Can a rainbow exist in the night’s sky? Stars aren’t just white…are they? Stars are exploding balls of gasses, and these gases are various temperatures. It’s these temperatures that determine the color of the star. We are not talking about just yellow and white, which at first glance might seem like the only two possibilities. There’s an entire array of colors in which these stars exist. Stars can show an entire spectrum of colors, but not as many as the rainbow. However, the brilliance of the color is relative from person to person. The reason for these discrepancies may be due to the human eye itself. The human eye is not designed for night vision. Couple this with an aging eye or an inexperienced eye and it makes for a controversial color battle.

Not only does one have to combat their visual ability, but also take into account the saturation factor. Saturation is defined as the observed degree of whiteness. We can see no more than about 10% Saturation. Zero color saturation is pure white, while 100% saturation is the pure color of the star. Experience has found that the more intense colors simply cannot be observed. The amount of saturation does vary slightly between different individuals, and is certainly dependent on the background color it is seen against.

It is clear that one has to take into account the factors mentioned above when deciphering the color of a particular star. A color scheme for the stars was first established by astronomer Chandler (1901)(Chandler Scale – CI). The approximate color and temperature range for stars is shown in the table below. The CI chart depicts the seven basic colors a star can take on; although a new scale called HCI (Hagen Color Index) has blended many of these colors and in doing so the HCI has up to fourteen colors.

Spectral Class------------Temperature--------------------Color

O---------------------------50,000 - 28,000-------------------Blue
B---------------------------28,000 - 10,000---------------Blue-white
A----------------------------10,000 - 7,500--------------------White
F----------------------------7,500 - 6,000------------------White-Yellow
G----------------------------6,000 - 4,900---------------------Yellow
K----------------------------4,900 - 3,500---------------------Orange
M----------------------------3,500 - 2,000-----------------------Red


The star’s temperature determines the absolute color of a star. However, it’s clear that a star’s perceived color is quite subjective and the lack of certainty is intriguing and mysterious. The temperature of a star along with our star gazing experiences and physical construction of the eye are the determining factors when deciphering the star’s perceived color, which could make for an interesting conversation.

~ Words by Steve Cullen and Sarah Stecher
~ Images by Space Telescope Science Institute
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