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star temperature redshift stellar-astrophysics
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This question is very large - there are very many techniques for estimating temperatures, so I will stick to a couple of principles and also examples. When we talk about measuring the temperature of a star, the just stars we deserve to actually resolve and also measure room in the regional universe; they do not have actually appreciable redshifts and also so this is hardly ever of any kind of concern. Stars do of course have line of vision velocities which provide their spectrum a redshift (or blueshift). The is a reasonably simple procedure to correct for the line of sight velocity the a star, because the redshift (or blueshift) applies to all wavelengths equally and also we can simply change the wavelength axis to account for this. I.e. We put the star ago into the rest-frame prior to analysing that is spectrum.
Gerald has actually talked about the blackbody spectrum - undoubtedly the wavelength the the optimal of a blackbody spectrum is inversely dependent of temperature with Wien"s law. This an approach could be supplied to estimate the temperatures of objects that have actually spectra which carefully approximate blackbodies and for which flux-calibrated spectra are obtainable that appropriately sample the peak. Both that these problems are tough to satisfy in practice: stars are in general not blackbodies, though your effective temperature - i m sorry is usually what is quoted, are identified as the temperature that a blackbody v the very same radius and luminosity that the star.
The effective temperature that a star is most accurately measure by (i) estimating the complete flux of light from the star; (ii) getting an exact distance from a parallax; (iii) combining these to give the luminosity; (iv) measuring the radius the the star using interferometry; (v) this provides the efficient temperature from Stefan"s law:$$ together = 4pi R^2 sigma T_eff^4,$$where $sigma$ is the Stefan-Boltzmann constant. Unfortunately the limiting element here is that it is an overwhelming to measure up the radii of all but the biggest or nearest stars. So dimensions exist for a few giants and a few dozen adjacent main succession stars; but these are the basic calibrators versus which other methods are compared and also calibrated.
A second significant secondary an approach is a detailed evaluation of the spectrum the a star. Come understand exactly how this functions we must realise that (i) atoms/ions have various energy levels; (ii) the way that these levels are populated depends on temperature (higher level are inhabited at greater temperatures); (iii) transitions in between levels can result in the emissions or absorb of irradiate at a certain wavelength that counts on the energy difference between the levels.
To use these properties we construct a version of the setting of a star. In basic a star is hotter on the inside and also cooler ~ above the outside. The radiation coming the end from the centre of the star is absorbed by the cooler, overlying layers, but this wake up preferentially at the wavelengths equivalent to energy level distinctions in the atoms the are absorbing the radiation. This produces absorb lines in the spectrum. A spectrum analysis consists of measure the staminas of this absorption present for plenty of different chemical elements and different wavelengths. The stamin of one absorption line depends primarily on (i) the temperature that the star and also (ii) the lot of a particular chemical element, but additionally on several various other parameters (gravity, turbulence, atmospheric structure). Through measuring several lines friend isolate these dependencies and emerge through a systems for the temperature that the star - regularly with a precision as great as +/-50 Kelvin.
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Where friend don"t have actually a good spectrum, the next best solution is to usage the colour of the star to estimate its temperature. This works due to the fact that hot stars are blue and cool stars space red. The colour-temperature connection is calibrated utilizing the measured colour of the an essential calibrator stars. Common accuracies that this an approach are +/- 100-200 K (poorer because that cooler stars).