I know the colours of the stars relate to their heat, however if I were standing on a different planet identical to Earth, but orbiting a blue Bright Giant or a Red Giant, or perhaps even a Red Dwarf, what colours in visible light would I be able to see? Is it the same as with our star, i.e. would any be missing such as if I'm in a room with a black light?


1 Answer 1


Compare the effective temperature of the stars with Planck's law, and with a light bulb (2000 to 3300 K): The color of a light bulb corresponds to spectral class L (red brown star) or class M (red star, including dwarfs and giants); violet, and some blue are missing.

Light of Brown Dwarfs (spectral class T) would look red from their black body radiation, but due to their chemical composition the actual color may vary a bit over different tones of red. They would mainly feel hot, and look dull red at the same time, similar to glowing iron. Colors can hardly be distinguished under these lighting conditions.

Some of the very hottest stars (spectral class O) may ressemble "black" light, looking bluish, and causing fluorescence due to to the shift of the spectrum into the ultraviolet, including x-rays. Without protective ozone/atmosphere layer, this wouldn't be healthy.

This may apply to some degree also to spectral class B (blue white stars); plasma cores of lightnings are of a similar temperature (up to 30,000 K or more) as the effectve temperature of class B or class O stars.

Any spectral class in-between (A, F, G, K) would look almost white, a little bluish for hot stars, yellowish for cooler stars, after some adaption of the eyes.

  • $\begingroup$ Thank you for the detailed explanation on how the stars would look, but I was actually wanting to know how all other objects would look in the light of the star. For example if I'm in a room lit by black lights, everything has a purple tone. I was wanting to know the correspondence between star type and available visible colours on objects. $\endgroup$ Apr 30, 2014 at 0:04
  • $\begingroup$ @simontemplar The available visible colours correspond to the spectrum of the stars. Stars looking red have almost no green or blue light in their spectrum, hence all objects in this kind of light look either red or black. Whitish stars provide all colors. Bluish stars also, but red-toned objects look darker and more yellowish than in white light; most colors are shifted a bit towards blue. $\endgroup$
    – Gerald
    Apr 30, 2014 at 0:15
  • $\begingroup$ Is this the case with our stars as well, are we just used to the tones of colours? I've never really noticed much of a difference in the colour of an object when outside versus inside with a white light bulb. $\endgroup$ Apr 30, 2014 at 2:42
  • $\begingroup$ @simontemplar Yes, unless it's too extreme, or if subtle color variations are relevant. Two colors may look the same with a white light bulb, but different with daylight. Especially, but not exclusively, blue tones are harder to distinguish from green tones with (glowing tungsten filament) light bulbs. It can be different for modern LED lamps; there are a couple of different types of LED lamps. You may also note the yellowish/reddish hue in (old-fashioned) photographs taken under light bulb illumination. Modern digital cameras may adjust to light bulbs; but this adjustment is limited. $\endgroup$
    – Gerald
    Apr 30, 2014 at 10:54
  • $\begingroup$ I see, I have noticed that in the past. I've often wondered why photographs taken indoors in the 70s and 80s appear to be more yellow. This whole question came up due to the film "Pitch Black," not hard scifi, but the film is on a planet in a trinary star system; everything has a blue hue until the blue sun sets, then the other two suns (like ours) make everything look suspiciously like the Australian outback. So I wondered if this would actually be how it would be experienced. $\endgroup$ Apr 30, 2014 at 13:05

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