Astronomers have identified the first genuinely green star on record, a dense white dwarf glowing from sodium-rich debris, a cosmic zombie timed perfectly for Halloween.
Researchers led by the University of Warwick report that white dwarf WD J1330+6435, about 326 light-years away, shows a true green hue. The finding appeared Thursday, Oct. 14, in the journal RAS Techniques and Instruments, and Space.com reported the details shortly after.
Team leader Mark Hollands and colleagues say the color is not a trick of the eye or a camera filter. Models point to rocky material the dead star has been pulling in, enriched with calcium, lithium, and sodium. That chemistry changes how the star’s light reaches us.
Most people grow up learning that stars run from blue-hot to red-cool. White dwarfs, the leftover cores of stars like the sun after they burn out, were long treated as plain white or pale blue. This work says that picture was incomplete.
Hollands put the basic rule simply before the surprise.
"Most stars, including most white dwarfs, behave like 'perfect radiators,' so their color is set almost entirely by temperature. But nobody had really looked into what else might be possible for white dwarfs."
In these objects, matter is packed millions of times denser than the surface of the sun. Under those conditions, carbon, calcium, and sodium can interact with a dense helium plasma and soak up light across a wider stretch of the spectrum than everyday stars do.
For WD J1330+6435, sodium does the decisive work.
"The traces of sodium in the atmosphere of this white dwarf absorb the orange part of the spectrum, leaving behind a ghostly green glow."
Hollands did not hide his reaction to the result.
"It turns out these incredibly dense stars caaaaan produce colors nobody expected, and some of them genuinely surprised me."
He added the image that sticks: standing on a planet under a green sun would feel like science fiction. The team frames the object as a kind of cosmic zombie, a stellar corpse still shining, and in this case shining green, as Halloween approaches.
The green star is not a one-off curiosity in the paper. The group also highlighted WD J1011+2845, only 48 light-years from Earth. Deep convection there pulls carbon from the core and warps the light into a deep salmon-pink. Researchers describe it as a candidate for the reddest star ever noted.
Across 151 white dwarfs within roughly 65 light-years of Earth, only five show extraordinary coloring. The team’s estimate is that about one in 30 of these dead stars carries an unusual tint, green, pink, cyan, yellow, or purple, depending on atmospheric chemistry and density.
Boris Gänsicke of Warwick’s Department of Physics put the numbers in perspective.
"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."
He also kept the baseline honest: take the median of a representative sample, and the average white dwarf really is white. The outliers matter because they expose what dense atmospheres and leftover planetary rubble can do to starlight.
White dwarfs form when stars of roughly the sun’s mass run out of fuel. What remains is an extremely dense core. If that core later accretes rocky planetary debris, the atmosphere can pick up metals and other elements that ordinary “perfect radiator” models never fully accounted for.
In WD J1330+6435, that accretion path supplies the sodium that cuts the orange wavelengths and leaves the green. In the pink case, carbon dredged up from deeper layers does different spectral damage. Same family of objects, different chemical fingerprints, different colors.
Earthbound observers never had a white dwarf close enough for these true colors to overturn the old assumption in plain sight. The new models and the Warwick-led analysis fill that gap with specific catalog objects and distances rather than guesswork.
Billions of years from now, the sun itself will become a white dwarf. The paper notes, as possibility rather than prediction, that if it later swallowed planetary material the right way, even our own star’s remnant could take on unexpected tints. That is context, not a forecast with a date.
Hard measurement and clear chemistry still beat the old textbook cartoon. The sky keeps a few surprises for anyone willing to look past the default white-and-blue story.
