How do visual telescopes show the temperature and luminosity of stars?
Answer Hello, Visual telescopes in and of themselves cannot show either the temperature or luminosity of stars. One must fit additional instruments to telescopes to gain an idea of their temperature – for example the spectroscope – which is capable of showing the spectral lines and whether these are absorption lines or emission lines. A most useful device today is the *spectrophotometer* which is capable of showing the variation of the radiative intensity with the wavelength. (And able to show a span of wavelengths not just those in the visual region). The hotter as star, then, the SHORTER the wavelength of the PEAK in the light profile obtained. Bear in mind here that stars radiate like what we call “blackbodies” – where a blackbody displays what is called a “blackbody shape” meaning a *Planck curve*. (Which you can google to learn more about). The visible range is only a small part of the whole blackbody spectrum. The main points to be aware of so far are: i) a wide range of a star’s
