Green Star Found: White Dwarf WD J1330+6435

Astronomers at the University of Warwick have identified what they call the first known green star, a cool white dwarf named WD J1330+6435. In a study published Oct. 15, 2026, in the journal RAS Techniques and Instruments, the team showed that the green star’s atmosphere, polluted with sodium from shredded rocky material, would give it a chartreuse glow if a person could see it up close.

The finding is part of a broader study showing that white dwarfs, the dense leftover cores of Sun-like stars, can appear in colors no ordinary star produces, including green, pink, cyan, yellow and purple. The paper, titled “Any colour you like: the diverse chromaticities of white dwarfs,” was led by Dr. Mark Hollands, a Warwick Prize Fellow in the university’s Astronomy and Astrophysics Group.

Why stars are usually orange, white or blue

For most stars, color works like a thermometer. Cooler stars look orange, stars like the Sun look white, and the hottest stars look pale blue. Warwick’s announcement compares this to a blacksmith’s iron that glows red, then orange, then white-hot as it heats up. Physicists call objects that behave this way “perfect radiators.”

“Most stars, including most white dwarfs, behave like ‘perfect radiators,’ so their colour is set almost entirely by temperature. But nobody had really looked into what else might be possible for white dwarfs,” Hollands said in the university’s release. “It turns out these incredibly dense stars can produce colours nobody expected, and some of them genuinely surprised me.”

How the green star gets its color

The key is density. The coolest white dwarf atmospheres can reach about 1 gram per cubic centimeter, roughly the density of water and millions of times denser than the visible surface of the Sun, according to Warwick. Under that pressure, trace elements such as carbon, calcium and sodium interact with the surrounding helium and absorb light across a much wider range of colors than they normally would.

WD J1330+6435 is roughly 4,000 degrees Celsius, and the paper’s model puts its temperature at 4,240 Kelvin. It has pulled in rocky debris from its old planetary system, which enriched its atmosphere with calcium, lithium and sodium. In the published paper, the authors explain that a strong, broad sodium feature absorbs orange light while calcium absorbs violet light. What is left peaks around 500 nanometers, which human eyes read as chartreuse green.

“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 said. “Imagine standing on a planet and looking up at a green star. It feels like something out of science fiction.”

As far as the researchers know, no other star, living or dead, has been credibly reported as green. That makes white dwarfs the only known way to produce a green star so far, the paper says.

Calculated, not seen: how the team measured color

No white dwarf is close enough for its color to be seen directly with the eye. Instead, the team started with each star’s spectrum, the pattern produced when starlight is split by wavelength, and ran it through a model of human color vision to work out what the light would look like to a person.

The researchers are open about the limits. The paper notes that the spectrum of WD J1330+6435 is “somewhat noisy,” so its exact shade could differ slightly in reality. An earlier model from the team’s 2021 work produced a similar hue, which the authors say gives them confidence the star really would look green. BBC Sky at Night Magazine also stressed that the green color comes from the team’s models.

A pink star and a one-in-30 rainbow

The study found that white dwarf colors fall into groups linked to what is in their atmospheres. Carbon-rich white dwarfs tend to look pink or purple. Those polluted with debris from shattered asteroids and comets lean yellow. Cooler stars with mixed hydrogen and helium atmospheres often look cyan or pale blue.

At the other extreme, the team identified what may be the reddest star ever recorded, WD J1011+2845, a white dwarf just 48 light-years from Earth. Carbon dredged up from its core squeezes almost all of its light into wavelengths beyond 600 nanometers, giving it a deep salmon-pink glow.

The researchers also examined all 151 white dwarfs within 20 parsecs, or about 65 light-years, of Earth. Five had unusual colors: two yellow and three pink. That suggests roughly one in every 30 white dwarfs shines with an unusual color, Warwick said.

Why it matters

The work shows how much information is packed into a star’s spectrum. Beyond temperature and chemistry, it can reveal true color, and in this case it also carries evidence of the planets and asteroids a dead star has swallowed. For more on how physicists are using new tools to dig into huge scientific datasets, see our report on CERN and Mistral’s plan for a Large Physics Model and our coverage of the 2026 Nobel Prize in Physics.

Featured image: NASA/ESA artist’s impression of the white dwarf Sirius B beside its bright companion Sirius A (not WD J1330+6435). Credit: NASA, ESA and G. Bacon (STScI), public domain, via Wikimedia Commons.

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Astronomers Find the First Green Star, a Rare White Dwarf