Hi Ken,
Quote:
Originally Posted by Merlin66
Hmmm, Vega Planck curve - not really....
Yes, you have to use common sense and work away from the Balmer discontinuity -
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This still does not give the "right" answer though even above the Balmer step. You routinely see claims that you can measure a star temperature (Teff) from the shape of the spectrum continuum. The problem is that the effective temperature Teff of a star is not based on the spectrum continuum (or even the surface temperature) of the star at all. It is a theoretical value defined as the temperature of a black body the same size and total luminosity of the star. For Vega this works out at 9500K. The shape of the continuum redwards of the Balmer step though roughly matches a Planck curve with temperature of 15000K. As well as H ionisation beyond the Balmer step, there are many other processes going on which affect the shape of the continuum. (Not forgetting the potential effects of interstellar extinction which makes stars look cooler than they actually are) All you can get from the continuum shape is a rough trend of temperature with spectral type.
Cheers
Robin