When starting out in stargazing, you will notice that instead of just seeing white coloured stars like you might have always assumed was the case, a closer examination will reveal many other different colored stars in the night sky. Here are some interesting facts about the color of stars:
1: Looking up at the night sky we are able to see up to 4,000 stars with the naked eye each coming in a variety of different colors. Studying the spectra of a star can then reveal intricate details about the nature of each individual sun, such as its temperature, distance, age, luminosity (brightness) and mass.
2: The stars roughly behave according to the physics of blackbody radiation, such as an iron rod for instance, which once heated changes color from red to orange, yellow, white and eventually blue as its temperature rises. Blue Giant Stars are amongst the hottest stars in the universe, a fine example of which is Rigel in the Orion constellation whose luminosity is 40,000 times greater than our own Sun.
3: From hot to cool, stars can be grouped into spectral classes as follows:
O – Blue
B – Blue/White
A – White
F – White/Yellow
G – Yellow
K – Orange
M – Red
This spectral sequence can easily be remembered by using the acronym; “Oh Be A Fine Girl (or Guy), Kiss Me.” In addition, these categories are further assigned a number from 0 to 9, with 0 indicating the hottest star and 9 the coolest. Our Sun, for instance, is a yellow Dwarf Star classified as G2.
4: Around 88% of stars in the universe are of the cooler K and M variety. G stars, such as are own sun, represent a mere 8% of all known stars, while O type stars comprise just 1 in 3 million stars.
5: Stars emit visible light of all different colors but their spectrum peaks at a particular colour. However, the spectrum extends far beyond the colors our eyes can see. A neutron star, for instance, emit most of its radiation as X-rays, while even green and purple stars are impossible for the human eye to distinguish. Green stars end up appearing white to us, while purple stars emitting a lot of violet light will appear blue.
6: A star’s color changes throughout its life-cycle depending on its initial mass and the phase of element burning it has reached during its stellar evolution.
7: When stargazing, a fine example of different color stars can be found in a grouping of six different constellations referred to as The Winter Circle. In the northern hemisphere, this asterism is prominent in the night sky from December to March and consists of the following colourful stars in a clockwise rotation:
– Rigel In Orion is a blue-white supergiant 900 light-years distant.
– Procyon in Canis Minor is a yellow-white star 11.4 light years away.
– Capella in Auriga is a yellow giant 42.2 light-years from Earth.
– Arcturus in Bootes is an orange giant found 34 light years distant.
– Castor (white) and Pollux (orange) in Gemini lie 33.7 light-years and 52 light-years away from Earth.
– Aldebaran in Taurus is an orange-red giant 65 light-years from our solar system.
– Betelgeuse in Orion is a red supergiant located 1400 light years away.