Named a white dwarf, but colored green – astronomers have described an unusual star

Named a white dwarf, but green in color — astronomers described an unusual star

The results were published in the journal RAS Techniques and Instruments. Scientists analyzed the radiation of white dwarf stars at various wavelengths using digital models that simulate human vision.

This is not about a simple photograph of a green star. The calculations are aimed at determining what color a human would see it as when observing it from a close distance.

White dwarfs are extremely dense objects remaining at the final stage of the evolution of stars like the Sun. Their size can be close to that of the Earth, but their mass constitutes a significant portion of the Sun's mass.

The color of ordinary stars mainly depends on their temperature. In white dwarfs, however, an extremely dense atmosphere and the chemical elements within it can strongly absorb certain parts of light, leading to the appearance of unusual colors.

The temperature of WD J1330+6435 is approximately 4,000 degrees Celsius. An ordinary star at such a temperature would look reddish-orange. However, sodium in the atmosphere of this white dwarf absorbs orange light, while calcium absorbs violet light. As a result, according to the model, the human eye perceives the remaining radiation as a pale green hue.

The total age of the star is estimated at approximately 8.4 billion years. Of these, it has spent nearly six billion years in the white dwarf state.

The study also noted other unusual colors. Some carbon-rich white dwarfs may appear pink or crimson-violet, while those with a cooler hydrogen-helium atmosphere may look turquoise or bluish.

Nevertheless, such colors are rare. Shades significantly different from white were identified in only about 3.4 percent of the studied white dwarfs.