner Durchmusterung. It was included on a 1947 Dearborn Observatory survey as star 41575, but that ID is hardly ever used.
V354 Cep has frequently been referred to as Case 75. This is from one of several listings of cool stars made using the Burrell Schmidt telescope at the Warner and Swasey Observatory of Case Western Reserve University, although Case 75 is mistakenly identified as the nearby F3V star BD+58°2450.
Distance
V354 Cep is too far away to have a measured parallax which would allow its distance to be determined directly. It is near the Cepheus OB1 stellar association and considered a likely member. This association is at a distance of approximately 3,500 parsecs.
Properties
The luminosity, and hence the size, of V354 Cep are disputed. Levesque et al. 2005, find a high luminosity and consequently very large size of 1,520 R☉, making it one of the largest stars. From the same data, Mauron et al. 2011 derive a much smaller luminosity of 76,000 L☉, which implies a much smaller size around 690 R☉. They note the discrepancy but are unable to explain it.
There are similar differences in the visual extinctions derived, between two and six magnitudes.