Scientists have recorded a green star in space for the first time. This star, named WD J1330+6435, is located in the constellation Draco, in the Milky Way galaxy, at a distance of about 280 light-years from Earth. It is a white dwarf that has absorbed fragments of planets that were previously orbiting it.
According to scientists' data, the green hue of the star is due to the interaction process between sodium, which came from these fragments, and helium present in the star itself. Usually, a star's color is determined by its temperature: cool stars appear orange, Sun-like stars are white, and hotter ones are pale blue. However, WD J1330+6435 deviates from this rule.
The study showed that elements such as calcium, lithium, and sodium, originating from destroyed planets, were found in the outer layer of WD J1330+6435. The green color of this star largely depends on sodium. Although sodium usually absorbs orange light (as seen in the orange color of streetlights), something different is happening in this case.
Scientists explain that this star has a very high density. Sodium atoms constantly collide with helium atoms, which changes how sodium functions. After this, it begins to absorb parts of the yellow, orange, and red light. This affects the light emitted by the star; when the balance of different colors in the light is disrupted, the star acquires a green tint, called charrage, which has a slight yellowish hue. Such a color is not observed in ordinary stars like the Sun.
White dwarfs form during the final stage of a star's life. Their size can be comparable to the size of the Earth, but they contain a huge amount of matter. Typically, a white dwarf can have a mass approximately equal to half the mass of the Sun. Due to extremely high density, even a small amount of sodium can have a significant impact on the light they emit. In the case of WD J1330+6435, most of the orange light is absorbed by sodium, leading to the visible green color of the star.
As part of this study, scientists examined the colors of 151 white dwarfs within 65 light-years of Earth. Most of them turned out to be white, but one appeared light pink. This dwarf, named WD J1011+2845, is located about 48 light-years away in the constellation Cygnus. Unlike the case with WD J1330+6435, the color change of this dwarf is related not to sodium but to carbon. Scientists believe that the release of carbon from inside the star influenced its coloration. The study also showed that some white dwarfs with high carbon content can appear pink or purple, while others containing elements from destroyed planets can be yellow.
To study the starlight, researchers used data obtained from a telescope in New Mexico, as well as computer models. During the work, information was gathered on the colors and composition of 151 white dwarfs. This analysis proved that a star's color is determined not only by its temperature but also by the elements contained within it and the structure of its outer shell. WD J1330+6435 is the first registered example of a green star in space.