White dwarf turns green in astronomers’ calculations
New research shows how the composition of dense stellar atmospheres can produce unexpected colours.
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Astronomers have identified a white dwarf that, according to their calculations, would appear green to the human eye. The study appeared on Thursday in RAS Techniques and Instruments. The colour was derived from spectra and models, rather than from a new photograph showing a green star.
The most striking star in the study is called WD J1330+6435. According to the University of Warwick, this white dwarf has absorbed rocky material from its planetary system. As a result, its atmosphere contains calcium, lithium and sodium, among other elements. In the research team’s calculations, this composition produces a yellow-green colour. The researchers say they know of no previously convincingly described example of a truly green star. That claim to a first is their scientific conclusion.
A star’s colour is generally closely linked to its temperature. Cooler stars tend to appear orange, while hotter stars shift towards white and blue. The new research concerns conditions in which this usual relationship is insufficient to explain the observed colour. White dwarfs have very dense atmospheres. In these atmospheres, chemical constituents can substantially alter the distribution of the emitted light, the authors describe in their article.
A white dwarf is the compact remnant of a star such as the Sun after it has reached the end of its ordinary stellar life. The name does not mean that every white dwarf has exactly the same colour. The researchers specifically examined the variation arising from differences in temperature and composition. The research therefore also tests a familiar name: how white are white dwarfs actually when their light is translated into human colour perception?
To do this, the astronomers used spectra: measurements in which light is broken down by wavelength. Such data can be used to calculate how the combination of colours would appear to the human eye. BBC Sky at Night describes this method in its report on the study. The colour representations accompanying the coverage are illustrations. They should therefore not be understood as direct colour photographs of the surfaces of these distant objects.
Sodium plays an important role in WD J1330+6435. According to the team, this element absorbs some of the orange light, meaning that the remaining distribution of light can give a green impression. The university gives a temperature of about 4,000 degrees Celsius. What matters here is the combination of atmospheric conditions and the substances present. Temperature alone would therefore be insufficient to explain the unusual colour.
The study was published in a scientific journal and underwent peer review: the publication records receipt on 11 August, acceptance on 3 September and publication on 15 October 2026. This makes it a peer-reviewed research finding, rather than an isolated internet claim about a striking photograph of a star. At the same time, publication does not mean that the colour has been independently established again. No separate replication is described in the sources consulted.
The significance lies primarily in how astronomers interpret starlight. An unusual colour can contain information about the atmosphere and the material that has ended up in it. The new study shows why temperature alone is not always sufficient for this. Precise wording therefore remains important for the green star: the researchers infer how it would appear, based on its light and their models.
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The publication and university sources support the research into unusual colours. The suggestion of a direct visual discovery has been replaced with a description of the calculated colour.
- confirmed The study was published on 15 October 2026 and accepted on 3 September. — The article history records both dates. source
- confirmed WD J1330+6435 has a yellow-green colour in the models. — Warwick explicitly describes the calculated appearance. source
- confirmed The stated temperature is about 4,000 degrees Celsius; the atmosphere contains calcium, lithium and sodium. — These properties are listed in the university’s report. source
- confirmed Dense atmospheres containing certain elements can deviate substantially from the usual relationship between temperature and colour. — This is the physical basis described in the publication’s abstract. source
- confirmed The colour was derived from spectra and calculations, rather than established through a new colour photograph. — The explanation of the method distinguishes the calculated colour from the artistic illustrations shown. source
1 correction(s) applied
- Was: Astronomers see a green star for the first time.Now: Astronomers identify a white dwarf that would appear green according to calculations. (The source describes an inference from spectra and models, rather than a direct visual observation of a green colour.)
Editor's note
The colour has been calculated; the object has not been directly photographed as a green star. The claim that this is the first convincing green star remains explicitly attributed to the research team.Sources
- Any colour you like: the diverse chromaticities of white dwarfs — RAS Techniques and Instruments
- Green, pink and purple: astronomers reveal the surprising true colours of white dwarf stars — University of Warwick
- Astronomy and Astrophysics Group — University of Warwick
- Scientists have found a green star: the science behind the discovery — BBC Sky at Night Magazine
More on this in Dutch media
- RTL Nieuws — „astronomie witte dwergen”
- NOS — „astronomie witte dwergen”
- Het Parool — „astronomie witte dwergen”