Astronomers have identified a remarkable exception to one of astronomy's familiar rules: a star whose light would appear green rather than the usual red, white or blue. The object, a dense stellar remnant called WD J1330+6435, owes its unusual chartreuse color to the chemistry of its atmosphere, according to research published on October 15, 2026, in the journal RAS Techniques and Instruments.
The white dwarf, located approximately 280 light-years from Earth in the constellation Draco, was already known to scientists. What is new is a detailed calculation of how its light would appear to human eyes. Rather than photographing a green stellar surface, researchers analyzed its spectrum and modeled how extreme atmospheric conditions change the wavelengths of light escaping into space.
The findings, described in a Reuters report published October 16, suggest that certain white dwarfs can display colors rarely associated with stars, including green, pink, purple and cyan.
Why This White Dwarf Could Appear Green
Most stars produce a broad range of visible wavelengths, with their apparent colors largely determined by surface temperature. Cooler stars generally look reddish or orange, while hotter stars tend toward white or blue. Green is unusual because even stars emitting strongly in the green portion of the spectrum also produce substantial red and blue light, which combine to create a different perceived color.
WD J1330+6435 is different because its dense atmosphere selectively absorbs significant portions of the light it produces.
The white dwarf contains elements including sodium, calcium and lithium associated with rocky material that entered its atmosphere from an earlier planetary system. Under ordinary conditions, sodium absorbs light across a relatively narrow region of the orange spectrum. But the extraordinary density of the star's helium-rich atmosphere changes that behavior.
Frequent interactions between sodium and surrounding helium atoms broaden the wavelengths sodium can absorb. As a result, much of the yellow, orange and red light is suppressed, while calcium absorption also modifies the violet portion of the spectrum.
The remaining visible light has a spectral distribution that researchers calculate would produce a distinctive pale yellow-green, or chartreuse, appearance.
The star's modeled effective temperature is approximately 4,240 kelvin. Its unusual color therefore cannot be explained by temperature alone. It emerges from the combined effects of atmospheric composition, density and the interaction of light with matter.
How Astronomers Calculated the Star's Color
The discovery emerged from a broader effort to determine what white dwarfs would actually look like if their stellar disks could be viewed directly by human observers.
Because these stars appear as unresolved points of light from Earth, astronomers cannot simply take a close-up photograph of their surfaces. Instead, they use spectroscopy, which separates incoming starlight into different wavelengths and reveals where specific elements absorb energy.
Researchers combined observational spectra, including data from the Sloan Digital Sky Survey, with detailed stellar-atmosphere models. They then translated the resulting light distributions into predicted human-visible colors.
In their published study, "Any colour you like: the diverse chromaticities of white dwarfs," Mark A. Hollands and colleagues used updated calculations of sodium absorption to better characterize WD J1330+6435.
The improved model indicates that the star's strongest emerging visible light lies around 500 nanometers, contributing to its unusual green appearance.
There is an important limitation: the available spectrum contains some noise, meaning the exact calculated shade remains uncertain. The researchers nevertheless found a similar green hue using an earlier atmospheric model, supporting their broader interpretation.
The result is therefore a scientifically grounded reconstruction of perceived color, not a direct visual observation of a green stellar disk.
Green, Pink and Purple: The Unusual Colors of White Dwarfs
The green white dwarf is part of a wider pattern. The researchers found that different atmospheric compositions can shift white dwarf colors well beyond the familiar range expected from temperature alone.
One particularly striking example is WD J1011+2845, approximately 48 light-years from Earth in the constellation Leo Minor. Its calculated appearance is salmon-pink, making it a candidate for one of the reddest-looking known stars.
Unlike the green white dwarf, whose unusual atmospheric chemistry is linked to material acquired from a planetary system, the pink star's color is influenced by carbon brought up from its deeper interior. Broad carbon-related absorption features reshape the visible spectrum and produce its distinctive hue.
The study also identified white dwarfs with purple, yellow and cyan-leaning appearances. Carbon-rich atmospheres can produce pink or purple colors, while some atmospheres containing mixed hydrogen and helium can create pale blue or cyan tones.
Most white dwarfs, however, remain comparatively ordinary in appearance. In a nearby sample of 152 white dwarfs within approximately 65 light-years, researchers identified five with colors that departed substantially from the usual temperature-based stellar color pattern. Their estimated frequency was approximately 3.4%, with considerable statistical uncertainty.
That result does not mean 3.4% of all stars are green, or even that green white dwarfs occur at that rate. The estimate applies to a particular nearby sample and a defined measure of unusual color. WD J1330+6435 itself lies beyond that nearby group.
The researchers also identified other white dwarfs with paler green hues, making WD J1330+6435 the most vivid green example examined rather than the only object with a modeled green appearance.
What These Stellar Colors Reveal About Dead Stars
White dwarfs are the compact remnants left behind when stars of relatively low or intermediate mass exhaust their nuclear fuel and shed their outer layers. They contain immense amounts of matter compressed into an object roughly the size of Earth.
That extraordinary density creates physical conditions unlike those found in the atmospheres of ordinary stars. Atomic interactions can significantly alter the way light is absorbed, allowing atmospheric chemistry to influence perceived color in unexpected ways.
The presence of heavier elements can also provide evidence about a white dwarf's past. Material from disrupted asteroids, rocky bodies or other remnants of an earlier planetary system may eventually reach the stellar surface, leaving chemical signatures that astronomers can detect.
In WD J1330+6435, the detected sodium and other elements help explain the unusual spectrum while pointing to the influence of rocky material. They do not, however, establish the precise identity of any individual destroyed planet or prove that researchers directly witnessed such an event.
The broader scientific significance extends beyond an unusual color. By combining spectroscopy with improved models of matter under extreme conditions, astronomers can investigate the chemistry, physical structure and evolutionary histories of stellar remnants that cannot be examined directly.
The green appearance of WD J1330+6435 illustrates how an apparently simple property of a star—its color—can encode information about the dense atmosphere surrounding it and material left behind by a planetary system long after its original star has died.
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