Looking for Roy G. Biv
Published 6:00 am Wednesday, November 11, 2026
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Stars in the night sky are different in their color. They run the entire gambit of the electromagnetic spectrum that is visible to the human eye. Almost all stars also radiate at either end of the electromagnetic spectrum from gamma ray to radio waves. With our eyes, we only view red to blue.
There were only five colors that were used until Isaac Newton added orange and indigo around 1665. Newton’s experiment with the prism led to his book ‘Opticks’ in 1704. It was the second major book that Newton wrote that revolutionized science.
In visible light, red has the longest wavelength, while violet has the shortest wavelength. The temperature of the star can be determined by its color. Red stars have the lowest temperature, while blue stars have the highest temperature. For comparison, our Sun is a yellow-white star with a temperature of around 6,000 Kelvin (K). The Kelvin scale was created by the 19th-century British scientist Lord Kelvin. This scale starts at zero and proceeds up. On the Kelvin scale, the freezing point of water is 273 K.
Red stars like Antares in Scorpius and Betelgeuse in Orion, run at 3,800 K. Red stars indicate the last stages, or stellar evolution, of a star’s life.
Orange stars are a combination of red and yellow stars. An example of an orange star would be the brightest stare Arcturus in Boötes. Its temperature runs about 4,300 K.
Yellow stars in the night sky are generally larger than normal stars. One that can be seen is Mirfak, which is located in Perseus. This star’s temperature is around 6,500 K.
Green stars are not visible. Until recently, there were no known green stars. In a study of white dwarf stars (stars the size of Earth) astronomers found one star would appear the color of a modelled chartreuse green. The greenish color results from unusually broad absorption by sodium and calcium in the star’s dense atmosphere. It is too far away and faint to be seen. Because the star is a white dwarf, its temperature is around 4,400 K, lower than a normal sized star. Normal green stars would have a temperature of around 6,700 K.
Blue stars are more common during winter. Rigel in Orion is an example of this color. Rigel’s temperature is around 12,100 K.
Indigo and violet stars don’t exist in nature. Stars at this temperature peak light shifted toward the blue and ultraviolet ranges. Astronomers classify stars based on their spectral characteristics and temperature, rather than the color.
This month try and locate each colored star in the acronym Roy G Biv.
Lunar and Planetary guide: On Nov. 7, Venus was above the crescent Moon in the early morning. Jupiter was close and below Mars on the same morning. The Moon will be above Saturn on the evening of Nov. 20. The Moon will be below Jupiter and to the upper right of Mars on Nov. 30.
