Atmospheric Pollution Creates the First Genuinely Green White Dwarf
Astronomers at the University of Warwick have identified what models indicate is the first genuinely green star in the galaxy. Named WD J1330+6435, the cool white dwarf sits approximately 326 light-years from Earth. Its unique chartreuse hue results from sodium and other rocky debris pulled from its planetary system, which absorbs the orange and red wavelengths of light.
Modeling the True Colors of Stellar Remnants
Published in the journal RAS Techniques and Instruments, the study examines how white dwarfs deviate from acting as perfect radiators. Most stars glow white, yellow, red, or blue depending strictly on temperature. However, dense white dwarfs develop complex atmospheric compositions when they accrete material from asteroids and comets. “The traces of sodium in the atmosphere of this white dwarf absorb the orange part of the spectrum, leaving behind a ghostly green glow,” Dr. Mark Hollands of the University of Warwick explained, according to Reuters. “Imagine standing on a planet and looking up at a green star. It feels like something out of science fiction.”
Unusual Atmospheric Signatures Across the Population
The research team applied human color vision models to stellar spectra to determine how these dead stars would appear up close. Their analysis revealed distinct color groupings tied to chemical enrichment. Carbon-rich white dwarfs take on pink or purple hues, while stars polluted by asteroid and comet debris tend toward yellow. Meanwhile, the team also identified WD J1011+2845 as potentially the reddest star ever recorded. Located 48 light-years away, this white dwarf features a deep convection zone that dredges carbon up from its core, squeezing almost all of its emitted light past 600 nanometres.
What the Discovery Means for Stellar Evolution
Despite these striking atmospheric anomalies, the researchers emphasize that the median white dwarf remains decidedly white. WD J1330+6435 is far too faint to be observed as green through amateur telescopes or the naked eye, remaining visible only through spectroscopic data. The findings nevertheless expand current understandings of stellar atmospheres and provide new parameters for identifying unusual remnants in large-scale sky surveys like Gaia.
