Researchers from the University of Warwick have identified WD J1330+6435 as the first known green star. The white dwarf's green hue results from sodium in its atmosphere absorbing orange light.
Astronomers have identified the first known green star, a white dwarf located approximately 326 light-years from Earth. The discovery, detailed in a study published in the journal RAS Techniques and Instruments, suggests that white dwarfs can exhibit a range of colors beyond the traditional white and blue, depending on their atmospheric composition and density.
The star, designated WD J1330+6435, is a cool white dwarf that has been accreting rocky material from a planetary companion. This process has enriched its atmosphere with calcium, lithium, and sodium. According to the research team, the specific chemical makeup alters how the star emits light.
"The traces of sodium in the atmosphere of this white dwarf absorb the orange part of the spectrum, leaving behind a ghostly green glow," said Mark Hollands of the University of Warwick, the team leader, in a statement. "Imagine standing on a planet and looking up at a green star. It feels like something out of science fiction."
The researchers note that while the human eye typically perceives stars as white, orange, or blue based on temperature, the extreme density of white dwarfs allows trace elements to interact with dense helium plasma. This interaction absorbs light across a wider range of colors than would occur at lower densities, shifting the star's apparent color away from the standard blackbody radiation curve.
The study indicates that white dwarf colors fall into distinct groups tied to the chemical makeup of their atmospheres. The researchers identified several categories:
The team also identified WD J1011+2845, located 48 light-years from Earth, as potentially the reddest star ever observed. This white dwarf features a deep convection zone that brings carbon from its core to the surface, creating a deep salmon-pink glow.
Despite the variety of colors identified in the study, the researchers emphasize that white remains the most common color for white dwarfs. The team analyzed 151 white dwarfs within approximately 65 light-years of Earth and found that only five had extraordinary coloring. Extrapolating this data to the broader population of white dwarfs, the team estimates that only one in 30 of these stellar remnants has an unusual color.
"One in thirty might not sound like a huge fraction, but across the entire population of white dwarfs in the universe, that is still a lot of oddly colored stars out there," said Boris Gänsicke of the Department of Physics at the University of Warwick. "Yet if we take the median across a representative population of white dwarfs, we found that the average white dwarf really is white."
This research challenges the long-held assumption that white dwarf color is determined almost entirely by temperature. By demonstrating that atmospheric composition and density can significantly alter a star's appearance, the study provides new tools for astronomers to interpret the chemical history of stellar remnants. The identification of WD J1330+6435 as the first credible green star highlights the diversity of the universe's stellar population and offers new insights into how white dwarfs interact with their surrounding planetary systems.
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This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.
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