page_title: S Doradus
section_title: Stellar properties
hierarchical_section_title: S Doradus / Stellar properties
caption_attribution_description: English: This image shows the position of S Doradus in the H-R diagram at maximum and minimum brightness according to different studies.
context_page_description: S Doradus is located 160,000 light-years away, and is one of the brightest stars in the Large Magellanic Cloud, a satellite of the Milky Way. It is a luminous blue variable and one of the most luminous stars known, having a luminosity varying widely above and below 1,000,000 times the luminosity of the Sun, but so far away that it is invisible to the naked eye.
context_section_description: The temperature of an LBV is difficult to determine because the spectra are so peculiar and the standard colour calibrations don't apply, so the luminosity changes associated with brightness variations cannot be calculated accurately.  Within the margins of error, it has often been assumed that the luminosity stays constant during all LBV outbursts.  This is likely if the outburst consists only of an opaque stellar wind forming a pseudo-photosphere to mimic a larger cooler star.
  Better atmospheric physics and observations of luminosity changes during some LBV outbursts have cast doubt on the original models. The atmosphere of S Doradus has been modelled in detail between a normal minimum at magnitude 10.2 in 1985 and a maximum at magnitude 9.0 in 1989. The temperature was calculated to drop from 20,000 K to 9,000 K, and the luminosity dropped from 1,400,000 L☉ to 708,000 L☉. This corresponds to an increase in the radius of the visible surface of the star from 100 R☉ to 380 R☉. A simpler calculation of the variation from the deep 1965 minimum at magnitude 11.5 to the 1989 maximum gives a temperature drop from 35,000 K to 8,500 K, and the luminosity drop from 2,000,000 L☉ to 910,000 L☉. For a brief period during the maximum in late 1999, the temperature dropped further to between 7,500 K and 8,500 K, without the brightness changing noticeably. This is normal in other LBVs at maximum and is as cool as they can get, but it has not been seen in S Doradus before, or since. Observations of AG Carinae have shown that any luminosity changes between minimum and maximum may occur abruptly over a small temperature range, with the luminosity approximately constant during the rest of the light curve.
  The mass of an LBV is difficult to calculate directly unless it is in a binary system. The surface gravity changes dramatically and is difficult to measure from the peculiar spectral lines, and the radius is poorly defined. LBVs are thought to be the direct predecessors of Wolf–Rayet stars, but may be either just evolved from the main sequence or post-red supergiant stars with much lower masses. In the case of S Doradus, the current mass is likely to be in the range of 20–45 M☉.
caption: S Doradus properties at minimum and maximum according to different studies: 
  - van Genderen (2001),[6] temperature at minimum derived from colour index 
  - Lamers (1995),[8] properties derived from non-LTE model atmosphere 
  - Humphreys & Davidson (1994),[37] temperature at minimum assumes constant luminosity
exif: {}