This is a very straightforward question, however I am a small confused. As far as i know, the temperature of a star is analyzed based upon the color of the irradiate it emits. So, if a star is moving away native us, then the light emitted by it will certainly be redshifted(or if the is stationary v respect come us and also the irradiate undergoes gravitational redshift), then exactly how do we recognize the exact temperature of that star or any other object since it is feasible that us observe red light however actually the star might be emitting yellow light.

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edited Apr 5 "15 at 17:04
Yashbhatt
asked might 6 "14 at 10:36
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This question is very broad - over there are very many methods for estimating temperatures, for this reason I will stick come a couple of principles and also examples. Once we talk around measuring the temperature that a star, the only stars we deserve to actually resolve and also measure space in the neighborhood universe; they do not have actually appreciable redshifts and so this is rarely of any concern. Stars do of course have line of vision velocities which give their spectrum a redshift (or blueshift). The is a reasonably basic procedure come correct for the line of vision velocity that a star, due to the fact that the redshift (or blueshift) applies to all wavelengths equally and also we can simply change the wavelength axis to account because that this. I.e. We placed the star ago into the rest-frame prior to analysing its spectrum.

Gerald has actually talked around the blackbody spectrum - undoubtedly the wavelength that the peak of a blackbody spectrum is inversely dependency of temperature with Wien"s law. This technique could be provided to calculation the temperatures of objects that have actually spectra which carefully approximate blackbodies and also for which flux-calibrated spectra are obtainable that correctly sample the peak. Both the these conditions are difficult to meet in practice: stars room in general not blackbodies, though your effective temperature - which is commonly what is quoted, are characterized as the temperature the a blackbody through the very same radius and also luminosity the the star.

The effective temperature that a star is most accurately measure by (i) estimating the full flux of light from the star; (ii) getting an exact distance native a parallax; (iii) combining these to provide the luminosity; (iv) measure the radius the the star making use of interferometry; (v) this offers the effective temperature native Stefan"s law:$$ l = 4pi R^2 sigma T_eff^4,$$where $sigma$ is the Stefan-Boltzmann constant. Unfortunately the limiting element here is the it is an overwhelming to measure up the radii of all however the biggest or nearest stars. So measurements exist because that a few giants and a couple of dozen nearby main sequence stars; yet these room the basic calibrators against which other approaches are compared and calibrated.

A second major secondary technique is a detailed analysis of the spectrum of a star. To understand just how this functions we need to realise that (i) atoms/ions have various energy levels; (ii) the method that this levels are lived in depends on temperature (higher level are lived in at greater temperatures); (iii) transitions between levels can result in the emission or absorption of irradiate at a particular wavelength that depends on the energy difference between the levels.

To usage these properties we construct a design of the setting of a star. In basic a star is hotter on the inside and also cooler on the outside. The radiation coming out from the center of the star is took in by the cooler, overlying layers, however this wake up preferentially in ~ the wavelengths equivalent to power level distinctions in the atoms that are taking in the radiation. This produces absorb lines in the spectrum. A spectrum analysis consists of measure the strengths of this absorption lines for countless different chemical elements and different wavelengths. The stamin of an absorption line depends primarily on (i) the temperature that the star and (ii) the quantity of a details chemical element, but additionally on several other parameters (gravity, turbulence, atmospheric structure). Through measuring many lines friend isolate this dependencies and emerge with a systems for the temperature the the star - often with a precision as great as +/-50 Kelvin.

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Where you don"t have actually a great spectrum, the next finest solution is to use the color of the star to estimate its temperature. This works due to the fact that hot stars room blue and also cool stars room red. The colour-temperature partnership is calibrated making use of the measured color of the fundamental calibrator stars. Typical accuracies that this an approach are +/- 100-200 K (poorer because that cooler stars).