Talk:WR 102ka

more info and a picture

[1] --Smkolins (talk) 13:45, 16 July 2008 (UTC)

I have no experience with downloading pix into wiki's image library, and especially how to qualify them for copyright availability. The larger picture is too big, but the smaller inset is kinda dull (just a star on a complex irrelevant background), so I have no strong feeling either way. Wwheaton (talk) 00:37, 17 July 2008 (UTC)

List of most luminous stars

The NASA press release yesterday claims WR 102ka as the second most luminous star in the Galaxy, after Eta Carinae. I have suppressed that claim in the article for now, in the light of several more luminous candidates in our List of most luminous stars. LBV 1806-20 tops that list, but I think the true record holder is probably uncertain pending more accurate studies of extinction and distance. Wwheaton (talk) 14:25, 16 July 2008 (UTC)

You're never going to know from one year to the next. The uncertainty in the luminosity of these stars is just huge. Wolf Rayet stars emit 90%+ of their energy in the UV, but we can only observe many of them in the infra-red. From observing less than 1% of the output, we have to extrapolate to what sort of star it is and then make assumptions about how bright such a star would be. They aren't even good black body radiators, with much of the output being in specific spectral emission lines. Eta Carinae is much closer, hundreds of times better studied, a less extreme temperature with much of its output in the visual (which we can actually observe!), and I still wouldn't put money on us knowing the luminosity within a factor of two. We didn't even understand it was a binary system until the last few years, with the secondary probably accounting for about 20% of the system output. It is worth pointing out that LBV 1806-20 has been consistently estimated at the lower end of the original estimates in more recent papers, luminous but not a record breaker. This is a fairly standard pattern, with selection bias meaning that record-breaking luminous (or massive) star discoveries are almost always downgraded when better information becomes available. Lithopsian (talk) —Preceding undated comment added 14:20, 29 June 2012 (UTC)

Mass

Where does the mass of 175 M_solar come from? The reference to the Spitzer release doesn't say anything about mass. —Preceding unsigned comment added by 128.100.76.206 (talk) 16:03, 1 December 2009 (UTC)

This mass is highly uncertain. The only published mass estimate I've found is for the initial mass of the star when it formed. This is beyond normal stellar models but is placed at 150-200. The current mass will be lower. There is no really good way to calculate the current mass unless a star is a binary or can be compared with similar stars and placed within the context of stellar models, and this star is just not comparable to anything else. Although the paper analysing WR102ka specifically states that it is not possible to give a good current mass estimate, it is interesting to note that the less luminous but somewhat similar WR102c in the same paper is considered likely to have less than half of its initial mass. The NASA press release was taking a few liberties as they tend to do. On the whole I wouldn't consider NASA press releases suitable sources for citations for Wikipedia. Lithopsian (talk) 13:56, 29 June 2012 (UTC)