What does this number measure?
A very luminous red supergiant observed in the direction of a Galactic cluster. The disc shown corresponds to the diameter, twice the adopted radius of 1290 nominal solar radii (1 nominal solar radius = 695 700 km). The value is a dated estimate, not an established size record. The radius is calculated using the Stefan-Boltzmann law from the luminosity and temperature of the SED model, Siebert et al. (preprint, September 2026), table 3. The temperature is adopted and the luminosity is uncertain: this star is not presented as a certain record holder.
Compare the stated dimensions
The comparison uses the number in each fact sheet: altitude, height, diameter, length or distance, depending on the reference. Two values in metres do not necessarily describe the same property.
Source and limitations
Radius calculated using the Stefan–Boltzmann law from the luminosity and temperature of the SED model, Siebert et al. (preprint, September 2026), Table 3. The temperature is adopted and the luminosity is uncertain; this star is not presented as a confirmed record holder.
RSGC1-F02: artistic illustration of a stellar photosphere. A shared generic pattern is used to compare diameters; this is neither a photograph nor a reconstruction of this star. The value and its uncertainties come from the object entry.